NEOGENE DIVERSIFICATION AND TAXONOMIC STABILITY IN THE SNAKE TRIBE LAMPROPELTINI (SERPENTES: COLUBRIDAE)
2009. Molecular Phylogenetics and Evolution 52: 524-529
R. Alexander Pyron & Frank T. Burbrink
The colubroid snakes are a diverse (>2500 species), globally distributed group (Lawson et al., 2005) which date to the early Cenozoic (Burbrink and Pyron, 2008). Of the several NW representatives of the group (Natricinae, Crotalinae, Elapinae, Colubrinae, and Xenodontinae), the colubrine tribe Lampropeltini is one of the most conspicuous and well- studied (Williams, 1978; Rodríguez-Robles and de Jesús-Escobar, 1999). The lampropeltinines (Rat, Corn, and Fox [Pantherophis, Bogertophis, and Pseudelaphe], King and Milk [Lampropeltis], Short-tailed [Stilosoma], Bull, Gopher, and Pine [Pituophis], Glossy [Arizona], Scarlet [Cemophora] and Longnose [Rhinocheilus] Snakes) are common constrictors, distributed from Canada to Ecuador (Williams, 1978; Conant and Collins, 1998; Stebbins, 2003). Several recent studies have found that the Lampropeltini form a monophyletic clade endemic to the NW, thus rendering the cosmopolitan genus Elaphe paraphyletic (Rodríguez- Robles and de Jesús-Escobar, 1999; Utiger et al., 2002; Burbrink and Lawson, 2007). Based primarily on trees inferred using mitochondrial evidence, the taxonomy of the group is in a state of flux and the monophyly of several genera (i.e. Pantherophis, Pituophis, and Lampropeltis) has been disputed, including the erection of a new genus (Mintonius) for the fox snakes (Pantherophis vulpinus; Bryson et al., 2007; Burbrink and Lawson, 2007; Collins and Taggart, 2008). Additionally, while many phylogeographic studies have used mtDNA to investigate biogeographic structure (Burbrink et al., 2000; Burbrink, 2002; Mulcahy, 2008; Rodríguez-Robles and de Jesús- Escobar, 2000), higher-level phylogenies based solely or primarily on mitochondrial data have not been well-supported (Rodríguez-Robles and de Jesús-Escobar, 1999; Burbrink and Lawson, 2007). Thus, multiple independent loci are desirable to infer phylogenies and estimate tree-based quantities such as divergence times (i.e. Wiens et al., 2008). Here, we present a phylogeny based on three nuclear genes (3368 bp), two of which are newly presented in this study, and six mitochondrial genes (4926 bp). We included representatives from all 31 of the traditionally described species of lampropeltinine. We use this phylogeny to address hypotheses regarding the timing of origin and diversification of the lampropeltinines, as well as generate a revised taxonomy of the
group.
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CNAH Notes on the taxonomy in Pyron & Burbrink (2009):
1. The Short-tailed Snake, Stilosoma extenuatum, is placed in the genus Lampropeltis (as L. extenuata); it is most closely related to the L. getula complex and a possible standard common name is Short-tailed Kingsnake.
2. The Scarlet Kingsnake, previously considered by many herpetologists to be a race of Lampropeltis triangulum, is recognized as a distinct species, Lampropeltis elapsoides, and retains the standard common name Scarlet Kingsnake.
3. The statement by Pyron & Burbrink (2009 page 528 column right) that the "taxonomic
conclusions of Burbrink & Lawson (2007) and Collins & Taggart (2008) are shown to be inaccurate" is . . . ummm . . . inaccurate. The taxonomic conclusion of Burbrink & Lawson (2007) was quite accurate, based on the available data and analysis; the more comprehensive data set in this latest paper has shown that the earlier taxonomic conclusion of Burbrink & Lawson (2007) to place all Rat Snakes in the genus Pituophis was simply premature. The taxonomic conclusions of Collins & Taggart (2008), however, are unaffected by this paper, since the two species in the genus Mintonius (gloydi and vulpinus) remain as sister taxa to the three species in the genus Pantherophis (emoryi, guttatus, and slowinskii), and both Mintonius and Pantherophis remain as sister taxa to the four species in the genus Scotophis. CNAH will continue to use an accurate generic taxonomy that includes Mintonius, Pantherophis, Pituophis, and Scotophis because it is more evolutionarily informative than placing them in the single genus Pantherophis. Both arrangements are correct and consistent with all available evidence, but four distinct and easily recognized genera, as adopted by CNAH, will always be a more informative and useful taxonomy than a single genus containing a wide variety of species.
