Phylogeny of snakes (Serpentes): combining morphological and molecular data in likelihood Bayesian and parsimony analyses

Copyright © 2007 The Natural history MuseumThe phylogeny of living and fossil snakes is assessed using likelihood and parsimony approaches and a dataset combining 263 morphological characters with mitochondrial (2693 bp) and nuclear (1092 bp) gene sequences. The ‘no common mechanism’ (NCMr) and ‘Markovian’ (Mkv) models were employed for the morphological partition in likelihood analyses; likelihood scores in the NCMr model were more closely correlated with parsimony tree lengths. Both models accorded relatively less weight to the molecular data than did parsimony, with the effect being milder in the NCMr model. Partitioned branch and likelihood support values indicate that the mtDNA and nuclear gene partitions agree more closely with each other than with morphology. Despite differences between data partitions in phylogenetic signal, analytic models, and relative weighting, the parsimony and likelihood analyses all retrieved the following widely accepted groups: scolecophidians, alethinophidians, cylindrophiines, macrostomatans (sensu lato) and caenophidians. Anilius alone emerged as the most basal alethinophidian; the combined analyses resulted in a novel and stable position of uropeltines and cylindrophiines as the second-most basal clade of alethinophidians. The limbed marine pachyophiids, along with Dinilysia and Wonambi, were always basal to all living snakes. Other results stable in all combined analyses include: Xenopeltis and Loxocemus were sister taxa (fide morphology) but clustered with pythonines (fide molecules), and Ungaliophis clustered with a boine-erycine clade (fide molecules). Tropidophis remains enigmatic; it emerges as a basal alethinophidian in the parsimony analyses (fide molecules) but a derived form in the likelihood analyses (fide morphology), largely due to the different relative weighting accorded to data partitions.Michael S. Y. Lee, Andrew F. Hugall, Robin Lawson & John D. Scanlo

Estudo histológico e histoquímico da glândula de Duvernoy de Clelia plumbea (Wied) (Serpentes, Colubridae, Xenodontinae) Histological and histochemical study of Duvernoy's gland from Clelia plumbea (Wied) (Serpentes, Colubridae, Xenodontinae)

<abstract language="eng">There are report two human envenenomations for species from Clelia Fitzinger, 1826 (opisthoglyph snake). The patients exhibited symptoms similar from bothropic accident. Then this work have with objective, the hystological and histochemical study of Duvernoy's gland from Clelia plumbea. For the hystological observation of the Duvernoy's gland were using, with paraffin's cutting edge, two methods: Hematoxylin + Eosin and Toluidine's Blue. With historesine's cutting edge were using three methods: Metilen's Blue, Toluidine's Blue + Floxine and Toluidine's Blue. For the histochemical detection were using six techniques, with paraffin's cutting edge: PAS, PAS + Alcian Blue pH 2,5, Alcian Blue pH 2,5, PAS + Salivar Amilase, Method of Lars Grimelius and Method of Lillie. It was evidenced the predominance of serous cells on Duvernoy's gland. In relation to the histochemical constituion of the duvernoy's gland, was verified the presence of glucoconjugates neuters, enzymes and cells with reduetive activity. By fact from this species to kill his preys by constriction, the predominance of serous cells in the duvernoy's gland, don' t must be direct related with the subjugation of his preys, but with the digestive processes. Histological and histochemical analysis showed cells of Duvernoy's gland are constituted for two populations: serous cells (prodution of enzymes) and mucous cells (prodution of glucoconjugates)