Arboreality drives heat tolerance while elevation drives cold tolerance in tropical rainforest ants

Lily Leahy, Brett R. Scheffers, Stephen E. Williams, Alan N. Andersen

Research output: Contribution to journalArticlepeer-review

20 Citations (Scopus)


Determining how species thermal limits correlate with climate is important for understanding biogeographic patterns and assessing vulnerability to climate change. Such analyses need to consider thermal gradients at multiple spatial scales. Here we relate thermal traits of rainforest ants to microclimate conditions from ground to canopy (microgeographic scale) along an elevation gradient (mesogeographic scale) and calculate warming tolerance to assess climate change vulnerability in the Australian Wet Tropics Bioregion. We test the thermal adaptation and thermal niche asymmetry hypotheses to explain interspecific patterns of thermal tolerance at these two spatial scales. We tested cold tolerance (CTmin), heat tolerance (CTmax), and calculated thermal tolerance range (CTrange), using ramping assays for 74 colonies of 40 ant species collected from terrestrial and arboreal habitats at lowland and upland elevation sites and recorded microclimatic conditions for one year. Within sites, arboreal ants were exposed to hotter microclimates and on average had a 4.2°C (95% CI: 2.7–5.6°C) higher CTmax and 5.3°C (95% CI: 3.5–7°C) broader CTrange than ground-dwelling ants. This pattern was consistent across the elevation gradient, whether it be the hotter lowlands or the cooler uplands. Across elevation, upland ants could tolerate significantly colder temperatures than lowland ants, whereas the change in CTmax was less pronounced, and CTrange did not change over elevation. Differential exposure to microclimates, due to localized niche preferences, drives divergence in CTmax, while environmental temperatures along the elevation gradient drive divergence in CTmin. Our results suggest that both processes of thermal adaptation and thermal niche asymmetry are at play, depending on the spatial scale of observation, and we discuss potential mechanisms underlying these patterns. Despite the broad thermal tolerance range of arboreal rainforest ants, lowland arboreal ants had the lowest warming tolerance and may be most vulnerable to climate change.

Original languageEnglish
Article numbere03549
Pages (from-to)1-11
Number of pages11
Issue number1
Early online dateOct 2021
Publication statusPublished - Jan 2022

Bibliographical note

Funding Information:
We thank the Jabalbina Yalanji Aboriginal Corporation and acknowledge the traditional owners of the Eastern Kuku Yalanji and Western Yalanji on whose lands this work was conducted. We thank two anonymous reviewers for their insight and comments. We thank our funders: The Explorer's Club, Wet Tropics Management Authority, Skyrail Rainforest Foundation, Holsworth Wildlife Research Endowment – Equity Trustees Charitable Foundation. LL is supported by a PhD scholarship from the Australian Government. Field research conducted under Permit WITK15811415 issued by the Queensland Government of Australia. Statement of authorship: the study was conceived by LL, BRS, SEW and ANA; LL collected all data; ANA identified ant species and managed the TERC ant collection; LL conducted all analyses and wrote the first draft of the manuscript; all authors contributed critically to subsequent drafts and gave final approval for publication.

Publisher Copyright:
© 2021 by the Ecological Society of America

Copyright 2021 Elsevier B.V., All rights reserved.


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