Pine rocklands are a fire-successional community unique to south Florida and the Caribbean. Less than 2% of the original extent of pine rockland (outside Everglades National Park) remains along the Miami Rock Ridge, in many small patches, now surrounded by urban and suburban development and agriculture; pine rockland is present also in the lower Florida Keys. The understory is diverse, with more than 250 native herb species, some of which are endemic, threatened or endangered due to habitat loss. We have examined a variety of pine rockland flowering plants to determine the effects of habitat fragmentation on their pollination, using flower visitation and fruit set as indicators of reproductive success after learning the intricacies of their floral biology and breeding systems. The hypothesis: plants with more specialized pollination relationships and those that are obligate outcrossers will suffer the effects of habitat fragmentation more than generalists that may self-pollinate.
We have examined species in a range of pollination syndromes: butterfly (Ruellia succulenta), bee (Angadenia berteroi, Byrsonima lucida, Pentalinon luteum), butterfly/bee/fly (Jacquemontia curtiissii), hummingbird (Ipomoea microdactyla), and hawkmoth (Echites umbellata, Guettarda scabra). Some of the species are entirely self-incompatible (Angadenia berteroi, Byrsonima lucida, Ipomoea microdactyla, Pentalinon luteum), while mixed-mating systems are found in others (Jacquemontia curtissii, Echites umbellata, Guettarda scabra) in which some individuals are somewhat self-compatible. Ruellia succulenta is entirely self-compatible, and automatically self-pollinates as the corollas fall from the flowers; some populations of Guettarda scabra also set fruit with no visitors to flowers.
Several of the species show shifts in pollinator guilds in fragments compared with continuous habitat (Ruellia, Guettarda), and some frequent visitors – previously assumed to be pollinators – actually do not effect much pollination (Angadenia, Pentalinon). All species so far studied are still pollinated and setting fruit, but some show changes in their pollinator fauna, pollen deposition on stigmas, and fruit set with habitat fragmentation; each species changes in different ways. The narrowing of genetic diversity (evidence from Ipomoea microdactyla) suggests there may be an extinction debt being incurred for pine rockland plants as their population numbers dwindle and connectivity disappears. Such negative consequences may be ameliorated in part by plantings in the matrix and gardening for pollinators.