Wednesday, January 22, 2014

A new arrangement for African plated lizards and two new genera

The lizard families Gerrhosauridae and Cordylidae form the clade Cordyliformes. But, there is  a long history of disagreement as to whether this clade comprises a single family, Cordylidae or two families: Cordylidae and Gerrhosauridae, or one family with two subfamilies (Cordylinae and Gerrhosaurinae).

In a recently published study in Zootaxa, Bates et al. (2013)  constructed a molecular phylogeny of the African plated lizard family Gerrhosauridae using two mitochondrial markers (ND2, 732 bp; 16S, 576 bp) and one nuclear marker (PRLR, 538 bp). The study showed that the subfamily Gerrhosaurinae consists of five major clades which the authors interpret as representing five genera. The genera Tetradactylus and Cordylosaurus were each recovered as monophyletic, but Gerrhosaurus as currently conceived is paraphyletic, consisting of three distinct genus-level assemblages. The two clades consisting of Gerrhosaurus major Duméril, 1851 and Gerrhosaurus validus Smith, 1849 are both described as new genera:  Broadleysaurus and Matobosaurus. Two subspecies of ‘Gerrhosaurus major’  were historically separated on the basis of differences in color pattern but were found not to be reciprocally monophyletic, so the authors placed Gerrhosaurus bottegoi Del Prato, 1895 in the synonymy of Broadleysaurus major (Duméril, 1851) is rendered monotypic. Gerrhosaurus validus maltzahni De Grys, 1938 is genetically and morphologically well differentiated from G. v. validus and the two taxa also occur in allopatry. The authors  therefore re-instate the former as Matobosaurus maltzahni (De Grys, 1938), resulting in Matobosaurus validus (Smith, 1849) being monotypic species. The authors also showed Gerrhosaurus comprises two major subclades, one consisting of Gerrhosaurus typicus + Gerrhosaurus skoogi and the other containing the remaining species. In this latter subclade the west-Central African.

Gerrhosaurus nigrolineatus is most closely related to Gerrhosaurus auritus rather than to G. nigrolineatus from East and Southern Africa. The west-Central African clade of G. nigrolineatus differs from the East and Southern African clade by a p-distance of 13.0% (ND2) and 6.9% (16S), and can be differentiated morphologically. The authors accordingly apply the name Gerrhosaurus intermedius Lönnberg, 1907 comb. nov. to populations from Kenya, Uganda, Rwanda, Tanzania, Malawi, Mozambique, Zimbabwe and South Africa previously identified under the name G. nigrolineatus. Their results also confirms  Gerrhosaurus bulsi Laurent, 1954 is a distinct species and the sister taxon to a clade containing G. nigrolineatus, G. auritus and G. intermedius. The last four taxa form a closely-related ‘G. nigrolineatus species complex’ with a widespread distribution in Africa. Most closely related to this complex of species is Gerrhosaurus flavigularis Wiegmann, 1828 which has an extensive range in East and Southern Africa, and displays genetic substructure which requires further investigation. The status of Gerrhosaurus multilineatus Bocage, 1866, and Angolan populations referred to G. nigrolineatus, remains problematic.

Citation
BATES MF, TOLLEY KA, EDWARDS S, DAVIDS Z. DA SILVA JM & BRANCH WR (2013). A molecular phylogeny of the African plated lizards, genus Gerrhosaurus Wiegmann, 1828 (Squamata: Gerrhosauridae), with the description of two new genera. Zootaxa, 3750(5), 465-493.

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