Functional importance of snakes in a strandveld ecosystem
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Gaps in our knowledge of the functional roles of snakes within ecosystems limit our ability to predict the potentially cascading effects their removal from an ecosystem might create. Extirpation of snake species could potentially result in losses of ecosystem functionality if those taxa are ecologically unique. I used pitfall and funnel trap arrays, artificial cover object surveys, active searching, and passive camera trapping, as well as pre-existing faunal diversity data to identify terrestrial tetrapod species within the Koeberg Private Nature Reserve. This resulted in a list of 265 species, of which 13 were snakes. I then gathered data on dietary and four additional functional traits for each species from the literature. Next, using hierarchical and partitioning around medoids clustering, I identified ten broad dietary guilds and 54 functional guilds within the terrestrial tetrapod community. Of the dietary guilds Dasypeltis scabra was the only snake species that formed a unique single species guild and was one of four snake species (Pseudaspis cana, Homoroselaps lacteus and Lamprophis guttatus) to form four unique single species functional guilds. The remaining snakes clustered together within groups of other vertebrate predators. Functional diversity analysis was then used to simulate losing eight major taxonomic groups (birds, passerines, non-passerines, mammals, reptiles, snakes, non-snake reptiles and amphibians) and gauge the effects of those losses on overall community dietary and functional diversity. Functional diversity analysis revealed that the loss of certain snake species resulted in disproportionate losses of overall community dietary and functional diversity while losing others had negligible effects. These findings provide ambivalent support for the dietary and functional uniqueness of snakes suggesting that certain snake species are fulfilling unique functional roles within the ecosystem. Additionally, it is likely that losing those non-redundant species would result in significant losses of ecosystem functionality.