A Sympatric Cryptic Species of Mammal: A New Species of Rhogeessa (Chiroptera: Vespertilionidae)

Abstract

A new species of bat from the genus Rhogeessa is described, which would not have been recognized as distinct if the karyotypes had not been available. The discovery of this species clearly documents that it is possible for two sympatric species of mammals to be so similar in external and cranial morphology that without chromosomal, genic, or some other data, a researcher would never realize a local sample contained more than a single biological species. (Cryptic species; karyotypes; morphometrics; Vespertilionidae; Rhogeessa.) In examinations involving defense of theses and dissertations, I have often heard the question asked, How do you know the sample of animals that you studied was not composed of two morphologically cryptic species? The question is a critical one, because the implications of data col- lected in many studies could be quite dif- ferent if more than a single species were included in a sample. However, I am not aware of an example from the class Mam- malia in which two sympatric species can- not be distinguished by classical methods utilizing morphology. The following de- scription of a new species is from a sample containing two species that would not have been recognized as distinct from each other if chromosomal data had not been available. This example serves as a warn- ing that two cryptic species of mammals may exist sympatrically, yet be indistin- guishable by classical methods of identi- fying congeneric taxa. In the course of chromosomal studies on New World bats, it has become apparent, for the reasons listed below, that there is an undescribed species in the tumida-par- vula complex of the genus Rhogeessa. The purpose of this paper is to describe this species and to point out the implication of its discovery.