Systematics and zoogeography of the bats of Paraguay

Taxonomic status and distribution of species of Paraguayan Chiroptera are reported. Examination of 4674 specimens and literature records documented the presence of six families and 54 species of bats. Platyrrhinus dorsalis. P. helleri. and Myotis levis also have been reported, but records are doubtful or based on misidentified specimens. Carollia brevicauda and Artibeus obscurus may occur also, but assignment remains tentative. Taxonomic issues remain to be resolved on species of Artibeus. Eptesicus. and Myotis. Status of populations of Eumops bonariensis and E. patagonicus also requires clarification. Geographic variation patterns previously described were evident in the samples examined. Molossids and vespertilionids from arid environments tend to be lighter in color and smaller than those from more humid areas. There is no sharp limit to these differences, but a northwest-to-southeast continuum.

Paraguay occurs at the interface of major South American biomes, in an area of low topographic relief and relatively low climatic variation. In the absence of marked geographic barriers, bat distributions in Paraguay are likely to be the result of environmental factors. Using Canonical Correspondence Analysis, two hypotheses were tested: (1) bat assemblages in Paraguay are random combinations of species that occur in the area; and (2) if they are not, then they are strongly associated with environmental factors, particularly vegetation. Additionally, vegetation effects were removed and residual patterns of bat associations were examined. A strong, significant relationship between composition of bat assemblages and vegetation features was found. Plant associations and bat assemblages formed three distinct groups (Dry Chaco, Floodable Lands, and Eastern Paraguay), corresponding to major characteristics of vegetation, geology, and soils. Frugivorous bats are restricted to the Eastern Region and sporadically occur in Floodable Lands. Most insectivorous and omnivorous species occur throughout the country; however, maximum abundance within each genus indicate a partial segregation of species to one of the three regions, and where congeneric species' maxima coincide, species differ considerably in size. This pattern and that of residual species variation suggest that interspecific relationships in addition to environmental factors determine the current composition of Paraguayan bat fauna.