Cytogenetics is the science of chromosome structure, function, behavior, and pathology. Chromosome investigations scan, at a gross level, the entire genome of an organism. In the field of human medicine, the involvement of chromosomes in diseases and developmental disorders is widely recognized by biologists and clinicians. For example, Down syndrome, Klinefelter's syndrome, and Turner's syndrome are but a few disorders in humans that are caused by chromosomal abnormalities (Verma & Babu, 1995; Batch et al., 1997). These abnormalities generally are the result of either gain, loss, or rearrangement of entire chromosomes or portions thereof. Techniques to diagnose chromosomal disorders in fetuses during early pregnancy have led to rapid growth of clinical human cytogenetics, and today, there are more than 400 laboratories worldwide that specialize in identification of chromosomal abnormalities (Knutsen & Rebolloso, 1998). In contrast, we estimate that only a handful of labs actively apply cytogenetics to the health and conservation of wildlife. Here, we will take an opportunity to review the role of cytogenetics in wildlife onservation and management, using as examples the results of some of our recent

Cytogenetic analyses are most effectively applied to problems of hybridization and species identification, but they can also be appropriate for some questions involving gene evolution, population structure and variation, and phylogeny (Hillis et al., 1996). The importance of cytogenetics to veterinary medicine and wildlife conservation lies with detecting numerical and structural chromosomal variation between and within populations, identifying chromosomally abnormal individuals and assessing potential reproductive fitness of heterozygotes. Reproductive consequences of chromosomal heterozygosity and hybridization can be determined with analysis of chromosomal configurations during meiosis.

Matings between chromosomally-different individuals can compromise reproduction in heterozygous progeny by increasing their mortality or reducing their fertility. Thus, if different geographical populations are distinguished by chromosomal rearrangements, then management practices, such as wildlife translocation, captive breeding, and reintroduction, might be jeopardized if specimens from these different populations are brought together (Benirschke & Kumamoto, 1991; Robinson & Elder, 1993). Furthermore, chromosomal rearrangements may be involved with protection of coadapted gene complexes (Sites & Moritz, 1987); consequently, well-intentioned conservation efforts involving chromosomally-distinct animals might inadvertently disrupt natural processes of evolution and speciation. Our cytogenetic research is largely focused on the mammalian family Bovidae, particularly the antelopes of Africa and Asia. Chromosome diploid (2n) numbers in antelopes and other bovids vary from 2n = 30 to 2n 60. Most of this variation is due to the rearrangement of chromosome arms through centric fusions, which involves fusion of two single-armed (acrocentric) chromosomes to produce a bi-armed (metacentric) chromosome. The evolutionary result of centric fusion is a decrease in the diploid number from that of the ancestor. Theoretically, centric fissions could produce two acrocentric chromosomes from one metacentric chromosome, resulting in an increase of the diploid number, but centric fusions are believed the dominant form of chromosomal evolution in the Bovidae (Gallagher & Womack, 1992).

Several species of antelopes are polymorphic for centric fusions, but the effect of these chromosomal rearrangements on reproduction seems to vary. In male goitered gazelles (Gazella subgutturosa), there is no indication that heterozygosity for a single centric fusion has a negative effect on meiosis (Kingswood et al., 1994). However, perinatal mortality rates of ca. 50-60% in Soemmerring's gazelles (G. soemmerringii) and 47-71% in suni (Neotragus moschatus) may be due to the captive breeding of chromosomally incompatible individuals. The polymorphisms in captive populations of suni and Soemmerring's gazelles, respectively, are the result of two and three centric fusions (Benirschke et al., 1984; Kingswood etal., 1998a).

Chromosomal variation in these two species of antelopes may reflect differences between geographical populations. For example, the captive-born sum in our study that are descendants of animals wild-caught at Mount Kenya (N. m. akeleyi) have 2n = 52 chromosomes, and those that are descendants of suni wildcaught in Natal, South Africa (N. m. zuluensis) have 2n = 56 chromosomes. The notion that populations of suni are chromosomally distinct, in spite of their phenotypic uniformity, exemplifies the importance of cytogenetics in identifying "management units," that is, populations experiencing such low levels of gene flow so as to function independently (Moritz, 1994).