Abstract
Identifying the mechanisms underlying the changes in the distribution of species is critical to accurately predict how species have responded and will respond to climate change. Here, we take advantage of a late‐1950s study on ant assemblages in a canyon near Boulder, Colorado, USA, to understand how and why species distributions have changed over a 60‐year period. Community composition changed over 60 years with increasing compositional similarity among ant assemblages. Community composition differed significantly between the periods, with aspect and tree cover influencing composition. Species that foraged in broader temperature ranges became more widespread over the 60‐year period. Our work highlights that shifts in community composition and biotic homogenization can occur even in undisturbed areas without strong habitat degradation. We also show the power of pairing historical and contemporary data and encourage more mechanistic studies to predict species changes under climate change.