Sexual selection and performance; A new approach for an old idea

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.  Recent work shows that the relative size of such sexual structures in male green anoles is an honest signal of maximum bite force, at lest for some size classes.  Further, other work shows that both biting performance and the relevance of this measure for male combat changes with size in green anoles.  This last finding is particularly important for sexual selection theory because it shows that one aspect of male "quality" is not necessarily appropriate for all males, and that indices of male quality can change with size.  Overall, this line of research is relatively  new to my laboratory, so check back for more updates later!An image of an extended throatfan from the anole Anolis cybotes from Hispaniola.  Photograph by D. J. Irschick

Relevant literature:

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.

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.