University of Glasgow 31.0.08

Do females have to learn the significance of male sexual ornaments?

Sexual ornaments are often under sexual selection and can be used either in male-male contests or for attracting females. This project will examine why females prefer males that exhibit these exaggerated features, and what consequence this preference has for the investment made by males. A well-known example of such a trait is the "sword" of the green swordtail fish (Xiphophorus helleri): females prefer males with longer swords if the males are of equal body size. Basic models of sexual selection explain such a pattern in terms of indirect benefits: either the females mating with the most ornamented males gain "sexy sons" (in the Fisherian model), or survival benefits to their offspring ("good genes"). Both cases predict a rather strong genetic component to female mate choice because of the genetic correlation between the ornament and the preference for it. However, we have data to show that when green swordtail females are reared in female-only groups, and presented visually with only one male at a time, they do not develop these documented mate choice preferences (Walling, Royle, Metcalfe & Lindström, submitted). We suggest that the normal development of female preferences in this species requires an opportunity to observe males in their normal social setting where they can interact, and therefore give the female information on their social rank.

This studentship will test the novel hypothesis that the female preference for longer swords arises because it is a badge of social status. The project will involve experiments in which juvenile fish are reared in different types of social group, so that their exposure to interactions between males is tightly controlled. The mate choice decisions by females given different exposures to males will then be compared, along with information on the age at sexual maturation, investment by males in sexual ornaments, interactions between males of differing morphology, and performance of the offspring that result from different mate choice preferences.

Applicants should submit a CV, a covering letter outlining their suitability for this project, and the names and addresses (including e-mail) of two academic referees to Dr Jan Lindström (j.lindstrom@bio.gla.ac.uk).

There is no fixed closing date for applications, but we are looking to appoint as soon as possible.


Funding Notes
The student will gain a broad training in behavioural ecology, experimental design, fish biology and life history evolution. S/he will be a member of both the Theoretical Ecology and Fish Biology Research Groups, both of which are currently thriving and which receive substantial NERC support.




Relevant recent publications by the supervisors:
Royle, N. J., Lindström, J. & Metcalfe, N. B. 2005: A poor start in life negatively affects dominance status in adulthood independent of body size in green swordtails Xiphophorus helleri. Proc. R. Soc. B 272,1917–1922.

Royle, N. J., Lindström, J. & Metcalfe, N. B. 2006: Effect of growth compensation on subsequent physical fitness in green swordtails Xiphophorus helleri. Biol. Letters 2,39-42.

Royle, N. J., Metcalfe, N. B. & Lindström, J. 2006: Sexual selection, growth compensation and fast-start swimming in green swordtails Xiphophorus helleri. Funct. Ecol. 20,662–669.

Walling, C. A., Royle, N. J., Metcalfe, N. B. & Lindström, J. 2007: Early nutritional conditions, growth trajectories and mate choice: does compensatory growth lead to a reduction in sexual attractiveness? Beh. Ecol. Sociobiol., 61,1007-1014.

Walling, C. A., Royle, N. J., Metcalfe, N. B. & Lindström, J. 2007: Green swordtails alter their age at maturation in response to the population level of male ornamentation. Biol. Letters 3:144–146.

http://www.findaphd.com/search/showproject.asp?projectid=15972