CONSERVATION OF ARABIAN GAZELLES - Nwrc.gov.sa

Morphometries: Some morphological criteria allow distinction between the two
sUbspecies. Adult females of C. s. subgutturosa tend to be hornless, but female C. s. marica have
well developed horns (Groves and Harrison, 1967; Harrison and Bates, 1991). C. s. m£lrica is also
smaller, is more rotund, lighter, and has a whiter face than C. s. subgutturosa. However, some
specimens can not be assigned with certainty to one of the two subspecies by relying on external
criteria because of the intergradation zone. Some individuals from southern Iraq showed mixed
characteristics of each subspecies (Harrison and Bates, 1991). Groves and Harrison (1967) also
found an intergradation zone between subgutturosa and marica, situated in the Tigris-Euphrates
valley. Specimens from this zone had intermediate characters in skull measurements, horn length and
occurrence of horns in female.
AI Bassri and Thouless (1988) have conducted a preliminary morphometric study on the
KKWRC population using horn and skull measurements. They compared eight specimens from
KKWRC with museum specimens of the subspecies marica, subgutturosa and hillieriana. Despite
the small sample size and the methodological biases, it was shown that the KKWRC specimens'
measurements were closest to the marica subspecies.
- Cytogenetic analysis: The two subspecies normally have different numbers of
chromosomes: 30, 31 for female and male sLlbgutturosa respectively (Wurster, 1972) and 32 and 33
chromosomes for marica (Kings wood and Kumamoto. 1988).
Cytogenetic studies performed on the North American zoo popUlation of sand gazelles,
originating from Jordan, found a chromosomal polymorphism involving two acrocentric pairs of
chromosomes (Kings wood and Kumamoto, 1988). The same polymorphism was discovered, with
different frequencies, in the captive populations at Qassim and at KKWRC by further studies
(Granjon et at., 1991; Vassart et at., 1993b). This results in a variation in the possible number of
chromosomes, with females having a diploid chromosome number of either 30, 31 or 32, and males
having either 31,32 or 33.
There are two different hypotheses about the origin of this chromosomal pOlymorphism,
inducing two controversial views about reintroduction policy. First, the polymorphism could be the
consequence of the introduction of individuals of the sLlbgutturosa subspecies into the marica
population (Granjon et al., 1991).
reintroduction, since they are not pure marica.
could Occur naturally as the result of a Robertsonian translocation.
In this case, the hybrid individuals should not be used for
The second hypothesis is that the polymorphism
A similar polymorphism has
already been found in some wild populations of impala Aepyceros melampus (Wallace and Fairall,
1967) and waterbuck Kobus ellipsiprymnus (Ryder et a/" 1990), In the Arabian sand gazelle, suc h a
polymorphism could be further complicated by a natural chromosomal cline between C. s.
subguttLlrosa and C, s. marica, with a ZOne of intergradation and populations with different
chromosome numbers in the north and south of Arabian peninsula. According to this hypothesis, the
diploid number 32/33 would then become more COmmon along a gradient towards the southern end of
the Arabian peninsula, and the diploid number 30/31 less common. The Arabian sand gazelles in
Oman would presumably all be 32/33. A similar cline has already been found in the Iranian wild
sheep (Valdez et al., 1978), which has two cytologically distinct populations and a hybrid zone
including individuals with heterogeneous and intermediate karyotypes. If this hypothesis is valid,
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