Seasonality, worker caste, and the interaction between island area and habitat type influence the thermal tolerance of ants on fragmented habitat islands

Abstract

Habitat fragmentation is a major cause of biodiversity loss. Fragmentation can alter thermal conditions on the remaining patches, especially at habitat edges, but few studies have examined variations in thermal tolerance of species in fragmented habitats. Ants are sensitive to both habitat fragmentation and temperature changes, and are an ideal taxon for studying these impacts. Here, we focused on the dimorphic ant species Pheidole nodus in a fragmented habitat island system (Thousand island lake) in China. We assessed critical thermal maximum (CTmax), minimum (CTmin), and range (CTrange) temperatures for both minor (workers) and major workers (soldiers) of 2307 individuals from 117 edge and interior colonies across 9 islands during relatively hot and cold seasons. Using mixed-effect linear models, we explored the effects of island area, habitat type (edge vs. interior), season, and caste (worker vs. soldier) on CTmax, CTmin, and CTrange. We found temperatures were 1–3 °C higher in edge than interior sites in relatively hot season. Yet, only CTmax and CTrange in edge populations were higher than those of interior sites on smaller islands. CTmax was higher in relatively hot season and CTmin was lower in relatively cold season, indicating seasonal plasticity in thermal tolerance. Workers consistently had higher CTmax and lower CTmin than soldiers. These findings underscore the importance of seasonality, worker caste, and interactive effect between island area and habitat type in shaping thermal tolerance of a dominant dimorphic ant species on fragmented habitat islands. Our study provides a roadmap for integrating thermal biology into studies of how fragmentation impacts biodiversity.

Special Topic: Ecology & Environmental Biology.

The online version contains supplementary material available at https://doi.org/10.1007/s42995-025-00288-8.

Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.

Keywords

Cold tolerance / Habitat fragmentation / Heat tolerance / Intraspecific variation / Pheidole nodus / Thousand island lake

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