Data from: Climate change, extinction, and Sky Island biogeography in a montane lizard

Around the world, many species are confined to “Sky Islands,” with
different populations in isolated patches of montane habitat. How does
this pattern arise? One scenario is that montane species were widespread
in lowlands when climates were cooler, and were isolated by local
extinction caused by warming conditions. This scenario implies that many
montane species may be highly susceptible to anthropogenic warming. Here,
we test this scenario in a montane lizard (Sceloporus jarrovii) from the
Madrean Sky Islands of southeastern Arizona. We combined data from field
surveys, climate, population genomics, and physiology. Overall, our
results support the hypothesis that this species’ current distribution is
explained by local extinction caused by past climate change. However, our
results for this species differ from simple expectations in several ways:
(1) their absence at lower elevations is related to warm winter
temperatures, not hot summer temperatures; (2) they appear to exclude a
low-elevation congener from higher elevations, not the converse; (3) they
are apparently absent from many climatically suitable but low mountain
ranges, seemingly “pushed off the top” by climates even warmer than those
today; (4) despite the potential for dispersal among ranges during recent
glacial periods (~18,000 years ago), populations in different ranges
diverged ~4.5–0.5 million years ago and remained largely distinct; and (5)
body temperatures are inversely related to climatic temperatures among
sites. These results may have implications for many other Sky Island
systems. More broadly, we suggest that Sky Island species may be relevant
for predicting responses to future warming.