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.

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.

Lab-meeting about selection, genetic drift and population divergence of a female mating polymorphism in diving beetles

This coming Wednesday (30 September 2010), we will discuss and give feedback on Tina Karlssons last manuscript: a study about population divergence of a female mating polymorphism in diving beetles and the relative role of genetic drift and selection. This paper is a study on three different species of diving beetles, all of which have the female mating polymorphism ("rough" and "smooth" females, respectively), but at various frequencies. Tina has studied population divergence in morph frequencies of these three species and compared with neutral molecular population divergence (AFLP-markers) to infer the relative roles of genetic drift, stabilizing selection and divergent selection in population divergence. This study is a follow-up study to the previous biomechanical study on male adhesion on these female morphs that we discussed at a  previous lab-meeting. 

Tina will send out this manuscript to interested participants on Monday. Please send her an e-mail (kristina.karlsson@zooekol.lu.se) if you have not received this manuscript by Monday and wish to participate in the discussion. Both positive and negative constructive feedback on this manuscript will be most welcome, as Tina will soon submit her thesis to the printer. The date of thesis defence will be Friday 26 November 2010, at 09.30, and the Faculty's opponent will be professor Nina Wedell from Exeter University (UK). 

Time and place for lab-meeting as usual: "Darwin" at 09.30, September 30 2010. Any fika-volunteer?

Lab-meeting on female mating polymorphisms in diving beetles

This coming Wednesday (8 September), we will discuss a manuscript by Kristina Karlsson that is part of her PhD-thesis, which will be defended on November 26, later this autumn. Both Tina and I would like to receive feedback on this manuscript before it is included in the thesis. The paper is a study which combines the field of sexual conflict with experimental biomechanics, and it has been done in collaboration with morphologist and entomologist professor Stas Gorb at Kiel University in Germany. 

Tina has investigated male adhesion on the surface of two female morphs in diving beetles: either "smooth" or "rough" female types. This polymorphism in female morphology is thought to be an adaptation against male mating harassment, similar to the one we have previously studied in the damselfly Ischnura elegans, which also has multiple female morphs co-existing within local populations.

Tina will send out the manuscript on Monday so that you can read it well in advance and be prepared for the lab-meeting. In case you do not receive it, send an e-mail to Tina (kristina.karlsson@zooekol.lu.se) and ask for a copy.

Time and place as usual: "Darwin", Wednesday 8 September at 10.15. Any fika volunteer?