Genomic patterns of native palms from the Leeward Antilles confirm single-island endemism and guide conservation priorities

Systematic study of the palm (Arecaceae) flora from the Leeward Antilles marked both Sabal antillensis and Sabal lougheediana as endemic to Curaçao and Bonaire respectively. Although both species are emergent, obvious and charismatic elements of the Antillean flora, they were only described within the last decade. Sabal lougheediana is in demographic crisis as a result of constant ungulate pressure prohibiting seedling establishment, while S. antillensis is thriving as a result of careful management. Given the surprisingly recent discovery of these two species, and the severity of the conservation concern, genomic data can help inform whether these taxa are in fact well-circumscribed species, and help to guide further conservation actions. To investigate genomic diversity, we employed RADSeq data from samples throughout the range of both species. Results show significant genetic distance and fixation between the two taxa as currently circumscribed, as well as reduced genetic diversity and increased inbreeding in both species. Multivariate analysis of genetic distance and Bayesian clustering analysis both show clear and significant separation of the two taxa. Parallel assay of ex situ collections informs how future development of germplasm reserves can help support conservation of both species. We provide recommendations to help conserve these two unique and distinct species.