Merry Christmas and Happy New EXEB-year!

Posted by Erik Svensson

The year 2015 is approaching the end, and I wish all EXEB-members a Merry Christmas and a Happy New Year. I think we have had a great year and many exciting and intellectually stimulating lab-meetings where (at least I) have learned a lot and got many new insights. EXEB has grown rapidly in short time - particularly since Tobias Uller have recruited several new co-workers - and we do now also have several hardworking interns, field assistants, laboratory assistants, PhD-students, Master's students and postdocs. All our permanent and temporary co-workers - nobody mentioned, nobody forgotten - do a tremendous job, both in terms of actual work performed, but also in contributing to a friendly and intellectually stimulating research environment.

Some statistics: If we count only the "core" EXEB members (who are in Lund and have formal positions), we are 11 in total (3 PI:s, 3 PhD-students, 4 postdocs and one research engineer). Counting a bit more generously, we are 13, since we have two affiliated PhD-students from Sussex University (Katrine Lund-Hansen)  and Manchester University (Miguel Gomez), who Jessica Abbott and I are co-advisors of, respectively.

Looking back upon 2015 in terms of research achievements, it has been a very succesful year, I think we can say without any hesitation. I have not made an official tally of joint publications, but I note that Tobias team had an interesting article about asymmetric species interactions in hybrid zones of lizards in Ecology Letters, and Jessica published a model paper about how self-fertilization and inbreeding might limit sexual antagonism in Journal of Evolutionary Biology. As for myself, I was happy to get our long-term time-series analysis of the signature of negative frequency-dependent selection in damselfly morphs published in American Naturalist. John Waller got his first thesis-chapter about imperfect detection and mark-recapture analysis of selection published in Methods in Ecology & Evolution. Lastly, and importantly, Jessica Abbott was awarded an ERC Starting Grant in October, the first of two at the Biology Department in Lund. All in all, a very succesful year for EXEB and its members, I think.

The future looks bright, I think, if the trend in 2015 will continue, but now for something lighter: the evolutionary origin of Santa Claus. It was Beatriz Willink pointed me to this very interesting blog post, which aims to do a phylogenetic analysis of the evolutionary origin and allopatric divergence of different Santa Claus phenotypes. It is from the blog "EEB and Flow", and R-code is provided, should you be interested in exploring this fascinating topic in depth. Enjoy!

Happy New EXEB year 2015!

Posted by Erik Svensson

On behalf of myself and all EXEB members, I wish us all a Happy New 2015, and I hope it will be a succesful as 2014 was. Here, I briefly summarize my own subjective impressions of the past year and speculate a little bit about the future.

2014 was very dynamic and a lot of positive things happened. Maren Wellenreuther and Machteld Verzijden got new jobs and moved to Denmark and New Zeeland, respectively. Tobias Uller started his position in Lund on 50 %, while finishing his position in Oxford. Viktor Nilsson-Örtman and Katie Duryea both got postdoctoral scholarships, from The Swedish Research Council (VR) and The National Science Foundation (NSF) and thus joined EXEB. Beatriz Willink started as a PhD-position in August. Thus, both influx and outflux in terms of members, and currently Tobias is in the process of recruiting several postdocs, so I anticipate that the EXEB meetings will be enriched by new faces with interesting new backgrounds soon.

In terms of major research grants, it has also been a succesful year. Both Jessica and I got grants from the Crafoord Foundation this spring, and Tobias got a three-year grant from the Swedish Research Council in November. It is if course very satisfying to get these grants, given the stiff competition and small margins these days, as they also help us to do the research we really want to do.

Publication-wise, it has also been a good year, with articles appearing in many good journals. For me and Jessica, perhaps the highlight was our PNAS-article about sexual selection on Wing Interference Patterns (WIP:s) in Drosophila melanogaster, and all the media attention it got. Tobias and his co-workers made a splash in Nature in October this year with their provocative essay "Does evolutionary theory need a rethink?", which also resulted in a discussion on this blog.

What about 2015 and the future? I am optimistic in both the short- and the long-term. I feel that we have been able to build a creative space for us as PI:s and for our students and postdocs and that we have an excellent platform to strengthen evolutionary biology in Lund within our department. It is now almost five years since the Department of Biology in Lund was formed as a merger between two old departments: The Department of Ecology and the Department of Cell- and Organismal Biology (COB). Evolutionary biology has, for several complex and historical reasons, not had a very strong visible profile in Lund.

The reasons for this historical neglect of evolutionary biology in Lund are both structural and a result of strong  and very biased personal opinions by past and some current leaders of our department. For several reasons (I strongly disagree with these views, however), evolutionary biology has not been percceived as a "real" or independent research field in Lund. Worse, it has sometimes even been dismissed by some with the argument that "everybody does evolutionary biology" or even "we should leave evolutionary biology to Uppsala instead, it is they who have an Evolutionary Biology Centre (EBC)".

Needless to say, I think these views are both wrong and outdated, but their existence points to some of the problems that we have ahead of us if we want to strengthen the evolutionary biology profile in Lund. I feel that it is more or less futile to try to convince the leadership at the department as a whole that evolutionary biology should become of one of Lund's profile research areas, because conservatism tends to increase up along the career ladder.

Instead, we need to build from below, by setting a good example: by recruiting excellent postdocs and PhD-students (which we do already have), by getting grants and by publishing our research in excellent high-quality scientific journals. Then, and only then, can we influence the department at the higher level and force the leadership to admit that evolutionary biology is indeed an independent and interesting research field in itself that deserves some higher recognition than it currently has got. And to achieve this goal, we should try to keep EXEB what it is already: an intellectually very dynamic research environment where we regularly meet and discuss science and exchange idéas, co-supervise students and postdocs and share equipment, skills and knowledge.

We should of course always be aware of the competition with other groups - both from within the department and from outside - but also do not hesitate to collaborate with other groups, such as the Theoretical and Population Ecology Group or Molecular Ecology and Evolution Laboratory, when it can help us to achieve our long-term goals to influence the Biology Department and strengthen evolutionary biology in Lund. 

Thankyou all for a very nice 2014 and see you again in 2015!

On elytral morphology, sexual conflict and female mating polymorphism in diving beetles: new paper in "Interface"

Posted by Erik Svensson

Forrmer PhD-student Kristina Karlsson-Green (currently postdoc in the "Metapopulation Research Group in Helsinkki, Finland) has published one of her last thesis-paper in the Royal Society Journal "Interface". This paper deals with a fascinating female mating polymorphism in diving beetles, where females have either a "rough" or "smooth" elytral morphology. She has quantified fine-scale female elytral morphology using scanning electron microscopy (SEM), as well as male morphological adaptations to clasp females during matings in the form of so-called "suction cups" (see picture above), and also used a biomechanical experiments to quantify male adhesion ability on the different female morphologies.

Results provide experimental support to the suggestion that this female mating polymorphism is maintained by sexually antagonistic and frequency-dependent selection caused by sexual conflict, and different male phenotypes show different ability to clasp the different female morphs. The experiments in this fascinating study were performed in collaboration with our colleague Prof. Stanislav N. Gorb, at Kiel University (Germany), and I personally like this combination of biomechanics and evolutionary biology very much. Below, you find a link and Abstract to the study.

Male clasping ability, female polymorphism and sexual conflict: fine-scale elytral morphology as a sexually antagonistic adaptation in female diving beetles

1. Kristina Karlsson Green, 
2. Alexander Kovalev, 
3. Erik I. Svensson and
4. Stanislav N. Gorb

During sexual conflict, males and females are expected to evolve traits and behaviours with a sexually antagonistic function. Recently, sexually antagonistic coevolution was proposed to occur between male and female diving beetles (Dytiscidae). Male diving beetles possess numerous suction cups on their forelegs whereas females commonly have rough structures on their elytra. These rough structures have been suggested to obstruct adhesion from male suction cups during mating attempts. However, some diving beetle species are dimorphic, where one female morph has a rough elytra and the other has a smooth elytra. Here, we used biomechanics to study the adhesive performance of male suction cups on the female morphs in two diving beetle species: Dytiscus lapponicus and Graphoderus zonatus. We compared adhesion on the rough and the smooth female morphs to infer the function of the rough elytral modifications. We found that the adhesive force on the rough structures was much lower than on other surfaces. These findings support the suggestion of sexual conflict in diving beetles and a sexually antagonistic function of the rough female structures. In addition, males differed in their adhesive capacity on different female surfaces, indicating a male trade-off between adhering to smooth and rough female morphs.

And now for some public outreach: About sex in humans and insects in "Bildningsbyrån" (Swedish Radio, P1)

Posted by Erik Svensson

I think most of us agree that public outreach and popular science is important, but it is easy to forget in the international world of Lund University that there is also a large Swedish audience who mainly listens to Sveriges Radio (SR), and its channel P1, and quite seldom read English scientific litterature (by the way, P1 is my personal favourite radio channel)

Although one does not reach (potentially) as many people in media channels which are restricted to Swedish, the response is usually very good, and it is often very appreciated. Likewise, I think it is important also to give popular science talks in Swedish, e. g. at "Gymnasiedagarna", as there are many swedes who, although they speak English, are not as familiar with the technical language of science. It is important to interact with your local community, as a scientist, and not only internationally, I think. After all, we live in Sweden, and it is the Swedish taxpayers money which are largely funding our research. They deserve to get some information about how their tax money is spent and why research is useful to the society (not necessarily restricting "useful" to economic benefits, of course).

Recently, Jessica Abbott and I were interviewed in the radio programme "Bildningsbyrån" in a series about sexuality. We were both interviewed in our profession as evolutionary biologists, and the interviewer was interested in what inferences that can be drawn from animal studies to understand sexual behaviour in humans. I think it became a nice and balanced interview, which I am certainly not embarrassed over. You can listen to it here, where the programme will be available for a couple of months. Enjoy!

På svenska:

Min kollega och jag blev nyligen intervjuade i radioprogrammet "Bildningsbyrån", som har en serie i sommar som handlar om sex.  Vi intervjuades som evolutionsbiologer och diskussionen handlar bl. a. om vilka paralleller som kan dras (eller inte dras!) mellan insekters sexualbeteenden och människors, samt vad modern evolutionsbiologi säger i detta ämne. Lyssna gärna här, programmet ligger uppe några månader till. 

"The Adaptive Landscape is dead - long live the Adaptive Landscape!" Review of our OUP-volume in TREE

Posted by Erik Svensson

In a forthcoming review in Trends in Ecology & Evolution, Andrew MacColl (University of Nottingham, UK), has an entertaining, albeit short, review of our edited volume "The Adaptive Landscape in Evolutionary Biology". 

The review is quite favorable, but will not be quoted in its entire length, but can be read here.  But I still want to cite one of the most entertaining part:

"A history of vicious power struggles in mediaeval Europe led to a desperate need to avoid interregna on the death of a monarch and, hence, the instantaneous proclamation of an heir's succession. The adaptive landscape, a king among metaphors, has been declared dead many times. Yet its dynasty continues; the power of its simple evocation supplantable only by a parliament of similar ideas that risks becoming all things to all people. A surprising aspect of The Adaptive Landscape in Evolutionary Biology (no criticism this, it could hardly have been otherwise) is that it cannot, even after the 80 years of academic endeavour that it celebrates, deliver a unified verdict on so apparently simple a concept. Instead, it does an excellent job of showcasing the radiation of ideas that has diverged from Wright's original [1]."

P.S.: You can order your copy here and if you are interested in reading the volume in a group of graduate students, postdocs or faculty members, there is an excellent study plan here. 

Praise for our book "The Adaptive Landscape in Evolutionary Biology"

As you hopefully remember, last year Ryan Calsbeek at Dartmouth College and I published an edited volume entitled "The Adaptive Landscape in Evolutionary Biology" (Oxford University Press 2012). Although we have generally gotten positive feedback and responses when talking research colleagues at meetings, relatively few reviews have yet appeared, probably because it is a relatively recent publication. Here is one very flattering review, however, published on the blog "Nothing in biology makes sense".

I thank the blog author for his kind words, and have to cite some of the nice formulations on a very long and thorough review:

"Unlike a recent book addressing aspects of the modern synthesis, Evolution: The Extendend Synthesis (Pigliucci and Müller, 2010) which called for a revolution, Svensson and Calsbeek have assembled authors that explore the innovations and contributions that build upon the fundamental ideas of population genetics and seek to grow the field. Early in this book, Pigliucci asks about the utility of the Adaptive Landscape metaphors, even titling his chapter with the question, “what are they good for?” I think the rest of the book provides a more than sufficient answer to his question."

and:

"Over the course of this semester, my colleagues and I read and discussed each of the chapters. Our group consisted of a diversity of backgrounds spanning evolution, ecology, and behavior. We included a range of experience from first and second year graduate students to postdocs as well as junior and senior faculty. While we read the book in the sequential order it was published in, each part could certainly be pulled out and read as a separately. Some of the chapters make cross references to each other but not enough that reading them independently would be impossible. While some chapters certainly provided more challenges to some, this forced our discussion to flesh out explanations that the text just didn’t have time to go into. I think that the first two parts might make particularly good set of readings to supplement an upper level Evolution or Population Genetics course."

and:

"My recommendationThis is a book ideally suited for a graduate level seminar in any Biology department. While it may be good to read a few chapters on your own, the book benefits from an active discussion of the content. We took 14 weeks to go through the entire book, reading one chapter most weeks occasionally two (or three). This pace allowed everyone to casually complete the readings. Going slowly through the book also allowed us to digest the material and make connections among the chapters without getting too overwhelmed with new information each week. You can follow this link to see the schedule we followed. If you are not convinced about the utility of this book yet, below I highlight some of the excellent contributions contained within the different parts."

and finally:

"CONCLUSION: I would strongly encourage students of population genetics to pick up this excellent volume and spend some contemplative weeks reading through the chapters. Better yet, grab a group of your department colleagues and argue about the 80 years of interpretation of the Adaptive Landscape. I personally cannot wait to see where this excellent metaphor leads us."

Happy New 2013!

Posted by Erik Svensson

The year 2012 is now behind us, and we are looking forward to 2013. The past year was, I dare to say, extremely successful in terms of grant applications, good publications, events and activities. To mention just a few things: three new postdocs joined the lab (Yuma, Lesley, Natsu), one PhD-student defended her thesis in May (Anna Runemark), one postdoc got a "Junior Project Grant" from the Swedish Research Council (Maren) and Jessica got a large grant from the Crafoord Foundation, that has made it possible for her to recruit a new PhD-student to work on the flatworm experimental evolution project. I myself, got a large grant from The Swedish Research Council too, which I am of course very happy for. I certainly hope that 2013 will be as successful, for all of us, as was 2012. Well done, all of you!

Among publications, I could mention some nice papers in Ecology, Molecular Ecology and Trends in Ecology & Evolution, but there are certainly more. I was also happy to get my new volume "The Adaptive Landscape in Evolutionary Biology" out at Oxford University Press (co-edited with Ryan Calsbeek from Dartmouth College, USA). 

Below are some pictures from the past year. Keep up the good work, friends!

In December, postdoc Lesley Lancaster visited Erik in Dalby to run some generalized linear models in "R" to investigate the role of temperature on mating conflicts in the polymorphic damselfly Ischnura elegans. 

Earlier in December, lab members from EXEB and other colleagues at the Evolutionary Ecology Unit went for our annual Christmas Meeting. Here John, Jasmine and Anna Nordén enjoy the Christmas Table in the evening after the talks. 

And here are Jessica and Yuma in the same evening.

In January and February, Erik went to South Africa for field work with odonates in the Western Cape Province with Master's student Anna Nordén (right) and undergraduate Johanna Eklund (left). Here they both enjoy some of the wine of the Stellenbosch district. 

The arrival of our two Japanese postdocs Yuma and Natsu in May enabled us to start up some new projects, including one on Wing Interference Patterns (WIP:s) in Drosophila melanogaster and their role in mate choice and sexual selection. Here we see Yuma, Natsu, Jessica and Jostein Kjarandsen in the lab, doing mate choice trials (Erik is behind the camera). 

Anna Runemark receives postdoctoral research grant from the Swedish Research Council

It is with great pleasure and happiness that we note that Anna Runemark, who defended her PhD-student in May earlier this year, has received a prestiguous postdoctoral grant from The Swedish Research Council (VR). Congratulations Anna! This requires celebration with some sparkling wine at tomorrow's lab-meeting (December 11 at 10.30). The new postdoctoral grant system means that Anna will be employed at the Biology Department in Lund, being part of our lab, but will work abroad at the University of Oslo (Norway) for two of the coming three years. She will then perform research on the genomic consequences of homoploid hybridization among Passer-sparrows in southern Europe. 

Anna's achievement is well-deserved and impressive, particularly in the light of the severe competition for such grants (23 % success rate). To my knowledge, Anna was the only evolutionary biologist this year who got such a postdoc among the natural sciences in Sweden. Anna's achievement is hers, and hers only, but as a former PhD-advisor I do of course take some pride too, and takes the opportunity to boost my already big ego a bit further. I am glad that Anna keeps up my good statistics in terms of former PhD-students who get VR-postdocs: She is number five, out of five in total, resulting in a 100 % success rate (future students in this lab should take it as an encouragement and not feel stressed about it, I hope). 

We also have several other reasons to celebrate tomorrow: our postdoc Maren Wellenreuther got a "Junior Researcher" grant from VR earlier in November this year, and I myself also got a four-year grant from the same agency. Further, Jessica Abbott recently got 380 000 SEK for  buying equipment to the fly lab, and Maren got 100 000 SEK from the "Nilsson-Ehle Foundation". All in all a very successful year for the lab members in terms o grants, and hopefully this will continue in the near future. 

These are achievements we all should be proud of, whether we actually got a grant or not ourselves, as research is a collective enterprise and scientists do not work in isolation. One colleague's success can largely be attributed to his/her colleagues too, who have contributed to create an intellectually and scientifically stimulating research environment, and this is true whether you are a PhD-advisor, professor, lecturer, postdoc, PhD- or Master's student. 

Our new paper about learning in sexual selection and speciation is now out in TREE

Our paper in Trends in Ecology & Evolution about the role of learning in sexual selection and speciation is now online, and you can find a link to it here. Soon the reprints will hopefully come, and then you can ask Machteld Verzijden for a copy (machteld.verzijden@biol.lu.se). Hopefully, this paper will stimulate increased interest and more experimental and observational studies in this fast moving field.

Below, you will find more details about the paper. Enjoy!

The impact of learning on sexual selection and speciation

• Machteld N. Verzijden 
• Carel ten Cate, 
• Maria R. Servedio, 
• Genevieve M. Kozak, 
• Jenny W. Boughman, 
• Erik I. Svensson

http://dx.doi.org/10.1016/j.tree.2012.05.007

Learning is widespread in nature, occurring in most animal taxa and in several different ecological contexts and, thus, might play a key role in evolutionary processes. Here, we review the accumulating empirical evidence for the involvement of learning in mate choice and the consequences for sexual selection and reproductive isolation. We distinguish two broad categories: learned mate preferences and learned traits under mate selection (such as bird song). We point out that the context of learning, namely how and when learning takes place, often makes a crucial difference to the predicted evolutionary outcome. Factors causing biases in learning and when one should expect the evolution of learning itself are also explored.

Our new book "The Adaptive Landscape in Evolutionary Biology" is now out!

Posted by Erik Svensson

Together with my colleague Ryan Calsbeek at Dartmouth College (USA), I am pleased to announce that our new edited volume "The Adaptive Landscape in Evolutionary Biology" (Published by Oxford University Press) is now out!

This volume marks the 80-year anniversary of late population geneticist Sewall Wright's first formulation of the Adaptive Landscape concept, which subsequently became so influential in population genetics, ecology and evolutionary biology. Both Ryan and I hope that this book will be of interest to both established researchers, postdocs and PhD-students.

We hope that graduate students will digest and discuss the contents of  chapters of this volume as part of reading groups, for instance. We have several prominent chapter contributors, and you can read more about them here.

You can order this book easily, either directly from Oxford,  or from Amazon.com. Order your copy today - before it is sold out!

New journal cover in Molecular Ecology: Vicariance divergence and gene flow among islet populations of an endemic lizard

I study genetic, morphological and behavioural divergence in islet populations of the Skyros wall lizard, Podarcis gaigeae. This species shows strong morphological divergence, including island gigantism (see the cover image, with adult male lizards from mainland populations to the left and islet populations to the right ). In this paper (found here) we have used isolation with migration models to investigate divergence times and levels of gene flow between islet populations and their closest mainland populations. Such background information is valuable for example for inferring rates of morphological and genetical divergence. Our results support that the studied islet populations have been sequentially separated by rising sea levels in the Aegean.

Abstract:

Allopatry and allopatric speciation can arise through two different mechanisms: vicariance or colonization through dispersal. Distinguishing between these different allopatric mechanisms is difficult and one of the major challenges in biogeographical research. Here, we address whether allopatric isolation in an endemic island lizard is the result of vicariance or dispersal. We estimated the amount and direction of gene flow during the divergence of isolated islet populations and subspecies of the endemic Skyros wall lizard Podarcis gaigeae, a phenotypically variable species that inhabits a major island and small islets in the Greek archipelago. We applied isolation-with-migration models to estimate population divergence times, population sizes and gene flow between islet–mainland population pairs. Divergence times were significantly correlated with independently estimated geological divergence times. This correlation strongly supports a vicariance scenario where islet populations have sequentially become isolated from the major island. We did not find evidence for significant gene flow within P. g. gaigeae. However, gene-flow estimates from the islet to the mainland populations were positively affected by islet area and negatively by distance between the islet and mainland. We also found evidence for gene flow from one subspecies (P. g. weigandi) into another (P. g. gaigeae), but not in the other direction. Ongoing gene flow between the subspecies suggests that even in this geographically allopatric scenario with the sea posing a strong barrier to dispersal, divergence with some gene flow is still feasible.

What do we need to know about speciation? Interesting TREE-review and discussion at Cell Press

Some of you might already have seen this, but I wish to draw your attention to an interesting TREE-review entitled "What do we need to know about speciation", published in Trends in Ecology & Evolution, and authored by Roger Butlin and co-workers in the FroSpecs-network (an ESF-funded research network focussed on speciation research). As you know, FroSpecs funds speciation conferences, meetings and small symposia, including one in Jyväskylä (Finland) next year, and one organized by us after the ISBE-meeting in Lund in August 2012 about behaviour, adaptive and non-adaptive speciation and ecological and non-ecological speciation.

The review by Butlin et al. aims to identify the most important future questions in speciation research in the coming years, and the article is also accompanied by an online discussion, where I was invited to participate, together with several other biologists, including Mike Ritchie, Maria Servedio and Andrew Hendry, to name some of our friends and colleagues. I encourage you to follow both the discussion and read the original article. In terms of speciation discussions, I would also like to recommend an interesting (albeit long!) blog post about "magic traits" on the research blog of Andrew Hendry.

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.

Calopterygid research from this summer covered by Swedish media

For those of you who have not followed Swedish TV- or radio the last days, I would like to point to a couple of programs where our research on Calopteryx splendens and Calopteryx virgo has been covered. First, the regional TV-news channel "Sydnytt" has a 2-minute interview with me at Klingavälsåns Naturreservat, where I am interviewed in the field, and where I discuss the potential consequences of future climate change. You can watch this programme here.

Second, the popular science radio programme "Vetandets Värld" has a 20-minute programme, where both I and Anna Runemark are interviewed, about our learning experiments on mate recognition. Also, our physics-colleagues are interviewed about the laser-studies that were performed at Klingavälsån och what they can inform us about the behaviour of damselflies. You can listen to this programme here.