Data from: The island-mainland species turnover relationship

Many oceanic islands are notable for their high endemism, suggesting that
islands may promote unique assembly processes. However, mainland
assemblages sometimes harbour comparable levels of endemism, suggesting
that island biotas may not be as unique as often assumed. Here, we test
the uniqueness of island biotic assembly by comparing the rate of species
turnover among islands and the mainland, after accounting for distance
decay and environmental gradients. We modeled species turnover as a
function of geographic and environmental distance for mainland (M-M)
communities of Anolis lizards and Terrarana frogs, two clades that have
diversified extensively on Caribbean islands and the mainland Neotropics.
We compared mainland-island (M–I) and island-island (I–I) species turnover
to predictions of the M–M model. If island assembly is not unique, then
the M–M model should successfully predict M–I and I–I turnover, given
geographic and environmental distance. We found that M–I turnover and, to
a lesser extent, I–I turnover were significantly higher than predicted for
both clades. Thus, in the first quantitative comparison of mainland–island
species turnover, we confirm the long-held but untested assumption that
island assemblages accumulate biodiversity differently than their mainland
counterparts.