Wednesday, March 28, 2012

Welcome Lesley Lancaster, our new postdoc

I am pleased to welcome Lesley Lancaster, our new incoming postdoc, funded by BECC ("Biodiversity and Ecosystem Services in Changing Climate"). Lesley will arrive to Lund in late May or early June, and she will work with me and Bengt Hansson on the population genetics and ecology of range limit evolution, particularly using our favourite model organism: the damselfly Ischnura elegans ("Common Bluetail") as the main study object. Both Bengt and I are very excited about this project and about recruiting Lesley, who will bring with her new skills and perspectives from her previous research.

Currently, Lesley is a postdoctoral scholar at  the National Center for Ecological Analysis and Synthesis (NCEAS) in Santa Barbara (California, USA), where she has been since 2009. Her main focus of research has been to reconstruct historical evolutionary processes of adaptation, speciation, extinction and migration using time-calibrated molecular phylogenies of various Californian plant clades. She is also interested in historical habitat tolerances of the unique California chaparral habitat. Her postdoctoral research has resulted in some interesting papers in BMC Evolutionary Biology and Systematic Biology.

Lesley's thesis research was on a quite different topic: maternal effects, reproductive strategies and evolutionary ecology of a colour polymorphic lizard (Uta stansburiana), where she worked in the laboratory of Barry Sinervo at University of California, Santa Cruz (UCSC). Her thesis work also resulted in a number of interesting and impressive publications in American Naturalist, Ecology Letters, Evolution and PNAS

Lesley is thus an extremely broad and well-rounded biologist and a very experienced postdoc, who has worked at quite different levels of biological organization, and moved her research focus from studies of individual behaviour and evolutionary ecology, to broader macroevolutionary and macroecological questions. It is for precisely these reasons we are excited to bring her in to Lund; she has both sufficient much in common with our already ongoing research,  yet has many complementary skills that will be of interest to us and our research.

Monday, March 26, 2012

On the antagonistic relationship between sexual selection and assortative mating

Posted by Erik Svensson

It is time for lab-meeting again, and this week we are happy to welcome Machteld Verzijden back from Rutgers University, where she has been working with Jessica Ware. Let's start the lab-meeting with her telling us about her work and the progress made during the visit.

Note the new time: Wednesday March 28 at 13.30 (not 13.00!).

After this, I was thinking we should discuss the relationship between sexual selection and assortative mating, two processes that are often confused and mixed up, particularly in the field of sympatric speciation. Although these processes are by no means totally independent, they are not identical and their population genetic consequences are very different. Moreover, they can counteract each other and hence could be antagonistic.

To understand the finer details of the complex relationship between assortative mating and sexual selection, we'll have to leave the murky shallow waters of "Adaptive Dynamics" and instead to turn to a clear thinker and a population genetic theoretician who knows what he is talking about: Mark Kirkpatrick från Austin (Texas). I was thinking we should read a much-cited papers from Proceedings of the Royal Society, entitled "Sexual selection can constrain sympatric speciation". Below, you will find the Abstract and here is a downloadable link to the PDF:

Sexual selection can constrain sympatric speciation
Source: PROCEEDINGS OF THE ROYAL SOCIETY OF LONDON SERIES B-BIOLOGICAL SCIENCES  Volume: 271   Issue: 1540   Pages: 687-693   DOI:10.1098/rspb.2003.2645   Published: APR 7 2004


Recent theory has suggested that sympatric speciation can occur quite easily when individuals that are ecologically similar mate assortatively. Although many of these models have assumed that individuals have equal mating success, in nature rare phenotypes may often suffer decreased mating success. Consequently, assortative mating may often generate stabilizing sexual selection. We show that this effect can substantially impede sympatric speciation. Our results emphasize the need for data on the strength of the stabilizing component of selection generated by mating in natural populations.

Tuesday, March 20, 2012

Former postdoc Sophia Engel got new job

Posted by Erik Svensson

I just got the happy news that our former CAnMove-postdoc Sophia Engel just got a new job as ornithologist for a non-profit organization in Germany. These days when job market in Europe is very tough, it is of course great news to hear that former co-workers get highly qualified jobs that are related to biology (nothing one can count on these days, unfortunately) and in fields close to their heart and interests. On behalf of myself, and hopefully on behalf of all other lab-members and colleagues in Lund, I congratulate Sophia and wish her good luck with her new position!

Sunday, March 18, 2012

On density-dependent diversification and speciation in birds

Posted by Erik Svensson

This coming Wednesday (March 21 at 13.30 NOTE TIME!!!!), we will discuss a paper about the (possible) density-dependent slowdown of cladogenesis in birds with the progress of adaptive radiation. It is a paper that was published relatively recently, although it is not entirely new, in PLoS Biology by Albert Phillimore and Trevor D. Price. The title of the paper is:
"Density-Dependent Cladogenesis in Birds"
The authors have used molecular phylogenies from various avian groups to test the hypothesis that diversification rates decline with the progress of adaptive radiation, and as we are approaching the present. Here is the Abstract to the article, which can be downloaded here (PLoS Biology is a "Open Acess"-publisher, which makes everything easier):


A characteristic signature of adaptive radiation is a slowing of the rate of speciation toward the present. On the basis of molecular phylogenies, studies of single clades have frequently found evidence for a slowdown in diversification rate and have interpreted this as evidence for density dependent speciation. However, we demonstrated via simulation that large clades are expected to show stronger slowdowns than small clades, even if the probability of speciation and extinction remains constant through time. This is a consequence of exponential growth: clades, which, by chance, diversify at above the average rate early in their history, will tend to be large. They will also tend to regress back to the average diversification rate later on, and therefore show a slowdown. We conducted a meta-analysis of the distribution of speciation events through time, focusing on sequence-based phylogenies for 45 clades of birds. Thirteen of the 23 clades (57%) that include more than 20 species show significant slowdowns. The high frequency of slowdowns observed in large clades is even more extreme than expected under a purely stochastic constant-rate model, but is consistent with the adaptive radiation model. Taken together, our data strongly support a model of density-dependent speciation in birds, whereby speciation slows as ecological opportunities and geographical space place limits on clade growth.

We meet at 13.30 (not 13.00!) to discuss this interesting article.

Saturday, March 3, 2012

Lab meeting March 7: challenges and prospects of quantitative trait studies

Posted by Maren Wellenreuther

For the next lab meeting, we will dive a bit deeper into the discussion that we started last week. At the last lab meeting, we read a paper by Rockman (2012) entitled ‘The QTN program and the alleles that matter for evolution: all that's gold does not glitter‘. The paper points out what has long been known (but forgotten by some): evolution often acts via large numbers of small-effect polygenes, that are on their own almost impossible to detect with the methods available to us. Thus studies are biased towards finding large-effect alleles. But are these representatives of evolution, or are they misleading about the nature of how evolutionary change comes about?
For the next EXEB lab meeting  (7th of March, start at 13:00 in Argumentet) I suggest we read a review article by Mackay et al. (2009) with the title ‘The genetics of quantitative traits: challenges and prospects’. 
I will bring fika.