Thermal Tolerance of Honeybees (Apis mellifera L.) Changes Across an Elevation Gradient in the Mexican Transition Zone

Abstract

The objective of this study was to determine the critical thermal minimum [CTmin], critical thermal maximum [CTmax], and thermal tolerance range of A. mellifera at three different elevations located in the Mexican Transition Zone: 11; 1,324, and 3,304 m.a.s.l. In general, we found that the CTmin of A. mellifera was lower at the site with the highest elevation (i.e., they tolerate colder temperatures). At the same time, the CTmax remained constant across the three studied elevations, revealing higher plasticity for cold tolerance rather than heat. Moreover, we did not find evidence that the body mass of the individuals was associated with their thermal tolerance at any of the three sampled elevations. Our findings suggest processes of local adaptation of A. mellifera populations in environmentally contrasting sites, allowing them to expand their range of distribution, which could be useful in predicting responses to future environmental change.