Many populations near receding low-latitude range: margins are declining in response to climate change, but most studies of trailing-edge populations have focused on single species. Using 10 years (2014–2023) of avian survey data from a high-elevation trailing-edge population hotspot in the Appalachian Mountains, USA, we tested the hypothesis that high-elevation communities would experience turnover through thermophilization, 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, peripheral populations decreased in abundance, and whereas 6 species exhibited little change. For warm-adapted populations near the core of their range, 1 of 16 decreased in abundance, 11 increased, and 4 exhibited no change. Within the most abundant species in this community, our results indicate that warm-adapted species are expanding their ranges faster than the rate at which ranges of cool-adapted species are contracting. Avoiding future community turnover may require conservation strategies that maintain microclimates for cool-adapted species facing novel abiotic and biotic conditions at high elevations.
LAY SUMMARY
Many populations of cool-adapted species at the edge of their geographic ranges are declining in response to climate change. At the same time, warm-adapted species are expanding their ranges as temperatures increase.
We tested the hypothesis that high-elevation communities would experience greater change in species composition than lower elevation communities, and become increasingly dominated by warm-adapted species.
Within the most abundant species in the community, several peripheral populations declined, whereas the majority of core populations increased or remained stable. The proportion of low elevation sites occupied by rear-edge populations also declined.
Our study suggests that abundant, warm-adapted species are expanding their ranges faster than the rate at which cool-adapted species are contracting. Forest managers should maintain closed canopy forests and dense understory vegetation on north facing slopes to conserve cool-adapted species near the southern edge of their breeding range.
Future research should determine if declines are the result of dispersal or decreasing fitness under changing climate conditions.
Muchas poblaciones cercanas a los márgenes de rango en retroceso en latitudes bajas están disminuyendo en respuesta al cambio climático, pero la mayoría de los estudios sobre poblaciones en el borde de salida se han centrado en especies individuales. Utilizando 10 años (2014-2023) de datos de censos de aves del borde de salida de un punto crítico poblacional en elevaciones altas en las montañas Apalaches, EEUU, evaluamos la hipótesis de que las comunidades de alta elevación experimentarían un cambio a través de la termofilización, ya que las especies adaptadas al calor cercanas al centro de sus rangos geográficos se expanden hacia regiones anteriormente dominadas por poblaciones periféricas de especies adaptadas al frío. Tres de las 9 poblaciones periféricas adaptadas al frío disminuyeron en abundancia, mientras que 6 especies mostraron pocos cambios. En el caso de las poblaciones adaptadas al calor cercanas al núcleo de su rango, 1 de 16 disminuyó en abundancia, 11 aumentaron y 4 no mostraron cambios. Entre las especies más abundantes en esta comunidad, nuestros resultados indican que las especies adaptadas al calor están expandiendo sus rangos más rápidamente que el ritmo al que se están contrayendo los rangos de las especies adaptadas al frío. Evitar un recambio comunitario futuro podría requerir estrategias de conservación que mantengan microclimas para las especies adaptadas al frío que enfrentan nuevas condiciones abióticas y bióticas en elevaciones altas.
