Open Access Highly Accessed Research article

Extensive population genetic structure in the giraffe

David M Brown1, Rick A Brenneman2, Klaus-Peter Koepfli1, John P Pollinger1, Borja Milá1, Nicholas J Georgiadis3, Edward E Louis2, Gregory F Grether1, David K Jacobs1 and Robert K Wayne1*

Author Affiliations

1 Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA, 90095, USA

2 Center for Conservation and Research, Omaha's Henry Doorly Zoo, 3701 South 10th Street, Omaha, NE 68107, USA

3 Mpala Research Centre, PO Box 555, Nanyuki, Kenya

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BMC Biology 2007, 5:57  doi:10.1186/1741-7007-5-57

Published: 21 December 2007

Abstract

Background

A central question in the evolutionary diversification of large, widespread, mobile mammals is how substantial differentiation can arise, particularly in the absence of topographic or habitat barriers to dispersal. All extant giraffes (Giraffa camelopardalis) are currently considered to represent a single species classified into multiple subspecies. However, 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.

Results

By analyzing mitochondrial DNA sequences and nuclear microsatellite loci, we show that there are at least six genealogically distinct lineages of giraffe in Africa, with little evidence of interbreeding between them. Some of these lineages appear to be maintained in the absence of contemporary barriers to gene flow, possibly by differences in reproductive timing or pelage-based assortative mating, suggesting that populations usually recognized as subspecies have a long history of reproductive isolation. Further, five of the six putative lineages also contain genetically discrete populations, yielding at least 11 genetically distinct populations.

Conclusion

Such extreme genetic subdivision within a large vertebrate with high dispersal capabilities is unprecedented and exceeds that of any other large African mammal. Our 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.