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Ear­lier this year, the last remain­ing male North­ern White Rhi­noc­eros (NWR) 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 rhi­nos’ sta­tus as crit­i­cally endan­gered. Yet, novel con­ser­va­tion efforts that make use of cry­op­re­served genetic mate­r­ial could save the NWR, and other threat­ened species, from extinction.

In a study pub­lished on 24 May in the jour­nal Genome Research, researchers inves­ti­gated the genetic his­tory of nine 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 diverge 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.”

Cyn­thia C. Steiner, co-​author, San Diego Zoo Insti­tute for Con­ser­va­tion Research, Cal­i­for­nia, USA.

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 pro­gramme for the NWR. 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 the NWR and other species that face sim­i­lar threats of extinc­tion. Recent efforts to this end are promis­ing. The first preg­nant SWR from arti­fi­cial insem­i­na­tion has been reported by the San Diego Zoo Insti­tute for Con­ser­va­tion Research, and it is hoped that sur­ro­gate SWR moth­ers may some­day give birth to NWR progeny.

(Source: Cold Spring Har­bor Lab­o­ra­tory Press news release, 24.05.2018)