Coexistence of Five Sympatric Piper (Piperaceae) Species in a Tropical Dry Forest

Abstract

Five Costa Rican species of Piper (Piperaceae) co—occur in evergreen forest sites at Santa Rosa National Park, Costa Rica. The species were found to have distinctive spatial distribution patterns with two species (Piper marginatum and P. pseudofuligineum) occurring in early successional sites and the others, P. amalago, P. jacquemontianum, and P. tuberculatum, occurring in less disturbed sites in dry forest, evergreen forest, and riparian forest, respectively. These habitat differences are associated with differences in seed and seedling biology and seasonal changes in the foraging behavior of the chiropteran seed dispersers of these plants. Excluding the uncommon P. tuberculatum, overall pairwise spatial overlap, measured by Pianka's (1974) symmetrical index, averaged 0.61. Relatively low phenological overlap allows the species to share animal visitors. Average pairwise flowering overlap (0.13) was about one—half the value of pairwise fruiting overlap (0.22). Responses to different rainfall cues and/or different inflorescence growth rates produce temporally separated phenological cycles. However, results of computer simulations suggest that observed phenological overlap was neither significantly lower nor significantly higher than expected by chance, for most pairs of species. Insect visitation is necessary for high seed—set, and species differ in their attractiveness to pollinators. Pairwise insect overlap (0.59) was greater than expected by chance, however. The plants also utilize the same six species of frugivorous bats as seed dispersers, and pairwise bat overlap was extremely high (0.96). Because they are important fruit sources for three common bat species, Piper species are keystone mutualists in dry tropical forests.