Measuring Behavior 2005: Kim et al.

Testing for mate preference and mate choice in Drosophila pseudoobscura

Y.-K. Kim, P. A. Gowaty and W. W. Anderson

Department of Genetics, University of Georgia, Athens, GA, USA

Natural selection is expected to adjust behavior to increase fitness. We tested this hypothesis with Drosophila pseudoobscura while observing the relationship between mate preference and fitness. Mate preference was determined in Amsterdam arenas where a single fly was allowed to choose between two flies of the opposite sex eliminating all possibilities for male-male competition, female-female competition and male coercion or manipulation of females which were involved in ordinary mate choice studies. We measured the time the chooser flies spent in front of partners, A and B, respectively. After the preference tests, matings were arranged with preferred (P) and non-preferred (NP) partners. Our early offspring viability studies have demonstrated that freely expressed mate preference affects the fitness of offspring, matings with non-preferred partners compensate for significantly lower viability from these matings by increasing the number of eggs or sperm and preferred partners, regardless of sexes, were significantly bigger in body size than NP partners. In attempts to investigate correlations between mate preference and mate choice, the same fruit flies collected from the mate preference tests were observed in Elens-Wattiaux mating chambers where behavioral interactions between sexes and individuals reinstated. Current data show that:

Females discriminated between P and NP males:
they mated significantly more with P males.
Males, however, randomly mated with P and NP females.
Both sexes mated significantly more with first courting or encountered partners.
The presence of another individual during copulation significantly reduced copulation duration between mates and so less sperm were delivered to females.

These results suggest that under ecological and social constraints individual Drosophila males and females facultatively vary behavior.

Paper presented at Measuring Behavior 2005 , 5^th International Conference on Methods and Techniques in Behavioral Research, 30 August - 2 September 2005, Wageningen, The Netherlands.