Metabolic rates of a widely distributed crayfish shift along a latitudinal gradient

Species are often exposed to novel thermal regimes as a result of anthropogenic activities. Understanding the extent to which populations are locally adapted to the thermal regime may allow us to better predict the response of organisms to novel thermal conditions. We collected virile crayfish, Faxonius virilis, from eight populations along a latitudinal gradient and measured their routine metabolic rates (RMR) and thermal tolerance. Countergradient variation suggests that organisms from northern latitudes may spend more energy foraging as an adaptation to the shorter growing season. Thus, we hypothesized that crayfish RMR would be positively related to latitude. We also expected high latitude populations to have a greater sensitivity to acute temperature change and a lower thermal tolerance. In support of our hypothesis, there was a significant positive relationship between latitude and crayfish RMR at night when crayfish are most active, and crayfish from high latitude populations were more thermally sensitive. Thus, changes in the thermal regime are likely to alter the activity level of this species, which could alter its ecological impacts. In addition, virile crayfish across the latitudinal gradient had a high thermal tolerance, which may contribute to the success of this species in novel environments.

Automated summary

This study examined the metabolic rate and thermal tolerance of virile crayfish along a latitudinal gradient. The results showed a positive relationship between latitude and crayfish metabolic rate, and high latitude populations were more thermally sensitive. These findings reveal the thermal adaptation differences among different populations.