Chromosomal Variation and Evolutionary Relationships of Vespertilionid Bats

Abstract

Intergeneric evolutionary relationships were studied in vespertilionid bats using G- and C-band data. In most cases, chromosomal variation can be explained by Robertsonian changes, centric fusions being by far the most numerous. There appear to be three karyotypic, evolutionary trends among vespertilionids. The first is to remain karyotypically primitive by retaining a high diploid number with many acrocentric chromosomes. The second is to become karyotypically specialized by a process of centric fusion leading to lower diploid numbers with many biarmed chromosomes. The third is to reduce greatly the diploid number by centric fusions and translocations. The latter is seen only in Lasionycteris (2n = 20), which evolved from an ancestor with a karyotype like that of Myotis (2n = 44). A phylogenetic sequence is proposed based on banding patterns. A Myotis -like group including Myotis, Pipistrellus, Lasiurus, Plecotus, Idionycteris , and Lasionycteris evolved from an ancestor with the Myotis karyotype. An Eptesicus -like group including Eptesicus, Rhogeessa, Antrozous , and Nycticeius evolved from an ancestor with a karyotype like that of Eptesicus. Miniopterus represents a karyological intermediate between the two groups. The ancestral karyotype for the family is hypothesized to have been similar to that of Myotis .