Pollination Ecology of Three Sympatric Palms of Southern Florida Pine Rocklands

Three native palms are dominant features of the pine rocklands understory of peninsular southern Florida: sabal palm (Sabal palmetto), saw palmetto (Serenoa repens), and silver palm (Coccothrinax argentata). Despite the abundance of these three palm species, the breeding system and pollination mechanisms need further clarification. We used controlled hand-pollination experiments to investigate the breeding systems of these three species. We also observed and captured floral visitors, as well as examined their bodies for pollen, to determine the pollinator assemblages. Our experiments demonstrated that all three palms are self-compatible, and some flowers may set fruit with no manipulation. Natural (open) pollination treatments yielded more fruit than either cross-or self-pollination, indicating no shortage of pollination and suggesting that multiple visits by many pollinators enhances fruit set. We observed a wider variety of visitors (Coleoptera, Diptera, Hymenoptera, Lepidoptera) to flowers of sabal and saw palmetto, as they offer both nectar and pollen. On flowers of silver palm, we observed only pollen-collecting bees. We found evidence of palm flower specialists in only two cases: Xylocopa micans bees carried only Coccothrinax pollen and Anartia jatrophae butterflies carried only Sabal pollen. All other visitors appeared to be generalists as they carried pollen from multiple plant species. These results highlight the importance of subcanopy palms in the pine rocklands ecosystem as they provide floral rewards for a wide array of insects that are beneficial for other plants of this imperiled habitat.