Lab-meeting on March 16 2011. New paper on condition-dependent sexual signalling by exiled lab-member Tom Gosden

Next week's lab-meeting we will not read any paper, but instead Machteld Verzijden and myself will give some informal presentations of the talks we will give in a small symposium on insect behaviour and evolution in Stockholm on Thursday, that is arranged by Professor Christer Wiklund in conjunction with a PhD-defence by his student Martin Bergman. Both Machteld and I will of course be happy for any feedback you might have, the day before our official presentations. The title of Machtelds talk is "Ethological speciation mechanisms" and mine is "Ecological vs. non-ecological speciation mechanisms".

If you nevertheless have time and are interested in reading a cool paper, there is one good one that has just been published in Journal of Evolutionary Biology by Tom Gosden and Steve Chenoweth. As you know, Tom is currently in exile in Australia, funded by a Marie Curie "outgoing" postdoc, where he now studies the fascinating and charismatic fruitfly Drosophila serrata, which has recently emerged as somewhat of a model organism in evolutionary quantitative genetics and sexual selection studies. Steve Chenoweth and Mark Blows are leading researchers in this field and have developed sophisticated statistical techniques to estimate breeding values and selection on such breeding values in this species.

The present study tests assumptions behind so-called "genic capture"-model of sexual selection, by looking at the degree of condition-dependence and genetic variation for in condition-dependence among males of Drosophila serrata in relation to a novel food source (yeast). Interestingly, the authors found evidence for condition-dependent sexual signalling, but apparently no genetic variation for condition-dependence, which indicates that it cannot evolve further, at least on this food source. Beware of some heavy maths and statistitics, before you decide to read this paper! Tom will return to Lund in 2012 (same year as Yuma) and bring in fresh new knowledge and skills to our group that he learned in Australia. Below is the abstract of their fascinating paper:

On the evolution of heightened condition dependence of male sexual displays

T. P. GOSDEN & S. F. CHENOWETH

The maintenance of genetic variation in male sexual display traits in the face of strong directional sexual selection from female preferences is an ongoing evolutionary conundrum. Condition dependence and the genic capture hypothesis are often cited as theoretical resolutions to this problem, yet little is known about the ability of condition dependence itself to evolve. We set out to test how a suite of cuticular hydrocarbons (CHCs) used in sexual displays are affected by adult diet and the potential for any condition-dependent response to evolve in a laboratory-adapted population of the Australian fruit fly Drosophila serrata. We performed a dietary manipulation within a half-sib breeding design, raising adult males either with or without access to live yeast, a manipulation that had previously shown strong effects on female fitness. Diet had strong phenotypic effects, with males from the different diets producing different CHC blends. The blend of CHCs under sexual selection showed a degree of elevated condition dependence. Regardless of the heightened sensitivity of favoured CHC blends to diet and the presence of genetic variance for the traits, we were unable to detect any genetic variance in the reaction norms for the male dietary response. Our results suggest that there is limited opportunity for males to evolve further condition dependence in response to yeast availability in this population.

Lab-meeting on intralocus sexual conflict on Wednesday 9 September 2009

This Wednesday (9 September), I thought we should discuss a recent TREE-article about intralocus sexual conflict, its origin and (possible) solution, which you can find here. The authors are Russel Bonduriansky and Steve Chenoweth,the latter Tom Gosden's postdoc host at Queensland University in Australia. It is a timely overview over a rapidly growing field, which was quite evident for those of us who participated in the ESEB-meeting in Turin, where a whole session was dedicated to the fascinating and increasingly popular topic of intralocus sexual conflict.

It was interesting for me to closely have seen this "explosion" of a field, which I have been familiar with for quite a while, but which few (at least in Lund) understood a few years ago, or realized the importance of. I strongly suspect that the term "gender load", which I had difficulties in explaining in some talks I gave in Lund, will soon enter the mainstream language of evolutionary biology. Perhaps future historians of science will see the signs of a minor conceptual and scientific "revolution" here, as people are increasingly viewing the genome not as a peaceful and harmonic and well-functioning "unit", but rather as something is constantly selected in different directions, the end-result becoming a compromise between male and female fitness optima (see figure above).

For those of you want some additional background reading, I can also recommend Robert Cox and Ryan Calsbeek's recent metaanalysis of intralocus sexual conflict, which was published in American Naturalist earlier this year, and which you can find here. You could also download my own paper (co-published with Andrew McAdam and Barry Sinervo) about intralocus sexual conflict over immune defence and how it affects sex-specific signalling in lizards. This paper is in press in Evolution and can be found here.

I suggest that we all read the TREE-review, and those who wants can also study the two other papers as a general background and bring them to the lab-meeting. We meet the usual time: 10.00 on Wednesday morning in "Darwin". Any fika volunteer?