Friday, January 6, 2017


Happy new year, everybody! Although many people are variously fed up with 2016 for the supposedly high number of celebrity deaths, Brexit and the US election, for me personally the past year was very enjoyable and successful, so I cannot really complain. Let's hope that 2017 will at least be better than so many of us expect.

Anyway, quite some time ago I wrote a series of posts on species concepts. Because a reviewer mentioned it, I had now reason to look into a concept that I was not familiar with, that of ochlospecies.

It was apparently developed by a tropical tree taxonomist called White in the 1960s, but the most useful source that is available online appears to be a 1998 review by Q.C.B. Cronk.

The idea is that there are different kinds of species that can be distinguished based on their patterns of variation. There are well-behaved, very distinctive species. There are species that are variable but in a way that is easily understood, for example because variation is nicely hierarchical, because several characters show correlation, or because there is a clear geographic pattern. And then there are the bad apples, species that show variation but without any clear structure. Several crucial characters appear to vary independently, no geographic pattern, just a mess. Those are then the ochlospecies.

What do I take from this?

Well, first to me this is a rather unexpected way of going about species concepts. The whole point, as far as I am concerned, is that before you embark on a taxonomic study you should set up clear criteria of how you will evaluate the evidence that you are going to collect.

That makes it science. So if you are dealing with the circumscription of genera, instead of making it up as you go you say in advance: I will know that a genus is acceptable if it turns out to be monophyletic. And if you are dealing with the circumscription of species, again, instead of making it up as you go you say in advance: In my study I will follow the Genotypic Cluster Species Concept, meaning I will circumscribe species based on gaps in morphological and/or genetic variation. Or whatever other species concept works for the group and the data that you can actually collect.

When I look at the ochlospecies, however, it looks to me as if it is not a criterion but a conclusion. Reading the Cronk review, it appears as if the taxonomist circumscribes species somehow (magical asterisk) and then labels some of the resulting species as ochlospecies after the fact. At a minimum that means that the concept has a different utility, if any, than the species concepts I have considered previously, than that of serving as a potential guideline.

So at the moment I am a bit at a loss as to what to do with the concept regarding my paper. As the concept is not directly useful methodologically, my options seems to reduce to name-checking it either in introduction or in discussion.

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