Sex-Specific and Trait-Dependent Phenotypic Plasticity in Carabus granulatus (Coleoptera, Carabidae) Along Macroclimatic Gradients

In the context of global climate change, understanding how bioclimatic factors influence organism morphology is paramount. Ground beetles of the genus Carabus serve as key bioindicators due to their high sensitivity to shifting climatic conditions. This study aims to identify variation patterns in the morphometric traits of Carabus granulatus (Linnaeus, 1758) (Coleoptera, Carabidae) under diverse climatic factors. The research was conducted on a sample of 10,172 individuals (3926 females and 6246 males of C. granulatus) collected from 71 sampling sites across 14 European regions and one Asian region of the Palearctic. Six morphometric parameters were examined: elytra length and width, pronotum length and width, head length, and interocular distance. The analysis incorporated 19 bioclimatic variables spanning the period 1970–2000. The proportion of explained variation differed across morphometric traits, with climatic factors showing the highest explanatory power for elytra length (R2 = 33%). Climate variations influence beetle morphology in complex, sex-specific ways. Elevated temperatures correlate with increased body size, whereas higher climate seasonality has a negative impact. Furthermore, increased precipitation shrinks the abdomen but expands the pronotum, while head size links to climate-driven local biotopes. Because distinct body parts respond heterogeneously to environmental drivers, predictive models and ecosystem health assessments must adopt a comprehensive approach accounting for individual sex.