The Distributional Patterns of New World Nectar-Feeding Bats

Abstract

Whereas in the Eastern Hemisphere, all nectar-feeding bats are members of the suborder Megachiroptera, in the tropical and subtropical portions of the Western Hemisphere (in the absence of megachiropterans) certain members of one family (Phyllostomidae) of the generally insectivorous suborder Microchiroptera have become adapted to nectar feeding. These adaptations involve such diverse areas as skulls, teeth, tongues, throat muscles, and stomach linings. Considerable diversity in these characters may be seen within the New World nectar feeders, dependent in part on whether insects or pollen are the prime protein source. The distributions of all currently recognized recent species (35 in 16 genera) are mapped. Patterns are diverse but with a majority of the genera and many species being widespread on the tropical American mainland. Origin in either South or Middle America and ecological restriction will explain the distributions of some, but for many, causes are still obscure. Of the two currently recognized subfamilies of New World nectar-feeding bats the Brachyphyllinae are endemic to the West Indies and have obviously been there for a long time whereas the Glossophaginae probably originated in South America and have reached the West Indies much more recently. While bats were originally strictly insectivorous, many species, particularly in the tropics (where most kinds of bats live), have become adapted for obtaining a variety of food, including fish, terrestrial vertebrates, blood, fruit, and nectar. It is with the nectar-feeders that we will be especially concerned here. Because this radiation is chiefly a tropical phenomenon and since the New and Old World tropics have been separate at least since the beginning of the Miocene, it has proceeded independently in the two hemispheres. In the Eastern hemisphere, the fruit- and nectar-feeders (with the exception of one New Zealand genus) all belong to the suborder Megachiroptera, which combines primitive skull and post-cranial characters with teeth which are highly modified for handling fruit, nectar, and pollen. Some members of this suborder have tongues which are highly specialized for extraction of nectar from flowers. All the insectivorous and carnivorous species belong to another suborder, the Microchiroptera. The members of this group have a number of modifications of the skull and post-cranial skeleton related to the catching of anthropod or vertebrate prey, but their Old World representatives, in general, show little in the way of dental modification. In the New World tropics, there are no Megachiroptera and no evidence that they ever occurred. In their absence a number of species of one of the endemic Western Hemisphere Microchiropteran families, the Phyllostomidae, have become adapted to feeding on fruit and nectar. Other members of the family feed on insects, terrestrial vertebrates, and blood. In connection with their diversity