Early-acting inbreeding depression in three species of Vaccinium (Ericaceae)

Greenhouse pollinations determine whether early-acting inbreeding depressio n is contributing to low levels of self-fertility in three Vaccinium specie s: I myrtilloides Michaux, V. angustifolium Aiton, and V. corymbosum L. All three species showed a significant reduction in self fruit set and in the proportion of fertilized ovules that developed into mature seed in self com pared to outcross fruit. Reductions were more severe in V. myrtilloides and V. angustifolium than in V. corymbosum; however, early-acting inbreeding d epression appeared to be the primary factor limiting self-fertility in all three species. Evidence for early-acting inbreeding depression included the presence and higher proportion of aborted ovules in self fruit than in out cross fruit, a correlation between levels of self and outcross seed set, an d pollen chase experiments demonstrating that self-pollen does fertilize th e ovules. Self-fertility in the three species was probably influenced by le vels of genetic load, ploidy level and outcrossing rates.