Molecular systematics of New World lampropeltinine snakes (Colubridae): implications for biogeography and evolution of food habits

We used mitochondrial gene sequences to infer phylogenetic relationships am ong North American snakes of the colubrid tribe Lampropeltini (Arizona, Bog ertophis, Cemophora, New World Elaphe, Lampropeltis, Pituophis, Rhinocheilu s, Senticolis, Stilosoma), and assessed thr implications of our findings fo r the biogeography and evolution of food habits among these serpents. The m aximum likelihood phylogeny identified Rhinocheilus as the sister taxon to all other lampropeltinines, and supported the monophyly of Lampropeltis (in cluding Stilosoma), New World Elaphe, and Pituophis, but not that of Bogert ophis. This phylogeny also suggested a sister group relationship between Ce mophora and Lampropeltis, and between New World Elaphe and Pituophis, and s trongly supported that Senticolis belongs within Lampropeltini, thus contra dicting previous suggestions that Senticolis is not a lampropeltinine. Usin g a method for approximating ancestral areas of clades, we determined that western North America was most likely the ancestral area of lampropeltinine s. Our survey of published studies, combined with unpublished data, indicat ed that lampropeltinines as a group feed mainly on mammals, less frequently on lizards, birds, and bird eggs, and only rarely on squamate eggs, snakes , anurans, and insects. Some individual species indeed emphasize mammals in their diets, bur others most frequently eat lizards, squamate eggs, bird e ggs, or snakes, whereas others take two prey types with similar frequency. Our reconstruction of the evolution of food habits among lampropeltinines s uggests that a diet emphasizing lizards is ancestral, and therefore diets t hat mostly consist of mammals, squamate and bird eggs, and snakes are deriv ed within the clade. In at least some species, smaller individuals prey mos tly on lizards and larger ones add mammals to their diets. (C) 1999 The Lin nean Society of London.