Tuesday, August 25, 2009
ESEB-meeting in Turin: impressions from first day
I am currently in Turin (Italy), participating in the European Evolutionary Biology Meeting, organized by European Society for the Study of Evolutionary Biology (ESEB). I travelled down to Italy with a dozen of my colleagues from the Ecology Department by train, a nice trip that took about 24 hours. We passed through the Alps and enjoyed the sight of the extensive grape fields in northern Italy before we reached our final destination. A nice experience that was also both climate-smart and environmentally friendly, compared to the usual flight trip.
What has happened this first day? Well, Hanna Kokko from University of Helsinkki gave an excellent keynote plenary about the need to incorporate ecology, particularly population dynamics, in evolutionary studies (and not only genetic factors). Being an ecologist myself, I could not agree more, and actually, tomorrow (Wednesday August 26) I am hosting a full-day symposium about the need to incorporate ecology, particularly information about selective agents (predators, parasites, inter- and intraspecific competitors etc.) and selective causes in studies of natural and sexual selection in the wild. Our two invited speakers tomorrow are Stevan J. Arnold and Craig Benkman, two well-known field evolutionary ecologists who have done excellent work in this spirit in natural populations of birds (crossbills) and amphibians (salamanders).
Back to Hanna Kokko. One of her most interesting points today was a critical re-evaluation of Bateman's principle, the idéa that differences in gamete size of males and females (i. e. eggs and sperm) is the main explanation for differences in reproductive strategies and sex-differences in parental care. This idéa has long been popular in evolutionary psychology and classical behavioural ecology, and it was taught to me as more or less a "truth" when I took courses in behavioural ecology and animal ecology in Lund in the late 80'ties and early 90'ties.
As many other popular idéas in behavioural ecology (a field with an unfortunate tendency of forming scientific "bandwagons") it was an oversimplification and Kokko convincingly argued that there are many other ecological factors than differences in gamete size that are likely to override these initial sex-differences and which are likely to be as important (or even more important) to explain sex differences in partental care. Among these factors are the operational sex ratio (OSR), which should (all else being equal) favor more male parental care when there are few females available and less mating opportunities, for a simple reason: males might then benefit more from providing parental care than try to hunt the few females that are available in the mating pool.
I suspect that Bateman's Principle will be start to become more critically questioned among evolutionary biologists in the future, although the hardcore dogmatic ones that remain (some of them in Lund) might not give up their pet idéa that easily and might be hard to convince. Paradigm shifts in the sense of science philosopher Thomas Kuhn sometimes need that some reactionary key figures retire, before new idéas can establish themselves, and this is also true for behavioural ecology and evolutionary biology.
Talking about pet idéas, another such (in Lund and at many other places) has been the so-called "good genes"-model of sexual selection. This popular hypothesis, which has actually quite limited empirical support in spite of its extreme popularity, was almost a dogma in the nineties in Lund and Uppsala and many other animal ecology departments. The idéa is that male secondary sexual ornaments (signals), like bright feathers and colour patterns, primarily evolve through the force of indirect selection for genetic fitness benefits of offspring.
Many workers have now pointed out, among them evolutionary geneticist William Rice, that the indirect fitness benefits are quite small and likely to be "swamped" by direct fitness costs (e. g. costs of mating, as shown in fruitflies) or direct fitness benefits (e. g. benefits of male parental care, which is probably present in most birds with parental care). Thus, even if indirect fitness exist, they are unlikely to be important in explaining the evolution of secondary sexual characters, which is of course frustrating for those bird behavioural ecologists who have invested a large part of their careers and prestige in to this particular scientific bandwagon which is no longer that fashionable anymore and actually contradicted by much new data and new theoretical models.
Recently, it has also been demonstrated in fruitflies, reed deer and some other animals that fitness benefits of alleles are sex-specific and that there exists intralocus sexual conflict in the genome: genes which have a positive fitness benefits on sons often have a detrimental fitness effect on daughters, which should further diminish the indirect fitness benefits of females mating to attractive males. This topic and other obstacles to the "good genes" were adressed in a symposium entitled Are “good genes” theories of sexual selection finally sinking into the sunset?. Well, one could hope so, or at least that people in behavioural ecology start to think more critically about this issue and that they do not take these "good genes" (important or not) as much as for granted as they have done in the past.