Rapidly evolving repetitive DNAs in a conservative genome: A test of factors that affect chromosomal evolution

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Abstract
The hypothesis that tandemly repeated DNA sequences may facilitate chromosomal rearrangements was tested by comparing a conservatively evolving karyotype of a bat species (Macrotus waterhousii) with data published for a rapidly evolving karyotype of an equid species (Equus zebra). Empirical data generated from the phylogenetic screening of rapidly evolving repetitive DNAs from approximately 0.1% of theM. waterhousii genome showed only one sequence that was repetitive inM. waterhousii but low in copy number or absent from the outgroupArtibeus jamaicensis. This compares to 34 such clones containing sequences which were repetitive inE. zebra but were low in copy number or absent from the outgroupCeratotherium simum. The bat sequence represents a single family of repeated sequences, whereas six families of sequences were identified inE. zebra. Southern blot analysis suggested that the sequence fromM. waterhousii is interspersed rather than tandemly repeated, as are the sequences inE. zebra. These data support the above hypothesis and suggest that species with conservatively evolving karyotypes have fewer numbers and families of rapidly evolving DNA sequences than do species such as the equids that possess a karyotype that is considered to have undergone rapid karyotypic evolution.