Saturday, June 24, 2017

Botany picture #246: Tanacetum vulgare


No energy to write something substantial at the moment, and instead I find myself thinking about plants. Here, Tanacetum vulgare (tansy, Asteraceae), Germany, 2016. It is in the Chamomile tribe of the daisy family. It has been on my mind because I was recently looking through our herbarium for specimens that have mature fruit on them, and while we have quite a few specimens there aren't any that fulfill that particular criterion.

Many daisies are usually collected in flower because they look rather less attractive in fruit, which is rather ironic given that there are many subgroups where fruits are extremely important for identification, e.g. among the dandelion tribe. But often you will at least get mature fruits as by-catch; the whole plant is collected because one head was in flower, but others lower down are already fruiting. In this case, however, the specimen is generally a single stem, and all its heads in the terminal corymbose panicle are at about the same stage, meaning none of them are fruiting. A bit frustrating.

Monday, June 19, 2017

Botany picture #245: Salvia patens


Today's botany picture is Salvia patens (Lamiaceae), a New World sage species photographed at the Botanic Gardens of Goettingen University while I was doing my PhD there. This plant has the most amazing blue flower colour, and consequently I was rather bemused to find a few years later that plant breeders have selected and were selling a white variant of this species. What is the point of that? It is like breeding an onion without taste, or a rose that doesn't produce flowers.

Okay, cranky get off my lawn mode deactivate.

Sunday, June 18, 2017

To publish or not to publish (locality information for rare species)

This week our journal club discussed Lindenmayer & Scheele, Do not publish (Science 356(6340): 800-801). While acknowledging the trade-offs involved, the paper argues for researchers, journals and data providers to self-censor locality information for rare species to keep them safe.

The problem, in short, is that some rare species are highly valued by professional poachers and private collectors, and they may in short order wipe out a rare species if they know where to find it. The article itself mentions a rare Chinese gecko; participants in our discussion provided other astonishing examples from various parts of the planet. It did not surprise me to learn that there are people digging up cycads to sell them to wealthy home-owners who want to adorn their front gardens, but I was definitely surprised to learn that rare beetles are traded for hundreds of dollars apiece by a demented subculture of beetle enthusiasts.

Nobody really disagreed with the sentiment of the article per se, but obviously people immediately raised scenarios where making the data available actually helped conservation. A particular concern is that it has to be known that a rare species exists in a spot when there is a development proposal; what is the use of keeping the information safe from poachers only to have an open-cut mine wipe out the species?

A comparison was made with medical data. While biodiversity researchers are used to having all data openly available, the medical research community has long had strict procedures for keeping safe medical information of individual people, but they still manage to do research. In other words, biodiversity science should not suffer from more restricted access to locality information if the right procedures are adopted. That being said, some raised the concern that this would simply add another layer of bureaucracy to a field already burdened with often unreasonable procedures around collecting permits and specimen exchange.

What the article and our discussion were mostly about are specimen data typed off the specimen labels and made available through databases such as GBIF or Australia's ALA. The idea would then be to have those data providers make the locality descriptions and GPS coordinates just fuzzy enough that nobody can find the exact spot where a species was seen or collected, while still providing that information to legitimate and trusted researchers. What should not be overlooked, however, is that currently a major push is underway to photograph the actual specimens and make those photos available online. Has anybody thought about systematically blurring out such locality information for rare species on the photographed labels? Not sure I have ever heard that discussed before.

Finally, there was some agreement that it would be good to have a global policy recommendation on this instead of leaving it up to individuals to self-censor without guidelines. Given that there are working groups agreeing on data formats etc. it should surely be possible to find agreement on this problem.

An off-topic excurs on hobgoblins

In this context it was interesting that somebody said, "consistency is the hobgoblin of small minds", a phrase that I have run into before. Of course, the idea here was that while a rule or recommendation is nice to have, people will still have to weigh trade-offs, and even if the recommendation would be to generally blur the data one may in some cases need to publish it (see a few paragraphs earlier).

And yes, I see where that is coming from. The fundamentalist wants a clear rule and apply it blindly, whether it makes sense or not; the intellectually mature realise that rules were introduced to achieve a good, and if applying the rule hurts that very same good then one should not apply the rule.

But still throwing a phrase like that around makes me a bit uncomfortable. In most cases consistency is important. When we are talking rules it should be clear that consistency is usually just another word for fairness. People who want to apply rules inconsistently would have to provide a very good reason for why they should not simply be seen as trying to get away with something that they would not let others get away with.

When we are talking argumentation, discussion and logic, intellectual consistency is the very first hurdle somebody has to clear to be taken seriously, and only then is it worth the investment to look into whether they have evidence on their side or not. People who are proud of being inconsistent in this sense (because it makes them Not Small Minds, you see) would have to explain carefully how they are not simply somewhere on the spectrum from slightly confused to totally insane, or alternatively on the spectrum from obfuscating the issue to gaslighting their conversation partner.

Monday, June 12, 2017

ANBG impressions

Although it is winter, and although it was foggy the first half of our visit, the Australian National Botanic Gardens always have something to see.


Moss cushion on a tree branch.


Golden everlasting flower-head waiting for the sun to come out.


Shadows cast onto a bridge in the rain forest gully.


Spider's web covered with dew.

Sunday, June 11, 2017

How the sausage is made: peer reviewing edition

One of the aspects of working as a scientist that I find most intriguing is peer reviewing each other's work. The main issue is that while how to write the actual manuscripts is explicitly and formally taught and further supported by style guides, helpful books and journals' instructions to authors, there is much less formal instruction on how to write a reviewer's report.

Essentially one is limited to (1) relatively vague journals' instructions to reviewers usually on the lines of "be constructive" or "be charitable", (2) deducing what matters to the editor from the questions asked in the reviewer's report form, and (3) emulating the style of the comments one receives on one's own papers. Apart from generic, often system-generated thank you messages there is generally no feedback on whether and to what degree the editors found my reviewer's reports appropriate and helpful or on how they compared with other reports.

In other words, most of it is learning by doing; after years of practice I now have a good overview of what reviewer reports in my field look like, but as a beginner I had very little to go by.

It is then no surprise that the style and tone in which reviewers in my field write their reports can differ quite a lot from person to person. There is a general pattern of first discussing general issues and broad suggestions and then minor suggestions line-by-line on phrasing, word choice or typos, and there is clearly the expectation of being reasonable and civil. But:
  • Some reviewers may summarise the manuscript abstract-style before they start their evaluation, while others assume that the editor does not need that information given that they have the actual abstract of the paper available to them.
  • Some stick to evaluating the scientific accuracy of the paper, while others obsess about wording and phrasing and regularly ask authors who are native speakers of English to have a native speaker of English check their manuscript.
  • Some stick to judging whether the analysis chosen by the authors is suitable to answer the study question, while others see an opportunity to suggest the addition of five totally irrelevant analyses just because they happen to know they are possible. And sometimes they recommend cutting another 2,000 words from the text despite suggesting those additions, as if those would come without text.
  • Some unashamedly use the reviewer's report for self-promotion by suggesting that some of their own publications be cited, relevant or not.
  • Some use a professional tone and make constructive suggestions on the particular manuscript in question, but others apparently cannot help disparaging the authors themselves. Luckily that behaviour is rare.
  • Some write one paragraph even when they recommend major revision (meaning they could have been more explicit about what and how to revise), others write six pages of suggestions even when their recommendation is rather positive.
Certainly then scientists in my field will have very different ways of approaching the task right from the start. Nonetheless, and for what it is worth, this is how I generally find it useful to do it.

First, I like to print the manuscript - I am old-fashioned like that. I try to begin reading it fairly soon after I accept the job, and for obvious reasons I also try to read through more or less over one day. Often I will read when I need a break from some other task like computer work, on a bus or in the evening at home.

Already on the first read I attempt to thoroughly mark everything I notice. Using a red or blue pen I mark minor issues a bit like a teacher correcting a dictation, while making little notes on the margins where I have more general concerns ("poorly explained", "circular", "what about geographic outliers?").

Usually the following day I order my thoughts on the manuscript and start a very rough report draft by first typing out all the minor suggestions. (I would prefer to use tracked changes on a Word document for that, but unfortunately we generally only get a PDF, and I find annotating those even more tedious than just writing things out.) Then I start on the general concerns, if any, merely by writing single sentences on each point but do not expand just then.

In particular if the study is valuable but has some weaknesses I prefer to sleep over it at this stage for 2-3 nights or, if the task has turned out to be a bit unpleasant, even a few days more, and then look at it again with fresh eyes. That helps me to avoid being overly negative; in fact I tend to start out rather bluntly and then, with some distance, rephrase and expand my comments to be more polite and constructive.

That being said, if the manuscript is nearly flawless or totally unsalvageable I usually finish my review very quickly. If I remember correctly my record is something like 45 min after being invited to review, because the study was just that deeply flawed. In that case I saw no reason to spend a lot of time on trying to develop a list of minor suggestions.

More generally I have over the years come to the conclusion that it cannot be the role of a peer reviewer to check if all papers in the reference list have really been cited or to suggest language corrections in each paragraph, although some colleagues seem to get a kick out of that. If there are more than a handful of language issues I would simply say that the language needs work instead of pointing out each instance, and if there are issues with the references I would suggest the authors consider using a reference manager such as Zotero, done. Really from my perspective the point of peer review is to check if the science is sound, and everything else is at best a distant secondary concern.

At any rate, after having slept over the manuscript a bit I will return to it and write the general comments out into more fluent text. I aim to do the usual sandwich: start with a positive paragraph that summarises the main contribution made by the manuscript and what I particularly like about it. If necessary, this is followed by something to the effect of "nonetheless I have some concerns" or "unfortunately, some changes are required before this useful contribution can be published".

Then comes the major stuff that I would suggest to change, delete or add, including in each case with a concrete recommendation of what could be done to improve the manuscript. I follow a logical order through the text but usually end with what I consider most important, or repeat that point if it was already covered earlier. To end the general comments on something positive I will have another paragraph stressing how valuable the manuscript would be, that I hope it will ultimately be published, etc. Even if I feel I have to suggest rejection I try to stress a positive element of the work.

Finally, and as mentioned above, there is the list of minor suggestions. Most other reviewers I have run into seem to structure their reports similarly.

When submitting the report, however, one does not only have to provide the text I have discussed so far, although it is certainly the most useful from the authors' perspective. No, nearly all journals have a field of "reviewer blind comments to the editor", which I rarely find necessary to use, and a number of questions that the reviewer has to answer. The latter are typically on the following lines:
  • Is the language acceptable or is revision required?
  • Are the conclusions sound and do they follow logically from the results?
  • Are all the tables and figures necessary?
And so on. The problem I usually have is that these questions are binary, but I would like to write something like "mostly yes, except for that instance here which really needs to be dealt with".

Thursday, June 8, 2017

Botany picture #244: Primula veris


Perhaps one of the most artsy pictures I have ever taken, this shows a Primula veris (Primulaceae) at the Zurich Botanic Gardens, taken in 2009. I was at that time involved in pollination experiments on the species.

Saturday, June 3, 2017

Reading up on biogeography part 5: time-slices

Today finishes up, at least for the moment and until the next special issue comes out, the little series on panbiogeography and vicariance geography. The last paper is

Corral-Ross V, Morrone JJ, 2017. Analysing the assembly of cenocrons in the Mexican transition zone through a time-sliced cladistic biogeographic analysis. Australian Systematic Botany 29: 489-501.

It uses area cladograms, as did one of the papers already discussed, but as the title indicates it does so in a way that examines different "time slices".

Before I get to the methodology I would like to establish an analogy.

Imagine you read a recipe for what are supposed to be very amazing pancakes. The instructions are as follows: (1) mix eggs and milk; (2) place the concrete in the deep freezer; (3) pour the mixture into the frying pan. Looking at such instructions you may well wonder first what concrete has to do with anything - not only would you not expect concrete to be part of pancake-making in the first place, but it does not even seem to be used for anything. Next you may notice that there is no mention of flour, although some kind of flour would appear to be necessary to produce pancakes.

There are now at least three possibilities. One is that the authors of this recipe have no idea how to make pancakes and merely pretend they do. Another is that they do in fact know what they are doing in the kitchen but merely wrote very incomplete and confusing instructions. Finally, there is the possibility that we, the readers, are just too ignorant or blinkered to understand the brilliance of the approach.

Some of the papers in cladistic biogeography and panbiogeography are very clear in their methodology, and I can immediately understand what they did and perhaps even what their logic is, even if I may have concerns. But with others I feel as if I am confronted with the above pancake recipe. Either the authors have no idea how to do biogeography, or the methods section could be clearer, or I have no idea how to do biogeography.

In the present case, the authors assembled 49 phylogenies ("cladograms") of various groups of organisms occurring in the Mexican biota that they were interested in. They then, as usual for area cladistics, replaced the names of the terminal taxa in the phylogenies with the areas those terminals occur in, and then extracted "paralogy-free subtrees" for analysis.

To this point it is the same approach as in the previous area cladistics paper, and once again I am a bit uncertain how precisely it works and, more importantly, how it could possibly be justified. When a molecular phylogeneticist removes paralogous alleles from the analysis they do so because we understand a lot about gene duplication, gene families, pseudogenes and suchlike. When an area cladist picks subtrees out of a larger area cladogram, what is the parallel? What is the theory behind it? How do they explain the existence of what they call paralogy in a way that does not make the whole idea of having area cladograms appear absurd? I cannot help but wonder if it is anything more than "this is too complicated so we will ignore it". Maybe I just haven't seen the proper justification, but the papers I have looked at so far seem to limit themselves to saying that paralogy exists and needs to be removed.

But now for the time-slicing. This is now really the pancake recipe: if it works the way I believe I understand the methods then it doesn't make any sense. But if it works in a different way that actually makes sense then it isn't explained well enough for me, at least, to understand. The way it looks to me is that the authors assigned each group of organisms for which they had a phylogeny in their analysis to a "cenocron", which they defined as a "set of taxa that share the same biogeographical history, which is recognised as a subset within a biota".

They then conducted three different analyses supposedly corresponding to the Miocene, the Pliocene and the Pleistocene, using phylogenies from only one, two and then all three cenocrons, respectively. In other words (again, if I understand correctly), the idea seems to be that only organisms from one of the cenocrons would have been in the study area in the Miocene, with the others arriving later. I think.

The conclusion after all this effort is that "the Mexican Transition Zone is a complex area that differs in delimitation from one analysis to another. The present study showed that the results may depend on the assemblage of the taxa analysed, with time-slicing being an adequate strategy for deconstructing complex patterns in cladistic biogeography". That is not exactly the most concrete conclusion I have ever seen. What is more, the second paragraph of the introduction already explained that "the Mexican transition zone, as defined by Halffter (1987), is a complex area", so at this moment I am not really on top of what new insights the analysis produced.

But my more important question is this one: How does the claim work that the "Miocene analysis" examines the Miocene time-slice when the authors appear to have used phylogenies of contemporary (that is Pleistocene) species? The Miocene was 5 to 23 million years ago. The species in the phylogeny would not have existed yet, only their distant ancestors would have, with potentially very different geographic ranges. We are talking the time of our common ancestor with the chimps and waaay beyond!

Do the authors assume that all contemporary species existed 20 Mya ago and have remained utterly static since that time? Where is the flour that one would absolutely need to get a pancake out of this? (Time-calibration of all the phylogenies they used followed by ancestral area estimation, in case that isn't immediately clear.)

Again: maybe I am missing something, perhaps even something that will be obvious to many others, which would make sense of this approach. But at the moment I pointlessly have a lump of concrete sitting in the freezer, and the promised pancake looks very much like a watery omelet to me.

Wednesday, May 31, 2017

Cogent Spam and, while we are at it, ARTOAJ spam

In the last two weeks several of the blogs I read have discussed an attempted 'hoax' publication that aimed to repeat for gender studies what Alan Sokal did for postmodern cultural studies in general when he made up a nonsense paper and got it published in a well-respected journal catering to that field. In the present case, Peter Boghossian and James Lindsay made up a deliberately nonsensical paper on the "conceptual penis as a social construct", but that is where the parallels end.

It seems as if they first submitted it to a relatively low ranking journal, were actually rejected, and then got it published in an even more obscure and, crucially, pay-to-play journal called Cogent Social Sciences. They then immediately went public explaining their hoax and declaring, "we suspected that gender studies is crippled academically by an overriding almost-religious belief that maleness is the root of all evil. On the evidence, our suspicion was justified". However, many people immediately pointed out it is not as easy as that.

They also, and actually first, discuss the problem of crappy pay-to-play journals, but as has been discussed elsewhere, we don't really get to use this experiment to prove two potential reasons why the paper was published at the same time. If it was published because Cogent Social Sciences is such a low quality journal that it will accept anything, then the stunt proves nothing about gender studies as a whole. Conversely, if the paper was published because the field of gender studies has no standards except the requirement to see maleness as evil, then it proves nothing about crappy publishers.

More concerning, however, seems to be the discussion that the 'hoax' has spawned. From a feminist perspective I have seen a blog post and an essay that both argued that the people celebrating it as a success can only be motivated by a hatred of feminism and a fear of women in power. I am not really sure where that comes from; the possibility should at least be entertained that the underlying motivation is the one that is stated, i.e. being fed up with postmodernist gibberish and the politicisation of academia.

On the other hand, I found it really frustrating how many people who are supposedly rationalists, skeptics, and generally science-savvy do not appear to understand at all the problem of crappy pay-to-play journals. Over and over, even in comments under articles that explained in detail what is going on here, people would write something to the effect of "but a social science journal accepted it, so there". Argh. If some guy operated a website called International Journal of Evolutionary Biology Research out of his garage, and a creationist paid him $200 in publication fee to get a nonsensical paper posted on that website, would that show that all of evolutionary biology is nonsense? Quite so. Then why the failure to appreciate the same problem in this case? Blind tribalism?

I was a bit torn at first when I had a look at the Cogent Open Access website myself. It looks much more professional than most obscure pay-to-play publishers I have seen so far, and I could at that moment not remember them spamming. Then again, I also never heard of that publisher before. Looking into a few papers they published in an area that I can judge I was not exactly overwhelmed, but okay. Just a few days ago, however, on some whim I looked into my junk mail folder, and what would I see but a spam eMail from Cogent Biology?


Again, it is not the worst I have seen, but let's count the ways in which it raises red flags for me:
  1. Well, first of all, it is a spam message, randomly soliciting papers from huge numbers of researchers who did not sign up to receive these message. This is not a practice generally associated with serious publishers.
  2. Promise of quick review and, in particular, suprisingly fast publication after acceptance.
  3. Suspiciously broad scope of the journal.
  4. Bragging about being 'indexed' in services that either are the usual suspects, or I have never heard of, or are mere utterly non-discriminating search engines like Google Scholar, as if any of that were a mark of quality.
  5. Unprofessional random bolding, italicisation, and colouring of words across the text of the message.
Add "greetings of the day!" and two more font colours and it would be utterly standard for the field. In other words, this clinches it, at least for me: I think publishing the 'hoax' paper in Cogent Social Sciences demonstrates absolutely nothing about gender studies (and nothing that we didn't already know about publishing).

Note, by the way, that the two following statements are completely independent:
  • This so-called hoax was a dud, and the people who celebrate it either don't understand its problems or exhibit a disconcerting failure of skepticism.
  • Gender studies as currently practiced is largely bollocks.
It is entirely possible to believe both at the same time, although personally I do not consider myself qualified to have an opinion on the second statement. More to the point, even if the second statement could be proved beyond doubt, it would not at all disprove the first. It is curious how many people do not seem to appreciate that, as they appear to try to demonstrate the success of the hoax by pointing at completely different papers that they also consider ridiculous.

---

While on the topic of science spam, on Monday I received a particularly hilarious instance:
Good Morning.....!
What a professional salutation.
Can we have your article for successful release of Volume 6 Issue 5 in our Journal?
Wait, what article are you talking about, specifically? Also: no.
In fact, we are in need of one article to accomplish the Issue prior 10th June; we hope that the single manuscript should be yours. If this is a short notice please do send 2 page opinion/mini review/case report, we hope 2 page article isn't time taken for eminent people like you.
So basically: send us whatever you want, we just want stuff!
Your trust in my efforts is the highest form of our motivation, 
Gibberish alert!
I believe in you that you are eminent manuscript brings out the best citation to our Journal.
I believe in you that you are poor at constructing English sentences. And this is just beautiful: they come right out and say that this is about what is best for their randomly capitalised "Journal" as opposed to what is best for science or the author. Ye gods.
Anticipate for your promising response.
Ding! Gibberish!
Regards,
Sophia Mathis
If that is really the name of the author of that message I will eat my hat.
Agricultural Research & Technology: Open Access Journal (ARTOAJ)
The names keep getting more ridiculous. I guess all the good ones are taken? Now for the finale:
*Note: Wanna get more citations for your articles publish with us as i-books, e-books & Videos.
"Wanna". Somebody thought they could emulate what a serious academic publisher would write and they came up with "wanna get more citations". The mind reels.

Monday, May 29, 2017

Botany picture #243: Cnicothamnus


It occurs to me that it has been quite some time since I posted a plant picture. Should do more of those again.

I took this particular photo on a field trip to Bolivia in 2007, without knowing what it was; I merely thought that it was a rather unusual-looking daisy. Years later I then read a phylogenetic study of the Gochnatieae, and when I saw its figure 2B I went, "hey, that looks familiar!"

I cannot be sure which species it is, but it sure seems like it is a Cnicothamnus (Asteraceae); the combination of unusual capitulum size and colour, many greyish capitular bracts, and geographic provenance seem to make it a safe conclusion.

Saturday, May 27, 2017

Reading up on biogeography part 4: track analysis for bioregionalisation

With two papers left, I was wondering whether there would still be any point to going on. The last two use track analysis and area cladograms, respectively, and those were already used by the first and second paper, so would there be any new insights into the methodology of pan- and vicariance biogeography?

However, the next paper,

Martinez et al., 2017. Biogeographical relationships and new regionalisation of high-altitude grasslands and woodlands of the central Pampean Ranges (Argentina), based on vascular plants and vertebrates. Australian Systematic Botany 29: 473-488.

... uses track analysis at least partly to do something different than the previous instance. There is the question of the "relationship" of a biome, but then there is also bioregionalisation. So that is a new angle.

The idea seems to be relatively simple. As before, the panbiogeographer looks at the occurrences of species, draws minimum-distance lines ("tracks") between them, and then identifies areas where the tracks of several species overlap as "generalised tracks". In the present case, a very short generalised track is then "used to recognise natural areas in terms of their biota because they result from more or less consistent overlapping distributions of two or more endemic taxa".

Okay, same question as always: does this make sense?

Well, more than the claim that generalised tracks are always evidence of vicariance, which this paper kind of only makes in passing (while, weirdly, explaining the panbiogeographic reasoning in words so identical to those used in the Romano et al paper that I wonder if they were in both cases copy-pasted from Croizat). To me the approach just seems part unnecessarily complicated, part not data-rich enough.

As for the first, yes, an area with several endemic taxa may well deserve recognition as a natural unit, a vegetation zone, a biome (whatever) in some area classification. But if the idea is to identify areas defined by endemic species, why do we need a track analysis as an intermediate step? Why not simply plot the occurrences of endemic species? At that point all the information is there, and tracks, generalised or not, do not add anything.

As for the second, as I mentioned before there are several other methods available for bioregionalisation. Some use clustering approaches to group grid cells or other small areas into larger areas based on shared species content or even the relatedness of those species. The newest ones use modularity or map equation analyses to examine networks of species and the grid cells they occur in; in contrast to clustering, where it is the researcher's somewhat subjective choice how many clusters to accept, these network approaches have algorithms for deciding more objectively how many truly distinct units there are.

In other words, in my eyes track analysis seems to be superfluous to requirements if we are merely interested in the simple measure of shared endemics, and it is unable to provide the depth of information that could be obtained from examining other shared distribution patterns.

Sunday, May 21, 2017

Reading up on biogeography part 3: Hopping between islands yes, hopping from continent to island no?

The third vicariance biogeography / panbiogeography paper in the special issue is

Grehan JR, 2017. Biogeographic relationships between Macaronesia and the Americas. Australian Systematic Botany 29: 447-472.

Despite being very long, its gist is easily summarised:

The mainstream explanation for the occurrence of plants and animals on the Macaronesian islands (Canary Islands, Madeira, etc.) is that they must have got there via long-distance dispersal, often from Africa but sometimes from the Americas, because the islands are of relatively young volcanic origin and distant from other land masses. However, the "model-based approaches" that this conclusion is based on cannot be accepted because they supposedly assume dispersal and ignore the possibility of vicariance.

This is followed by many pages of example cases of plants and animals illustrated with maps and phylogenies. It is not clear to me what that is supposed to show, because without a time axis it doesn't move the inference either way; at best it could show that some of the groups have a pattern that is consistent with vicariance, but if a lineage is too young then vicariance is still out, and the same if the lineage is much older than the island.

Finally, there is some speculation, again illustrated with maps, about whether there were always volcanic islands in the same area, all through from the time when the Atlantic started to open. They would have been transient on a geological scale, so the local lineages supposedly produced by vicariance when Africa and the Americas started moving apart would have had to island-hop as new volcanoes rose and older ones eroded away, over more than 100 million years.

In contrast to the previous two papers I did not really gain new insights into the methodologies favoured by vicariance biogeographers. In a sense the present paper is closer to an opinion piece or perhaps a review article than to a research study.

The supposed assumptions of "model-based approaches"

The paper claims
"Model-based approaches to Maccaronesian biogeography assume the that the [sic] sequence of phylogenetic relationships reflects a sequence of chance dispersal. Although often cited as Hennig's progression rule, it is not a rule but an assumption that does not address the equal applicability of sequential differentiation across a widespread ancestor."
And further on:
"Model-based methods use chance dispersal to explain divergence and allopatry, ..."
Unfortunately this claim at least is demonstrably false. There are various models available to do ancestral area inference (see this graphic as an example), and DIVA and very popular DEC, for example, include vicariance. That's what the V in the acronym DIVA means! If a model-based analysis with a model that allows vicariance infers no vicariance then we can assume it is not because the model does not allow vicariance, but because the data didn't support that conclusion.

I am also reasonably certain that Hennig's progression rule does not only apply to long distance ("chance") dispersal but would just as well apply to a series of range expansions followed by speciation events across a single land mass. It simply applies the principle of parsimony to historical biogeography, arguing that if several lineages along a grade occur in an area then that would probably, all else being equal, have been (at least part of) the ancestral range, because other explanations require more dispersal and/or extinction events.

It is interesting, by the way, how the word "model" seems to be used in this context, as if a mathematical description of a system is something bad.

What distribution patterns would we expect under vicariance and long-distance dispersal, respectively?

"The progression rule also assumes that a 'basal' grade is located in the source region or centre of origin, but some Macaronesian clades are basal to large continental clades, and there are also clades with 'reciprocal monophyly' in which a diverse Macaronesian clade is the sister group to a diverse continental clade. These phylogenetic and geographic incongruities do not arise in a vicariance interpretation of phylogeny, because a basal clade or grade marks only the location of the intial phylogenetic break or breaks within a widespread ancestral range."
I don't really understand the reasoning here. The idea seems to be that if an island clade is nested within a continental grade, then it may make sense to conclude dispersal, but if an island clade and a continental clade are sister to each other then it is somehow "incongruent" (with what?) and can only be explained by vicariance. Why?

I would look at the nearest outgroup to get more information, but even if that occurred in neither region then we would still have to ask if additional continental or island lineages may have simply gone extinct. The key questions are whether the lineage split is so recent that it happened considerably after continental break-up and whether an island lineage is older than the island(s). Really I don't see how we can conclude anything with confidence without a time axis.

Perhaps the idea is to equate "distribution of the species along a basal grade is evidence of a centre of origin" with "absence of such a basal grade is evidence of absence of a centre of origin"? If so, that would not be logical; absence of evidence for A is not evidence for not-A.

The paper also discusses other patterns, in this case non-overlapping ranges of related species (allopatry):
"Model-based methods use chance dispersal to explain divergence and allopatry, and yet allopatric divergence requires isolation, which cannot exist if there is effective dispersal."
The point of the second half of this sentence is a false dichotomy set up between dispersal that is so frequent that it makes speciation impossible and no dispersal at all. It seems obvious to me that the excluded middle is dispersal that happens but is too rare to make speciation impossible.
"In the same way that allopatric lineages within Tarentola are incongruent with the expectations of chance dispersal, so too is the allopatry of Tarentola and its New World sister group."
Again this makes no sense to me whatsoever, and again there seems to be some very black-and-white reasoning behind it: if species can disperse to distant islands everything should occur everywhere; but we observe that all species do not occur everywhere, so we have to conclude that dispersal is completely impossible. But this is one-to-one equivalent to the argument that you cannot produce random numbers with a die because when you cast it the second time it came up with a different number than the first time. Really, that seems to be the logic here.

One might also add that there is another fairly obvious reason why one would find patterns of allopatry even if the same region was reached two or three times by the same lineage: competitive exclusion. It is a well established, empirically tested insight of biogeography that islands (and by extension restricted areas in general) have a carrying capacity, both in overall diversity and in the number of species trying to occupy about the same ecological space. In the case of islands in particular, their species diversity is a function of size (the more land, the more species, mostly because lower area increases extinction rate) and distance from the nearest larger land mass (the closer, the more species, mostly because of higher immigration / dispersal rates filling up the species pool).

This makes a lot of intuitive sense. Assume you have a seed of a continental shrub species blown onto an island that so far has only been colonised by mosses, lichen, one species of grass, and a bunch of insects eating the former. Your shrub niche is still free, and there is nothing on the island that is adapted to eating you, so even if at first you are in a bit of trouble genetically (inbreeding) and ecologically (not used to this soil and climate) you have a reasonable chance of establishing. Now fast forward 500,000 years, and the single seed of that shrub has diversified into six species occupying every niche on the island that they could adapt to in that time, forming thick scrubland from coastal dunes to the highest peak. A new seed of a related continental shrub species ends up on the island - but now everything is occupied by relatives that have become well-adapted to this new environment. Are we really surprised that the second comer will have a harder time establishing?

Time-calibration of phylogenies, again

We had that one already in the Ung et al paper, but once more:
"Model-based methods, with rare exceptions, present molecular divergence ages as falsifications of early origins, at or before continental breakup, even though they are calibrated by fossils that can generate only minimal divergence dates. Although it is widely claimed that molecular-clock analyses are generate [sic] evidence of dispersal (Sanmartin et al., 2008), molecular divergence estimates artifically constrain the maximum age of taxa that may be much older than their oldest fossil or the age of the current island they occupy (Heads 2009a, 2012, 2014a, 2014b, 2016)."
I like the little caveat "with rare exceptions", although it is unclear what it refers to. But it is not a method, but the researcher using a method, who would draw the conclusion that a lineage diverging 12 Mya would not have diverged because of a tectonic event that happened 120 Mya. And yes, that conclusion makes a lot of sense to me, and no, "model-based" methods do not magically transform minimum ages into maximum ages. This has been discussed repeatedly in rebuttals to Heads' papers. What is more, people have run analyses using the alternative approach suggested by Heads and in the present paper and found that the results are generally absurd, such as pushing the age of the daisy family back before the origin of multi-cellular life.
"The timing of ancestral differentiation may be assessed either by fossils (including molecular extrapolations) or tectonic-biogeographic correlation."
First, fossil calibration or using estimated substitution rates are really two completely different data sources, so the former does not really "include" the latter. Second, using continental breakup to calibrate splits in the phylogeny would, as mentioned before, be circular reasoning. It would build the assumption of vicariance into the analysis to subsequently conclude vicariance as a result. I think that's not how science is supposed to work.
"Fossil data provide only the minimum known-age of taxa and [sic] fossils are often lacking for clades of interest to Macaronesia. In tectonic correlation, the estimate of clade age is more precise, because it refers to a particular, dated event, rather than a minimal (fossil-calibrated) age."
Yes, a fossil provides a minimum age. But unless I severely misunderstand something, a continental break-up could, at best, provide only a maximum age, if we assume that divergence would not have been possible before break-up. (And even that seems fishy to me, given that there are plenty of speciation events on the same landmass.) If it were to be taken as "precise" that would, once more, automatically exclude the possibility that the divergence happened later, after dispersal from one continent to the other, and that would be circular reasoning.

Even the vicariance approach would need long distance dispersal to work

Finally, I am puzzled by the idea of how the lineages would have stayed in place after the supposed vicariance event that would have happened long before the present islands came into existence:
"Island biota survives erosion and subsidence of island habitats by local dispersal onto newer volcanoes"
What I don't get is this: if a vicariance biogeographer can accept that a species hops across the ocean from one volcanic island to another, why can they not accept that it hops across the ocean from Africa onto one of the volcanic islands? What's the difference? Why is this discussion taking place again? I must be missing something very subtle here.

Friday, May 19, 2017

Reading up on biogeography part 2: Panbiogeographic Track Analysis

The second paper in this little series of posts is
Romano MG et al, 2017. Track analysis of agaricoid fungi of the Patagonian forests. Australian Systematic Botany 29: 440-446.
What I appreciated about reading it was first that it was concisely written, and second that it gave me insight into the Panbiogeographic methodology of Track Analysis. It had so far been merely a bunch of arcane terms to me, which of course makes it impossible to judge its meaning. And in contrast to the previous paper, which left out most the details of its methodology and instead referenced earlier papers, this one gives a clear explanation. This kind of stuff is exactly why I am reading through the journal issue.

So, how exactly does Track Analysis work?

First, you need species with disjunct areas of distribution - or at least species that are poorly enough sampled that they appear to be disjunct. Then you draw a line along the shortest distance between any two of their occurrences. Let's assume we have a species occurring on two islands of this little landscape I just generated in GIMP:


Panbiogeographers call this red line, with the occurrences of the species forming the end points, a Track.

If you have more than one species showing the same Track, you promote that line on the map to a Generalised Track:


To cite the present paper, in panbiogeographic logic "a generalised track ... allows inference of the existence of an ancestral biota widely distributed and fragmented by vicariance events, suggesting a shared history."

Now you may come up with other tracks in the same study group that do not run parallel. Where generalised tracks cross each other, panbiogeographers draw a circle with an X in it and call that place a Node, like this:


In this case, their interpretation is that this is "a complex area, where different ancestral biotic and geological fragments interrelate in space-time as a consequence of terrain collision, docking or suturing".

Aaaaand... that was it, really. Draw some lines on the map, conclude vicariance and "complexity". The rest of the conclusions in the present paper are largely about the need for more sampling, and that fungi can also be used as a study group.

Does this approach make sense?

Unfortunately, I don't really see it. The logic behind the panbiogeographic interpretation of Generalised Tracks is that patterns of disjunction shared by several taxa are evidence of vicariance, presumably because they assume that chance dispersal would have to be utterly random and create different distributional patterns in each and every species.

But a little contemplation should blow that idea out of the water. There are several other good reasons why disjunct ranges can be shared across taxa. One would be an a priori lack of alternative habitat - if you have two wet patches and otherwise only steppe, then all wetland species will be restricted to those two patches, even if one of the two wetlands was colonised from the other entirely through long distance dispersal. And that restriction alone will produce a shared history, without vicariance. Another option would be prevailing wind or ocean currents, which make long distance dispersal decidedly more probable in some directions even as it is still a stochastic process (dice, but a bit loaded) and, more importantly, not vicariance.

The interpretation of Nodes as showing things like terrain collision also seems to be missing a few crucial steps, at least in my eyes. Don't get me wrong, I am as aware of fossil ranges being an important part of evidence in geology as the next biologist, but still I'd actually prefer to consult a geologist instead of trying to deduce geological history from patterns of distribution alone.

Finally, this whole approach appears to have a weakness that seems quite critical. Science does not proceed by knowing how to confirm, it proceeds by knowing how to reject a hypothesis. Now the question here is this. Yes, panbiogeographic track analysis is apparently designed to conclude vicariance and an area being "complex". But if a disjunction really has not been caused by vicariance, how would a panbiogeographer conclude that? Would they ever do so?

That, alas, is left unexplained, at least in this paper.

Sunday, May 14, 2017

Reading up on biogeography part 1: area cladogram for the southwest Pacific

As mentioned in the previous post, I am hoping to learn more about the reasoning behind panbiogeography and area cladistics by going through the relevant papers in the recent special issue of Australian Systematic Botany. Starting with area cladistics, I have today finished reading

Ung V, Michaux B, RAB Leschen, 2017. A comprehensive vicariant model for Southwest Pacific biotas. Australian Systematic Botany 29: 424-439.

To the best of my understanding the key steps of the study can be summarised in a very bare-bones fashion as follows. The authors...
  1. State that very little is still known about area relationships, as most research focuses on ancestral area inference for individual taxa.
  2. Summarize at length - over nearly four pages - the geological and tectonic history of the region. I cannot judge any of this at all and will consequently take it as given, although it is puzzling that no reference seems to be provided for the claim that the now largely submerged region had much more dry land when it broke away from Gondwana.
  3. Divide the study region into areas - the details don't matter for present purposes.
  4. Compile 76 phylogenies for plant and animal taxa occurring in the study region, and replace the species with the combination of areas in which they occur.
  5. Discuss the 'problems' of incongruence between the area relationships in these individual phylogenies, of terminal taxa occurring in several areas, which they call "taxonomic paralogy", and of the same area occurring in different branches of a phylogeny, which results in what they call "paralogous nodes". They decide to exclude these confounding nodes and to use only "paralogy-free subtrees" by applying a "transparent method" that I had not heard of before.
  6. Turn the trees into "three-item statements" and use those to produce a consensus area cladogram.
  7. Present the consensus area cladogram.
  8. Argue that one larger area that they had hypothesised is not a "real biogeographic entity" because it is paraphyletic on the area cladogram.
  9. Argue that New Caledonia's "highly endemic flora and fauna are ancient" because of its "basal" position on the area cladogram. I am not sure that this follows, and am a bit concerned about the potential of scala naturae thinking here, but that is not the main point here.
  10. Agree with panbiogeographer Michael Heads that any and all time-calibrated phylogenies are unreliable. Then they proceed to a lengthy attempt at time-calibrating their area cladogram based on plate tectonics.
I would like to explore in a bit more depth items #1, #5 and #10.

Does the concept of area relationships even make sense?

I cannot say that this paper has me convinced. To quote a few sentences where the authors themselves discuss problems:
In real-world situations, individual areagrams are unlikely to be congruent with each other and the problem, therefore, arises as to how best to deal with this incongruency [sic]. The main sources of incongruency [sic] are the occurrence of widespread taxa (multiple areas on a single terminal, or MASTs, for short), redundant areas (resulting in taxonomic paralogy), missing areas and inadequate methods of analysis (dos Santos 2011). Redundancy, the repeated occurrence of the same area in different branches on the areagram is nigh on universal and results in paralogous nodes. [...] [These] yield no information about area relationships and obscure the real relationships between areas.
Honestly, when I read this I am drawn to a very different conclusion than that we have to exclude all "paralogous nodes": maybe there is so much noise because stuff moves around too much. In other words, the concept of an areagram or area cladogram makes exactly as much sense as trying to force members of the same sexually reproducing animal population into a phylogenetic tree. Where there is no phylogenetic structure, phylogenetic trees are not an appropriate representation of the data.

Another issue I wonder about is the use of the term paralogy in this context. The word comes from gene evolution. Imagine a gene has duplicated in a distantly ancestral species, and subsequently both copies A and B evolved to have different functions. (This is, of course, one of the main ways in which new genes come into existence.) All descendant species inherit both genes. If we now look at a bunch of descendant species and want to figure out their relationships, we need to make sure we compare only the A copies or only the B copies. Comparing the A copy from one descendant with the B copy of the other misleads our analysis; the A and B copies are called paralogues of each other, and the A copies from different species are called orthologues of each other.

What I do not understand is how the situation in areagrams is supposed to be equivalent enough to use the same terminology. Areas are not genes that are inherited by species lineages. At best, it is the other way around: if the assumptions of area cladistics are true (which I doubt), then species lineages are comparable to genes inherited by areas. The same mistake as taking two paralogues as orthologous in genetics would then be to treat two species lineages in different areas as orthologues although they already diverged before continental breakup.

But the way the word is used here is in the former sense, when contemplating areas on a phylogeny, not when contemplating lineages in areas. This use of genetic terminology is rather confusing, I have to say.

What is the problem with time-calibrated phylogenies?

The open access de Queiroz paper in the same issue does a good job at discussing Heads' and the present authors' criticism of molecular dating, so just very quickly, there are two arguments here:

First, that
using substitution rates derived from modern taxa and then applying them over evolutionary time, often to groups only distantly related, is not justifiable
This is true as far as it goes, but the problem is that to the best of my understanding for the conclusions favoured by Heads to be realistic, substitution rates would have to be off by an utterly unrealistic factor. We are talking cases here where he sees a divergence as having happened tens of millions of years ago when the molecular data say a few million years. And why would we assume such massive shifts conveniently in just the direction needed to make vicariance a viable explanation, and in the absence of any other argument? Sorry to say, but that looks a bit like ad-hoccery to me.

I hope this is not taken to be too inflammatory, but it reminds me of those young earth creationists who are worried about the starlight problem and then argue that a few thousand years ago the speed of light must have been orders of magnitude higher. There is, indeed, a very practical parallel: just like the creationists in question do not take into account what such a change would do to other physical parameters (E=mc^2, meaning that our planet would have been incinerated), so in this case nobody seems to consider what a massively higher mutation rate would have done to the biology of the affected species.

The second argument is that
the same can be said for dating phylogenies using the age of the oldest fossil, which, despite giving only a minimum age for divergence, becomes a maximum estimate by proxy (Heads 2014b)
As has been discussed at length in rebuttals of Heads, including again in the aforementioned de Queiroz contribution, this is half nonsense and half, let me say, odd. It is nonsense in the sense that fossils are indeed used as minimum ages, not as maximum ages. I have myself recently used the R package chronos to time-calibrate trees, and you simply tell the analysis to make a divergence no younger than so and so, and that's that. Admittedly you generally also want to have some realistic maximum age for the entire tree, but that can be way higher than any minimum age you set. In fact, I wrote a blog post about this stuff not too long ago.

In Bayesian analyses, it is true, it is necessarily the case that there will be a limit to how much older than the fossil the results can realistically be because calibration is usually done with priors. The user sets a prior probability distribution where the probability of divergence, which necessarily has to add up to 100% over all possible times, will become so close to zero as to make no difference if we only go far enough back in time. It is, after all, impossible to stretch 100% out over infinity years and still have 10% per million years left.

But here is where the argument also gets distinctively odd. What Bayesian phylogeneticists do in practice is to set a relatively high probability around the time where the fossil was dated, and then have it peter off towards the past. The question is now: what else would one do? Is it not eminently reasonable to assume that the further into the past we go from the known existence of a lineage, the less likely it is that it already existed? Surely it is reasonable to assume that if the oldest known fossil of a plant genus is from 20 Mya, then it is quite likely that the genus already existed around, say, 21 Mya, a bit less likely that it existed 30 Mya, still less likely that it existed 50 Mya, and vanishingly unlikely that it existed as long as 200 Mya?

The problem with time-calibrating a tree based on plate tectonics is, in turn, that it front-loads the analysis with the assumption that there is no dispersal between areas. For the purposes of the discussion around vicariance and dispersal it is circular reasoning.

But to end on a positive note, despite approvingly citing panbiogeographers the authors of the present paper actually do not seem to argue that dispersal between areas is impossible; they merely kick out the data that I would interpret as showing such dispersal to infer the 'real area relationships'. Admittedly that could be seen as equivalent to kicking out all the genes I share with my father to claim that my genetic relationship with my mother is the 'real' one, but well, it still makes more sense to me than hostility to the mere possibility of dispersal!

Thursday, May 11, 2017

Panbiogeography and area cladistics galore

Today the newest issue of Australian Systematic Botany came out, and oh boy is the content interesting. It is the first in a series of special issues on biogeography - but that is not the main point, to which I will come later.

I have tried before to systematise for myself what biogeography is actually about. What is its research program? Trying again, and perhaps in a way that reflects my current thinking:

1a. Inferring ancestral ranges, and closely related to that...
1b. Inferring biogeographic events and their timing.


This kind of research is focused on a given clade and tries to understand how its species came to occupy the ranges they do today. It uses a number of approaches and software tools that attempt to infer ancestral ranges given a generally time-calibrated phylogenetic tree of the study group, contemporary distributions at the tips of the tree, and a model specifying what biogeographic processes are 'allowed' to happen. Examples include originally parsimony-based Dispersal And Vicariance Analysis (DIVA), the Dispersal, Extinction and Cladogenesis model (DEC), and others.

A typical result would be on the lines of, "the ancestral range of this genus was in the south-east of the continent, and we estimate ca. three sympatric speciation events and ca. two vicariance events in its history", often illustrated with a phylogeny whose branches are labelled with the relevant ancestral ranges and biogeographic events.

2. Species distribution modelling

Research in this field tries to estimate where a species can occur, usually given presence data for the species and climatic, soil and other data for those known locations. This can be used, for example, to predict to where approximately in Australia an invasive species could spread out if it were introduced from its native range in, say, South America. Computationally intensive, species distribution modelling is a relatively recent development. That being said, it was the big hot new thing when I did my first postdoc, so recent is to be taken relative.

Obviously, a typical result would be a map with different colours indicating different probabilities of the species being able to exist in those locations.

3. Spatial studies

This field divides a study region into cells, often equal area grid cells, and attempts to quantify diversity metrices such as species richness, endemism, and phylogenetic diversity. Hotspots of diversity can then be targeted for conservation, or they simply provide information on the evolution of present diversity, especially if they are hotspots of palaeo- or neoendemism. This work has only really become possible with the availability of large biodiversity databases of geo-coded specimens.

A typical results would be on the lines of, "the study group shows the highest endemism scores in the south-west and the tropics".

4. Bioregionalisation

The idea here is to distinguish bioregions across the landscape that are significantly different from each other in their species or lineage content, and to figure out where their approximate borders are. Traditionally this was done very intuitively and based mostly on the presence or absence of key taxa. Today researchers often use computers and grid cell-based approaches similar to those in spatial studies, only that they compute pairwise dissimilarity scores between grid cells. Cells are then clustered into bioregions or, in the most novel approaches, submitted to network analysis.

A result might read: "Our analysis shows four major bioregions, the monsoonal tropics, the Eremaean, the south-west, and the temperate south-east. The border between the monsoonal tropic cluster and the Eremaean cluster is, however, considerably further south than estimated by a previous study..."

5. Area cladograms

And this is where I am leaving my comfort zone, because while I have used #1 and #3 and at least dabbled in #2 and #4, this one is weird to me and will probably remain so.

The idea in this case is to use areas or bioregions as the units of an analysis that is supposed to show how the areas are related. In other words, something like a phylogenetic analysis of areas, using their species content as data, and with a result on the lines of "the Australian temperate rainforests are sister to the New Zealand temperate rainforests, and together they are sister to the Patagonian ones" (not necessarily a true result, just to get the concept across). There are a few methods available for this, and they are generally parsimony based and by now quite dated.

The obvious problem here is that this whole procedure is based on a number of assumptions that I can only consider dubious. Just like phylogenetic reconstruction of the tree of life must assume, in that case rather sensibly I believe, that there is no significant gene flow between, say, cattle and primroses, building a tree of bioregions must assume that there is no significant dispersal or species exchange between the various area it uses as units of analysis. And that is where it all falls down for me, because of course species disperse happily from area to area. There are no barriers that are remotely as strong as as the barriers to gene flow between different species.

The present issue of Australian Systematic Botany

So we arrive at the present issue of Australian Systematic Botany, which is, as mentioned, the first in a planned series on biogeography. My personal perception is that of the above fields of research, the cutting edge is today in ancestral range inference and spatial studies. Species distribution modelling is often more seen as part of ecology rather than systematics; the scope for large numbers of bioregionalisation studies is obviously somewhat limited, given that there are considerably fewer bioregions than species; and I thought that area cladograms were more a thing of the 1980s or so.

But the papers in the present issue show that they are still being done - and so is panbiogeographic track analysis!

This is going to be very interesting, because when I read either of these approaches I have the same feeling as when examining some of the pro-paraphyly literature: intellectual challenge in the sense of having to understand a mode of thinking that is very, very alien to me. But that just makes it more important to try and follow the reasoning, even should it ultimately not be found convincing.

In particular I am looking forward to seeing a track analysis in action when I come to those papers, because so far it really has not clicked for me what they are supposed to show and how their conclusions can possibly be justified.

To summarise, the articles in the issue are:

1.&2. Two very short introductions.

3. Alan de Queiroz rebutting an earlier article by panbiogeographer Michael Heads. This one is open access, and otherwise stands out in that it seems to be the only article by a mainstream biogeographer. As I pretty much agree with everything it says I will not have any comments on it.

4. Ung et al. constructing an area cladogram for "southwest Pacific biotas", with the abstract indeed containing phrases such as "the islands of the Southwest Pacific are more closely related to each other than they are to Australia". Interestingly, they call their results a "model".

5. Romano et al's panbiogeographic track analysis of agaricoid fungi of the Patagonian forests.

6. An extremely long article by panbiogeographer John Grehan on relationships between America and Maccaronesia.

7. Martinez et al. conducting a panbiogeographic track analysis on plants and animals of the Argentinean pampas.

8. And with Corral-Rosas & Morrone another area-cladistic analysis, this time with Mexico as the study area.

Ancestral range reconstruction for individual clades or spatial analyses, on the other hand, are clearly MIA. So at a minimum one would have to say that this is, at the moment, still a rather narrow representation of the field of biogeography.

Friday, May 5, 2017

A good read on superhuman artificial intelligence

This essay written by Kevin Kelly must be the most sensible text on superhuman artificial intelligence (AI) and the allegedly imminent "singularity" that I have ever read.

Although it appears to get a bit defensive towards the end, I am in complete agreement with all main points. In my own words, and in no particular order, I would like to stress:

There is no evidence that AI research is even starting to show the kind of exponential progress that would be required for an "intelligence explosion".

There is no evidence that intelligence can be increased infinitely; in fact there are good reasons to assume that there are limits to such complexity. What is more, there will be trade-offs. To be superb in one area, an AI will have to be worse at something else, just like the fastest animal cannot at the same time be the most heavily armoured. Finally, we don't want a general purpose AI that could be called "superhuman" anyway, even if it were physically possible. We want the cripplingly over-specialised ones. That is what we are already doing today.

Minds are most likely substrate-dependent. I do not necessarily agree with those who argue that consciousness is possible only in an animal wetware-brain (not least because I am not sure that the concept of consciousness is well defined), but it seems reasonable to assume that an electronic computer would by necessity think differently than a human.

As for mind-uploading or high-speed brain simulation, Kelly points out something that I had not previously thought of myself, even when participating in relevant discussions. Simulations are caught in a trade-off between being fast because they leave lots of details out on one side, and being closer to reality but slower, because more factors have to be simulated. The point is, the only way to get the simulation of, say, a brain to be truly 1:1 correct is to simulate every little detail; but then - and this is the irony - the simulation must be slower and more inefficient than the real thing.

Now one of the first commenters under the piece asked how that can be true when emulators can simulate, 1:1, the operating system of computers from the 1980s, and obviously run the same programs much faster in that little sandbox. I think the error here is to think of the mind as a piece of software that can be copied, when really the mind is the process of the brain operating. Simulating all the molecules of the brain with 1:1 precision, and faster, on a system that consists of equivalent molecules following the same physical laws seems logically impossible.

Finally, one point that Kelly did not make concerns the idea that a superhuman AI could solve all our problems. He discussed that more than just fast or clever thinking is needed to make progress, experiments for example, and those cannot be sped up very much. But what I would like to add is that of our seemingly intractable problems the really important and global ones are political in nature. We already know the solutions, it is just that most people don't like them, so they don't get implemented. Superhuman AI would merely restate the blatantly obvious solutions that human scientists came up with in the 1980s or so, e.g. "reduce your resource consumption to sustainable levels" or perhaps "get the world population below three billion people and keep it there". And then what?

Friday, April 28, 2017

Arguments for paraphyletic taxa: orchid taxonomy edition

As usual, the following is my personal opinion and not necessarily the official stance of any person or institution that I am affiliated with or related to, and so on.

One of the recurrent topics of this blog is the controversy around the acceptance of paraphyletic taxa. Although I have become a bit jaded over the years, my original stance was, and to a certain degree still is, that I am trying to understand the reasoning offered by colleagues who think that paraphyletic taxa are acceptable or even unavoidable. Because, who knows?, there may be a novel argument that shows cladism to be misguided after all, and I want to keep an open mind.

Sadly, however, it is mostly the same few talking points that lost the discussion in the 1970s and 1980s, resurfacing again and again. It is rare, although not unheard of, that a new and truly interesting argument is presented.

Today's candidate paper freshly online is
Baranow et al. 2017. Brasolia, a new genus highlighted from Sobralia (Orchidaceae). Plant Systematics and Evolution. DOI 10.1007/s00606-017-1413-z
The authors present phylogenetic analyses and change the classification of the titular orchid genus. The only point of interest for present purposes is that they argue for the recognition of Sobralia section Sobralia at the genus level despite that group being paraphyletic, and in what follows I do not want to imply any criticism of any other part of the publication or of the hard work the authors have put into their study. It is only the theory of classification that I like to hash out.

The argumentation in favour of paraphyletic taxa runs across three paragraphs in the discussion section. Let's see if I can learn something new!
In the light of phylogenetic outcomes, the proposed taxon is paraphyletic, which means that its species have a common ancestor, but the taxon does not include all its descendants (e.g., Elleanthus).
Polyphyletic taxa also have a common ancestor, so by the reasoning implied here one could justify any classification whatsoever. I am consequently unsure what the point of this first sentence is.
Monophyly in its broader definition describes groups with a common ancestry, including both paraphyletic and monophyletic groups (sensu Hennig 1950); therefore, Hörandl and Stuessy (2010) advocate returning to this broader definition of monophyly and, adopting Ashlock's term, holophyly for monophyly s.str.
Again I am afraid I must be missing the point. The controversy is really about whether we should consistently classify by relatedness or not. I don't mean to be uncharitable, but this could potentially be taken to mean the authors hope that recognising non-monophyletic taxa would become more palatable to mainstream systematists if one could hoodwink them into forgetting what monophyletic means. It would then be equivalent to hoping that your child will accept a mountain hike instead of the promised trip to the beach if you just said "mountains are also a kind of beach" with enough conviction. Nice try, but there will still be no swimming in the ocean, and little Tommy sees right through it.
Paraphyly is a natural transition stage in the evolution of taxa (Hörandl and Stuessy 2010). According to Brummitt (2002), paraphyletic taxa are ''products of the evolutionary process, which is left behind as evolution moves on to a new level of organization.''
The logic of these quotations appears to be as follows: "We really, really want to recognise paraphyletic taxa. So we draw a paraphyletic taxon onto the phylogenetic tree. Look, cladist, there is a paraphyletic taxon in the evolutionary process! Why are you so unreasonable not to accept it?" Unfortunately, circular reasoning does not become more convincing just because it has been published somewhere and can now be cited.

To clarify, there are no paraphyletic taxa out there in nature; there is only a tree of life, and phylogenetic systematists consistently circumscribe taxa on that tree to be monophyletic, while 'evolutionary' taxonomists circumscribe some taxa on that tree to be paraphyletic.
We realize that this is in conflict with commonly accepted phylogenetic methods which declare that monophyly s.str. should be the only criterion for grouping organisms.
A "phylogenetic method" is what produced the orchid phylogeny, so I assume what is meant here is "approach to classification". But whatever, that is not the point, so onwards.
However, a somewhat analogical situation has been recognized within Coelogyne (Gravendeel et al. 2001). In this case, the authors interpreted the morphology of the studied species as not corresponding to the cladograms, probably as a result of convergent evolution and they decided to maintain polyphyletic Coelogyne. Kolanowska and Szlachetko (2016) postulate to maintain paraphyletic Odontoglossum.
This appears to be an instance of the argumentum ad populum, and not even very much populum at that. Consider: is it a good idea to shoot a stapler into your own foot? Okay, so there will have been at least two people in the history of humanity who have done that, so you could now cite them for support. But does that make shooting a stapler into your foot any more sensible? Exactly; a better argument is needed here.

Also, as I only realised some time after first drafting this, the senior author of the present paper is the same as in one of those two references. So this is apparently also an instance of the rarely seen ipse dixit. (It is, of course, valid to cite one's own prior research results, but in this case we are dealing not with an empirical question but simply with the argument that an action is acceptable because it is not unprecedented.)
Recognition of distinctive characters which have evolved in a group is essential for an understanding its evolution (Brummitt 2006).
Quite the opposite, in my eyes: having an accurate classification is essential for understanding evolution, because paraphyletic taxa mislead us about relationships. In the present case, treating Elleanthus as a subgroup of Sobralia would (correctly) show that Elleanthus evolved out of Sobralia, whereas treating Sobralia and Elleanthus as separate genera implies (wrongly) that they are evolutionarily distinct units, side by side.
This point of view is shared by numerous other authors (Sosef 1997; Dias et al. 2005; Nordal and Stedje 2005) who state that traditional classification is the optimal tool for cataloging biodiversity and requires recognition of paraphyletic taxa.
This reads like more argumentum ad populum, and sadly it is left unmentioned why paraphyletic taxa are supposedly required.
We decided to follow the Darwinian (evolutionary) classification, which requires consideration of two criteria: similarity and common descent.
Leaving aside the obvious argument from name-checking here, which is exactly as relevant as using Newton to reject Einstein (and for the same reasons), the problem remains that trying to classify by two criteria at the same time will lead to a useless classification that is not reliably reflecting either.

Assume I have never heard of Sobralia before, and then it is mentioned to me for the first time. Given a phylogenetic classification, I know that it constitutes a natural group whose members are each other's closest relatives. Given a classification as argued for in the present paper, it could be a natural group... but it could also be a group defined by similarity that includes species more closely related to another genus than to any other species of Sobralia. I just won't know.
The approach will allow us to propose a classification based on the phylogenetic relationships, but at the same time it will be practical--with clearly defined and recognizable units.
No, sorry to say so, but it quite simply will not. First, it will not be based on phylogenetic relationships, because in one crucial instance phylogenetic relationships will be ignored. Second, and again, it will not be practical, because if two criteria are mixed the end user cannot know without going back to the original publications whether a given group was circumscribed based on relatedness or based on 'similarity', see above.

Now obviously I understand that this is not a theory paper arguing for a wholesale shift in our practice of classification. What is more, I know we cannot expect all solutions to be easy or all groups immediately to be circumscribed as monophyletic the moment somebody looks at them. I can happily accept a paper concluding "we know this group is probably paraphyletic, but for the moment we don't have a better solution, let's wait until more data are in", or "the group is clearly polyphyletic, but at this moment we do not want to make hasty taxonomic changes", or something along those lines.

But the three paragraphs quoted above were specifically meant to justify the ultimate recognition of paraphyletic genera, so one would expect to find a convincing justification. Sadly I, personally, have to admit to being anti-convinced by this paper, which as previously mentioned I take to mean an argument had the effect of making me even more convinced of the idea it was meant to refute, in this case classification by relatedness.

Sunday, April 23, 2017

The unexpected dangers of rerooting phylogenies

A couple of days ago a colleague circulated the following recently published paper,
Czech L, Huerta-Cepas J, Stamatakis A, 2017. A critical review on the use of support values in tree viewers and bioinformatics toolkits. Molecular Biology and Evolution. DOI: 10.1093/molbev/msx055
The authors found something that, in retrospect, seems glaringly obvious. Phylogenetic trees are nearly always saved in the Newick format of nested brackets, for example as follows:
(A:2,(B:1,C:2)99:1);
In this case we are dealing with a rooted tree of only three taxa. A is sister to a clade of B and C. The numbers after the colons indicate branch lengths, and the 99 directly after the brackets is a support value, most likely bootstrap, for the sister group relationship (B,C).

The problem explored by Czech et al. is ultimately that under the Newick format branch support values or other branch annotations are not actually attached to branches; they are attached to nodes. In this case, for example, the 99 is attached to the node that is the hypothetical common ancestor of B and C. Logically, because the tree is rooted we can assume that the support value is meant for the branch leading down from the ancestor of B and C towards the root.

But what if we reroot a tree with node annotations that are really meant to be branch annotations a posterioiri? (My post on the various options for rooting phylogenies can be found here.) Czech et al. found that the behaviour of the these values is undefined. For some software they were able to demonstrate that the branch annotation ended up on the wrong branch after rerooting.

How serious an issue is that? I guess it depends on what one's practice is. The problem should be pretty much limited to analyses producing unrooted trees (e.g. in RAxML, PAUP or MrBayes) under the assumption of reversibility, where the user then uses outgroup rooting to polarise the tree a posteriori. Any analysis using a clock model would avoid it, as would asymmetric step-matrices or, crucially, those analyses specifying the outgroup before the start of the analysis.

In addition, it seems as if the problem would be limited to a few branches between the pseudo-root used to save unrooted trees and the new root after rerooting, so that most relationships should be fine. I may look at one or two of my published phylogenies to see if I ever had that problem, but I am not worried; in the most recent case where support values were a critical part of my argumentation, for example, they are fairly deep inside the tree, because we sampled widely around the ingroup, and I also used Templeton tests and suchlike to demonstrate the non-monophyly of certain taxa.

Apparently Czech et al. have already achieved some success at getting software providers to make changes that will help solve the confusion around where the branch annotations end up. But nonetheless my main take-home from this is to be less blasé about a posteriori rooting. In the future I will make sure to always define an outgroup already when I set up a PAUP or RAxML run, so that the need to reroot does not arise.

Thursday, April 20, 2017

Botany picture #242: Gentianella muelleriana


Gentianella muelleriana (Gentianaceae) as seen today on the ascent to Mount Stillwell, Kosciusko National Park, New South Wales. One of the few plants still in flower this late in the season.

In the European Alps, gentians are, of course, generally blue and rarely yellow, but here white seems to be the preferred colour.

Friday, April 14, 2017

Back from Queensland

Unfortunately I was unable to transfer the pictures I had taken to a computer until I got back home, so here are the ones I want to put on the blog all in one post. We drove west from Brisbane to Chinchilla with a major stop along the way, had a day trip north to the vicinity of Wandoan, spent half a day around Chinchilla and Kogan the following day, and then returned to Brisbane.


Rainforest of Boombana in D'Aguilar National Park just west of Brisbane.


A fern climbing up a liana that climbs up a tree trunk.


Not many daisy species like rainforests, but this one does: Acomis acoma (Asteraceae). It was the reason for our detour into D'Aguilar. Admittedly it is not found in the darkest and wettest parts.


View from Jolly's lookout, still in D'Aguilar National Park.


In the Chinchilla area ecologists showed us several field sites and conservation management actions. Near Wandoan we happened to see this population of treelets with rather impressive fruits. Still need to figure this species out; we suspected it may be a native Australian lemon (Citrus, Rutaceae). But I have not seen one of those before, only other Rutaceae genera.


We learned more about what is clearly the most problematic weed in the area, buffel grass (Cenchrus ciliaris, Poaceae). As seen in the picture it forms clumps that suppress a lot of other vegetation but are not dense enough to avoid soil erosion from the gaps between individual plants - the worst of both worlds! It also accumulates litter causing very intense bush fires in a local habitat (dry rainforest and vine thicket) whose key species are not fire-adapted. On the other hand, we were told that farmers liked buffel grass due to its drought resistance and high food value for stock.


One of the species the trip was about is this phyllodinous wattle, Acacia wardellii (Fabaceae). Although currently not in flower it is quite attractive due to its straight growth and strikingly white stem. It is locally common after disturbance but has a very restricted range.


Near Kogan we were shown this site, which I found particularly interesting. The habitat is on a ridge with very poor, rocky, shallow soil, and features species that are very localised to those conditions.


Scattered across the ground was Brunoniella (Acanthaceae). I worked on a genus of the Acanthaceae family for my Diplom thesis (roughly equivalent to honours), so that brought back nice memories. However, while my study group then were large shrubs, this species is herbaceous and in fact seems to remain fairly small. I assume it spends most of its life as dormant root-stock underground and then sends these little shoots up if there has been enough rain to be worth the while.