GENETIC INTERACTIONS BETWEEN HYBRIDIZING CYTOTYPES OF THE TENT-MAKING BAT (URODERMA BILOBATUM).

Abstract

The vast majority of described hybrid zones between cytotypes (conspecific populations which differ karyotypically) are narrow and generally involve organisms of restricted vagility. Theories regarding the evolutionary genesis and fate of such zones most often have been hypothesized to be a direct function of low vagility and its effects upon population parameters. Recent investigations (Baker et al., 1972; Baker et al., 1975; Baker, 1979, 1981), describe an extensive zone of intergradation between hybridizing cytotypes of the tent-making bat, Uroderma bilobatum (Phyllostomatidae: Stenoderminae). Uroderma bilobatum convexum (2n = 38) and U. b. davisi (2n = 44) come into contact along the coast of the Golfo de Fonseca in Honduras and karyotypic intermediates range from west central Guatamala to northwestern Nicaragua. A culmination of the chromosomal data available for these cytotypes is presented in the companion paper to this manuscript (Baker, 1981). Gand C-band data (Baker, 1979) reveal the uniqueness of the individual chromosomal differences between the two parental races which enable relatively unambiguous identification of hybrids and backcross individuals. Baker (1981) characterized the nature of contact between parental types, distribution of hybrids and backcrosses within the zone, and success of each of the individual rearrangements in populations dominated by other cytotype. He concluded that negative heterosis against hybrids and backcrosses is not severe and that limited hybridization supplemented by backcrossing and dispersal produce long lasting chromosomal polymorphism over a broad zone. The present study was designed to use electrophoretic techniques to determine the population genetic characteristics of U. b. davisi and U. b. convexum and the nature of genetic interaction across the broad contact zone between them.