A Genetic Approach to the Management and Conservation of the Hartebeest (Alcelaphus Buselaphus) in Kenya
A lot of effort is put on 'proximate' threats to conservation, overlooking the 'ultimate' conservation goals in the process. Ultimately, attempts need to be made to conserve not just individuals or populations, but processes that have been on-going over vast geographical space and long evolutionary time, such as gene flow and natural selection. So far, little is known about these historical processes that decisions affecting the management of species in fragmented landscapes are always made without any systematic information. Fortunately, these processes can be largely reconstructed from natural patterns of DNA sequence variation that persist to the present day within and among populations. Adopting genetic tools, a suite of evolutionary issues critical to the conservation of hartebeest (Alcelaphus buselaphus) in Kenya was addressed. This species is naturally subdivided, but is declining over much of its range in Africa or has already gone locally extinct. Active management is required to restore and conserve the natural population structure of this species. However the genetic information needed to form the basis of these important processes is still lacking. The objectives of this study were to elucidate the phylogeography and the genetic structure of hartebeest populations in Kenya, using cytoplasmic (mitochondrial DNA) markers. The genetic history of Alcelaphus buselaphus lelwel (A.b. lelwel) and A.b. cokii, and the focal Laikipia population of central Kenya, were emphasized. A minimum of 489 base pairs in the mitochondrial D-Ioop region were sequenced in 75 individuals, representing 6 localities in Kenya and northern Tanzania, and including two of the 7 extant hartebeest 'subspecies' (A.b. cokii and A.b. lelwel). Samples were obtained from Laikipia, Ruma National Park (NP), Naivasha (Kongoni Sanctuary), Nairobi NP, Serengeti NP and Ngorongoro. The sequence data were then compared to published data from previous hartebeest studies. Results reveal that genetic distinctions exist between populations in Kenya, but are subtle, derived largely from differences in allele frequency, not from fixed allele differences, or phylogenetically separate lineages. With the exception of Ruma, patterns of sequence variation, nucleotide and haplotype diversity show that genetic variation within populations in this study were moderate to high. Most populations within a subspecies were more closely related to each other than they were to populations assigned to different subspecies in the study, implying no gene flow between these subspecies. From the pattern of the distribution of the number of differences between each pair of haplotypes, populations from Serengeti, Naivasha and Laikipia recorded high stability, Ngorongoro showed rapid expansion, while Nairobi was shown to have gone through a bottleneck and is recovering. Ruma was an exception, having very low variation compared to the other populations, possibly as a result of severe and/or prolonged bottlenecks leading to high levels of inbreeding in the population. These findings provide initial genetic criteria on which the Kenyan conservation authorities can base informed management and restoration policies for locally extinct or threatened hartebeest populations. It further supports the general principle that hartebeest populations in Kenya having similar horn morphology can be considered equivalent and hence interchangeable for management purposes. The present genetic findings point out that this principal can be applied irrespective of the distance separating populations. Genetic variation in Ruma, however, may need to be augmented by importing individuals from another, outbred population, probably Laikipia. Finally, it is emphasized that management decisions should be based on more than a single criterion, whether morphological or genetic, particularly one with such an anomalous mode of inheritance as mtDNA. Additional genetic data, using multiple nuclear markers (preferably microsatellite), are also required, particularly to address hybridization issues, for which mitochondrial data alone are uninformative.
- MST-Zoological Sciences