Radiation within the advanced snakes (Caenophidia) with special emphasis on African opistoglyph colubrids, based on mitochondrial sequence data

Abstract

A parsimony analysis of parts of the mitochondrial genes 12s and 16s (722 base pairs) from 43 species of the advanced snakes (Caenophidia) resulted in two most parsimonious topologies. Based on a strict consensus of these the following objectives were addressed: (1) Which groupings of caenophidian taxa can be recognized? (2) Is Acrochordus sister group to, or included in, Caenophidia? (3) Are boigine snakes (sensu stricto) a monophyletic grouping and where do these taxa belong in a broader caenophidian context? (4) What are the systematic affinities of the African egg-eating genus Dasypeltis? The phylogeny was then used to discuss: (5) the evolution of the posterior maxillary dentition and the composition of the retinal visual cells. The results reveal that, when using Boa constrictor as outgroup, Acmchordus is the sistergroup to the remainder of the ingroup, and a further eight clades are defined. Five genera of elapids did not appear to be monophyletic and a number of colubrids (sensu lato) such as Mehelya, Lycodonomorphus, Lampmphis, Atractaspis, and Buhoma (formerly Geodipsas), which have traditionally been problematic to place systematically, did not group with any of the larger clades. These taxa are together with the elapids representatives of very early radiations in the evolution of the Advanced snakes. The homalopsine Enhydris enhydris appears as a sistergroup to the viperine clade (Clade 1). When plotted onto the topology the posterior maxillary dentition appear to express three, maybe four, independent origins of the Opistoglyph State. The retinal evolution also appeared very complex. The suggested very primitive placing of the Boigine snakes (sensu stricto) due t o their lack of double cones in the retina of the eye was not supported here; instead the sequence data suggests this observation to be the result of a secondary loss.

Molecular phylogeny of advanced snakes (Serpentes, Caenophidia) with an emphasis on South American Xenodontines: a revised classification and descriptions of new taxa

“…1). We found no support for a sister group relationship between homalopsines and Homoroselaps (Kelly et al, 2003), nor with viperids (Gravlund, 2001); however, these associations were not strongly supported in either of these last studies.…”

“…More recently, molecular studies have provided new insights on the higher-level phylogeny of caenophidians, corroborating some long-held views and suggesting new hypotheses for evaluation (e.g., Alfaro et al, 2008;Cadle, 1984aCadle, ,b, 1988Cadle, , 1994Crother, 1999a,b;Glaw et al, 2007a,b;Gravlund, 2001; informative data. Although data have been plentiful, colubroid molecular phylogenies have been unstable due to their inherent sensitivity to taxon sampling (Kelly et al, 2003;Kraus & Brown, 1998).…”

“…Our results corroborate Lawson et al (2005) in positioning Acrochordus as the sister group to all other caenophidians. A sister-group relationship between Acrochordus and other caenophidians is a wellsupported hypothesis in all recent morphological phylogenetic analyses (Tchernov et al, 2000;Lee & Scanlon, 2002;Apesteguía & Zaher, 2006), as well as other molecular studies and combined molecular/ morphological analyses (Gravlund, 2001;Lee et al, 2004; and references therein). In contrast, Kelly et al (2003) and Kraus & Brown (1998) found Acrochor-dus to cluster with Xenodermus-Achalinus (Xenodermatinae); in addition, Kraus & Brown (1998) found their Acrochordus-xenodermatine clade to cluster well within other caenophidians.…”

The evolution of venom-delivery systems in snakes

“…Gravlund (2001) compared mitochondrial sequence data from 43 species of colubroid snakes to identify monophyletic groups and determine the relationships among them. The result was a trichotomy.…”

Adaptation in the African egg‐eating snake: a comparative approach to a classic study in evolutionary functional morphology

“…The relationship between Dasypeltis and other African colubroid snakes remains unresolved, although Gravlund (2001) suggests a close affinity to the Boiginae. The sister relationship between Dasypeltis and the group that includes L. getula is convenient for adaptive comparison.…”