Forelimb Bone Morphology and its Association with Foraging Ecology in Four Families of Neotropical Bats

Abstract

The form-function paradigm postulates the existence of a correlation between form and function; a remarkable example of this is the transformation of the forelimb of bats into wings. The wings of bats are complex structures made of membranes, muscles, tendons, cartilages, bones, and joints. Forelimb bones are critical elements of wings because they form an essential part of the alar mass, serve to support soft tissue, and resist deformations. Only a few studies have attempted to detect relationships between morphology and ecology of the forelimb bones in bats in an assemblage context. Here, we explored ecomorphological patterns of 180 specimens belonging to 22 genera and 37 species of four families, occurring in northern Argentina. We quantitatively characterized bones and analyzed their relation with wing shape, as described by aerodynamic parameters, and ecological habits in a phylogenetic context. For the analyses, we used eight ecological categories, five wing variables that included three aerodynamic indexes, 29 linear measurements of the bones (humerus, radius, and scapula), and lengths of digits III and V. As expected, specimens distribution in morphospace showed that species tend to be segregated on the basis of size and morphology. Interestingly, Molossidae and Lasiurini occupy nearby areas in the morphospace, which can reveal patterns of functional convergences between them. A significant correlation between wing shape and morphology of forelimb bones was detected, showing a link between the latter and aerodynamic variables. We observed a remarkable morphological variation in the structures of the proximal and distal ends of the humerus, the proximal end of the radius, and in the acromion of the scapula. Our results highlight that these variations reflect the degrees of specialization in different modes of flight and ecological habits. We also observed that phylogeny explained in part the morphological patterns and shows a strong covariation with ecological habits, finding different phylogenetic patterns among the main lineages (Molossidae, Vespertilionidae, and Phyllostomidae).