Area, isolation, and climate explain the diversity of mammals on island worldwide

Identifying the determinants of insular biodiversity at large scales
remains a question in biogeography. We conducted a global test of island
biogeography theory by evaluating the importance of island physical,
environmental, and historical characteristics on mammal species richness
and endemism. We quantified the effects of island characteristics while
accommodating variation among biogeographic realms by fitting generalized
linear and mixed models. Analyzes were also performed separately for bats
and non-volant mammals. Diversity patterns were most consistently
influenced by the physical characteristics of the islands. Area positively
affected mammal diversity, in particular the number of non-volant
endemics. Island isolation, both current and past, was associated with
lower richness but greater endemism. Flight capacity modified the relative
importance of past versus current isolation, with bats responding more
strongly to current and non-volant mammals to past isolation.
Environmental effects on biodiversity were more variable, with a tendency
for greater effects on endemism than on richness. Unexpectedly, climate
change velocity was positively associated with endemism. In line with
island biogeography theory, we found that area and isolation were among
the strongest drivers of overall mammalian biodiversity. Moreover, our
results support the growing evidence on the importance of past conditions
on current patterns, particularly on non-volant species.