Classification of Small-Mammal Metacommunity Structures Along Elevational Gradients with Connections to Metacommunity Networks
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Small-mammals respond quickly to habitat changes and serve an important role in ecosystem function as prey and sources of seed dispersal. To assess the interaction structure, or metacommunity structure, of small-mammal assemblages, I collected presence-absence surveys of non-volant, terrestrial mammals weighing less than nine kilograms along elevational gradients from the literature at local and regional scales. In total, fifty-nine sources were used to delimit 337 species incidence matrices from 104 study sites and six taxonomic groups. Small-mammal metacommunity structures were predominantly quasi-anti-nested and anti-nested, but could differ depending on taxonomic group. Elevational gradients were highly correlated with the latent environmental gradient, implying anti-nested small-mammal metacommunity structures were likely the result of species-specific responses to changes in the elevational gradient. Random metacommunity structures generally reflected disconnected metacommunity networks. Metacommunity networks treat species as nodes with connecting edges weighted by species co-occurrence at elevational bands. Metacommunity structure and additional nestedness metrics I calculated did not depend on maximum elevation, average annual mean temperature, average annual precipitation, or the number of species clusters in the network. Relativized nestedness was the only nestedness metric that increased as the species deletion ratio (a measure of network connectivity) increased, demonstrating highly nested metacommunities were also highly connected.