Fewer than 11,000 individuals of all five species survive in small scattered populations throughout Africa, India, and Southeast Asia. The black rhino (Diceros bicornis), the focus of this study, has suffered the most dramatic decline, disappearing faster than any other large mammal. The species once occupied most of sub-Saharan Africa and numbered in the hundreds of thousands (Fig. 1). Even by the turn of the century, large, nearly contiguous populations of black rhino were spread across much of central, eastern, and southern Africa. However, by 1970 their numbers had declined to 65,000 and over the past 18 years poaching has reduced this number by 95%. The remaining 3,800 animals are split into some 75 populations, only ten of which have more than 50 animals (Western & Vigne 1985; Du Toit et al. 1987; Wildlife Conservation International News 1988).
These findings for the black rhino stand in sharp contrast to the level and distribution of mtDNA differences reported for the white rhino. The southern white rhino, Ceratotberium simum simum, has recovered quite well from a population bottleneck that occurred at the turn of the century, and now more than 3,000 members of this population can be found in South Africa and other African countries (Penny 1988). The status of the northern white rhino, Ceratotberium simum cottoni, is much bleaker, with only 22 individuals known to exist in the wild (Western 1987). Management plans originally proposed supplementing the northern race with members from the southern population. Based on a survey of one individual from each of the two races, however, George et al. (1983) reported a very high level of mtDNA divergence (approximately 4.0% ). Partially as a result of this study, managers decided against inter- breeding the two races. Unlike the black rhino, the white rhino subspecies have existed in nonoverlapping ranges, at least during historical times. George et al suggest, on the basis of their molecular data, that the two white rhino subspecies have been isolated from each other for at least two million years. However, recent research on variability of nuclear-coded allozymes found little differentiation between the northern and southern subspecies (Merenlender et al. 1989), suggesting a more recent isolation.
These findings for the black rhino stand in sharp contrast to the level and distribution of mtDNA differences reported for the white rhino. The southern white rhino, Ceratotberium simum simum, has recovered quite well from a population bottleneck that occurred at the turn of the century, and now more than 3,000 members of this population can be found in South Africa and other African countries (Penny 1988). The status of the northern white rhino, Ceratotberium simum cottoni, is much bleaker, with only 22 individuals known to exist in the wild (Western 1987). Management plans originally proposed supplementing the northern race with members from the southern population. Based on a survey of one individual from each of the two races, however, George et al. (1983) reported a very high level of mtDNA divergence (approximately 4.0% ). Partially as a result of this study, managers decided against inter- breeding the two races. Unlike the black rhino, the white rhino subspecies have existed in nonoverlapping ranges, at least during historical times. George et al suggest, on the basis of their molecular data, that the two white rhino subspecies have been isolated from each other for at least two million years. However, recent research on variability of nuclear-coded allozymes found little differentiation between the northern and southern subspecies (Merenlender et al. 1989), suggesting a more recent isolation.
Differences in Ceratotherium simum. These findings for the black rhino stand in sharp contrast to the level and distribution of mtDNA differences reported for the white rhino. The southern white rhino, Ceratotberium simum simum, has recovered quite well from a population bottleneck that occurred at the turn of the century, and now more than 3,000 members of this population can be found in South Africa and other African countries (Penny 1988). The status of the northern white rhino, Ceratotberium simum cottoni, is much bleaker, with only 22 individuals known to exist in the wild (Western 1987). Management plans originally proposed supplementing the northern race with members from the southern population. Based on a survey of one individual from each of the two races, however, George et al. (1983) reported a very high level of mtDNA divergence (approximately 4.0% ). Partially as a result of this study, managers decided against interbreeding the two races. Unlike the black rhino, the white rhino subspecies have existed in nonoverlapping ranges, at least during historical times. George et al suggest, on the basis of their molecular data, that the two white rhino subspecies have been isolated from each other for at least two million years. However, recent research on variability of nuclear-coded allozymes found little differentiation between the northern and southern subspecies (Merenlender et al. 1989), suggesting a more recent isolation.
The shortage of manpower and resources within national conservation departments across Africa is a primary factor in the decline of the rhino (Leader-Williams & Albon 1988). Consolidating groups is an easier and less expensive way to re-establish former densities. The idea of creating more sanctuaries, which are effectively ?species parks,' has received widespread interest following the increase in Kenya's rhino populations in such sanctuaries. However, management strategies such as this are complicated by the fact that each remaining population has been assigned to one of several subspecies, based upon aspects of external morphology such as horn shape and body size. The genetic and evolutionary relationships of these morphologically defined subspecies are unknown.
