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Within the neotropical bat family Phyllostomidae, species of the subfamilies Glossophaginae and Lonchophyllinae have many derived traits adapted to nectarivory, including elongated snouts and jaws and the ability to perform hovering flight. We compared patterns of cranial variation within and between these groups with respect to within-group allometric trajectories, based on 19 linear morphometric variables collected from 221 specimens representing all genera and 62% of the species in the two subfamilies. In a pooled principal component analysis, species belonging to Lonchophyllinae and Glossophaginae occupy similar regions in morphospace, though the latter species have a greater variance. Principal components and common principal components analyses for separate taxonomic lineages (subfamilies, tribes and subtribes) revealed distinct static allometric trajectories among these groups, with variables associated with elongation of the rostrum having distinct allometric coefficients. Our results indicate that distinct cranial morphotypes associated with the degree of elongation of the rostrum in phyllostomid nectarivores are allometrically characteristic of each lineage. The patterns suggest that cranial integration in phyllostomid nectarivores reflects primarily their phylogenetic history rather than adaptive pressures resulting from specialization to particular feeding resources.
Size-standardized craniometric variation was investigated among species of the genus Artibeus. Eleven extant and one extinct species were examined using geometric and linear morphometric analyses to evaluate morphological differences among species. Based on 19 landmarks located in the ventral side of the cranium, 29 size-standardized linear measurements were calculated and used for statistical multivariate analyses. Discriminant Function Analysis showed major interspecific differences in shape between A. anthonyi and A. concolor with respect to the remaining extant species of Artibeus. These two species are described as morphologically unique morphotypes with a broader rostrum, enlarged squamosal region, and wider basicranium. Specifically, a broader premaxilla is the character that better discriminates A. anthonyi from all other species, whereas a broader squamosal region (particularly the deep mandibular fossa, and elongated squamosal) and wider braincase are the main characters differentiating A. concolor. All other species of the genus overlap to varying extents in their morphology showing high shape similarities. The least variant shape features include the pterygoid fossa, the glenoid (mandibular) fossa, the maxillae, and the occipital region; these regions in all cases contribute to mechanical aspects of jaw function and bite. The fact that the least variant aspects of skull shape all involve feeding is consistent with the hypothesis that selection has favored a specific diet-associated morphology rather than divergence or character displacement in Artibeus.
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