Intraspecific and geographical variation of G <i>lossophaga commissarisi</i> in Mexico: morphological approach

Abstract Cryptic species represent a major challenge in biodiversity research due to their subtle and poorly defined morphological boundaries. This study investigates morphological variation within Glossophaga commissarisi, focusing on the differentiation between its two recognised subspecies, G. c. commissarisi and G. c. hespera, and evaluating the influence of biogeographic provinces, latitude, altitude, and sex. We applied geometric morphometrics (GM) to cranial structures and linear morphometric analysis (LM) to cranial and wing traits to assess patterns of variation. Significant shape differences were detected between subspecies, particularly in the fronto-maxillary region, independent of size, while the mandible showed size-dependent variation. Additionally, geographical factors, specifically elevation, latitude, and biogeographic province, emerged as key drivers of morphological divergence. Sexual dimorphism was evident in mandible and wing structures, with females displaying distinct mandibular and wing traits, potentially linked to reproductive and ecological roles. In G. c. hespera, geographic variation is noted in fronto-maxillary elevation; and by biogeographic provinces in ventral differentiation, with higher-altitude specimens differing from those of lowland populations in the Northern Pacific region. Similarly, G. c. commissarisi shows latitudinal variation, with Chiapas populations (16°N) distinct from those at 15°N and 17°N. These findings suggest that morphological differentiation in G. commissarisi may be better understood through biogeographic and ecological perspectives, complementing traditional morphological analyses. However, genetic and ecological data remain critical for clarifying taxonomic boundaries and evolutionary processes within these cryptic taxa. Limited sample availability due to the rarity of this species underscores the need for broader regional sampling in future research.