COS 268-1 - Demography and phenology of the endangered cacti Leptocereus grantianus: implications for its management and conservation

Background/Question/Methods

The natural history of the archipelago of Puerto Rico has been in a race against uncontrolled urban development. Because of this, there is a considerable lack of scientific data value on its ecology. The genus Leptocereus is part of that but, more specifically, the Leptocereus grantianus species, which is endemic to the island municipality of Culebra. The U.S Fish and Wildlife Service designed a recovery plan, but data on the biology and ecology of the species is scarce, limiting the application of conservation plans. This project aims to fill in the ecological information gap of this critically endangered species. In 2021 we started to monitor the demography and phenology of L. grantianus to understand its population dynamics better. We tagged 62 individuals in 3 different sites (Punta Soldado, Melones, and Cascajo) to measure growth, count the number of buds and flowers monthly, and establish a surveillance system to capture budding dynamics.

Results/Conclusions

Preliminary results indicate that growth rates differ significantly among populations (F=5.59, p= 0.045). Such a difference can be explained by the higher growth rate observed at Melones, where the cacti grew six and twelve times faster than at Punta Soldado and Cascajo, respectively. Likewise, the bud production of these populations showed a significant difference (F= 9.22, p= 0.00327), being the Melones site the most productive (56%) compared to Punta Soldado while no bud production was registered in Cascajo. Despite observing bud production at Punta Soldado and Melones, only a single flower was open completely in Melones. Our data and observation suggest the difference between growth and bud production among the population may be related to variation in precipitation and light variability. These results provide valuable information on this species that will be used to develop a proper demographic-based conservation and restoration plan.