Warm-adapted encroachment outpaces cool-adapted retreat in a hotspot of
trailing-edge population diversity
Abstract
Many populations near low-latitude range margins are declining in
response to climate change, but most studies of trailing-edge
populations have focused on single species. Using ten years (2014–2023)
of avian survey data from a trailing-edge population hotspot in the
Appalachian Mountains, USA, we tested the hypothesis that high-elevation
communities would experience turnover through thermophilisation, as
warm-adapted species near the center of their geographic ranges expand
into regions formerly dominated by peripheral populations of
cool-adapted species. Three of the nine cool-adapted populations
decreased in abundance whereas six species exhibited little change. For
warm-adapted populations, one of 16 decreased in abundance, 11
increased, and four exhibited no change. Our results indicate that
warm-adapted species are expanding their ranges faster than the rate at
which ranges of cool-adapted species are contracting, suggesting that
community turnover will lag behind encroachment by warm-adapted species.