Identifying Refugia and Barriers to the Spread of A. graminifolia and D. crumenatum in Puerto Rico

Establishment of new populations is contingent on overcoming abiotic and biotic barriers. While this applies to all species, these hurdles are at the forefront of invasion biology where prediction, prevention, eradication, and control strategies depend on an understanding and exploitation of barriers to establishment and spread. Arundina graminifolia and Dendrobium crumenatum are two invasive orchids spreading throughout Puerto Rico. Current records on their distributions across the island are sparse, and their interactions with the surrounding ecosystem are unknown. Through a direct population survey of all known localities, we identified a new, acquired enemy of both orchids: the orchid-specialist weevil, Stethobaris polita. In this study, we used niche modelling to identify suitable habitats for each orchid on the island and map their current distributions and interactions with S. polita, along with their distributions in the most extreme climate scenario in 2050, in order to contextualize projected patterns of establishment on the island. Our findings show that D. crumenatum flourishes in urban environments which also provide refugia from S. polita. In contrast, there is currently no refugia for A. graminifolia from S. polita attack, as it is more sensitive to the same climatic variables as S. polita. Furthermore, projections into the most extreme climate scenario suggests Puerto Rico will be unsuitable for A. graminifolia and S. politas survival, and become less suitable for D. crumenatum, by 2050.