ECOLOGICAL RELATIONSHIPS BETWEEN COLUMNAR CACTI AND NECTAR-FEEDING BATS IN MEXICO

A bibliographical and herbarium investigation on the pollination syndr ome of Mexican columnar cacti (tribe Pachycereeae) was conducted. Most Mexican species of columnar cacti show a chiropterophilic - pollinati on syndrome and they flower synchronously in March to May. The floral biology, reproductive system and visitors (to both fruits and flowers) of Neobuxbaumia tetetzo, the most abundant and dominant columnar cact us of succulent forest in the Tehuacan Valley, were studied. This spec ies reached densities of c. 1200 individuals ha-L. The bats Leptonycte ris curasoae and Choeronycleris mexicana were its only pollinators, wh ilst a more diverse array of visitors disperse seeds. Contrary to find ings for multiple pollinators of columnar cacti in extratropical deser ts in North America, the relationships between N. tetetzo and nectar-f eeding bats was strong and tightly coupled in Mexico.