Pollination Biology of Harrisia portoricensis (Cactaceae), an Endangered Caribbean Species

Abstract

Information on the breeding system of endangered plants is often useful piece of information for conservation and management of wild populations. This is so as the foraging behavior of the pollinators and the plant breeding system are factors that may also affect fruit-set and therefore plant reproductive success (Boch & Waser 2001). Harrisia portoricensis is an endangered cactus endemic to Puerto Rico and geographically restricted to three small Caribbean Islands located to the west of Puerto Rico: Mona, Monito and Desecheo (USFW 1990). The population at Mona Island is the largest population identified to date.Little is known about the breeding system of this cactus species but we do know that Harrisia portoricensis appears to be genetically uniform throughout its distribution range based on studies of allelic variation in allozymes (Santiago-Velez 2000). This is somewhat surprising given that most of the columnar cacti studied so far in the tropics have been characterized as self-incompatible hermaphrodite plants (Valiente-Banuet et al. 1997, Fleming 2002). Based on this general observation one would have expected H. portoricensis individuals to be more variable. One possibility for this lack of variation may relate to the presence of breeding systems conducive to inbreeding. Here we present data on the floral traits, floral visitor, and breeding system of H. portoricensis to address the extent by which this cactus breeding system promotes self-fertilization events.