Flower biology and subspecies concepts in Micropholis guyanensis (Sapotaceae): evidence of ephemeral flowers in the family

Abstract

Micropholis guyanensis (A.DC.) Pierre is a tree from the rainforests of tropical South America and includes two recognised and one informal subspecies. The species has a wide geographic distribution from Central America, northern and western South America to Amazonia and Bolivia, and is morphologically variable. All subspecies occur in the Reserva Florestal Adolpho Ducke just outside Manaus, Amazonas State in Brazil, and it can be questioned how they can grow in sympatry and retain their identity. We have studied vegetative variation, flower morphology and, to some degree, reproductive barriers. The species is dioecious, has five-merous, cream to greenish flowers that produce pollen, nectar and scent to attract pollinators. The flowering period is between June and October, and the plants set fruits, one seed in each, between November and April. There was no overlap in flowering period in the study area between two of the presumed subspecies, but both have similar floral morphology and are pollinated by the same species of butterflies and bees. We are not able to find any clear distributional or morphological discontinuities between the subspecies and we, therefore, suggest that M. guyanensis should be considered a variable species without formally recognised subspecies. Flowers of M. guyanensis are highly ephemeral and persist only for 1 day (~27 h) before falling to the ground. We predict that this is typical for many species of Sapotaceae, which can explain why the corolla is missing from the majority of herbarium specimens that at first sight have flowers.