CHROMOSOMAL EVOLUTION IN DUIKER ANTELOPE (CEPHALOPHINAE, BOVIDAE) - KARYOTYPE COMPARISONS, FLUORESCENCE IN-SITU HYBRIDIZATION, AND RAMPANT X-CHROMOSOME VARIATION

Fluorescence in situ hybridization (FISH) and conventional banding tec hniques were used to identify patterns of similarity among the genomes of six species of antelope, subfamily Cephalophinae. The G-banded euc hromatic portions of the autosomes were invariable in all species; how ever, significant modifications of the X chromosomes were detected. Tw o of the taxa, Cephalophus maxwellii and C. monticola, were characteri zed by acrocentric X's, while X chromosome morphology varied from subm etacentric to metacentric in the remaining species (C. dorsalis, C. na talensis, Sylvicapra grimmia, and C. silvicultor). The short arm of th e X was heterochromatic in each species. Total genomic DNAs from these antelope were used as hybridization probes against Cephalophus metaph ase chromosomes and resulted in robust fluorescence in the pericentrom eric region of each autosome and in the heterochromatic short arm of t he X chromosome, indicating complimentarity of DNA sequences in these regions. Conversely, chromosome painting involving genomic DNAs derive d from the subfamilies Alcelaphinae (Pygargus dorcas) and Neotraginae (Oreotragus oreotragus) showed a marked absence of hybridization at th ese sites. Additionally, X chromosome comparisons between the Cephalop hinae and Bovinae (represented by Bos taurus) revealed two euchromatic pericentric inversions which had occurred since their common ancestry . There is good G-band homoeology between the inverted cattle chromoso me region Xq12 --> q34 and most of the proximal portion of Xq in duike rs, as well as between the distal third of the duiker Xq and the cattl e Xp. The latter rearrangement was further confirmed by in situ hybrid ization using a probe containing an insert spanning bands p12 to p14 o f the cattle X chromosome.