Abstract
Curacao, a semi-arid island of the Netherlands Antilles, has seven bat species, all of which are threatened. Three species of columnar cacti, Subpilocereus repandus, Stenocereus griseus, and Pilosocereus lanuginosus, occur on Curacao and are pollinated by the two species of nectar-feeding bats of this island. Because the columnar cacti share pollinators, they may compete for this resource. P. lanuginosus produced flowers in response to rainfall, but S. griseus stopped producing flowers. I detected no effect of rainfall on flower production in S. repandus. The flowering times of S. repandus and S. griseus overlap (80%), but their sharing pollinators may result in convergence rather than divergence because there is no evidence of exploitative and interference competition. Bat species seem to differ in effectiveness of pollination for both S. repandus and S. griseus: Leptonycteris curasoae, the larger of the two bat species, seems more effective in pollinating Subpilocereus repandus than Glossophaga longirostris. Conversely, the latter species appears to be more effective in pollinating Stenocereus griseus than Leptonycteris curasoae. The nectar-feeding bats depend on cacti as food resources for survival, but columnar cacti are no longer very abundant. The carrying capacity of these cacti for the bats is low and further destruction of the natural environment is expected to lead the nectar-feeding bats to extinction, as well as limit the abundance of animals that rely on cactus fruits.