Is spider resting metabolic rate more strongly associated with ecological guild or extreme habitat conditions?

Ectotherms with lower maintenance costs and broader environmental tolerances are generally more resilient in human-altered landscapes and under current climate change, enhancing their chances of survival and colonization. In this study, we explored how habitat use and foraging strategy are associated with the resting metabolic rate (RMR) of spiders from habitats with significant temperature variability due to anthropogenic disturbance: native forests and young pine plantations, both in the Southern Atlantic Forest. Using open-flow respirometry at 25°C, we measured CO₂ production in immobile spiders to calculate their RMR. Key findings include: (1) all spiders showed 22%-57% lower RMR than predicted by standard metabolic equations; (2) continuous gas exchange patterns, typical of mesic-adapted species, were observed in all cases; (3) the metabolic rate scaling exponent was 0.65; (4) there were no significant RMR differences between habitats, but a negative correlation between RMR and microhabitat thermal amplitude was noted; and (5) active foragers had higher RMRs than passive foragers. These findings enhance our understanding of spider biology, physiology, and ecology, particularly in their responses to anthropogenic stressors.