The biochemical systematics of the Southern African Felidae
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University of Cape Town
The classification of the family Felidae (cats) is problematical due to the conservative nature of their morphology. Some workers classify the family into as many as 20 genera (Ewer, 1973) while others divide it into three genera (Walker et al., 1964). Such studies have largely been based on morphological and behavioural characters. Recently, molecular studies, namely, protein albumin immunological distances (Collier and O'Brien, 1985) and protein electrophoresis (Randi and Ragni, 1991) have been used to try and resolve the problems underlying this family. To complement the previous studies, in the present study we use mitochondrial (mt) DNA to construct a· phylogeny of eight members of the southern African Felidae namely, African wild cat, Felis lybica; domestic cat, Felis catus; caracal, Caracal caracal; European wild cat, Felis sylvestris; leopard, Panthera pardus; lion, Panthera leo; and cheetah, Acynonyx jubatus. Mitochondrial DNA (mt DNA) was utilized instead of nuclear DNA since it accumulates point mutations at a rate which is 5 to 10 times as fast as the nuclear DNA and is therefore particularly useful for studying more closely related organisms between sub-species, species and genera. Its apparent potential to be used as a tool for constructing genealogical trees and time scales makes it a method of choice in evolutionary studies. We used the restriction mapping approach to generate data for phylogenetic analysis. Restriction mapping was utilized since it gives good resolution at the species and genus level and evolutionary estimates derived from this method are considered more accurate than those obtained by methods such as the restriction fragment size comparison. We have also attempted to develop the methodology for sequencing part of the cytochrome b region of mt DNA following polymerase chain reaction (PCR) amplification. Both cladistic and distance approaches were used for phylogenetic construction. This study will be both of academic value and may have relevance to practical conservation management since these molecular approaches help to identify or confirm specific status especially with respect to the relationship between the domestic cat and the African and the European wild cats. Furthermore, such approaches can be used at the intraspecific level to address problems in biogeography and population genetics. Our results are in concordance with the previously determined morphological studies and albumin immunological distance studies. The restriction maps for the African wild cat and the domestic cat are identical, emphasizing their close relationship and the African origin of the domestic cat. The European wild cat showed a slight variation with the African wild cat or the domestic cat with four different restriction sites and a sequence divergence of 0.9. This suggests that the common ancestral mt DNA of these cats existed about 450 000 years ago. The lion and the leopard are monophyletic in both cladistic and distance approaches. The precise placement of caracal has yet to be resolved but it is deeply rooted in the phylogenetic analysis which would be more consistent with a separate generic status of the latter species rather than its inclusion within either Felis or Panthera. The distance analyses are consistent with the placement of the cheetah as the most distantly related species amongst the eight Felid species examined.
Mda, N. 1992. The biochemical systematics of the Southern African Felidae. University of Cape Town.