Earlier this year, the last remaining male northern white rhinoceros died in captivity, nearly cementing the fate of this subspecies for extinction. In the wild, continuing threats of poaching, habitat destruction, and small population size have contributed to the rhino's status as Critically Endangered. Yet, novel conservation efforts that make use of cryopreserved genetic material could save the northern white rhino--and other threatened species--from extinction.
In a study published today in the journal Genome Research, researchers investigated the genetic history of nine northern white rhino (NWR) cryopreserved cell lines compared to that of a closely related subspecies, the southern white rhino (SWR). Genome analyses demonstrated that the NWR and SWR represent two distinct populations that diverged nearly 80,000 years ago, each with fairly high genetic variation compared to other threatened species. Importantly, genetic analyses of variation and inbreeding facilitated identification of cell lines, which may serve as valuable pools of genetic material for genetic rescue. Lead author Tate Tunstall, of the San Diego Zoo Institute for Conservation Research, emphasized the importance of this finding, stating "the SWR went through a severe genetic bottleneck, but is now the most populous of all forms of rhino at ~20,000 individuals, suggesting that a genetic rescue utilizing these cell lines could be the foundation for a similar recovery in the NWR."
This work presents the first genome sequence of the NWR and thus the current, albeit limited, gene pool of this species. Tunstall and colleagues propose that this knowledge can help guide a tailored recovery program for the NWR.
"Our study demonstrates the emerging role for whole genome sequencing analysis to evaluate the potential for population recovery," said Cynthia C. Steiner, who directed the study. Furthermore, advanced sequencing technologies, cryopreservation efforts like that of the San Diego Zoo Frozen Zoo, as well as novel reproductive strategies can be developed to improve recovery efforts for other species that face similar threats of extinction.
Researchers from the San Diego Zoo Institute for Conservation Research; Veterinary College, University of London; Dv?r Králové Zoo; and the University of California, Santa Cruz contributed to this work. The study was funded by grants from the Seaver Institute and the Caesar Kleberg Foundation for Wildlife Conservation.