At. Kumamoto et al., Centric fusion differences among Oryx dammah, O-gazella, and O-leucoryx (Artiodactyla, Bovidae), CYTOG C GEN, 86(1), 1999, pp. 74-80
G- and C-banded karyotypes of the genus Oryx were compared using the standa
rd karyotype of Bos taurus. Chromosomal complements were 2n = 56 in O. gaze
lla gazella, 2n = 58 in O. g. beisa and O. g. callotis, 2n = 56-58 in O. da
mmah, and 2n = 57-58 in O. leucoryx. The number of autosomal arms in all ka
ryotypes was 58. Nearly all variation in diploid number was the result of t
hree independent centric fusions, but one 2n = 57 specimen of O. g. gazella
deviated from the normal complement of 2n = 56 due to XXY aneuploidy. A 2;
17 centric fusion was fixed in O. g. gazella, whereas O. g, beisa and O. g.
callotis lacked this fusion and had indistinguishable karyotypes. Oryx dam
mah was polymorphic for a 2;15 centric fusion, and O. leucoryx was polymorp
hic for an 18;19 centric fusion. The five Oryx taxa shared a fixed 1;25 cen
tric fusion; the small acrocentric element involved in the 1;25 fusion was
identified by fluorescence in situ hybridization using a cosmid specific to
Bos chromosome 25. The X and Y chromosomes were also conserved among the f
ive taxa. Oryx g. gazella differed from the other Oryx species because of t
he fixed 2;17 centric fusion. This difference reflects an apparently longer
period of geographic isolation between O. g. gazella and other populations
of Oryx, and it is consistent with the classification of O. gazella and O.
beisa as distinct species (see Kingdon, 1997). The lack of monobrachial re
lationships among the Oryx taxa indicates that sterility barriers between s
pecies have not developed. Viability of hybrid offspring constitutes a thre
at to captive breeding programs designed for endangered species. conservati
on; in the case of Oryx, the 2;15, 2;17, and 18;19 metacentrics could serve
as marker chromosomes for assessing hybridization between certain Oryx tax
a.