The ecological drivers of variation in pectoral girdle anatomy in frogs

In this ecomorphological study, we investigate how the ventral pectoral girdle morphology of anurans correlates with their locomotor modes, habitat preferences, and phylogenetic relationships. We analysed 18 morphometric variables of the pectoral girdle's ventral region across 19 anuran species, encompassing diverse locomotion modes (jumping, hopping, walking, and swimming) and habitats (arboreal, bushy, terrestrial, and aquatic). Our findings, predominantly explained by the Ornstein–Uhlenbeck model, reveal evolutionary adaptations in pectoral girdle morphology driven by habitat-specific demands. Notably, bushy and walker-jumper species exhibit large clavicles, coracoids, and sternums, along with a broad medial pectoral girdle and bigger epicoracoid. Terrestrial and arboreal- jumpers have a larger omosternum area compared to predominantly swimming species. Arboreal walkers show shorter epicoracoid horns and narrower coracoids. Interestingly, bushy and terrestrial species have a higher proportion of bone tissue in their pectoral girdles. This indicates a potential adaptation to support the additional to adaptation to participate in shock absorption. The patterns recovered underscore the intricate relationship between anatomical evolution and environmental adaptation in anurans.