Heat tolerance in tropical Lepidoptera varies with microclimate, life stage, and larval feeding strategy

Understanding heat tolerance variation and its drivers is crucial for
predicting climate change impacts on biodiversity. While most studies
focus on adults and macroclimate effects on heat tolerance, how
microclimate shapes heat tolerance variation across life stages and
feeding strategies remain largely untested. We quantified heat tolerance
(Critical Thermal Maximum: CTmax) variation in 35 species of moth larvae
(caterpillars) within a seasonal tropical forest. For 17 species we were
also able to measure the CTmax of adults. We tested how seasonal
macroclimate and life stage-specific microclimate drove CTmax variation
across life stages, and how feeding strategy-specific microclimate drove
CTmax variation in caterpillars. We found strong seasonal effects, with
caterpillars and adults exhibiting higher CTmax in the hot season.
Caterpillars exhibited higher CTmax than conspecific adults in the cool
season, but this pattern was reversed in the hot season. Shelter-building
caterpillars experiencing cooler microclimates exhibited lower CTmax than
free-living caterpillars. Our study highlights the complex drivers of heat
tolerance and the importance of microclimate in shaping heat tolerance
variation across life stages and feeding strategies.