There is debate whether the northern white rhino should be considered a separate species, rather than a subspecies, of the white rhinoceros.
Based on morphological and genetic differences, estimated time since divergence from a common ancestor and phylogenetic species concepts, Colin Groves and co-workers have argued that the northern white rhino, (NWR,) should now be considered a separate species.
There are a number of alternative ways to classify species and there has not been universal agreement on this issue. Groves has been criticized on a number of grounds and his recommendation has not been universally accepted. A detailed rebuttal of Groves’ proposal is also being prepared by a rhino geneticist, thus it is premature to come to a final conclusion on the issue at this time.
It’s also been argued that, given conservation objectives, the issue of whether or not northern white rhino should be treated as a species or subspecies is for practical purposes somewhat academic given: 1. the high degree of relatedness of the three remaining NWRs at Ol Pejeta (calculated Founder Genome Equivalent of only 1.71); 2. the fact that any pure-bred offspring from remaining animals would be inbred; 3. the need to maximize reproductive output from all these NWR animals, (only one of which is young,) to try to retain as many adaptive NWR genes as possible by minimizing loss of genetic diversity through genetic drift; and 4. constraints to reproductive output given that the male is old and there are only two females.
There can be no guarantee that a final attempt to conserve adaptive NWR genes will succeed. Inter-crossing may end up not being successful and, in due course, this would provide some support to Groves’ proposal that the NWR should be classed as a separate species.
• Image | © Josh More, Some Rights Reserved (CC BY-NC-ND 2.0)
• Sources | (Groves, Fernando, & Robovsky, 2010; Emslie, 2012)
