The taxonomy of Australian elapid snakes: a review

Abstract

Published data on Australian elapid snake taxonomy are reviewed. Both classical morphological studies and relevant ecological, chromosomal and biochemical data are summarized. Attention is focused on two major areas: (1) the phylogenetic relationships between Australian terrestrial elapids and other proteroglyphs; and (2) the interrelationships among the Australian terrestrial elapids. From this review four key questions are identified: (1) Are the continentally endemic groups of terrestrial elapids confamilial? (2) Do the Australian elapids represent a distinct familial group? (3) Are the Australian elapids monophyletic or have the extant forms been derived from distinct lineages which may represent more than one invasion of the continent? (4) What is the precise relationship between laticaudine and hydrophiine sea snakes and the Australian elapids? There is considerable disagreement concerning generic allocations and suprageneric relationships within the Australian proteroglyphs. Ecological, cytological and biochemical studies currently under way may be useful adjuncts to morphological information in resolving these questions.

Phylogenetic Relationships of Terrestrial Australo-Papuan Elapid Snakes (Subfamily Hydrophiinae) Based on Cytochromeband 16S rRNA Sequences

“…The first of these findings concerns methodology, in that the data suggest a plausible reason for the long history of difficulties experienced by workers who have attempted to assess evolutionary relationships among the Australo-Papuan elapid snakes. Despite considerable effort over a long period of time, involving the application of diverse data sets (including information on internal and external anatomy, karyology, electrophoresis, venom proteins, molecular sequences, and ecological traits), the continued instability in elapid taxonomy (Mengden, 1983) bears strong witness to the magnitude of the problems that all workers in this field have encountered. Why should this be so?…”

“…Much of the work devoted to terrestrial hydrophiine relationships has been concerned only with the Australian species, in an attempt to address the high degree of taxonomic instability which has dominated the group (reviewed in Mengden, 1983), despite broad consensus that the endemic Melanesian genera (with the possible exception of Parapistocalamus) and 20 Australian genera are members of a single clade (McDowell, 1967(McDowell, , 1969a(McDowell, , 1969b(McDowell, , 1970Schwaner et al, 1985;Keogh, 1998a). McDowell (1967McDowell ( , 1969aMcDowell ( , 1969bMcDowell ( , 1970 was the first to address the problem within an evolutionary framework; he identified a number of putative ''natural groups'' through the descriptive study of cranial osteology, myology, and hemipenis anatomy.…”

Molecular phylogeny of elapid snakes and a consideration of their biogeographic history

“…Hence, they do not appear to represent separate invasions of the region from different elapid stock. The immunological distinctiveness of Demansia may be attributable to accelerated rates of albumin molecular evolution in this genus, as has been found in Naja (Ma0 et al, 1983, Guo et al, 1987. Among the terrestrial Australian elapids, the diverse viviparous species have been hypothesised to be a more recent monophyletic radiation within the terrestrial Australian elapids (Shine, 1985).…”

“…Elapids are comprised of a number of distinct putatively monophyletic lineages, with a very uneven spread of species and generic level diversity among lineages and .geographic regions (Table 1). Of the terrestrial groups, the Australian species are most diverse at both the generic and specific level (Mengden, 1983;Hutchinson, 1990). The African elapids are intermediate in diversity, comprising mostly cobras, with allies which range through tropical and sub-tropical Asia.…”

Evolutionary implications of hemipenial morphology in the terrestrial Australian elapid snakes

“…Elapids (variously referred to families Elapidae and Hydrophiidae [Smith, Smith & Sawin, 19771 or family Elapidae [Underwood, 1967a;Dowling, 19741) number approximately 300 species in 61 genera and are distributed across much of the tropical and subtropical world including the Americas, Africa, Asia, Melanesia, Australia, and the oceans (Mengden, 1983;Golay et al, 1993). Elapids are primarily defined by their unique proteroglyphous venom delivery system comprised of two small erect canaliculate fangs at the end of the maxilla (McDowell, 1968;McCarthy, 1985).…”