Reproductive phenology of the Caribbean cactus Harrisia portoricensis: rainfall and temperature associations

Phenological patterns often influence the extent of reproductive success of plants as well the interaction among species. In this study, we evaluated the association of local climatic factors and plant size with the reproductive phenology of the threatened cactus Harrisia portoricensis in the Caribbean dry forest of Mona Island. Analyses of phenological data gathered monthly in 572 plants over 2 years concluded that for this species, reproductive activity is continuous throughout the year and reproductive output is positively correlated with plant size. Bud production in H. portoricensis was positively associated with temporal changes in monthly mean and minimum temperatures, while flower production was positively associated with total monthly rainfall. When compared with other columnar cacti species, the combined phenological responses to temperature and rainfall in H. portoricensis represent a different strategy. We hypothesize that contrasting phenological responses among columnar cacti may stem from site-specific differences in the degree of intra-annual rainfall or temperature variability. If that is the case, then monitoring reproductive responses of cacti to expected changes in climate at a global scale would require gathering phenological data for this taxon across different geographic regions.