Biology, life cycle, and environmental gradients of cool-adapted stag beetles: insights into Italian Platycerus species (Coleoptera: Lucanidae)

Saproxylic beetles play a key role in forest ecosystems, yet the ecology of many species, particularly cool-adapted taxa, remains poorly understood despite growing conservation concerns. In Europe, the genus Platycerus (Coleoptera: Lucanidae) inhabits temperate forests, but its ecological traits and responses to environmental change remain poorly understood, partly due to its elusive habits. This study investigates elevational and temporal patterns in the biology of Platycerus spp. in Italy, with a primary focus on larval and adult stages. A detailed description of the life cycle is provided for the first time, including evidence of occasional extra-year larval development. Morphometric analyses highlighted both interspecific differences in larval traits and intraspecific variation across environmental gradients, with parasitism incidence and adult flight activity also shifting along elevation. A preliminary analysis further indicated an earlier onset of adult activity in recent years, suggesting potential sensitivity to climate-related factors, though additional research is needed to confirm these patterns. Collectively, these findings improve the knowledge of Platycerus autecology and underscore the importance of integrating data on morphometry, life cycle, and ecology to assess the responses of these cool-adapted saproxylic beetles to environmental gradients and emerging climatic pressures.