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Miss Jessica Stephenson 

 My project will investigate the effect of parasitism and diet-related condition on individual variation in the use of multiple cues employed by female guppies during mate choice. In dissecting the mechanism by which parasitism can alter mate choice in this species, the project will increase our understanding of how sexual selection changes in parasitized populations. Furthermore, this could provide an explanation for the maintenance of anomalously high Major Histocompatibility Complex (MHC) allelic diversity in parasitized fish populations1.

How an individual’s mate choice preferences change over time is an understudied area of evolutionary ecology. Condition-dependent variation in mate choice preferences between individual female guppies has been demonstrated2,3. It is likely, though little tested, that there is also within-individual variation in preference because condition will change through time. One mechanism by which preferences may vary both between and within individuals is through alteration in the rank females attribute to each of the several cues used during mate choice4. These cues in guppies have been well studied; in healthy females mate choice appears to be based largely on visual cues: females prefer males with intense carotenoid colouration and high display rate5. The role of olfaction in guppy mate choice has received little attention and is uncertain6, though it is through olfaction that animals (including fish) assess MHC compatibility7. Susceptibility to parasites is linked to MHC genotype in guppies8, so choosing mates based on MHC compatibility is likely to increase guppy reproductive fitness. Olfactory information is potentially more important in parasitized than healthy females. Female guppies infected with Gyrodactylus turnbulli (a common ectoparasitic worm) do not choose the same males as healthy females2, and yet this is unlikely to be due solely to reduced energy reserves of females; females raised on low quality diets are less sexually responsive but choose the same males as those raised on high quality diets3. Olfactory cues may also serve to ‘prime’ the visual system, as has been found in zebrafish9.

Using behavioural experiments, I will test for changes in female mate choice preference and the relative importance to females of visual and olfactory mate choice cues. I will test for variation due to within-female changes in infection and diet quality, variation between females from separate populations differing in infection status, and the role of olfactory cues in mediating visual sensitivity.

1. van Oosterhout, C., Joyce, D., Cummings, S., Blais, J., Barson, N., Ramnarine, I., Mohammed, R., Persad, N., Cable, J. 2006. Evolution 60:2562-2574. 2. López, S. 1999. Anim Behav. 57: 1129-1134. 3. Syriatowicz, A., Brooks, R. 2004. BMC Ecology 4:5 4. Møller, A., Pomiankowski, A. 1993. Genetica 89:267-279. 5. Kodric-Brown, A. 1993. Behav Ecol Sociobiol. 32:415-420. 6. Archard, G., Cuthill, I., Partridge, J., van Oosterhout, C. 2008. Behaviour 145:1329-1346. 7. Reusch, T., Häberli, M., Aeschilmann, P., Milinski, M. 2001. Nature 414:300-302. 8. Fraser, B. A., Neff, B. D. 2010. Genetica 138:283-278. 9. Stephenson, J., Whitlock, K., Partridge, J. in review. J Fish Biol.