Taxonomic and functional implications of dorsal scale characters in the Viperidae (Reptilia: Serpentes).

An atlas of scanning electron micrographs of 122 dorsal scales from 118 viperid species comprising all subfamilies (Azemiopinae, Causinae, Crotalinae, and Viperinae) is presented. Analyses of character states derived from new dorsal scale patterns and morphological characters taken from the literature are used to estimate phylogenetic relationships among viperid snakes. Dorsal scale patterns which facilitated the estimation of phylogenetic patterns within the Viperinae (as determined by rescaled consistency indices) included: apex shape, microdermatoglyphics, minidermatoglyphics, keel morphology, and apical pit microdermatoglyphics, Within the Crotalinae, apical pit size, minidermatoglyphics, apical pit number, and microdermatoglyphics played important roles in the outcome of the phylogenetic analyses. Phylogenetic analyses of the subfamilies places Azemiopinae in a basal position relative to a trichotomy composed of Causinae, Crotalinae, and Viperinae. Within the Viperinae, Vipera (sensu lato) is polyphyletic; however, the proposed resurrection of Daboia (Gray) is supported. Echis, Atheris, and Bitis each form monophyletic groups with two or more species. Cerastes forms a monophyletic lineage with basally placed Eristicophis and Pseudocerastes. Within the Crotalinae, Agkistrodon (sensu lato) is made polyphyletic by the inclusion of Hypnale, and Agkistrodon contortrix is a monotypic sister group to Calloselasma. Lachesini (Lachesis, Trimeresurus, and Bothrops (sensu lato)), minus Bothrops godmani, is monophyletic as a group. However, neither Lachesis, Trimeresurus, or Bothrops form monophyletic genera. Bothrops godmani is a monotypic sister group to Crotalini (Crotalus and Sistrurus). Crotalus is made polyphyletic by the inclusion of Sistrurus, and it is suggested that Sistrurus be considered a synonym of Crotalus. A framework for testing adaptational hypotheses on a phylogenetic tree is presented. Chi-square tests of association are used to isolate general correlations between character states and habitat. Subsequent concentrated-changes tests are used to elucidate potential apomorphic function associated with correlated character states. Here, habitat is coded as terrestrial or arboreal. Only one scale character (apex shape) has a significant level of concentrated-changes within the arboreal habitat. This indicates apex shape, in arboreal species, may be influenced by factors other than phylogeny.PhDBiological SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/104572/1/9527776.pdfDescription of 9527776.pdf : Restricted to UM users only