Sexual selection and life history allocation
I am interested in sexual selection, especially regarding the evolution and maintenance of preference in species where there are no apparent direct benefits to the ‘choosy’ sex (typically females).
Variation in male fitness depends on differences in multiple traits, including exaggerated ornaments and weapons. When animals are competing for the attention of – or access to – potential mates, they often have at their disposal an incredible array of displays of sights, sounds and smells, not to mention fearsome weapons. How can we explain such diversity?
By integrating life history theory and sexual selection, we can compare the relative costs and benefits of these sexual traits. A universal cost involves the resources required to create and maintain them – if resources are used to make one trait, there is a cost incurred because those resources cannot be invested in any other traits. This ‘trade-off’ typically causes covariance between an organism’s resource budget and its level of sexual trait expression. We often talk about this in economic terms: the more money you have, then the more you have to spend (even after paying the bills!). This covariance between budget and sexual trait expression is known as condition-dependence.
Condition-dependence has several implications. It may be particularly important for ornaments signalling genetic quality, by helping to maintain the genetic variation that favours mate choice. It may also reduce extinction risk in sexually selected populations, by helping to weed out mutations that are detrimental to an individual’s overall vigour. Crickets make a useful study organism because the males have a ‘costly’ sexual trait – they rub their wings together to make a loud noise that attracts potential mates. Calling is costly because it requires energy to do it; the more energy a male has, the more calling he may be able to perform, and the more females he may attract. This type of trait means that different ‘strategies’ are available for the allocation of resources, as the investment level is highly dynamic. In my PhD, I used the decorated cricket Gryllodes sigillatus to study the interdependence of resource budgets and allocation strategies in a species where males express a sexually-selected trait repeatedly across their lifetime.
Houslay, T. M., Houslay, K. F., Rapkin, J., Hunt, J. and Bussière, L. F. (2016), Mating opportunities and energetic constraints drive variation in age-dependent sexual signalling. Functional Ecology (in press). doi:10.1111/1365-2435.12766
Houslay, T. M., Hunt, J., Tinsley, M. C. and Bussière, L. F. (2015), Sex differences in the effects of juvenile and adult diet on age-dependent reproductive effort. Journal of Evolutionary Biology, 28: 1067–1079. doi: 10.1111/jeb.12630
Houslay, T.M. and Bussière, L.F. (2012), Sexual selection and life history allocation. Encyclopaedia of Life Sciences.
Individual differences in behaviour
…all coming soon…