By Gerald Wilkinson
This workshop took place on May 15-16, 2014, in the Large Seminar Room at Wallotstraße 19, Berlin. The convenors were Felix Breden, Judith Mank, and Gerald Wilkinson, Fellows of the Wissenschaftskolleg, and Seth Barribeau, Fellow in the College of Life Sciences. All four also participated in the 2013-2014 Focus group on the Genomics of Exaggerated Traits. Additional participants in the workshop included six invitees from outside of the Wissenschaftskolleg (Julie Jacquiery, University of Rennes; Patrick Phillips, University of Oregon; Jacek Radwan, Jagellonian University; Suzy Renn, Reed College; Locke Rowe, University of Toronto; and Walter Salzburger, University of Basel), a short-term Fellow of the Wissenschaftskolleg (Hanna Kokko, Australian National University), two additional Fellows in the College for Life Sciences (Andy Higginson, University of Bristol and Elena Arriero, University of Madrid), and two past Fellows of the Wissenschaftskolleg (Adam Wilkins, Berlin and Robert Trivers, Rutgers University).
The impetus for this workshop came from the realization that recent changes in sequencing technologies have transformed the research horizon in biology but have not been uniformly adopted. This lack of integration with genomics is particularly true for studies of sexual selection, which seek to understand how competition for mates can influence the evolution of elaborate male traits and, more broadly, drives the evolution of major phenotypic differences between males and females. The answers to questions that have been major foci since Darwin, such as the relative forces of natural versus sexual selection, the tempo and mode of phenotypic change, and the mechanisms by which one genome can encode radically different male and female phenotypes, seemingly should now be answerable. But, given the paucity of case studies to date, a gulf appears to exist between genomic and phenotypic approaches to sexual selection. Thus, the purpose of this Workshop was to bring together people who utilize both genomic and phenotypic perspectives in their research to discuss reasons for this gap and propose ways in which future studies of sexual selection can be brought into the postgenomic era.
The structure of our two-day workshop was as follows. On Thursday morning, May 15, each participant gave a short talk that summarized recent work relevant to the theme of the workshop. The twelve talks were divided into two groups, with talks on invertebrates followed by talks either on vertebrates or theoretical issues. Barribeau began by describing how genes involved in the bumblebee immune system respond to various challenges, including mating. Jacquiery followed by explaining how comparing sex chromosomes to autosomes in aphids can be used to study sexual conflict and genome evolution. Radwan then described how gene expression differs between male morphs of bulb mites. Rowe then presented results from studies on water striders and other organisms to make the case that males tend to be genetically and phenotypically more variable than females perhaps due to underlying, but as yet undetermined, genomic differences. Phillips then described studies of sexual conflict in nematodes, in which the sex determination pathway is well understood and can be manipulated genetically. I summarized how sexual dimorphism in stalk-eyed flies is influenced by widespread genomic changes on the X chromosome due to meiotic drive.
After a break Kokko described how mate sampling, in which female cost increases with sampling effort, alters conventional models of sexual selection. This talk inspired Trivers to explain how sexual conflict could result in female choice for males carrying alleles beneficial to females. Renn then described how plasticity in gene expression may influence plasticity in sex-biased behaviors of cichlid fishes. Salzburger discussed African cichlid fish radiations and gave examples of genes involved in sexually dimorphic traits and behaviors. Breden followed by describing how sexual selection may have influenced the evolution of the genes involved in signal transduction in the visual system of guppies and related fishes. Finally, Mank described how the Z-chromosome in birds is stratified with regard to the rate at which genes acquire male-biased expression.
After lunch, we convened as a large group and attempted to list major questions in sexual selection that might be answered by genomic approaches. This exercise proved sufficiently encouraging that after a break, we broke into three small groups with each group discussing and, if possible, drafting an outline of 1) the benefits of finding the genetic basis of sexually selected traits, 2) the evidence and issues underlying sexual dimorphism in gene expression, and 3) alternative potential genomic methods and experimental designs for studying sexual selection. The small groups then reconvened and shared the results of their discussions before dinner.
On the second day of the workshop the group agreed that there was sufficient material to write a paper on how genomic approaches could be applied most effectively to studies in sexual selection. Thus, the day was devoted to additional discussions of the topics identified during the first day with the express goal of creating an outline for this paper. This decision focused the discussion, but also led to interesting debates on the intellectual merit of collecting data that may or may not be able to resolve long-standing controversies in the field. The extensive discussions that ensued during the day, as well as over meals and evening excursions to the city, were a highly successful feature of this workshop.
On Saturday, May 17, several members of the workshop (Barribeau, Higginson, Phillips, Renn, Breden and Wilkinson) spent several additional hours refining the outline and then over the next month, Breden, Mank and Wilkinson produced a draft of a paper for publication in a scientific journal. The manuscript is currently being circulated among members of the workshop with the goal of submission before the end of the summer. We are extremely grateful to the Otto and Martha Fischbeck Stiftung for their financial support of this stimulating workshop. We also thank the College of Life Sciences for additional financial support.