Secondary sexual traits and lineage diversification in the giant blister beetle Berberomeloe insignis (Coleoptera: Meloidae)

Abstract The evolutionary dynamics of morphological traits can often blur the boundaries between interspecific divergence and intraspecific variability, complicating species recognition. This study investigates the variation in secondary sexual traits and the existence of potential speciation processes within what is now considered Berberomeloe insignis (Coleoptera: Meloidae), an endangered blister beetle taxon endemic to southeastern Spain. Despite previous evidence of substantial genetic and phenotypic differentiation, key characters as the morphological variation in secondary sexual traits, such as antennomeres, remain unexplored. Using geometric morphometrics, we analyzed the shape variation of male and female antennomeres VII–XI across all previously recognized lineages of B. insignis . Our results reveal significant morphological differentiation, particularly in antennomeres VII, IX, and XI, which correlate broadly with genetic lineages. Based on the study of newly recorded populations, we confirm that cephalic coloration patterns correspond with mitochondrial lineages, further supporting the existence of geographic lineage differentiation within what was previously considered B. insignis . Climatic niche modeling indicates low climatic niche overlap between the isolated western lineage and the remaining lineages, which also show relatively low to moderate overlap, suggesting that ecological factors could have contributed to the divergence among them. These findings underscore the intricate interplay of genetics and ecology, highlighting the importance of integrating multiple data sources for accurate species delimitation. Based on our results, we describe B. nazari sp. nov . and B. insignis trisanguinatus ssp. nov . reflecting the evolutionary history of this group.