Abstract
BackgroundGenetic and ecological factors influence morphology, and morphology is compatible with function. The morphology and bite performance of skulls of bats show a number of characteristic feeding adaptations. The great evening bat, Ia io (Thomas, 1902), eats both insects and birds (Thabah et al. J Mammal 88: 728-735, 2007), and as such, it is considered to represent a case of dietary niche expansion from insects to birds. How the skull morphology or bite force in I. io are related to the expanded diet (that is, birds) remains unknown. We used three-dimensional (3D) geometry of the skulls and measurements of bite force and diets from I. io and 13 other species of sympatric or closely related bat species to investigate the characteristics and the correlation of skull morphology and bite force to diets.ResultsSignificant differences in skull morphology and bite force among species and diets were observed in this study. Similar to the carnivorous bats, bird-eaters (I. io) differed significantly from insectivorous bats; I. io had a larger skull size, taller crania, wider zygomatic arches, shorter but robust mandibles, and larger bite force than the insectivores. The skull morphology of bats was significantly associated with bite force whether controlling for phylogeny or not, but no significant correlations were found between diets and the skulls, or between diets and residual bite force, after controlling for phylogeny.ConclusionsThese results indicated that skull morphology was independent of diet, and phylogeny had a greater impact on skull morphology than diet in these species. The changes in skull size and morphology have led to variation in bite force, and finally different bat species feeding on different foods. In conclusion, I. io has a larger skull size, robust mandibles, shortened dentitions, longer coronoid processes, expanded angular processes, low condyles, and taller cranial sagittal crests, and wider zygomatic arches that provide this species with mechanical advantages; their greater bite force may help them use larger and hard-bodied birds as a dietary component.
Highlights
Genetic and ecological factors influence morphology, and morphology is compatible with function
Such interspecific differences existed in cranial morphology. (i) Dorsal cranium: the first four Principal component (PC) explained 69.81% of the total variance (PC1 = 41.41%, PC2 = 12.89%, PC3 = 8.55%, PC4 = 6.96%)
Ia io and its related species were located on the positive end of the PC axis; the skulls of these species possess shortened heads and rostras, high sagittal crests, and convex supraoccipital bones (Fig. 1c; Fig. S1c, Additional file 1). (iii) Ventral cranium: the first four PCs explained 78.13% of the total variation (PC1 = 51.87%, PC2 = 11.35%, PC3 = 7.76%, PC4 = 7.15%)
Summary
Genetic and ecological factors influence morphology, and morphology is compatible with function. Evolutionary history, and ecology (e.g., biological interactions with environmental variables) though (2020) 17:8 have evolved morphological characteristics related to their diets. These morphological differences are partly reflected in bone structure and body size [13]. The variation in skull morphology in various bat species are related to feeding ecology in bats [19, 20], different food types are matched by the morphological and functional cranial specializations [21], and skull characteristics can be used to predict phylogenetic relationships [22], food composition, and feeding niche breadth. Bite force is the basis of numerous types of functional demands of vertebrates (e.g., feeding, mating, defense, and competition) and is closely related to body size and skull morphology [20, 23, 24]. Increased bite force can broaden the spectrum of available prey [7], and the difference in bite force among various taxa is linked to skull shape divergence and a variety of ecological challenges, such as food acquisition, mating, and predator avoidance [25,26,27,28]
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