Local-scale temperature gradients driven by human disturbance shape the physiological and morphological traits of dung beetle communities in a Bornean oil palm–forest mosaic

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Abstract

1. Temperature change is an often-assumed, but rarely tested, mechanism by which sensitive species may decline in forest landscapes following habitat degradation, fragmentation and destruction.
2. Traits mediate how species respond to environmental change, with physiological, morphological and behavioural traits key to determining the response of ectotherms to temperature.
3. We collected data on traits linked to thermal sensitivity (critical thermal maxima, body size, cuticle lightness and pilosity) for 46 dung beetle species (Scarabaeinae) in a forest–oil palm mosaic in Malaysian Borneo. By combining these data with a large-scale community sampling campaign (>59,000 individuals sampled from >600 traps) and an airborne Light Detection and Ranging-derived thermal map, we investigated how traits mediate species- and community-level responses to temperature.
4. Using hierarchical models, we found that critical thermal maxima predicted how species respond to maximum temperatures. These results were mirrored in community-level analyses alongside similar patterns in other thermal traits. Increased body size and decreased pilosity were associated with higher temperatures, while cuticle lightness showed a complex relationship with temperature across the disturbance gradient.
5. Our findings highlight the potential mechanisms by whichforest specialists decline in human-modified landscapes, resulting in changes to community patterns and processes.