Diet and the evolution of digestion and renal function in phyllostomid bats

Bat species in the monophyletic family Phyllostomidae feed on blood, insect s, small vertebrates, nectar, fruit and complex omnivorous mixtures. We use d nitrogen stable isotope ratios to characterize bat diets and adopted a ph ylogenetically informed approach to investigate the physiological changes t hat accompany evolutionary diet changes in phyllostomids. We found that nit rogen stable isotopes separated plant-eating from animal-eating species. Th e blood of the latter was enriched in N-15. A recent phylogenetic hypothesi s suggests that with the possible exception of carnivory, which may have ev olved twice, all diets evolved only once from insectivory. The shift from i nsectivory to nectarivory and frugivory was accompanied by increased intest inal sucrase and maltase activity, decreased trehalase activity, and reduce d relative medullary thickness of kidneys. The shift from insectivory to sa nguinivory and carnivory resulted in reduced trehalase activity. Vampire ba ts are the only known vertebrates that do not exhibit intestinal maltase ac tivity. We argue that these physiological changes are adaptive responses to evolutionary diet shifts.