PARENT SESSION
Poster Session #35: Reproductive Ecology.
Wednesday, August 7. Presentation from 5:00 PM to 6:30 PM. Exhibit Hall B & C, TCC

A comparison of male and female responses to inbreeding in Cucurbita texana.

Hayes, Nelson^*,1, Breault, Steven¹, Stephenson, Andrew, ¹ The Pennsylvania State University, University Park, PA

ABSTRACT- Accurate estimates of inbreeding depression are necessary in order to predict the evolutionary dynamics of a population, but many studies estimate inbreeding depression based solely on components of female function such as fruit set, seed set, and seed quality. Because both male and female functions contribute to total fitness in hermaphroditic plants and different suites of genes are involved in pollen development/pollen tube growth and ovule/fruit/seed development, it is necessary to measure components of both male and female function to estimate total fitness and to estimate the magnitude of inbreeding depression. To compare the effects of inbreeding on male and female function, seedlings of Cucurbita texana, a hermaphroditic annual vine related to zucchini, representing inbreeding coefficients of 0 and 0.75 were planted in an experimental garden, and several components of male and female fitness were measured over the course of the growing season. Inbred individuals produced significantly fewer fruits than outcrossed individuals, and percent germination of seeds from inbred individuals was significantly lower than seeds from outcrossed individuals. Inbred plants also produced significantly fewer pollen grains per flower than outcrossed plants, and pollen from inbred plants grew significantly more slowly in vitro than pollen from outcrossed plants. Multiplicative estimates of inbreeding depression revealed that responses of male and female functions to inbreeding is highly correlated in C. texana.

KEY WORDS: inbreeding depression, male function, Cucurbita, pollen performance