WELCH, A.W.: How do parental genetic quality and genetic compatibility affect offspring growth in gray tree frogs?

Females in many species discriminate among potential mates, and one benefit of mate choice can be enhanced genetic quality of offspring. Offspring genetic quality may be enhanced if a female selects a mate of high genetic quality or a mate with whom she is genetically compatible. Most investigations of genetic benefits of mate choice have tested the hypothesis that preferred mates are of higher genetic quality. Here, I test the relative importance of genetic quality and genetic compatibility for offspring performance in gray tree frogs (Hyla chrysoscelis). If general genetic quality varies among potential mates, then different males in a population will sire offspring of different quality, regardless of female identity. Alternatively, genetic compatibility suggests that the genetic ‘value’ of a male depends on the female’s genetic contribution. In order to differentiate these two hypotheses – general genetic quality and genetic compatibility – I have conducted a series of maternal and paternal half-sibship crosses in H. chrysoscelis. Sperm from four males was used to fertilize eggs from up to four females, resulting in up to 16 unique full-sibships. This design was repeated four times, with different males and females, for a total of 52 unique full-sibships. Tadpoles resulting from artificial crosses were raised in the laboratory, and survival, growth rate, and age and size at metamorphosis were measured. One mechanism that may contribute to genetic compatibility is inbreeding depression. In future studies, I will assess the cost of inbreeding in gray tree frogs by comparing performance of these offspring with the relatedness of their parents, using similarity at microsatellite markers as a measure of relatedness.