Multifaceted Biodiversity Patterns and Influencing Factors of <i>Lucanus</i> Stag Beetles (Coleoptera, Lucanidae) in China

As keystone decomposers in forest ecosystems, stag beetles occupy unique ecological niches within forest carbon and nitrogen cycles. While previous studies have predominantly focused on taxonomic inventories of this group, we present a multidimensional assessment integrating taxonomic, phylogenetic, and functional diversity patterns across the model genus <i>Lucanus</i> of stag beetles in China. Using random forest analyses, we identify key environmental factors influencing these biodiversity dimensions-contemporary climate factors, habitat heterogeneity, and paleoclimatic fluctuations. Our results show that maximum species richness and phylogenetic diversity (Faith's PD) emerge in southwest mountain ranges (Hengduan and Gaoligong Mountains), primarily regulated by annual temperature range constrictions. This region also retains older lineages and shows phylogenetic dispersion, while South China and Taiwan exhibit more recent differentiation and phylogenetic aggregation, primarily influenced by precipitation and temperature anomalies. Functional richness and functional dispersion are higher in the southeastern region, whereas the southwest displays greater functional evenness and functional divergence, reflecting stronger environmental filtering. Functional diversity indicators are mainly driven by precipitation. These multidimensional diversity patterns exhibit geographical decoupling, with mountain ecosystems consistently serving as biodiversity arks. Our findings establish an integrative framework for insect conservation in Asian forest ecosystems, emphasizing the need for topography-sensitive management strategies.