Mammalian Cytogenetics and Conservation of Species

Charter

et al. 2000

G- and C-banded karyotypes of four species of the genus Kobus were compared using the standard karyotype of Bos taurus. Chromosomal complements were 2n = 50–54 in K. ellipsiprymnus, 2n = 50 in K. kob, 2n = 48 in K. leche, and 2n = 52 in K. megaceros. The number of autosomal arms in all karyotypes was 58. Fifteen autosomal pairs were conserved among these four species, including the 1;19 and 2;25 centric fusions, and autosomal differences involved eight centric fusion rearrangements. Five centric fusions were each unique to a particular taxon: 3;10 (K. leche), 3;11 and 6;29 (K. kob), and 5;17 and 7;11 (K. ellipsiprymnus). The 4;7 fusion occurred in K. leche and K. megaceros, whereas the 5;13 fusion occurred in K. kob and K. leche; the 6;18 fusion was found in three species but was absent in K. kob. Differences between the X chromosomes of the four Kobus species were attributed to heterochromatic additions or deletions, and Y-chromosome differences may have been the result of pericentric inversion. G-banded karyotypes of putative K. l. leche and K. l. kafuensis appeared identical, as did C-banded karyotypes of the two subspecies. Karyotypes of K. e. ellipsiprymnus and K. e. defassa differed as a result of the 6;18 centric fusion, which was polymorphic in K. e. defassa, and the 7;11 centric fusion, which was polymorphic in K. e. ellipsiprymnus but absent in K. e. defassa. Several centric fusions were related by monobrachial chain-IV complexes; however, records of hybridization indicate that reproductive isolation between at least certain species of Kobus is incomplete. Karyotypic differences between K. ellipsiprymnus (including K. e. ellipsiprymnus and K. e. defassa), K. kob, K. leche, and K. megaceros support the validity of these taxa, as well as the need to manage them as separate populations.

Section: Discussionsupporting

confidence: 92%

supporting

confidence: 68%

Chromosomes of the antelope genus Kobus (Artiodactyla, Bovidae): karyotypic divergence by centric fusion rearrangements

Charter

et al. 2000

“…Reproduction can be compromised by increased mortality or reduced fertility in heterozygous progeny produced by matings between individuals from chromosomally distinct populations (Benirschke and Kumamoto, 1991;Robinson and Elder, 1993). Furthermore, chromosome rearrangements may play a role in protecting co-adapted gene complexes (White, 1978;Sites and Moritz, 1987); thus, well-intentioned conservation efforts involving animals from cytogenetically different populations might inadvertently disrupt natural processes of evolution and speciation.…”

Section: Resultsmentioning

confidence: 99%

Comparative cytogenetics of tapirs, genus Tapirus (Perissodactyla, Tapiridae)

Houck

2000

Chromosomes of the four species of Tapirus were 2n = 52 in T. indicus, 2n = 76 in T. pinchaque, 2n = 80 in T. bairdii, and 2n = 80 in T. terrestris. The number of autosomal arms was 80–94. G-banded karyotypes indicated that a heterochromatic addition/deletion distinguished chromosomes 2 and 3 of T. bairdii and T. pinchaque, respectively. There were at least 13 conserved autosomes between the karyotypes of T. bairdii and T. terrestris, and at least 15 were conserved between T. bairdii and T. pinchaque. In G- and C-banded preparations, the X chromosomes of T. bairdii, T. indicus, and T. terrestris were identical, whereas the X chromosome of T. pinchaque differed from the X of the other species by a heterochromatic addition/deletion. The Y chromosome was a medium-sized to small acrocentric in T. bairdii, T. indicus, and T. pinchaque, but it was not positively identified in T. terrestris. There appeared to be fewer homologies between T. indicus and the three species occurring in Central and South America. Future cytogenetic studies of tapirs from the entire range of each of the four species might provide additional insight into their evolutionary biology and aid wildlife conservation efforts aimed at these threatened mammals.

“…These heterozygotes may be the result of hybridization in captivity between individuals representing chromosomally different wild populations (Benirschke et al, 1984;Kingswood et al, 1998). Cases such as these demonstrate the importance of cytogenetics in wildlife management and conservation, a notion advanced by Benirschke and Kumamoto (1991) and Robinson and Elder (1993).…”

Section: A B C Discussionmentioning

confidence: 99%

Centric fusion differences among Oryx dammah, O. gazella, and O. leucoryx (Artiodactyla, Bovidae)

Charter

et al. 1999

G- and C-banded karyotypes of the genus Oryx were compared using the standard karyotype of Bos taurus. Chromosomal complements were 2n = 56 in O. gazella gazella, 2n = 58 in O. g. beisa and O. g. callotis, 2n = 56–58 in O. dammah, and 2n = 57–58 in O. leucoryx. The number of autosomal arms in all karyotypes was 58. Nearly all variation in diploid number was the result of three 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 dammah was polymorphic for a 2;15 centric fusion, and O. leucoryx was polymorphic for an 18;19 centric fusion. The five Oryx taxa shared a fixed 1;25 centric 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 five taxa. Oryx g. gazella differed from the other Oryx species because of the 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 relationships among the Oryx taxa indicates that sterility barriers between species have not developed. Viability of hybrid offspring constitutes a threat to captive breeding programs designed for endangered species conservation; 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 taxa.