Not all the giraffes are equal: Genetic diversification in the giraffe populations
All extant giraffes (Giraffa camelopardalis) are currently considered to represent a single specie, native of the African continent. Geographic variation in traits such as pelage pattern is clearly evident across the range in sub-Saharan Africa and abrupt transition zones between different pelage types are typically not associated with extrinsic barriers to gene flow, suggesting reproductive isolation.
In a research article published in 2007 in the open access journal BMC Biology, Brown et al. shown that despite a high capacity for dispersal, the giraffe exhibits extensive population genetic structure in both mitochondrial and nuclear DNA markers. Further, the results indicate that neighboring subspecies as well as those that are geographically separated are essentially reproductively isolated, suggesting that some might represent distinct species rather than a single polytypic form. Minimally, the seven lineages that are reciprocally monophyletic in the mtDNA tree need to be considered evolutionarily significant units if not species, even under the most conservative definition of the term, whereas the remaining populations should be considered independent genetic units, all needing separate population management.
Such extreme genetic subdivision within a large vertebrate with high dispersal capabilities is unprecedented and exceeds that of any other large African mammal. Those results have significant implications for giraffe conservation, and imply separate in situ and ex situ management, not only of pelage morphs, but also of local populations.
Photo: Giraffe at Borakalalo National Park, South Africa | ©Derek Keats
Graphic: Genetic subdivision in the giraffe based on mitochondrial DNA sequences | Brown et al. (2007)