Floral demography and reproductive system of Pterocereus gaumeri, a rare columnar cactus endemic to Mexico

Abstract

The floral demography, reproductive phenology, breeding system and pollination agents of Pterocereus gaumeri, a rare columnar cactus endemic to Mexico, were studied. The critical phases of the reproductive process occurred during the transition from bud to flower and during the maturing of the fruit. The number of buds, flowers and immature fruits were a function of plant size, although this was not reflected in the production of seeds, due to high predation on the immature fruits. Both inter- and intra-population variability were evident in the production of the reproductive structures. The number of buds, flowers and immature fruits varied from year to year but the number of mature fruits did not. The plants with hermaphroditic flowers have nocturnal anthesis. Ninety percent of the flowers exposed to nocturnal pollination set fruit, but no fruit was produced by the flowers exposed to diurnal pollination. The bat Glossophaga soricina is the most probable pollinator. Reproduction lasted from January to June, with a flowering peak during the first half of March. This species is exclusively outcrossing and self-incompatible. The results of this study support findings that columnar cacti inhabiting tropical regions depend on bats for successful reproduction.