Depth and temperature drive patterns of spatial overlap among fish thermal guilds in lakes across Ontario, Canada

Abstract

Aim: The spatial distribution of ectotherms is strongly dependent on the temperature of their environments. In temperate lakes, fishes with different thermal optima can become spatially segregated during summer stratification. This habitat partitioning, or niche complementarity, may play a role in the coexistence of trophically similar species; however, the extent of partitioning is dependent on the resources available within each habitat. Although habitat partitioning of fish thermal guilds has been studied in individual lakes, broad-scale patterns of spatial overlap and segregation are not yet understood. In this study, we explore the patterns and drivers of spatial overlap among thermal guilds (cold-, cool-, and warm-water) at a broad scale. Location: Ontario, Canada. Methods: We built a multivariate regression tree to explore patterns and environmental drivers of spatial overlap in freshwater fishes across three thermal guilds from 438 lakes. Results: We identified five clusters of lakes exhibiting different patterns of spatial overlap among the three thermal guilds. Temperature (growing degree days) and maximum lake depth were strong drivers of the spatial overlap patterns. Main Conclusions: These findings provide a better understanding of broad-scale patterns of spatial overlap and allow us to predict how spatial overlap, and ultimately species interactions and competition, may change under a warming climate.