Thermophilization: Concepts, Methods, and Implications of Changes in Community Composition due to Global Warming.

With global warming, many species will shift their geographic ranges coldward (i.e., towards higher latitudes and elevations) to remain within suitable thermal conditions. At the community level, these range shifts result in "thermophilization"-the increasing relative abundance of warm-adapted ("thermophilic") species and the concomitant decrease of cold-adapted species over time. Quantifying rates of thermophilization provides a powerful approach to assessing responses to rising temperatures at the community level, particularly in high-diversity systems where the detailed spatial data needed to calculate species-level responses to warming for thousands of individual species are often unavailable. This review synthesizes our current understanding of thermophilization across terrestrial, marine, and aquatic systems. We detail the most common methods used to quantify thermophilization, primarily through the calculation of the Community Temperature Index (CTI, °C), which aggregates species' thermal affiliations into a single community-level metric that can then be tracked through time to calculate an annualized thermophilization rate (TR, °C year