Find the Food First: An Omnivorous Sensory Morphotype Predates Biomechanical Specialization for Plant Based Diets in Phyllostomid Bats

The role of mechanical morphologies in the exploitation of novel niche
space is well characterized. However, the role of sensory structures in
unlocking new niches is less clear. Here we investigate the relationship
between the evolution of sensory structures and diet during the
diversification of noctilionoid bats. With a broad range of foraging
ecologies and a well-supported phylogeny, noctilionoids constitute an
ideal group for studying this relationship. We used diffusible
iodine-based contrast enhanced computed tomography (diceCT) scans of 44
noctilionoid species to analyze relationships between the relative volumes
of three sensory structures (olfactory bulbs, orbits, and cochleae) and
diet. We found a positive relationship between frugivory and both
olfactory and orbit size. However, we also found a negative relationship
between nectarivory and cochlea size. Ancestral state estimates suggest
that larger orbits and olfactory bulbs were present in the common ancestor
of family Phyllostomidae, but not in other noctilionoids. This
constellation of traits indicates a shift toward omnivory at the base of
Phyllostomidae, predating their radiation into an exceptionally broad
range of dietary niches. This is consistent with a scenario in which
changes in sensory systems associated with foraging and feeding set the
stage for subsequent morphological innovation and diversification.