Seminar by Nina Wedell on selfish genetic elements and sexual selection and PhD-thesis defency by Kristina Karlsson

This week our department will be visited by Professor Nina Wedell (Exeter University, UK), who will act as an external faculty opponent on the thesis of Kristina Karlsson Green, on Friday November 26 (09.30, "Blue Hall", Ecology Building).


Nina Wedell is well-known for her research on sperm competition, sexual selection and mating system evolution in insects. You can read more about her research here, and here you can find some of her publications. Here is an article about Ninas recent research on the evolutionary consequences and benefits of female promiscuity.


Nina Wedell will arrive to our department already on Thursday (November 25), and will present a research seminar at 14.00 entitled: 


"Selfish genetic elements and sexual selection"


This talk is co-arranged with The Research School in Genomic Ecology (GENECO), and there will also be another talk by Sören Molin the same afternoon and the same place (Lecture Hall, Biology Building, Sölvegatan 35 A), but at 15.15. Note that both these talks do not take place in the "Blue Hall", but in a separate building ("The Biology Building").

Papers for labmeeting on November 24: genomics and sex ratio evolution

This Wednesday, we will discuss two short papers, one in Nature Genetics and the other one in Nature. They are both very short, but should make interesting reads. The first paper was suggested by Bengt Hansson, and is an example of how the sequencing of entire genomes can shed light over local adaptation, in this case of the plant Arabdopsis lyrata to serpentine soils. You can download that paper here. The second paper is an example of how climatic factors can drive population divergence in sex determination systems, in this case over an altitudinal gradient of an Australian lizard species. You can download that paper here. Abstracts of both papers are provided below.

I hope you enjoy these papers and that we will have a good discussion. Time and place as usual: "Darwin" at 10.15 (Wednesday November 24). Fika volunteers are encouraged to step forward.

Population resequencing reveals local adaptation of Arabidopsis lyrata to serpentine soils  

Thomas L Turner, Elizabeth C Bourne, Eric J Von Wettberg, Tina T Hu & Sergey V Nuzhdin

Nature Genetics 42: 260–263 (2010)

DOI: doi:10.1038/ng.515

A powerful way to map functional genomic variation and reveal the genetic basis of local adaptation is to associate allele frequency across the genome with environmental conditions. Serpentine soils, characterized by high heavy-metal content and low calcium-to-magnesium ratios, are a classic context for studying adaptation of plants to local soil conditions. To investigate whether Arabidopsis lyrata is locally adapted to serpentine soil, and to map the polymorphisms responsible for such adaptation, we pooled DNA from individuals from serpentine and nonserpentine soils and sequenced each 'gene pool' with the Illumina Genome Analyzer. The polymorphisms that are most strongly associated with soil type are enriched at heavy-metal detoxification and calcium and magnesium transport loci, providing numerous candidate mutations for serpentine adaptation. Sequencing of three candidate loci in the European subspecies of A. lyrata indicates parallel differentiation of the same polymorphism at one locus, confirming ecological adaptation, and different polymorphisms at two other loci, which may indicate convergent evolution.

Climate-driven population divergence in sex-determining systems

Ido Pen, Tobias Uller, Barbara Feldmeyer, Anna Harts, Geoffrey M. While & Erik Wapstra

Nature 468: 436–438 (18 November 2010)

DOI: doi:10.1038/nature09512

Sex determination is a fundamental biological process, yet its mechanisms are remarkably diverse. In vertebrates, sex can be determined by inherited genetic factors or by the temperature experienced during embryonic development. However, the evolutionary causes of this diversity remain unknown. Here we show that live-bearing lizards at different climatic extremes of the species’ distribution differ in their sex-determining mechanisms, with temperature-dependent sex determination in lowlands and genotypic sex determination in highlands. A theoretical model parameterized with field data accurately predicts this divergence in sex-determining systems and the consequence thereof for variation in cohort sex ratios among years. Furthermore, we show that divergent natural selection on sex determination across altitudes is caused by climatic effects on lizard life history and variation in the magnitude of between-year temperature fluctuations. Our results establish an adaptive explanation for intra-specific divergence in sex-determining systems driven by phenotypic plasticity and ecological selection, thereby providing a unifying framework for integrating the developmental, ecological and evolutionary basis for variation in vertebrate sex determination.

evoecogeomorphometrical fun

Hello from the wilds of Athens, Ohio! As Sophia said, we're geeking out on the study of shape. Such analyses receive less attention than they should, but think about it: everything has shape! Its a serious matter. As Houle (2010 PNAS) noted, we would benefit greatly from a revolution in "phenomics" to compliment recent advances in genomics.

Here's one of the papers Sophia and I read, which can be found on Dean Adams' web page:

Adams, D. & M. L. Collyer. 2009. A general framework for the analysis of phenotypic trajectories in evolutionary studies. Evolution 63: 1143-1154.

This paper is simply an analytical technique, but it is broadly applicable to all sorts of questions in biology, and my brain was exploding with ideas as I read it. While you are checking out Adams' web page, read a few other papers, too -- he's one of my favorite scientists.

Speaking of favorite scientists: it turns out the Donald Miles in the Department of Biological Sciences here at Ohio University is also interested in geometric morphometrics. We recently discussed the possibility of forming a GMM reading group this winter, or even working through the book "Morphometrics with R" (Julian Claude, 2008), which is valuable but not easy. These ideas are preliminary, and it may or may not happen exactly this winter (it will happen, though) -- if you'd like to join in remotely (Skype meetings?) shoot me an email.

Working here with Sophia has been an absolute blast! Y'all are very lucky to have her among your ranks!!! In addition, I'm very excited to have the opportunity to contribute in a small way to the ongoing studies of Calopteryx splendens, which I view as a system with extraordinary potential. Together, Sophia and I have studied GMM, made chili, eaten burritos at the Burrito Buggy, cruised around in my 1983 VW bus (her name is Betsy), and drank quite a few beers and glasses of wine. We also found the salamander shown above (picture stolen off of Amphibiaweb). LIfe is good.

Peace.

Hi from Athens.

I’m having a good time here, filled with damselfly wings and the theory of Geometric Morphometrics during the daytime, and socializing and beers in the evenings. Shawn is part of a very lively and nice department!

The first week spoiled me with balmy summer temperatures (well, almost) and a spontaneous multiplication of my salamander species counts! There are gorgeous species to be found here, my favorite is the Red Salamander (Pseudotriton ruber) because of its beautiful coloration, and it is well worth strolling through the beautiful forest and looking under logs and stones for a (rare, I’ve been told) glimpse of it.

Our literature seminars are usually attended just by Shawn and me, but we gladly share our reading list in the hope to spark your interest in morphology and the statistical methods for its analysis:

The study of Dean C. Adams (Evolutionary Biology 2010, 10:72) is a nice real-world example of character displacement in salamanders driven by competitive selection in sympatric populations.

The underlying theoretical framework for such studies is described in an earlier paper by the same author (Dean C. Adams and Michael L. Collyer (2009) Evolution 63-5: 1143-1154), and historical overview and review of available methods for shape analysis can be found in Adams et al. 2004 (Ital. J. Zool. 71: 5-16. Another review paper by Christian P. Klingenberg (Nature 2010, Vol 11, 623-635) approaches the topic from an evo-devo perspective.

Dreaming of partial warps in Procrustes space…

Sophia

Recently we have published two studies based on the isopod system of Asellus aquatics. This species occurs in two ecotypes, which resides in different habitats. As the ecotypes are present in several Swedish lakes, this system has been studied in depth with regard to parallel evolution. Our new articles address differences in mating behavior between the ecotypes. As other crustaceans, A. aquaticus exhibits precopulatory mate guarding where the male captures a female before she is receptive and carries her beneath him until she is ready to mate. This behavior is target for sexual conflict in several isopods as the optimal initiation of pairbonding may differ between the sexes.

One of our articles, published in the latest number of Journal of Evolutionary Biology, deals with differences between the ecotypes in mate guarding duration, but also in differences in female survival and offspring production. Among other things, we found a pattern of parallel evolution in these traits. The other article, published in open access journal PLoS ONE, deals with differences in mating propensity between the ecotypes and how this is affected by demographic factors. Here, we found that the novel ecotype seem to have evolved a plastic behavior as response to sex ratio, in contrast to the ancestral ecotype.

You could find both abstracts below, and both articles are included in Kristina Karlsson Green’s thesis that will be defended on next Friday.

Parallel divergence in mate guarding behaviour following colonization of a novel habitat

K. Karlsson, F. Eroukhmanoff, R. Härdling & E.I. Svensson

Abstract

Ecological factors can have profound effects on mating system and mating behaviour. We investigated the effect of altered ecological conditions, following colonization of a novel habitat, on precopulatory mate guarding in a freshwater isopod (Asellus aquaticus). This isopod occurs in two different ecotypes, which coexist within several different lakes in Sweden but which utilize different habitats. These ecotypes have rapidly (ca. 40 generations) diverged in parallel among lakes in several phenotypic characters, presumably as a response to different predatory pressures. Here, we demonstrate that also mate guarding characteristics have diverged in parallel between the ecotypes in different lakes. This is one of the few studies reporting parallel evolution of mating behaviour. Furthermore, our results also indicate a potential sexual conflict, as the length of mate guarding appears to lower components of female fitness. We discuss how novel environments might have strong and rapid effects on mate guarding dynamics and mating behaviour.

Phenotypic Plasticity in Response to the Social Environment: Effects of Density and Sex Ratio on Mating Behaviour Following Ecotype Divergence

Kristina Karlsson^*, Fabrice Eroukhmanoff, Erik I. Svensson

Abstract

The ability to express phenotypically plastic responses to environmental cues might be adaptive in changing environments. We studied phenotypic plasticity in mating behaviour as a response to population density and adult sex ratio in a freshwater isopod (Asellus aquaticus). A. aquaticus has recently diverged into two distinct ecotypes, inhabiting different lake habitats (reed Phragmites australis and stonewort Chara tomentosa, respectively). In field surveys, we found that these habitats differ markedly in isopod population densities and adult sex ratios. These spatially and temporally demographic differences are likely to affect mating behaviour. We performed behavioural experiments using animals from both the ancestral ecotype (‘‘reed’’ isopods) and from the novel ecotype (‘‘stonewort’’ isopods) population. We found that neither ecotype adjusted their behaviour in response to population density. However, the reed ecotype had a higher intrinsic mating propensity across densities. In contrast to the effects of density, we found ecotype differences in plasticity in response to sex ratio. The stonewort ecotype show pronounced phenotypic plasticity in mating propensity to adult sex ratio, whereas the reed ecotype showed a more canalised behaviour with respect to this demographic factor. We suggest that the lower overall mating propensity and the phenotypic plasticity in response to sex ratio have evolved in the novel stonewort ecotype following invasion of the novel habitat. Plasticity in mating behaviour may in turn have effects on the direction and intensity of sexual selection in the stonewort habitat, which may fuel further ecotype divergence.

Journal cover in "Evolution" and the role of learned mate preferences in population divergence

Most of you have already seen this - but I post it again in case somebody missed it. We've got the journal cover in the November 2010 issue of Evolution, featuring our article about learned mate preferences in the banded demoiselle (Calopteryx splendens). This paper has also been highlighted by the popular science site Science Daily, and it will also be covered in a popular science radio programme in Germany, since I was recently interviewed about the study by a journalist from our southern neighboring country.

Apart from our own article, the same issue contains a number of interesting other articles about sexual selection, most notably Richard Prums paper about null models in sexual selection in which he argues that the Lande-Kirkpatrick (NK)-model as the most appropriate such null model, a paper we discussed at the lab-meeting last week. Here is the title and abstract of our own paper:


A ROLE FOR LEARNING IN POPULATION DIVERGENCE OF MATE PREFERENCES  


Erik I. Svensson, Fabrice Eroukhmanoff, Kristina Karlsson, Anna Runemark & Anders Brodin

Article first published online: 13 JUL 2010

DOI: 10.1111/j.1558-5646.2010.01085.x

Learning and other forms of phenotypic plasticity have been suggested to enhance population divergence. Mate preferences can develop by learning, and species recognition might not be entirely genetic. We present data on female mate preferences of the banded demoiselle (Calopteryx splendens) that suggest a role for learning in population divergence and species recognition. Populations of this species are either allopatric or sympatric with a phenotypically similar congener (C. virgo). These two species differ mainly in the amount of wing melanization in males, and wing patches thus mediate sexual isolation. In sympatry, sexually experienced females discriminate against large melanin wing patches in heterospecific males. In contrast, in allopatric populations within the same geographic region, females show positive (“open-ended”) preferences for such large wing patches. Virgin C. splendens females do not discriminate against heterospecific males. Moreover, physical exposure experiments of such virgin females to con- or hetero-specific males significantly influences their subsequent mate preferences. Species recognition is thus not entirely genetic and it is partly influenced by interactions with mates. Learning causes pronounced population divergence in mate preferences between these weakly genetically differentiated populations, and results in a highly divergent pattern of species recognition at a small geographic scale.

Null models in sexual selection

For next week's labmeeting I suggest to read the paper by Richard Prum in the most recent issue of Evolution about making the Lande-Kirkpatric model of sexual selection the null model, kind of like a Hardy-Weinberg equilibrium. The abstract is posted below. I saw Richard Prum give a presentation at the ISBE this last month, and I really liked his talk. He does not propose any new models for sexual selection, but rather gives ideas for a new perspective on the existing models & the data. Good food for thought, right?

And, to liven up the blog a bit here are some pictures of odonates from my recent trip to Borneo. Enjoy! (both the paper and the pictures).

Abstract:

The Lande-Kirkpatrick mechanism is the null model of evolution by intersexual selection: implications for meaning, honesty, and design in intersexual signals.

The Fisher-inspired, arbitrary intersexual selection models of Lande (1981) and Kirkpatrick (1982), including both stable and unstable equilibrium conditions, provide the appropriate null model for the evolution of traits and preferences by intersexual selection. Like the Hardy–Weinberg equilibrium, the Lande–Kirkpatrick (LK) mechanism arises as an intrinsic consequence of genetic variation in trait and preference in the absence of other evolutionary forces. The LK mechanism is equivalent to other intersexual selection mechanisms in the absence of additional selection on preference and with additional trait-viability and preference-viability correlations equal to zero. The LK null model predicts the evolution of arbitrary display traits that are neither honest nor dishonest, indicate nothing other than mating availability, and lack any meaning or design other than their potential to correspond to mating preferences. The current standard for demonstrating an arbitrary trait is impossible to meet because it requires proof of the null hypothesis. The LK null model makes distinct predictions about the evolvability of traits and preferences. Examples of recent intersexual selection research document the confirmationist pitfalls of lacking a null model. Incorporation of the LK null into intersexual selection will contribute to serious examination of the extent to which natural selection on preferences shapes signals.

New thesis from the lab by Kristina Karlsson, nailing and next lab-meeting

Probably, the proudest moment in the life of PhD-student advisors is when their students has finished his/her thesis. This has now happened once again in our lab, and I am of course extremely happy that my fourth PhD-student Kristina Karlsson has now gotten her PhD-thesis back from the printer. Before Tina, Jessica Abbott (2006), Tom Gosden (2008) and Fabrice Eroukhmanoff (2009) has previously succesfully finished their theses, and I am of course happy to soon be able to kall Tina Dr. Karlsson.

The second proudest moment in the life of the PhD-student advisors is usually the thesis defence. This will take place on Friday November 26 2010 in the "Blue Hall" (Ecology Building). The external opponent on Tinas thesis will be Professor Nina Wedell (Exeter University, UK), and the thesis defence will start at 09.30.

Prof. Wedell will also give an invited research seminar the day before Tinas thesis dissertation (November 25) with the title: "Sexual selection and selfish genetic elements". This talk will take place in the "Red Room" (Ecology Building) at 14.00 on November 25 2010. Needless to say, both Prof. Wedell's talk on November 25 as well as the dissertation ceremony on November 26 are open to the general public and everybody who is interested.

Tina will "nail" her thesis on the "Oak" outside the Biology Library next Wednesday (November 10, 2010) at 15.00. Drinks will be served after this ceremony, and again, it is open to anyone who wish to attend. The same day, our regular lab-meeting will take place as usual (10.15-12.00 in "Darwin"). Anna Runemark will send out a manuscript of ours about sexual selection in mainland and island populations, with the hope to get some input and criticisms. If you do not receive this manuscript, please send Anna an e-mail and she can send you a copy (anna.runemark@zooekol.lu.se). Fika volunteers are particularly welcome to this meeting.