Vertical and temporal niche partitioning in Amazonian butterflies: implications for the evolution of thermal tolerance

Abstract

Closely related species living in sympatry are often partitioned into divergent ecological niches. Such specialization can be enabled by the evolution of divergent traits enhancing adaptation to different niches. In this study, we investigate the partitioning of closely related butterfly species into different forest strata and daily activity time and test the effects of such spatio-temporal niches on the evolution of thermal traits. First, using experiments in the field in Amazonia, we precisely characterized the daily activity patterns of nine species of Morpho butterflies, therefore documenting extensive temporal segregation among species and observing significant variations in temperature between their respective niches. Using controlled experiments in the lab, we then tested the thermal tolerance of wild individuals to both hot and cold conditions. The vertical distribution of species (understory versus canopy micro-habitats) had a significant effect on several thermal traits, even when controlling for the phylogenetic distances between species, suggesting that forest stratification may have shaped thermal adaptation in these tropical butterflies. However, butterfly activity time did not correlate with any thermal traits measured. The extensive temporal segregation observed between these sympatric species might thus stem from ecological interactions observed between species rather than thermal factors.