Phylogeography, genetic diversity, and population structure of Nile crocodile populations at the fringes of the southern African distribution
Date
2018
Journal Title
Journal ISSN
Volume Title
Publisher
Public Library of Science
Abstract
Nile crocodiles are apex predators widely distributed in sub-Saharan Africa that have been
viewed and managed as a single species. A complex picture of broad and fine-scale phylogeographic
patterns that includes the recognition of two species (Crocodylus niloticus and
Crocodylus suchus), and the structuring of populations according to river basins has started
to emerge. However, previous studies surveyed a limited number of samples and geographical
regions, and large areas of the continent remained unstudied. This work aimed at a fine
scale portrait of Nile crocodile populations at the fringes of their geographic distribution in
southern Africa. Wild and captive individuals were sampled across four major river systems
(Okavango, Lower Kunene, Lower Shire and Limpopo) and the KwaZulu-Natal region. A
multi-marker approach was used to infer phylogeographic and genetic diversity patterns,
including new and public mitochondrial data, and a panel of 11 nuclear microsatellites. All
individuals belonged to a phylogenetic clade previously associated with the C. niloticus species,
thus suggesting the absence of C. suchus in southern Africa. The distribution of mitochondrial
haplotypes indicated ancestral genetic connectivity across large areas, with loss
of diversity along the north-south axis. Genetic variation partitioned the populations primarily
into western and eastern regions of southern Africa, and secondarily into the major river systems.
Populations were partitioned into five main groups corresponding to the Lower
Kunene, the Okavango, the Lower Shire, and the Limpopo rivers, and the KwaZulu-Natal
coastal region. All groups show evidence of recent bottlenecks and small effective population
sizes. Long-term genetic diversity is likely to be compromised, raising conservation concern.
These results emphasize the need for local genetic assessment of wild populations of
Nile crocodiles to inform strategies for management of the species in southern Africa.
Description
Van Asch, B., et al. 2018. Phylogeography, genetic diversity, and population structure of Nile crocodile populations at the fringes of the southern African distribution. PLoS ONE, 14(12):e0226505, doi:10.1371/journal.pone.0226505.
The original publication is available at https://journals.plos.org/plosone
Publication of this article was funded by the Stellenbosch University Open Access Fund.
The original publication is available at https://journals.plos.org/plosone
Publication of this article was funded by the Stellenbosch University Open Access Fund.
Keywords
Phylogeography, Nile crocodile -- Geographical distribution, Nile crocodile -- Conservation -- Africa, Southern, Nile crocodile -- Genome mapping -- Africa, Southern
Citation
Van Asch, B., et al. 2018. Phylogeography, genetic diversity, and population structure of Nile crocodile populations at the fringes of the southern African distribution. PLoS ONE, 14(12):e0226505, doi:10.1371/journal.pone.0226505