Thermal Tolerance and Species Distributions: Interactions Between Latitude, Elevation and Arboreality in Ants

Abstract

Aim

Global warming has highlighted the importance of understanding the role of thermal tolerance as a driver of species distributions, especially for ectotherms. Here we analyse interactions between latitude, elevation and arboreality as predictors of geographic patterns of thermal tolerance in ants.

Location

The collected data are distributed globally.

Methods

We first tested the effect of latitude, elevation and its interactive effect on ant CT_max and CT_min. Second, we tested whether CT_max and CT_min are phylogenetic clustering. Finally, we tested whether CT_max and CT_min can be explained by nesting microhabitat (ground vs. tree-nesting species) and whether the probability of occurrence of tree-nesting species along thermal gradients helps explain the global pattern in ant CT_max.

Results

CT_max and CT_min displayed high and low phylogenetic signals respectively and therefore showed different responses to geographic gradients. Notably, we found that CT_max was higher in higher latitudes. This was explained by a lack of elevational turnover at high latitudes among tree-nesting species, which are exposed to warmer microclimates and have higher CT_max compared with ground-nesting species. CT_min decreased with elevation at low latitudes, but did not vary with elevation at higher latitudes.

Main Conclusions

Our findings highlight the important influence of arboreality on the macroecology of thermal tolerance, substantially modifying traditional notions of variation along latitudinal and elevation gradients.