Phylogeny influences the relationships linking key ecological thermal metrics for North American freshwater fish species

Habitat temperature is a major determinant of performance and activity in fish. We summarize published studies of 173 North American freshwater fish species to examine the interrelationships among thermal response metrics associated with three types of individual performance: growth (optimal growth temperature (OGT), final temperature preferendum (FTP)), survival (upper incipient lethal temperature (UILT), critical thermal maximum (CTMax)), and reproduction (optimum spawning temperature (OS), optimum egg development temperature (OE)). We found that all metrics were highly correlated, especially those associated with a specific performance type. Differences in thermal metrics were also significantly linked to traditional thermal guild classifications, spawning season, and strategy. We found an overall decline in correlation strength when we used phylogenetically independent contrasts to control for the effect of phylogeny. This decline was much greater for growth and survival metrics than for reproduction. This suggests that the role of evolutionary history in determining thermal sensitivity at the species level varies greatly across the range of performance types that can be used to characterize the behaviour of an individual.