Extreme temperatures can constrain foraging behavior, and individual differences in thermal tolerances may affect foraging performance within and among species. Ambient temperatures may thus mediate competitive interactions among species that share resources. Different species of desert seed-harvesting ants (genus Messor) forage for similar food resources, and colonies can overlap in foraging areas. Because Messor species differ in body size distributions, and thermal tolerance is often size related in ants, we hypothesized that body size differences within and between Messor species would predict individual variation in worker thermal tolerances. Body size effects on thermal physiology could have implications for interspecific competition. We measured tolerances of extreme high (maximum critical temperature or CTmax) and low temperatures (CTmin) in two Messor species simultaneously at the same study site, smaller bodied M. ebeninus and larger bodied M. arenarius. Although the species did not differ significantly in CTmin or CTmax, tolerance of high temperatures was significantly size dependent for M. ebeninus: worker tolerances of high temperatures decreased with body size in this species. The patterns suggest the foraging activity of the smallest workers of smaller bodied species could be more constrained by high ambient temperatures, which could impact the division of labor within colonies as well as interspecific interactions.

中文翻译：

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不同物种的工人体型对收获种子的沙漠蚂蚁（Messor ebeninus 和 M. arenarius）的临界热极限的影响不同

极端温度会限制觅食行为，热耐受性的个体差异可能会影响物种内部和物种之间的觅食性能。因此，环境温度可能会介导共享资源的物种之间的竞争性相互作用。不同种类的沙漠种子收获蚂蚁（Messor 属）觅食相似的食物资源，并且在觅食区域可以重叠群落。由于 Messor 物种的体型分布不同，并且热耐受性通常与蚂蚁的体型有关，我们假设 Messor 物种内部和之间的体型差异可以预测工人热耐受性的个体差异。体型对热生理的影响可能对种间竞争产生影响。我们在同一研究地点同时测量了两种 Messor 物种（体型较小的 M. ebeninus 和体型较大的 M. arenarius）对极高（最大临界温度或 CTmax）和低温 (CTmin) 的耐受性。尽管该物种在 CTmin 或 CTmax 方面没有显着差异，但 M. ebeninus 的高温耐受性显着依赖于体型：工人对高温的耐受性随着该物种体型的增大而降低。这些模式表明，体型较小的物种的最小工人的觅食活动可能更受高环境温度的限制，这可能会影响群体内的劳动分工以及种间相互作用。尽管该物种在 CTmin 或 CTmax 方面没有显着差异，但 M. ebeninus 的高温耐受性显着依赖于体型：工人对高温的耐受性随着该物种体型的增大而降低。这些模式表明，体型较小的物种的最小工人的觅食活动可能更受高环境温度的限制，这可能会影响群体内的劳动分工以及种间相互作用。尽管该物种在 CTmin 或 CTmax 方面没有显着差异，但 M. ebeninus 的高温耐受性显着依赖于体型：工人对高温的耐受性随着该物种体型的增大而降低。这些模式表明，体型较小的物种的最小工人的觅食活动可能更受高环境温度的限制，这可能会影响群体内的劳动分工以及种间相互作用。