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Title: City limits: Heat tolerance is influenced by body size and hydration state in an urban ant community
Abstract

Cities are rapidly expanding, and global warming is intensified in urban environments due to the urban heat island effect. Therefore, urban animals may be particularly susceptible to warming associated with ongoing climate change. We used a comparative and manipulative approach to test three related hypotheses about the determinants of heat tolerance or critical thermal maximum (CTmax) in urban ants—specifically, that (a) body size, (b) hydration status, and (c) chosen microenvironments influenceCTmax. We further tested a fourth hypothesis that native species are particularly physiologically vulnerable in urban environments. We manipulated water access and determinedCTmaxfor 11 species common to cities in California's Central Valley that exhibit nearly 300‐fold variation in body size. There was a moderate phylogenetic signal influencingCTmax, and inter (but not intra) specific variation in body size influencedCTmaxwhere larger species had higherCTmax. The sensitivity of ants’CTmaxto water availability exhibited species‐specific thresholds where short‐term water limitation (8 hr) reducedCTmaxand body water content in some species while longer‐term water limitation (32 hr) was required to reduce these traits in other species. However,CTmaxwas not related to the temperatures chosen by ants during activity. Further, we found support for our fourth hypothesis becauseCTmaxand estimates of thermal safety margin in native species were more sensitive to water availability relative to non‐native species. In sum, we provide evidence of links between heat tolerance and water availability, which will become critically important in an increasingly warm, dry, and urbanized world that others have shown may be selecting for smaller (not larger) body size.

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NSF-PAR ID:
10458051
Author(s) / Creator(s):
 ;  
Publisher / Repository:
Wiley Blackwell (John Wiley & Sons)
Date Published:
Journal Name:
Ecology and Evolution
Volume:
10
Issue:
11
ISSN:
2045-7758
Page Range / eLocation ID:
p. 4944-4955
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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