Saturday, August 8, 2009

Lab-meeting on August 12: ecological or non-ecological speciation?

This coming Wednesday (12 August 2009), we will have our first lab-meeting for this semester. I suggest that we discuss this TREE-article by Rundell and Price about ecological and non-ecological speciation (and adaptive and non-adaptive speciation).

This article, as well as the second author's recent book Speciation in birds has been somewhat of an eye-opener, at least to me. Trevor Price's recent speciation-book might seem somewhat taxonomically narrow, since it only deals with birds. However, the book is a superb reading, also for those who work with other organisms (including insects!). Trevor makes a strong case for learning playing an important but under-appreciated role in the speciation process of birds, and backs up his claims by massive empirical data in a thorough review.

This was one of the major insights I got from reading his book during the summer, the other one was that I realized that the evidence for ecological speciation (and sympatric speciation, which is a sub-set of ecological speciation) is not that strong as one might think after reading Dolph Schluters equally excellent book The Ecology of Adaptive Radiation. In reality, many workers have in the recent past demonstrated ecological differences between closely related taxa, which is not the same thing as evidence for ecology playing a major role during the speciation process that formed the same taxa. Thus, the ecology of species differences is not the same thing as ecological speciation, just as the genetics of species differences is not the same thing as the genetics of speciation!

These subtle, but important issues, are dealt with in detail in Trevor's critical overview of the state-of-the-art of the speciation field. In practice, we might never be able to confidently state that a group of closely related species speciated because of ecological differences caused the reproductive isolation, particularly when the taxa are old and when it becomes difficult or impossible to infer ancestral character states (ecologies). Trevor makes a strong case in the article, and in his book, that many species of birds most probably did not speciate because of ecological factors, but rather because of geographical isolation during a prolonged period in allopatry. Ecological differences between species often emerged later, upon secondary contact in sympatry. He might be correct, although you will have to read the book and the article for yourself to decide where you stand on these issues.

Full reference and abstract to the article (in case the link above does not work):

Adaptive radiation, nonadaptive radiation, ecological speciation and nonecological speciation

Rundell, R.J.; Price, T.D.


Radiations of ecologically and morphologically differentiated sympatric species can exhibit the pattern of a burst of diversification, which might be produced by ecological divergence between populations, together with the acquisition of reproductive isolation ('ecological speciation'). Here we suggest that this pattern could also arise if speciation precedes significant ecological differentiation (i.e. through geographical isolation and nonadaptive radiation). Subsequently, species ecologically differentiate and spread into sympatry. Alternative routes to producing ecologically differentiated sympatric species are difficult to detect in old radiations. However, nonadaptive radiations are common and might therefore regularly be responsible for currently ecologically differentiated sympatric species (e.g. among groups that are not susceptible to ecological speciation). Species evolving nonadaptively over long periods might eventually replace young, ecologically produced species.

Trends in Ecology & Evolution 24: 394-399

Time as usual: 10.00 on Wednesday (12 August) in "Darwin".

Any fika-volunteer?

1 comment:

  1. Since we got our QST paper accepted in Molecular Ecology, I will bring fika... Nice choice of paper by the way Erik, it looks like a promising discussion.