Sexual selection and performance
Colorful belly patches of Sceloporus clarkii. Photograph by D. J. Irschick
Sexual selection most often refers to the potentially disparate processes of male competition and female choice, and yet this topic has most often been investigated from a purely ethological or life-history perspective. Although these approaches have proven to be valuable, a more functional approach is increasingly emerging as an important paradigm for understanding sexual selection. Are males that are good performers also good competitors? Do females prefer males that are good performers? How does ontogeny affect the ability of males to compete, both with one another, and for access to females? Our approach has been to examine this issue using a combination of laboratory experiments, field demographic techniques, and functional techniques. Lizards in particular are excellent model systems for investigating this issue because of their often spectacular sexually dimorphic structures, such as the colorful throatfans and "badges" of males, and the fact that male lizards often compete intensely for access to territories.
Further, we are examining the process by which natural and sextual selection interact in the field with sexual traits and integrated performance traits. Understanding the selective basis of performance is acrucial step for evolutionary theory because selection is expected to operate first on performance, and only secondarily on morphology and behavior. We are utilizing a vareity of genetic tools to understand paternity, and its links to morphology and performance, as well as examining hormone levels. This work will therefore provide a mechanistic link between hormone expression, paternaity, and performance in nature. This work will also test the long-held belief that "good performers" should also enjoy high fitness within animal populations.
Lailvaux S, Herrel A, VanHooydonck B, Meyers J, Irschick DJ. 2004. Performance capacity, fighting tactics, and the evolution of life-stage male morphs in the green anole Lizard (Anolis carolinensis). Proceedings of the Royal Society of London, B. 271:2501-2508.
VanHooydonck B, Herrel A, Meyers J, Van Damme R, Irschick DJ. 2005. The role of the dewlap as a visual cue depends on age and sex in an A. carolinensis population. Behavioral Ecology and Sociobiology. 59:157-165.
Bloch N, Irschick DJ. 2006. An analysis of inter-population divergence in visual display behaviour of the green anole lizard (Anolis carolinensis). Ethology. 112:370-378.
Irschick DJ, Ramos M, Buckley C, Elstrott J, Carlisle E, Lailvaux S, Bloch N, Herrel A, VanHooydonck B. 2006. Are morphology->performance relationships invariant across different seasons? A test with the green anole lizard (Anolis carolinensis). Oikos. 114:49-59.
Meyers J, Irschick DJ, VanHooydonck B, Herrel A. 2006. Divergent roles for multiple sexual signals in a polygynous lizard. Functional Ecology. 20:709-716.
Lailvaux S, Irschick DJ. 2006. A Functional Perspective on Sexual Selection: Insights and Future Prospects. Animal Behaviour. 72:263-273.
Irschick DJ, Herrel A, Vanhooydonck B, Van Damme R. 2007. A functional approach to sexual selection. Functional Ecology (Cover). 21:621-626.
Irschick DJ, Meyers JJ. 2007. An analysis of the relative roles of plasticity and natural selection on morphology and performance in a lizard (Urosaurus ornatus). Oecologia. 153:489-499
Vanhooydonck B, Irschick DJ, Herrel A, Huyghe K, Van Damme R. 2007. A performance based approach to the index versus handicap debate in sexual selection studies. Functional Ecology (Cover). 21:645-652.
Calsbeek R, Irschick DJ. 2007. The quick and the dead: Correlational selection on morphology, performance, and habitat use in island lizards. Evolution. 61:2493–2503.
Dial KP, Green E, Irschick DJ. 2008. Allometry of Behavior. Trends in Ecology and Evolution. 23:394-401.
Irschick DJ, Meyers JJ, Husak JF, Le Galliard JF. 2008. How does selection operate on whole-organism functional performance capacities? A review and synthesis. Evolutionary Ecology Research (Cover). 10:177-196.
Vanhooydonck B, Herrel, A, Meyers JJ, Irschick DJ. 2009. What determines dewlap diversity in Anolis lizards? An among-island comparison. Journal of Evolutionary Biology. 22: 293-305
Henningsen JP, Irschick DJ. 2012. Manipulating dewlap size reveals that performance is more important than signal size in determining the outcome of staged dominance interactions in male green anole lizards. Functional Ecology (Cover). 26:3-10.