Realized climatic niche of North American plant taxa lagged behind climate during the end of the Pleistocene

Abstract

Predicting species responses to climate change has become a dynamic field in global change research. A crucial question in this debate is whether-or-not species have been and will be able to respond quickly enough to keep up with changing climatic conditions. Focusing on fossil pollen records and paleoclimatic simulations, this work assesses the change in realized climatic niches (climatic temporal trajectories) of 20 plant taxa over the last 16000 yr, and whether this tracking has been the same for different climatic niche dimensions. Climatic factors showed a consistent trend toward warmer temperatures and higher precipitation. Although the response types varied across taxa, species' realized climatic niches lagged in response to changes in climatic conditions. Temperature niches responded to late Pleistocene (16000-11000 yr ago) climate change, but did so at slower rates than changes in climatic conditions during the same period. In contrast, precipitation niches were relatively stable from 16000 to 11000 yr ago, but still lagged behind changes in climatic conditions. Changes in temperature and precipitation niches eventually stabilized during the Holocene (11000-1000 yr ago). These results underscore how the climatic niche realized at any one moment represents a subset of the climate conditions in which a taxon can persist, particularly during times of fast climatic change. Variability in the rates of temporal trajectories across evaluated climatic variables showed taxa specific responses to changes in climatic conditions over time and emphasizes the need to incorporate variation, intensity, and duration of lag effects in assessments of the possible effects of climatic change.