A second try to go the Himalayas

 Posted by Erik Svensson

Since we did not have time to discuss the paper on avian species diversity in eastern Himalaya last week, due to the fact that we enjoyed so much listening to Jessica's talk and drinking cava, we make a new try this coming week. Here is the paper by Trevor Price and his colleagues in Nature.

 For a short summary of the findings in the paper I also recomment this a brief comment about the study by Arne Mooers, in a "News & Views"-article in the same issue of Nature, which is also worth reading.

The picture above shows the national bird of Nepal, the charismatic Himalayan Monal, a pheasant that I was lucky to see myself during my bird watching tour to Nepal in 1991, along the slopes of the Anapurna Trekk. The paper interests me for personal reasons, as already as a young bird watcher in 1991, I wondered about the amazing species diversity and how it came about, before I was very knowledgeable in ecology and evolutionary theory.

Date and time: Tuesday September 30, 10.30
Where: "Argumentet", second floor (Ecology Building)

I will bring fika!

Lab-meeting on ERC-interview, PNAS-accept, niche-filling, supply and demand and avian species richness in the Himalayas

Next week, we will listen to Jessica Abbott, giving her "practice talk" before her interview in Brussels (Belgium) for an ERC Junior Grant, which we certainly hope she will get this time (it is the second year in a row that Jessica has been shortlisted for this prestiguous grant). We should all try to give good feedback to Jessica so that her chances to get this grant are maximized!

We will also celebrate that Jessica, I, our two former postdocs Natsu and Yuma and Jostein Kjaerandsen got an accept on our paper on sexual selection on Wing Interference Patterns (WIP:s) in Drosophila melanogaster in Proc. Natl. Acad. Sci. USA. Jessica has promised to bring some nice "fika", and I will bring some "bubble" to celebrate this.

Finally, Jessica asked me to pick a short paper to discuss as well, and I have chosen a relatively recent paper on adaptive radiation, speciation and niche filling in the Himalayan bird fauna. I do this partly for personal reasons, as this is a fascinating and extremely species-rich region of the world where I travelled as a young student and avid bird watcher in 1991, just before the start of my PhD in 1992. I hope you will enjoy this beatiful paper (Abstract is provided below). You might also want to read the "News and Views" comment on this paper by Arne Mooers, which summarizes the main findings.

Date and time: Tuesday, September 23, 10.30
Where: "Argumentet", 2nd floor, Ecology Building. 
  
Trevor D. Price et al.

Niche filling slows the diversification of Himalayan songbirds

Nature 509, 222–225 (08 May 2014) doi:10.1038/nature13272

Speciation generally involves a three-step process—range expansion, range fragmentation and the development of reproductive isolation between spatially separated populations1, 2. Speciation relies on cycling through these three steps and each may limit the rate at which new species form1, 3. We estimate phylogenetic relationships among all Himalayan songbirds to ask whether the development of reproductive isolation and ecological competition, both factors that limit range expansions4, set an ultimate limit on speciation. Based on a phylogeny for all 358 species distributed along the eastern elevational gradient, here we show that body size and shape differences evolved early in the radiation, with the elevational band occupied by a species evolving later. These results are consistent with competition for niche space limiting species accumulation5. Even the elevation dimension seems to be approaching ecological saturation, because the closest relatives both inside the assemblage and elsewhere in the Himalayas are on average separated by more than five million years, which is longer than it generally takes for reproductive isolation to be completed2, 3, 6; also, elevational distributions are well explained by resource availability, notably the abundance of arthropods, and not by differences in diversification rates in different elevational zones. Our results imply that speciation rate is ultimately set by niche filling (that is, ecological competition for resources), rather than by the rate of acquisition of reproductive isolation.

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.

Abstract

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?

"The Origin of Species - 150 years later"

I am currently at the Marin Biology Research Station in Kristineberg (Fiskebäckskil) in Bohuslän att symposium in celebration of Charles Darwin. This year (2009), it is 150 years since "The Origin of Species" was published, and 200 years since Darwin was born. To celebrate the memory of Darwin, Hans Ellegren (professor of evolutionary genetics in Uppsala) and Staffan Ulfstrand (professor emeritus of animal ecology, also from Uppsala) has arranged a symposium in the beatiful archipelago on the swedish west coast. Funding for this meeting comes from The Wennergren Foundation. Unfortunately, this meeting was only open for a small group of invited people, apart from the speakers, so here is a little report from the first day.

The theme of today has been theory and genetics of speciation, with some great contributions from evolutionary theoreticians Michael Turelli (University of California, Davies) and Sergey Gavrilets (University of Knoxville, Tennesse). Turelli talked about Haldane's rule and the genetics of postzygotic isolation, and Gavrilets presented models for the tempo and mode of adaptive radiations. Although some of these topics have been presented before by these two leading theoreticians, it is always nice to get un update.

Gavrilets have apparently got a big grant from the National Science Foundation (NSF) to set up a centre for mathematical and biological synthesis in Knoxville, similar to the ecological synthesis centre in Santa Barbara and the evolutionary synthesis centre in North Carolina. Worth checking up: there will be funding opportunities for both postdocs and workshops.

More "naturalistic" talks were given by Trevor Price (University of Chicago) and Jim Mallet (London) about bird and butterfly speciation, respectively. Trevor presented some idéas and phylogenetic patterns on bird diversification in the Himalayas, which challenges the current ecological speciation paradigm, which has almost been taken a bit too much for granted based on a few well-investigated model systems such as the Galápagos finches. Mallet questioned the views by Ernst Mayr about the reality of species and argued that Darwin's view on species was more realistic than some of the views that were advocated by Mayr and other architects of the so-called "Modern Synthesis" in the 1940'ties. In particular, Mallet argued that some of their idéas about reproductive isolation evolving to protect the "genetic integrity" of species relied on naive group-selectionism.

Two swedish contributions were by Kerstin Johannesson (parallell evolution of reproductive isolation in Littorina-snails) and Anna Qvarnström (genetics of speciation in Ficedula-flycatchers). In general, I would say that this meeting has been good to get updated on the classical concepts and discussion topics, although there has not been many surprising news. In that sense, I have the feeling that perhaps the field of speciation might have reached a plateau (perhaps temporary) where it has now entered what science philosopher Thomas Kuhn would call "normal science" or "problem solving". Perhaps I am wrong, but I have the distinct feeling that we need some new idéas to focus on, as the classical allopatry-sympatry controversy seems to fade away and people loose interest. To me, the most thought-provoking talk today was the one by Trevor Price, although I do not necessarily agree with everything he had to say. In any case, his book "Speciation in birds" is highly recommendable.

Hopefully, I will be able to publish another bloggpost tomorrow about the genomic aspects of speciation, which will be discussed tomorrow. Food here is excellent, by the way.