A review of the systematics and taxonomy of Pythonidae: An ancient serpent lineage

David G. Barker, Tracy M. Barker, Mark A. Davis, Gordon W. Schuett

Research output: Contribution to journalArticle

Abstract

Here we review research over the past quarter century regarding the systematics and taxonomy of an ancient, popular and economically valuable group of snakes referred to as pythons (Serpentes, Pythonidae). All recent phylogenetic studies recognize the pythons as monophyletic; however, the phylogenetic relationships at supraspecific levels are conflicting, and many of the relationships recovered are paraphyletic. We identify several taxonomic changes as necessary to clarify supraspecific relationships and which resolve the issue of paraphyly recovered in several studies. Overall, our review of the phylogenetic systematics of pythons points to considerable incongruence among recovered relationships. Instances of paraphyly emerge, low node support is detected, and terminal taxa are unstable across phylogenetic hypotheses. We thus recognize that pythonid gene trees have been unable, for various reasons, to reveal the true species tree. This occurrence is not unexpected and can arise from incomplete taxon sampling, long-branch attraction and repulsion, homoplasy, ancestral polymorphism, and, more notably, the anomaly zone. These phenomena ultimately yield incomplete lineage sorting, or the failure of lineages to coalesce over evolutionary time. We discuss future directions to resolve these troubling issues. Without resolution, adaptive hypotheses about pythons will be limited, including hypotheses of geographic origin. Analyses that recover the clade Python as sister to the Indo-Australian clade are interpreted to support a Laurasian origin of Pythonidae. In contrast, a Gondwanan origin is supported when the Indo-Australian clade is recovered as basal to the Python clade. We describe the morphology of two recently proposed genera. Finally, we designate and describe the neotype for Morelia azurea and offer a list of the currently accepted python species and their taxonomy.

Original languageEnglish (US)
Pages (from-to)1-19
Number of pages19
JournalZoological Journal of the Linnean Society
Volume175
Issue number1
DOIs
StatePublished - Sep 1 2015

Keywords

  • Ancestral polymorphism
  • Anomaly zone
  • Homoplasy
  • Incongruence
  • Long-branch attraction
  • Morphology
  • MtDNA
  • NDNA
  • Neotype of Morelia azurea
  • Phylogenetics
  • Python

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Animal Science and Zoology

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