DISSERTATION RESEARCH: Cryptic Female Choice and Sperm Competition in a Novel Vertebrate Model

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Females of many species mate with multiple males in a breeding season. One explanation for this behavior is that it facilitates mate choice after copulation. Female choice that occurs after copulation is detectable because not all the female's mates have equal paternity; it is called cryptic female choice because the process is hidden. For example, females may transport sperm from particular males to storage sites near where fertilization occurs, which could result in paternity biased towards those males. Cryptic female choice can have profound effects on the strength and direction of sexual selection, the evolution of mating systems, and the coevolution of female and male reproductive traits that leads to speciation. However, the cryptic nature of postcopulatory female choice has made it extremely difficult to document. The PIs have developed a method to label live sperm with fluorescent particles so that the fate of the sperm can be observed in vivo. By observing both where sperm are stored and which sperm fertilize eggs, it will be possible to measure the extent of cryptic female choice. The work will be conducted with garter snakes and the methods are likely to be valuable for many species.The PIs will develop and pilot an integrated inquiry-based lecture, field and laboratory unit appropriate for upper-level high school biology students. This program builds on a successful module that the PIs developed for middle-school students. The PIs also intend to sustain their commitment to undergraduate research opportunities by training at least two undergraduates in PCR, genotyping, and paternity analysis.