Chromosomal Homology and Evolution of Phyllostomatoid Bats

G- and C-banding analyses were used to determine chromosome homology from representatives of bat families Mormoopidae, Noctilionidae and Phyllostomatidae, subfamily Phyllostomatinae. The karyotype of Macrotus waterhousii 2n = 46, FN = 60 is proposed as primitive for the Phyllostomatoidea. The major strategy involved in karyotypic evolution of taxa analyzed appears to have been reduction of the number of autosomal linkage groups by Robertsonian fusion from the 22 of Macrotus waterhousii to near 15 for the majority of taxa. Chromosome arms were found to be highly conserved. The X chromosomes of all taxa did not vary and were similar to the pattern thought to be characteristic of the primitive X of mammals. Two systematic groups appear recognizable within the Phyllostomatoidea above the family level (Phyllostomatidae in one group and the Noctilionidae and Mormoopidae in the other), whereas three systematic groups are discernible within the Phyllostomatinae. The three groups within the Phyllostomatinae include Macrotus waterhousii in the Macrotus-group, Tonatia minuta, Mimon crenulatum, Phyllostomus discolor and P. hastatus in the Tonatia–Mimon–Phyllostomus-group, and Micronycteris nicefori, M. brachyotis, and M. minuta in the Micronycteris-group. Tonatia bidens and Micronycteris megalotis were karyotypically so divergent that based solely on chromosomal data they could not be placed with any grouping. Examples are shown where extensive chromosomal evolution has been accompanied by little morphological evolution and where extensive morphological evolution has been accompanied by little chromosomal evolution. Such examples are the basis for questioning the hypothesis that chromosomal changes altering the position of regulator genes are a primary mechanism in the evolution of the large magnitude of morphological differentiation in the class Mammalia.