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Journal of Undergraduate Research

Keywords

phylogenetic relationships, North America, heterodontine snakes

College

Life Sciences

Department

Biology

Abstract

Among extant snakes (~3150 species), Caenophidia or “advanced” snakes are a monophyletic group comprising the great majority of species (~2620) of species (Vidal et al. 2010). The American caenophidian snake fauna comprises five families: the Viperidae and Elapidae – both displaying a front fanged venom system- and the colubroidean families Natricidae, Colubridae and Dipsadidae. The latter is one of the largest families of snakes (>700 species), with all living representatives restricted to the New World. Previous higher level studies generally agree on the delineation of three major clades of Dipsadidae broadly consistent in their distribution, a South American clade including the West Indies, (xenodontines sensu stricto), a Central American clade (dipsadines) and a North American clade (North American xenodontiines). Despite the fact that this last group includes only five genera (Carphophis, Contia, Diadophis, Farancia, and Heterodon) and nine species (with the possibility of several cryptic species) herpetologists have disagreed on the phylogenetic and systematic arrangement of these North American snakes for more than 70 years. Past studies have placed these snakes within the Dipsadidae, the Xenodontidae, the Natricidae, the recognition of new families (Carphophinae and the Heterodontinae), or distributed them across multiple families. (Cadle 1984; Pinou et al. 2004; Lawson et al. 2005; Zaher et al. 2009; Vidal et al. 2010) (Figure 1). Because the phylogenetic position of these snakes remains controversial, they have been termed as “relicts” and are assumed to lack closely related living relatives. However, the confusion surrounding these snakes could be due to a limited sampling, the use of limited molecular data or different molecular markers, or different topologies resulting from different analytical methods. Most studies have focused on the use of a single locus (the mitochondrion) or the combination of a mitochondrial data and a single nuclear locus. This is the first study to: (1) include all “relict” genera and species, and (2) incorporate multiple independent loci, to infer the phylogenetic relationships of the North American xenodontines and their relationships to other New World xenodontine and dipsadine snakes.

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