Larval diet type and voltinism are linked with adult body size in European Erebidae (Lepidoptera)

Abstract Body size is one of the most characteristic traits of every animal species and strongly influences its ecological niche. Identifying life-history traits that are associated with body size and investigating possible causalities behind such contingencies is thus a central topic in evolutionary ecology. In this study, we examined whether adult body size in Lepidoptera relates with resource type used at larval stage, larval dietary specialisation, voltinism, or adult diel activity. Based on previous findings, we hypothesised that species associated with woody plants are overall larger than those feeding on herbaceous plants or alternative food sources (e.g., lichens, detritus etc.). We further hypothesised that larger body sizes are associated with a lower degree of dietary specialisation, a univoltine life style, and nocturnal activity in adults. To test our hypotheses, we focussed on more than 220 species of European Erebidae moths, one of the taxonomically and ecologically most diverse Lepidoptera families worldwide. Increasing availability of molecular data for this group, coupled with advances in phylogenetic comparative methods, allowed us to study these trait relationships by accounting for shared evolutionary history among species, and– in addition to that– investigate potential causalities driving the detected patterns. We found adult body size to be positively linked with woody plant feeding and a univoltine life cycle, supporting the respective hypothesis. Our results further indicated that resource type affects the evolution of body size, while the latter strongly determines voltinism. Contrary to expectation, body size was neither related with larval dietary specialisation nor with adult diel activity. In conclusion, our study suggests that smaller body sizes, frequently associated with feeding on herbaceous plants or alternative food sources, are of evolutionary advantage as they facilitate the realisation of multiple generations per year and thus allow for faster adaptations to changing environmental conditions.