CHROMOSOMAL EVOLUTION IN RHOGEESSA (CHIROPTERA: VESPERTILIONIDAE): POSSIBLE SPECIATION BY CENTRIC FUSIONS

Within the Rhogeessa tumida-parvula complex, there are seven cytotypes involving diploid numbers of 30, 32, 34, 42, 44, and 52. Based on G-band analysis, the 30, 32, 34, and 44 forms differ from each other by centric fusions (13 different fusions were identified). Two 2n = 32 samples (one from Belize and one from Nicaragua) having essentially identical standard karyotypes differed from each other by eight fusion events. Cytotypes are allozymically distinct; however, other studies indicate that the cytotypes are morphologically very similar if not indistinguishable (LaVal, 1973; Baker, 1984). G-band chromosomal data are best interpreted as indicating that, within this complex, several species exist which should be maintained by a post-mating isolating mechanism resulting from meiotic problems in F₁ individuals. Mus musculus (Capanna et al., 1977; Capanna, 1982; White, 1978) and the Rhogeessa tumida-parvula complex are unusual among mammalian species thus far studied in their pattern of chromosomal variation and presumptive mode of speciation. Strong evidence exists suggesting that in both groups populations differing by multiple centric fusions are biological species. It appears that the population and reproductive biology of Mus and Rhogeessa are quite different and any model that attempts to explain the mode of speciation in these two diverse taxa, must be compatible with their different biological characteristics.