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Completed Project

To Mate or not to Mate: Behavioral Quantitative Genetics in a Bean Beetle

Daniel Moskop, Vassar College ’18 and Prof. Mary Ellen Czesak
The bean beetle species Callosobruchus maculatus is an agricultural pest with prolific reproduction, short lifespans, and fast generation times. Female reproductive fitness is maximized by mating with fewer males who are able to donate large ejaculates containing the nutrients used in egg production. Conversely, male fitness is at its peak through mating with as many females as possible. We implemented a half-sib breeding design across 4 lines (2 populations x 2 rearing hosts, one novel and one native host per population) to compare the influence of population and rearing host on mating behaviors, life history traits, and their heritability and genetic correlation estimates. Population had a significant effect on both total mating duration and the amount of time it took the female to dislodge the male and terminate mating (dismount duration); beetles from the Burkina Faso lines had longer times than those from Southern India. The differences among lines in dismount duration might explain why there was no significant difference in male ejaculate size between the lines despite the disparity in mating duration. Additionally, rearing host had a marginally significant effect on total duration and a significant effect on dismount duration in that mung bean hosts resulted in longer durations than cowpea hosts. Population, rearing host, and their interaction also played an important role in the time it took for a male to first attempt mating with a female. These data suggest that the effects of population persist even when switched to a novel host for several generations and that rearing host does play a key role in certain mating behaviors. Immediate future work includes estimating heritabilities and genetic correlations among behaviors and life history traits, specifically female fecundity.