The Mammals of Coastal Texas: A Comparison between Mainland and Barrier Island Faunas

Abstract

Biodiversity patterns of non-volant mammals on oceanic and land-bridge islands have been well documented, but little information is available about the biodiversity of barrier islands. We compared the mammalian fauna of the barrier islands of Texas with the adjacent mainland by using historical trapping records and recent field work. The barrier islands of Texas have a depauperate mammalian fauna when compared to that of the Texas coast. A number of factors have influenced this, including hurricane events, mainland species pool for the island to draw upon, and the degree of isolation of the island from the mainland. Differences in species richness and composition among islands can be attributed to the biotic province to which an island is adjacent and island area. Differences in species richness among island complexes can be attributed to island complex length. Regression analysis demonstrates a significant correlation between species richness and island area, and a highly correlated relationship between richness and island complex length. Two similarity indices indicate that the mammalian fauna of islands within each complex is more similar than the fauna between complexes. Two nested subset analyses reveal the islands contain a nested distribution of mainland species. It appears that the dearth of mammals on the islands has not resulted from a lack of colonization events, but rather the inability of mammals to survive in the harsher island environments.