REPRODUCTIVE ALLOCATION AND POLLINATOR DISTRIBUTIONS IN CAULIFLORUS TREES IN TRINIDAD

Little information is available to test the various theories which hav e been proposed to explain the evolution of cauliflory. This study pro vides such data from observations in Trinidad of the numbers of potent ial pollinators visiting trunk and canopy flowers and on the size of c anopy and trunk flowers and fruits. Subsidiary observations were made on the partitioning of resources between the sexes within flowers. Sig nificantly more potential insect pollinators were trapped around the t runk Bowers of two cauliflorous species than were caught around their canopy flowers. Trunk flowers were found to be larger than canopy flow ers in four of the seven cauliflorous species studied, but they were s maller in one species. The higher probability of fruit set on trunks t han in the canopy may have selected for cauliflory and subsequently in creased trunk flower size in insect-pollinated understorey tropical tr ees. There was a tendency for flowers on the trunk not only to be larg er but also to allocate relatively more dry weight to female parts and result in larger fruit than those in the canopy. These observations a re consistent with Wallace's theory of the evolution of cauliflory, wh ich argues that the condition arose in the dark understorey of the tro pical forest, as a result of selection for trunk flowers which are mor e apparent to pollinators than are canopy flowers. However, other expl anations for the evolution of cauliflory are not precluded as they are not mutually exclusive.