Lab-meeting on gene expression and sexual conflict + WIP-genetics

Posted by Erik Svensson

Next week's lab-meeting will take place in the afternoon, due to some conflicting activites, and we will be in "Darwin", rather than the usual "Argumentet". We will discuss the paper about gene expression differences and sexual conflict in Nature Communications that we did not have time to digest last week, and this will be followed by a short summary by Jessica about our work in progress regarding the molecular genetic basis of Wing Interference Patterns (WIPs) in Drosophila melanogaster.

When: Tuesday, April 8, 13.30 (NOTE: Changed time!)
Where: "Darwin", 2nd floor, Ecology Building

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.

On cliff effects, male mate preferences and niche use in Calopteryx

#by Maren Wellenreuther

I am following Erik’s recommendation that we should all start to more actively promote our own research, and will present some of my most recent publications.The first work  that I would like to highlight is a paper that was started in 2007, when Shawn Kuchta and I arrived in Sweden to start our postdocs on the two charismatic Calopteryx damselfly species found in Sweden, C. virgo and C. splendens. We both arrived just at the start of the field season in May 2007 and had never worked on odonates before. It was an exciting time: we were both living at the University's field station in the middle of the forest, which was also used as a military training ground, and so we could relax in the evening after a hard day in the field, while watching the military training tanks and troops drive through the forest and fields outside the station. Shawn had worked for many years on salamanders while I had studied marine fish, and the different view points and ideas that came along with having studied such different study systems made our conversations about science and evolution rich and interesting. Shawn's work on  Calopteryx damselflies is seeking to measure the strength of natural selection acting on the two Calopteryx species (see photograph below), by collecting wings from feeding stations and comparing them to the variation present in natural populations. Although Shawn has left Sweden and is now an Assistant Professor at Ohio University, he is still actively involved in Calopteryx research and is currently writing up this data-so stay tuned for more on this soon!

Calopteryx splendens (left) have wing patches that cover roughly 50% of the wings, while C. virgo have almost fully melanised wings.

At that time that Shawn and I started our work on Calopteryx damselflies in Sweden, another member joined the lab group. Her name is Elodie Vercken, and she was a newly finished postdoc from France who had worked with Jean Clobert on colour morphs and alternative strategies in the common lizard Lacerta vivipara. She is now a researcher at INRA (National Institute for Agronomical Research) in Sophia Antipolis in France.

Elodie Vercken in the field in Sweden catching damselflies fort mate choice experiments.

Together with Elodie, I spent my days out in the field to measure male and female mate choice in different populations, and trying to relate this mate preference data to population ecology and phenotypic traits (sympatry versus allopatry and so on). It was a hot summer and we tried to stay cool while tethering males and females of both species to bamboo sticks and painting their wings to perform mate presentation experiments. It was great fun.

Maren Wellenreuther presenting tethered damselflies in the field

Part of the data that we gathered during that summer was recently used in a modeling paper on cliff-edge effects, which tests the counterintuitive idea that the trait value associated with the maximum of an asymmetrical fitness function is not necessarily the value that is selected for when the trait shows variability in its phenotypic expression.
Vercken E, Wellenreuther M, Svensson EI, Mauroy B (2012) Don't Fall Off the Adaptation Cliff: When Asymmetrical Fitness Selects for Suboptimal Traits. PLoS ONE 7(4): e34889.

From that field season, Elodie, Erik and I also published a paper on male mate preferences in C. splendens, to address the question whether males can distinguish between immigrant and resident females, something previously found for females.

Wellenreuther M, Vercken E and Svensson EI (2010) A role for ecology in male mate discrimination of immigrant females in Calopteryx damselflies? Biological Journal of the Linnean Society 100: 506-518

In addition to these two papers, I further delved into an area that I had investigated extensively during my PhD work: Habitat use and divergence in habitat space between species. The idea was to extent the work that was previously done by our lab and other groups on the habitat use of the two Calopteryx species, by expanding the spatial scale so that broader questions can be asked. To do this, a large data set for the whole of Fennoscandia was generated using field data and museum records, and niche modelling was used to estimate the extent of niche divergence versus conservatism and to identify the most important environmental variables that correspond to niche differences.  The large data set in this paper also allowed us to look into the following question: what is the extent of niche divergence in species that are thought to have primarily evolved through sexual selection on secondary sexual traits? Based on our results, we argue that adaptive niche diversification appears to play a relatively minor role in speciation and evolutionary divergence in species groups such as salamaders, East African cichlids, and odonates where sexual selection on secondary sexual traits is pronounced and a key element of diversification. This work was done in collaboration with Keith W Larson who has excellent modelling skills and likes to analyze large data sets.

Wellenreuther M, Larson K W and Svensson E I. (in press) Climatic niche similarity and geographic range limits in ecologically similar co-existing damselflies –Ecology

Maybe Anna Runemark, who is currently finishing her PhD thesis on the Skyros Wall lizard, would like to write the next blog post by telling us about her most recent articles.


Happy Researching!

The abstracts to the papers are posted below. 

Vercken E, Wellenreuther M, Svensson EI, Mauroy B (2012) Don't Fall Off the Adaptation Cliff: WhenAsymmetrical Fitness Selects for Suboptimal Traits. PLoS ONE 7(4): e34889.

Abstract: The cliff-edge hypothesis introduces the counterintuitive idea that the trait value associated with the maximum of an asymmetrical fitness function is not necessarily the value that is selected for if the trait shows variability in its phenotypic expression. We develop a model of population dynamics to show that, in such a system, the evolutionary stable strategy depends on both the shape of the fitness function around its maximum and the amount of phenotypic variance. The model provides quantitative predictions of the expected trait value distribution and provides an alternative quantity that should be maximized (“genotype fitness”) instead of the classical fitness function (“phenotype fitness”). We test the model's predictions on three examples: (1) litter size in guinea pigs, (2) sexual selection in damselflies, and (3) the geometry of the human lung. In all three cases, the model's predictions give a closer match to empirical data than traditional optimization theory models. Our model can be extended to most ecological situations, and the evolutionary conditions for its application are expected to be common in nature.

Wellenreuther M, Vercken E and Svensson EI (2010) A role for ecology in male matediscrimination of immigrant females in Calopteryx damselflies? Biological Journal of the Linnean Society 100: 506-518

Abstract: Sexual selection against immigrants is a mechanism that can regulate premating isolation between populations but, so far, few field studies have examined whether males can discriminate between immigrant and resident females. Males of the damselfly Calopteryx splendens show mate preferences and are able to force pre-copulatory tandems. We related male mate responses to the ecological characteristics of female origin, geographic distances between populations, and morphological traits of females to identify factors influencing male mate discrimination. Significant heterogeneity between populations in male mate responses towards females was found. In some populations, males discriminated strongly against immigrant females, whereas the pattern was reversed or nonsignificant in other populations. Immigrant females were particularly attractive to males when they came from populations with similar predation pressures and densities of conspecifics. By contrast, immigrant females from populations with strongly dissimilar predation pressures and conspecific densities were not attractive to males. Differences in the abiotic environment appeared to affect mating success to a lesser degree. This suggests that male mate discrimination is context-dependent and influenced by ecological differences between populations, a key prediction of ecological speciation theory. The results obtained in the present study suggest that gene-flow is facilitated between ecologically similar populations.

Wellenreuther M, Larson K W and Svensson E I. (in press) Climatic niche similarity and geographic range limits in ecologically similar co-existing damselflies –Ecology
The factors that determine species' range limits are of central interest to biologists. One particularly interesting group are odonates (dragonflies and damselflies), which show large differences in secondary sexual traits and respond quickly to climatic factors, but often have minor interspecific niche differences, challenging models of niche-based species co-existence. We quantified the environmental niches at two geographic scales to understand the ecological causes of northern range limits and the co-existence of two congeneric damselflies (Calopteryx splendens and C. virgo). Using environmental niche modelling, we quantified niche divergence first across the whole geographic range in Fennoscandia and second only in the sympatric part of this range. We found evidence for interspecific divergence along the environmental axes of temperature and precipitation across the northern range in Fennoscandia, suggesting that adaptation to colder and wetter climate might have allowed C. virgo to expand further northwards than C. splendens. However, in the sympatric zone in southern Fennoscandia we found only negligible and non-significant niche differences. Minor niche differences in sympatry lead to frequent encounters and intense interspecific sexual interactions at the local scale of populations. Nevertheless, niche differences across Fennoscandia suggest that species-differences in physiological tolerances limit range expansions northwards, and that current and future climate could have large effects on the distributional ranges of these and ecological similar insects. 

On blogging, tweeting and non-ecological speciation

One of the reasons to have a scientific blog, whether an individual-based or a group-based one like ours, is that you might increase the attention to your research, and hopefully also increase the interest in your work, boost your citation rates and perhaps become more succesful as a scientist in grant applications. But is there any real evidence for this, or is it pure wishful thinking? As a matter of fact, some quantitative evidence is starting to accumulate now, that blogging and tweeting does increase the interest in your work, as judged by increasing number of downloads. Thus, unlike many other scientists who might consider blogging waste of time, I think it is a mistake to dismiss social media in the scientific process these days.

In the spirit of this, and with the hope to increase the interest in my research, I post my latest article that is published in Organisms, Diversity & Evolution and which is entitled: "Non-ecological speciation, niche conservatism and thermal adaptation: how are they connected?" It is a critical review of the current state of ecological speciation theory, its assumptions and limitations, and with a discussion about some alternatives to ecological speciation. Download it, read it or cite it (or do it all!)! I also present some thermal image data on the thermal niches of two sympatric calopterygid damselflies: Calopteryx splendens and C. virgo.

This paper was fun to write, and it largely grew out of discussions I had with Andrew Hendry and some other folks at Uppsala last year, when I visited the Evolutionary Biology Centre (EBC) in conjunction with the PhD-student defence's of Niclas Vallin and Paolo Innocenti. The Abstract and paper details are given below. Now, perhaps Maren Wellenreuther and Anna Runemark will post about some other recent lab-publications that have come out recently?

Abstract

During the last decade, the ecological theory of adaptive radiation, and its corollary “ecological speciation”, has been a major research theme in evolutionary biology. Briefly, this theory states that speciation is mainly or largely the result of divergent selection, arising from niche differences between populations or incipient species. Reproductive isolation evolves either as a result of direct selection on mate preferences (e.g. reinforcement), or as a correlated response to divergent selection (“by-product speciation”). Although there are now many tentative examples of ecological speciation, I argue that ecology’s role in speciation might have been overemphasised and that non-ecological and non-adaptive alternatives should be considered more seriously. Specifically, populations and species of many organisms often show strong evidence of niche conservatism, yet are often highly reproductively isolated from each other. This challenges niche-based ecological speciation and reveals partial decoupling between ecology and reproductive isolation. Furthermore, reproductive isolation might often evolve in allopatry before ecological differentiation between taxa or possibly through learning and antagonistic sexual interactions, either in allopatry or sympatry. Here I discuss recent theoretical and empirical work in this area, with some emphasis on odonates (dragonflies and damselflies) and suggest some future avenues of research. A main message from this paper is that the ecology of species differences is not the same as ecological speciation, just like the genetics of species differences does not equate to the genetics of speciation.

Keywords  Mike May Festschrift – Calopteryx – Learning – Learned mate preferences – Niche – Sexual conflict – By-product speciation – IR-camera – Thermal imaging – Ectotherms – Sexual isolation

Lab-meeting on sexual selection, sexual conflict and cross-sexual transfer

It is time for a last lab-meeting before I go to South Africa for field work for three weeks. After a discussion with Jessica Abbott, I thought it would be fun to diskuss a recent conceptual paper by Russel Bonduryansky entitled: "Sexual Selection and Conflict as Engines of Ecological Diversification". You will find a copy of this paper here, and the Abstract below.

Due to other committments, I suggest we meet at 13.30,  not 13.00, in "Argumentet" on Wednesday January 18 2012.Looking forward to see you all and an interesting discussion.

Abstract: Ecological diversification presents an enduring puzzle: how do novel ecological strategies evolve in organisms that are already adapted to their ecological niche? Most attempts to answer this question posit a primary role for genetic drift, which could carry populations through or around fitness "valleys" representing maladaptive intermediate phenotypes between alternative niches. Sexual selection and conflict are thought to play an ancillary role by initiating reproductive isolation and thereby facilitating divergence in ecological traits through genetic drift or local adaptation. Here, I synthesize theory and evidence suggesting that sexual selection and conflict could play a more central role in the evolution and diversification of ecological strategies through the co-optation of sexual traits for viability-related functions. This hypothesis rests on three main premises, all of which are supported by theory and consistent with the available evidence. First, sexual selection and conflict often act at cross-purposes to viability selection, thereby displacing populations from the local viability optimum. Second, sexual traits can serve as preadaptations for novel viability-related functions. Third, ancestrally sex-limited sexual traits can be transferred between sexes. Consequently, by allowing populations to explore a broad phenotypic space around the current viability optimum, sexual selection and conflict could act as powerful drivers of ecological adaptation and diversification.

Active males, reactive females: stereotypic sex roles in sexual conflict research?

In Animal Behaviour you could now find an article by Kristina Karlsson Green and Josefin Madjidian on the possible use anthropomorphic sex-stereotypes in sexual conflict research. Probably all research on animal behaviour is at the risk of using anthropomorphic descriptions and interpretations but perhaps research dealing with males and females is at special risk. This may be so because sex role stereotypes are among the most common stereotypes in Western society, something which may be difficult to get rid of although we as researchers strive for objectivity. Differences in how the sexes’ are characterised and how research tends to focus on certain aspects of the theory for males and other aspects of the theory for females has been discussed within sexual selection research. Although sexual conflict research also has an extensive focus on the sexes, to our knowledge, our study is the first which addresses how the sexes are conceptualised within this research field. Below you could read the abstract and here you can find the article. You can also find a previous discussion on our blog where the outline of this study first was presented.

Active males, reactive females: stereotypic sex roles in sexual conflict research?

Kristina Karlsson Green and Josefin A. Madjidian

Abstract

Sexual selection research has always been a subject for debate. Much of the criticism has concerned the imposition of conventional sex roles based on an anthropomorphic view of animals imposed by the researcher. This conventional view may have hampered research, for example from acknowledging male mate choice. Sexual conflict theory is a fast-growing research field, which initially stems from sexual selection research. We investigated how the sexes are described in sexual conflict research and what characteristics they are assigned. We assessed these topics with literature studies of (1) the terminology used and (2) what parameters are incorporated in sexual conflict models. We found that males and females are consequently described with different words, which have different connotations regarding activity in the conflict. Furthermore, theoretical models mainly investigate conflict costs for females, although costs for both sexes are necessary for coevolutionary dynamics. We argue that sexual conflict research uses stereotypic characterizations of the sexes, where males are active and females reactive. Thus, previous discussions on the use of anthropomorphic terms in sexual selection seem not to have had any impact on sexual conflict research, which is why the topic of stereotyping the sexes is still of current importance. We suggest that scientific gains can be made by eliminating a sex-stereotyped perspective.

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.

TREE-article about antagonistic coevolution, resistance and tolerance

Together with my colleague Lars Råberg, I have recently published an "Opinion"-article in Trends in Ecology & Evolution, that has just come out on "early view". This article deals with the different roles of resistance and tolerance in antagonistic coevolutionary interactions involving animals.

Basically, we argue that the evolution of victim tolerance, instead of resistance, might halt coevolutionary arms races and make them less probable, in contrast to if the victim evolves resistance instead. This idéa has been floating around for quite a while in the plant litterature, but we extend the idéa to animals and to other types of enemy-victim interactions. We illustrate this using a variety of empirical examples from several different types of antagonistic enemy-victim interactions involving animals. Here is the abstract and link if you are interested:

Resistance and tolerance in animal enemy–victim coevolution

References and further reading may be available for this article. To view references and further reading you must purchase this article.

Erik I. Svensson and Lars Råberg

Victim defence against enemies can be divided into resistance (minimizing successful enemy attacks) and tolerance (minimizing the fitness impact of enemy attacks). Although resistance has a negative effect on enemy fitness, tolerance, by this definition, does not necessarily; the relative importance of resistance and tolerance within a population might therefore affect enemy–victim coevolution. Resistance and tolerance have been distinguished in studies of plant defence, whereas most studies of antagonistic interactions in animals have focused on resistance, neglecting tolerance. We suggest that tolerance is also an important means of defence in animal victim–enemy interactions such as brood parasitism, mating interactions and territoriality. We discuss the potential coevolutionary consequences of tolerance variation in these animal enemy–victim interactions.

Jessica Abbott: Summary of Research at Queen's

Erik asked me to post an update on the research I've been pursuing since joining the Chippindale lab in 2007. Since I've been in Kingston I've been conducting work on intralocus sexual conflict in Drosophila melanogaster. For those who aren't familiar with intralocus sexual conflict, it is related to the fact that males and females often have different reproductive interests, and therefore different phenotypic optima for a variety of traits. If antagonistic selection pressures are combined with positive intersexual genetic correlations for these traits, one or both sexes may be significantly displaced from their optimum. This displacement is known as intralocus sexual conflict, and has now been demonstrated in both natural and laboratory populations from a wide variety of taxa.

The Chippindale lab has used a powerful method for investigating intralocus sexual conflict: male-limited (ML) evolution in Drosophila melanogaster. When expression of specific haploid genomes was limited to males for over 80 generations, this resulted in an increase in fitness in ML males, and a parallel decrease in fitness in ML females. The phenotypic basis for these fitness differences has been shown to be linked to a displacement of both sexes closer to the male optimum in developmental time, body size, and reproductive behaviour. In addition, it has been demonstrated that intralocus sexual conflict can actually cancel out fitness benefits of sexual selection. When high quality females were mated to high quality males (as would be expected from female choice), this resulted in the production of low-quality offspring, due to the effects of intralocus sexual conflict.

After arriving at Queen's I started an investigation of patterns of phenotypic masculinization in ML flies. I also looked for evidence of increased developmental stability in experimental populations. Using geometric morphometric analysis of wing morphology, I found evidence of masculinization of wing size and wing shape in ML flies of both sexes. I also found increased developmental stability in ML males, which seems to have resulted in decreased developmental stability in ML females. This nicely parallels the results for fitness, where ML males had increased fitness and ML females had decreased fitness (relative to controls).

Because the ML lines had been maintained for over 80 generations when I arrived in 2007 there were concerns about their continued viability, and they were terminated shortly after I started working at Queen's. Once my analysis of wing morphology was finished I therefore decided to start a new male-limited evolution experiment of my own, this time focussing on the X-chromosome. This MLX experiment will also allow me to look at imprinting effects on fitness due to the nature of the experimental evolution protocol.

The protocol for ML X-chromosome evolution is as follows:
Males are mated to females with a double X-chromosome. These DX females (DX = double X) have two X-chromosomes connected at the centromere. They also possess a Y chromosome, so when DX females are mated to normal males, they produce sons that have inherited the Y chromosome from their mothers and the X-chromosome from their fathers. Triple-X and double-Y individuals are not viable. See figure (paternal sex chromosomes are shown in blue, maternal in red, and autosomes in grey).

This father-son transmission of the X-chromosome means that individual X-chromosomes are never expressed in females as long as males are mated to DX females generation after generation. Crucially, this results in male-limited evolution of the X-chromosome. In order to avoid clonal evolution approximately 4-10% recombination between X-chromosomes is allowed using a “recombination box” protocol (see Prasad et al., 2007 for details). This experiment is simultaneously being carried out for two different source populations (LH and Ives) which have completely different histories and culturing protocols. Within each source population I have three replicate populations of selected and control flies, with effective population sizes of 480 individuals for the LH populations and approximately 1500 individuals for the Ives populations. X-chromosomes are usually transmitted from father to daughter, so the father-son transmission generated by this experimental design means that it can be extended to investigate the importance of genomic imprinting to intralocus sexual conflict.

I expect to find similar results to the previous ML experiment (i.e. an increase in male fitness and decrease in female fitness) since the X-chromosome is predicted to be particularly rich in sexually antagonistic loci. I also expect to find a decrease in male fitness due to father-transmission of the X-chromosome. Since X's are usually transmitted father to daughter, you can expect that males might imprint their X chromosomes to benefit female fitness. A male with an X primed to be in a female may therefore have reduced fitness, and some preliminary evidence collected by Stéphanie Bedhomme (a former postdoc in the Chippindale lab) is consistent with this. Perhaps the most interesting aspect of this study is that the MLX evolution protocol will potentially allow short-term evolution of the genomic imprint to adapt to father-son transmission. This is something I will also investigate. I'm currently in the middle of a preliminary fitness assay to investigate imprinting effects. I'm also planning a collaboration with Ted Morrow in Uppsala to look at differences in gene expression due to MLX evolution. I can post more about this later on.

So that's it for now. I'm also planning on running a reciprocal female-limited X-chromosome evolution experiment later on if possible, but I can write more about that later in that case.

Thoughts from a sexual selection workshop and presentation of an article idea.

As Erik mentioned earlier, I and Josefin met Janne Kotiaho during his visit here for a short discussion on biases in sexual selection/sexual conflict research. We actually met Janne already at the workshop on gender biases in sexual selection research in Uppsala last October, which some of you may remember that we, and Åsa Lankinen, participated in. The workshop in Uppsala was organised by Malin Ah-King and Ingrid Ahnesjö, who are both evolutionary ecologists, but also have an interest in gender issues. Malin Ah-King has done a post doc at GenNa, which is a centre at Uppsala University where researchers from different fields study what kind of “knowledge about gender and gendered knowledge are produced in the intersection between the natural and cultural sciences”. Also Ingrid Ahnesjö has been involved in GenNa, at least for a shorter period. Invited speaker at the one day workshop was Patricia Gowaty from UCLA who is a feminist evolutionary ecologist. During the workshop she gave two talks on the history of sexual selection and on a neutral sexual selection model she and Steve Hubbell have been (and still are) working on (see Gowaty and Hubbell 2005). The rest of the day was devoted to group discussions.

Participants came from mainly Sweden and Finland but also Switzerland, working with sexual selection and sexual conflict in animals (either with conventional sex roles or with reversed sex roles) and in hermaphrodites (animals and plants). Although the cause for joining the meeting, and the idea of what gender bias in research actually is, differed between participants (which, to be honest, made the discussions sometimes a bit vague) some main problems were outlined. These mainly concerned the sex roles we assign our study objects. E.g. why conventional (active male/passive female) sex roles are applied in sexual selection research and the impact this has on how we perform science, if we have to use conventional sex roles, how sexual selection theory should be applied on hermaphrodites including plants, and how we can overcome our possible preconceptions of how males and females “should” behave.

Our, and Janne’s, impressions from the workshop was that it was indeed interesting and inspiring and especially Janne had received a new way of thinking. What in particular opened Janne’s eyes was how and why we nominate systems that do not behave as “normal” as sex role reversed – because what is actually the “normal” state in nature? We thought that Janne would continue on this topic for his Thursday seminar during his visit to Lund, but instead he gave a very interesting talk on the history of sexual selection, publication biases and how researchers strive towards fitting in the “format” which at the moment leads to publications. He exemplified this with his own critical studies on the lek paradox (paradoxes can’t exist!).

With Janne, besides reflecting on the workshop, we discussed an idea of an article that we are working on. Now we’d also like to present our thoughts here to get your opinions, if any, and receive some (critical) feedback! Emerging from the Uppsala workshop, but also from the recent criticism on sexual selection theory, (see e.g. Clutton-Brock 2007, Kokko and Jennions 2008), we would like to write a comment or a discussion article on potential biases in sexual conflict research. We’d like to ask the question whether some parts in a conflict dynamics may be left out by us researchers (compare e.g. male mate choice) due to our potential preconceptive view of how the sexes should act. For example, in sexual conflict theory both sexes are striving for their own optimum when it comes to mating and reproduction, and if this is made at a cost for the opposite sex there will be a conflict. However, our impression is that it is mainly a female cost that is being searched for in sexual conflict research and that the terminology used, although stemming from a neutral theory, implies that males make the offensive act and females barely defend themselves, without any impact on the male. But if the males are not affected why should they continue an arms-race?

Thus, by starting off with the recent progress and criticism in sexual selection research, we want to investigate and discuss three main issues in sexual conflict research. First, we will investigate what terminology is used in the most cited articles in “sexual conflict” and “sexually antagonistic coevolution”. By doing that we will know which terms have the widest impact in the field. Second, we will discuss how semantics may influence our perception and how it thus may form our thoughts and ideas, and third, we survey all theoretical models made on sexual conflict to see what parameters are incorporated – and thus are given the potential to affect the result; if male cost is never incorporated it will never be of significance and may furthermore not stimulate to empirical research.

We are just at the starting point, currently surveying the litterature, but we’d love to hear your thoughts on this project. We are not saying that our impression is correct (and we don’t even know what we will find yet!), but we’d like to open up for discussions or at least implant some thoughts on this topic. And, as we are speaking of biases, yes, we may be biased as well! J By being interested in gender issues in the human society we may be more prone to think of these topics also in evolutionary science, however, our aim is not a feminist inflammatory speech and hope that it will not be considered as such. We are not aiming for equality in the animal/plant world – it doesn’t matter if conventional sex roles actually are the truth and that all female individuals are coy, that is not the point. Instead we think that by considering these questions and potential preconceptions one may discover interesting evolutionary aspects that otherwise may be overlooked.

Have a nice weekend and enjoy the sun!
Tina