` The correct one is Lopez and Maxson's 1995 study comparing mitochondrial DNA among ratsnakes and racers. They compared the mtDNA of N. American and Eurasian Elaphe with those of a large number of racers. All of the racer species are basal to Elaphe in their tree. Since racers are the sister taxa of the ratsnakes, this is a good test to see if different species of Elaphe are in fact only convergently similar. If Elaphe is polyphyletic, some species should be closer to some of the racers than they are to each other. This is clearly not the case. All species of Elaphe form a clade along with Cemophora, Lampropeltis and Pituophis.'



I would add that Rhinechis is in this clade. That said, only four species of Elaphe sensu lato were included, and these belong to only two of the seven lineages within Elaphe sensu lato recognized by Utiger et al. There aren't enough taxa to support any conclusions about the phylogenetic relationships within Elaphe sensu lato, but even so, though the monophyly of the ratsnakes relative to the racers (whose monophyly is not supported) is supported, Lopez and Maxson's data support Utiger et al.'s conclusions that the relationship between Pantherophis and Elaphe is distant, and that Pantherophis is a derived taxon within Lampropeltini.



I can also add:

Lenk, Joger, and Wink, `Phylogenetic relationships among European ratsnakes of the genus Elaphe Fitzinger based on mitochondrial DNA sequence comparisons.' Amphibia-Reptilia, 22:329-339.

to the list of papers concluding that Elaphe sensu lato is polyphyletic. It's also worth mentioning that both Lenk et al. and Utiger et al. argue for East-Asian origins for the ratsnakes. Given that the taxa found by Lopez and Maxson to group most closely with the ratsnakes are European or Mediterranean (Coluber viridis, Coluber hippocrepis, and Spalerosophis diadema), this suggests that the closest relatives of the ratsnakes may not have been included in Lopez and Maxson's study.



Patrick Alexander

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