Breeding system and pollination of a narrowly endemic herb of the Lower Florida Keys: impacts of the urban-wildland interface

We examined the breeding system and pollination of Chamaecrista keyensis Pennell (Fabaceae: Caesalpinioideae) and the effects of urban edge and mosquito control on reproduction of this rare endemic herb of the Lower Florida Keys. Controlled hand-pollination treatments were applied to plants in the field. Although C. keyensis flowers are self-compatible, they are not capable of automatic selfing. Inbreeding depression was observed in both seed set and percentage seed germination. Bees of seven genera were observed visiting C. keyensis flowers during the peak flowering season (June to July). Only Xylocopa micans and Melissodes spp. may be effective pollinators for C. keyensis, as they were the only bees that "buzz pollinate" this species, which has poricidal anther dehiscence. Chamaecrista keyensis received substantially more visits by X. micans, but fewer visits from Melissodes spp. in urban-edge vs. forest sites. Aerial mosquito spraying may exacerbate the existing pollinator limitation suffered by C. keyensis by reducing the number of visits by the buzz-pollinating bees. Individuals of C. keyensis at urban edges produced fewer seeds per fruit than did individuals in a pristine forest mainly because of greater insect seed predation.