REPRODUCTIVE ECOLOGY OF CARYA (JUGLANDACEAE) - PHENOLOGY, POLLINATION, AND BREEDING SYSTEM OF 2 SYMPATRIC TREE SPECIES

Observations and experiments on both shagbark (Carya ovata) and mockernut (C. tomentosa) hickories in a New Jersey forest were performed. Phenological observations indicated significant differences between the species for almost all vegetative and reproductive characters examined, though a large amount of overlap was observed. Pollen limitation is not a significant factor in reducing fruit set in these anemophilous species. The large surface area of vegetative structures at the time of pollination may retard the flow of pollen into and out of the canopy, increasing self-pollination. Trees were both geitonogamous and xenogamous to varying degrees. A high frequency of putative interploidal cross-compatibility was also observed. Fruits from these interspecific crosses were germinable. Dichogamy may help to reduce selfing and promote outcrossing in this breeding system. While most trees exhibited a temporal separation of genders, they switched between protogyny and protandry between years. -from Authors