The biogeography of terrestrial organisms across the Florida Keys archipelago is poorly understood. We investigated genetic structure and spatio-ecological modelling of the Amblypygi Phrynus marginemaculatus to understand general patterns of species in the Florida Keys and mainland South Florida. We sequenced a 646 bp fragment of mtDNA (COI) for 22 individuals of P. marginemaculatus from 13 sites in the Florida Keys and South Florida. We used population genetic, phylogenetic, and ecological modeling analyses to understand the distribution and genetic structure of the species.
We found clear genetic structure between the mainland, Key Largo, upper keys, and lower keys. The lower keys, in particular, support populations separate from those in other regions studied. Ecological modeling and genetic analyses showed the highest habitat suitability and genetic isolation in the lower keys, but urban development across the species range has resulted in the loss of most historical habitat. Habitat with a suitability threshold above 0.5 amounted to only 180–301 km2 of habitat depending on the ecological model, of which 35–44% has already been lost to human development.
Ocean currents likely play a role in metapopulation dynamics and gene flow for terrestrial keys species like P. marginemaculatus, but genetic patterns also matched patterns consistent with geologic history. Suitable habitat, however, is limited and under threat of human destruction. While tourism is driven largely by marine habitats, terrestrial ecosystems in the Florida Keys, and especially the lower keys, are unique, with species on evolutionarily-distinct trajectories. We argue that this species and others in the terrestrial Florida Keys would benefit from a deeper understanding of the population genetic structure and ecology of the archipelago.