Extinctions, genetic erosion and conservation options for the black rhinoceros (Diceros bicornis)

Abstract

The black rhinoceros is again on the verge of extinction due to unsustainable poaching in its native range. Despite a wide historic distribution, the black rhinoceros was traditionally thought of as depauperate in genetic variation, and with very little known about its evolutionary history. This knowledge gap has hampered conservation efforts because hunting has dramatically reduced the species’ once continuous distribution, leaving five surviving gene pools of unknown genetic affinity. Here we examined the range-wide genetic structure of historic and modern populations using the largest and most geographically representative sample of black rhinoceroses ever assembled. Using both mitochondrial and nuclear datasets, we described a staggering loss of 69% of the species’ mitochondrial genetic variation, including the most ancestral lineages that are now absent from modern populations. Genetically unique populations in countries such as Nigeria, Cameroon, Chad, Eritrea, Ethiopia, Somalia, Mozambique, Malawi and Angola no longer exist. We found that the historic range of the West African subspecies (D. b. longipes), declared extinct in 2011, extends into southern Kenya, where a handful of individuals survive in the Masai Mara. We also identify conservation units that will help maintain evolutionary potential. Our results suggest a complete re-evaluation of current conservation management paradigms for the black rhinoceros.

Mitochondrial DNA Phylogenetics of Black Rhinoceros in Kenya in relation to Southern Africa Population

“…In this study, phylogenetic analysis of these populations using mtDNA D-loop region (Figure 1) shows that the two populations fall into two different clades that have further separated into monophyla clusters over time. This is concurrent with previous observations that the D. b. michaeli and D. b. minor populations become distinct genetically [27,29,30]. However, the phylogenetic tree branch lengths of two clades of black rhinoceros are closely linked and are distantly related to white rhinoceros, C. s. simum, and Sumatran rhinoceros, D. s. harrissoni [16], indicating that the Eastern Africa and Southern Africa black rhinoceros separation is recent.…”

“…The Tanzanian D. b. michaeli cluster has admixtures populations with lineages from Kenya likely at the geographic areas separated by national boundary but also has lineages close to southern black rhinoceros. The voucher specimen, AF187834 (Figure 1), was born in Cincinnati zoo, Ohio, USA, from a Kenya lineage [31] while D. b. rovumae voucher is now extinct but has closely related lineages in the southern black rhinoceros that can be used in genetic supplementation [27,31] Inbreeding depression versus outbreeding depression are concerns in management policies of rhinoceros populations in sanctuaries [32,33]. The current sanctuaries hold fragmented pockets of rhinoceros after near demise in the 1970s due to anthropologic issues but mainly poaching.…”

“…Black rhinoceros became critically endangered species in the 1970s mainly due to poaching and historical game hunting during colonial era and also due to expansion of agricultural land in Africa [25][26][27], prompting implementation of remedial conservation strategies to intensively manage the remaining population within high security sanctuaries [5,9]. These management fragments started with low numbers of founding population with periodical translocation between the sanctuaries managed in coordination with local government wild life services [7,28].…”

Museum specimens as Noah’s Arc of lost genes. The case of a rhinoceros from Sumatra in the Zoological Museum Hamburg

“…The importance of museum samples for the understanding of historic distribution ranges and the loss of genetic diversity is also highlighted in recent studies on the genetic diversity of the African black rhinoceros (Kotzé et al 2014;Moodley et al 2017) that examined the rangewide genetic structure of historic and modern populations of the species using both mitochondrial and nuclear datasets. Moodley et al (2017) described a staggering loss of 69% of the mitochondrial genetic variation on the basis of recently collected material and historic samples of the black rhinoceros during the 20 th century, including the most ancestral lineages that are now absent from modern populations.…”

“…Moodley et al (2017) described a staggering loss of 69% of the mitochondrial genetic variation on the basis of recently collected material and historic samples of the black rhinoceros during the 20 th century, including the most ancestral lineages that are now absent from modern populations.…”