Establishment of new populations is contingent on overcoming abiotic and biotic barriers. These hurdles are at the forefront of invasion biology where prediction, prevention, eradication, and control strategies depend on an understanding of these processes, particularly as environmental conditions change. Arundina graminifolia and Dendrobium crumenatum are two non-indigenous orchids spreading across Puerto Rico. Each appears sensitive to climate in different ways, but both have acquired a native herbivore and seed predator, Stethobaris polita, an orchid-specialist weevil known to have strong demographic effects on its hosts. We anticipate that under expected climate change scenarios, the two orchids will respond quite differently, and given the lack of shared evolutionary history with the weevil, responses to climate change among the three should be independent. With recently acquired presence records of the three species, land cover data and BioClim variables, we used Maxent to model their potential distributions under current conditions and those projected under the least (RCP2.6) and most (RCP8.5) extreme climate scenarios for 2050. We also looked at distribution overlaps to quantify the scale of biotic interaction between the three species across all projections.
Results/Conclusions
All Maxent models exhibited good to excellent model fits (minimum AUC: 0.884), with predicted current distributions matching our observations. We show a strong possibility for both orchid species to continue to spread across the island under the current climate. Dendrobium 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 the orchid is more sensitive to the same climatic variables as the weevil. Furthermore, projections into all climate scenarios suggests Puerto Rico will be unsuitable for the persistence of A. graminifolia and S. polita and become less suitable for D. crumenatum by 2050. Our results emphasize how climate change over the next few decades may be detrimental to current native and non-native species and their interactions, and could even act as natural management of some invasive species.