The Phenotypic Landscape of Phloeosinus baumanni: Spatial Patterns of Morphological Variation and Their Implications for Ecology and Taxonomy

Morphological characters are widely used for species delimitation in Scolytinae, yet their stability under intraspecific variation remains poorly understood. Here, we analyzed phenotypic variation in specimens currently assigned to Phloeosinus baumanni across its distribution in Mexico to evaluate the effects of sexual dimorphism and locality on morphological traits. A total of 25 characters were examined using univariate and multivariate analyses. Pronounced sexual dimorphism was detected, with significant differences in more than half of the evaluated traits and a clear separation between sexes in multivariate space, particularly in body size, cephalic proportions, and elytral declivity features. Locality-associated variation was also detected, particularly within the better-sampled localities of the Transmexican Volcanic Belt. However, localities showed broad overlap in morphospace, with no consistent clustering across biogeographic provinces. Several traits commonly used for species delimitation exhibited substantial variation associated with both sex and geography. These results indicate sex- and locality-associated phenotypic variation among specimens currently assigned to P. baumanni and highlight the risk of taxonomic overestimation when variable morphological traits are overemphasized. Incorporating intraspecific variability into taxonomic frameworks is essential to improve species delimitation in Scolytinae.