cokei796
H79-LAIK
H8-NAIV
H34-NAIR
cokei747
H20-LAIK
H13-RUMA
H32-RUMA-s
Laikipia Hartebeest: Exactly what are we attempting to conserve?
H69-LAIK
cokei748
swaynei10
swaynei9
swaynei13
swaynei7
swaynei8
swaynei45
swaynei5
swaynei6
RESULTS
Nicholas Georgiadis
and Collins Ouma
Mpala Research Centre
THANKS TO: Our collaborators were Drs. Al Roca,
Olivier Hanotte, Nick Oguge, and Joel Ochieng. We
thank Dr. Oystein Flagstad, Nasser Olwero, Tee Taylor,
Robert Mills, Edward Parfet, Joseph Kioko, Dr. Richard
Bagine, and KWS staff in Nakuru, Ruma and Nairobi
NP’s.
The project was supported by the Whitley
Foundation, Lincoln Park Zoo, St. Louis Zoo, Mpala
Wildlife Foundation, African Wildlife Foundation, Nancy
and Lambeth Townsend, and Joan and Robert Weiss.
RATIONALE
Species’ geographical ranges are today so fragmented, it is often difficult to know whether remnant populations
were once connected by dispersal and migration, or isolated by natural barriers. We need to know this information
when action must be taken to conserve a species, for example, when individuals from one location are added to
those in another. Fortunately, the required information can be reconstructed by analyzing patterns of genetic
variation that is encoded in the DNA of individuals from different locations. We used this approach to examine the
genetic makeup of hartebeest in Laikipia, asking, Exactly what, in the evolutionary sense, are we attempting to
conserve?
cokei794
H61-SERO
H54-SERO
H43-NAIR
H7-NAIV
cokei800
cokei786
H5-SERO
H58-NAIV
cokei797
We found only subtle genetic differences between hartebeest with Lelwel morphology (in
Laikipia and Ruma NP) and those with Cokes morphology (in Naivasha, Meru NP, Nairobi NP,
the Mara-Serengeti, and Ngorongoro), and the genetic transition between them appeared
seamless. This was surprising because morphological differences between the two are
striking, even over distances as short as 100 km (Fig. 1).
H57-NAIV
cokei35
cokei789
cokei783
H2-NGOR
cokei798
H27-NGOR
H12-NAIV
cokei802
cokei792
cokei790
cokei803
cokei804
H9-NAIV
cokei46
cokei806
cokei809
cokei807
cokei791
Previous analyses have suggested that different hartebeest forms in Africa diverged over the
last two hundred thousand years when climate changes triggered continent-wide habitat shifts,
‘temporarily’ confining separate hartebeest populations to isolated savanna patches. Our
results agree with this scenario, but further suggest that Cokes and Lelwel subsequently recontacted each other and interbred, presumably after the climate cycle reversed, and
hartebeest spread as the savannas expanded once more. As a result, the populations in
Laikipia, Ruma NP, and Meru NP are all hybrid, but each has a subtly unique genetic makeup
(Table 1) and morphology. The former two have greater affinities with Lelwel, the latter, at least
morphologically, with Cokes. Despite their morphological similarities, the Meru NP hartebeest
were not closely aligned with Cokes in Nairobi NP and Naivasha in the genetic sense (Fig. 3).
H3-SERO
cokei795
cokei787
lelwel3
lelwel44
lelwel727
lelwel730
neumanni
lelwel729
tora78
major57
lelwel72
tora33
swaynei68
lelwel32
lelwel42
lelwel73
lelwel4
major79
lelwel41
lelwel43
H18-LAIK
H17-LAIK
H76-LAIK-s
lelwel74
H1-SERO
cokei784
lelwel2
lelwel726
lelwel728
tora76
tora532
Naivasha
Serengeti NP
Nairobi
Ngorongoro
tora75
swaynei815
swaynei1
swaynei2
swaynei3
swaynei23
swaynei4
swaynei12
somali
swaynei11
swaynei14
Laikipia
Ruma NP
HORN SHAPES
AND SAMPLING LOCATIONS
For a century hartebeest in this ecosystem have been known
to be morphologically ‘different’ from hartebeest elsewhere
(Fig. 1). They have been variously referred to as ‘Laikipia’,
‘Jackson’s’, ‘Kenya’, or ‘Lelwel’ hartebeest, but rarely with
formal reference or definition. Many resemble true Lelwel
hartebeest, with robust horns that stand upright then sweep
backwards, but there is broad variation in horn shape and
size. Lelwel hartebeest were once distributed between
central Kenya and the Central African Republic, but persist
today in highly fragmented remnants (Fig. 2). Hartebeest in
Laikipia have long been considered to be hybrid between
Lelwel and Cokes hartebeest, the common form in southern
Kenya and northern Tanzania.
major7
major732
Meru NP
buselaphus
major6
major58
Fig. 3. Cluster diagram of focal hartebeest populations based on
genetic (microsatellite) similarities. Numbers represent % bootstrap
values, an index of confidence in the robustness of each node.
Nairobi
Meru
NP
liecht757
liecht754
caama723
0.01 substitutions/site
Fig. 4. Mitochondrial DNA genealogy of
hartebeest, colour-coded by morphotype:
cokei (yellow), lelwel (blue), swaynei (light
green), tora (dark green), and major (red).
Southern African hartebeest (lichtensteini and
caama) were used as outgroups.
Table 1. Values of Fst, an index of the degree to
which pairs of populations are genetically
subdivided (on a scale of 0-1), based on
mitochondrial (below diagonal) and microsatellite
data (above diagonal). Asterisks indicate values
significantly greater than 0.
NP
Collecting samples with biopsy darts, from dung, and from
incidental mortality, we compared the genetic makeup of
hartebeest in Laikipia with those in Ruma NP, Meru NP,
Naivasha, Nairobi NP, Mara-Serengeti NP, Ngorongoro, and
elsewhere in Africa, using both mitochondrial DNA
sequences and nuclear (microsatellite) markers.
CONSERVATION IMPLICATIONS
Laikipia
Ruma
Fig. 2. Distribution of hartebeest in Africa, with different
symbols denoting different morphotypes. Symbols are
filled grey if previously published mtDNA sequences from
that location were used in this analysis, and black where
new populations were added by this study.
major731
major746
major735
major734
major736
District
NP
Fig. 1. Variation in hartebeest horn shape
among the focal populations. Note the similarity
between Nairobi (A. b. cokei) and Meru NP, and
the hybrid appearance of Laikipia hartebeest.
A conventional approach to conserving hartebeest might aim to preserve or restore populations wherever they occurred
naturally, particularly in protected areas. A more contemporary approach would attempt to conserve or even recreate the
fragmented and diverse remnants of intricate evolutionary processes that have been operating over vast space and time, such
as the one described here involving hybridization between different hartebeest forms. For example, dwindling numbers in
Meru NP prompted conservation managers to propose supplementing the Meru hartebeest with individuals imported from
elsewhere. Similarities in gross morphology might suggest a suitable source population to be Naivasha or Nairobi NP. A
preferable strategy would aim to conserve the evolutionary products of hybridization by breeding up the remaining individuals
at Meru in a large, predator-free area. If supplementation from elsewhere becomes mandatory, the goal would be to maintain
a population with hybrid characteristics.
The Laikipia population is also declining and is nowhere formally protected. A strategic plan should be designed to conserve
the remaining hartebeest in Laikipia, particularly those in Solio Ranch in the extreme south, which holds by far the highest
densities (if necessary, moving them elsewhere in Laikipia or beyond, but still retaining their identity). Similarly, suitable
alternative refuges should be identified to keep the Ruma NP hartebeest intact, should this protected area not survive extreme
pressures from surrounding humanity.
In Kenya there has been little unnatural mixing of wildlife populations by translocation, so opportunities to define and conserve
ongoing evolutionary processes persist, and should be strenuously pursued. As this project has shown, the relevant research
can be achieved by Kenyans through collaborations among national and international partners, in this case Mpala Research
Centre, Kenyatta University, the Kenya Wildlife Service, the International Livestock Research Institute in Nairobi, and the
Laboratory of Genomic Diversity in Maryland.