Data set incongruence and correlated character evolution: An example of functional convergence in the hind-limbs of stifftail diving ducks

Kevin McCracken, John Harshman, David A. Mcclellan, Alan D. Afton

Research output: Contribution to journalArticle

84 Citations (Scopus)

Abstract

The unwitting inclusion of convergent characters in phylogenetic estimates poses a serious problem for efforts to recover phylogeny. Convergence is not inscrutable, however, particularly when one group of characters tracks phylogeny and another set tracks adaptive history. In such cases, convergent characters may be correlated with one or a few functional anatomical units and readily identifiable by using comparative methods. Stifftail ducks (Oxyurinae) offer one such opportunity to study correlated character evolution and function in the context of phylogenetic reconstruction. Morphological analyses place stifftail ducks as part of a large clade of diving ducks that includes the sea ducks (Mergini), Hymenolaimus, Merganetta, and Tachyeres, and possibly the pochards (Aythyini). Molecular analyses, on the other hand, place stifftails far from other diving ducks and suggest, moreover, that stifftails are polyphyletic. Mitochondrial cytochrome b gene sequences of eight stifftail species traditionally supposed to form a clade were compared with each other and with sequences from 50 other anseriform and galliform species. Stifftail ducks are not the sister group of sea ducks but lie outside the typical ducks (Anatinae). Of the four traditional stifftail genera, monophyly of Oxyura and its sister group relationship with Nomonyx are strongly supported. Heteronetta probably is the sister group of that clade, but support is weak. Biziura is not a true stifftail. Within Oxyura, Old World species (O. australis, O. leucocephala, O. mnccoa) appear to form a clade, with New World species (O. jamaicensis, O. vittata) branching basally. Incongruence between molecules and morphology is interpreted to be the result of adaptive specialization and functional convergence in the hind limbs of Biziura and true stifftails. When morphological characters are divided into classes, only hind-limb characters are significantly in conflict with the molecular tree. Likewise, null models of synonymous and nonsynonymous substitution based on patterns of codon-degeneracy and chemical dissimilarity indicate that the nucleotide and amino acid changes postulated by the molecular tree are more plausible than those postulated by the morphological tree. These findings teach general lessons about the utility of highly adaptive characters (in particular those related to foraging ecology) and underscore the problems that convergence can pose for attempts to recover phylogeny. They also demonstrate how the concept of natural data partitions and simple models of evolution (e.g., parsimony, likelihood, neutrality) can be used to test the accuracy of independent phylogenetic estimates and provide arguments in favor of one tree topology over another.

Original languageEnglish (US)
Pages (from-to)683-714
Number of pages32
JournalSystematic Biology
Volume48
Issue number4
StatePublished - Dec 1999
Externally publishedYes

Fingerprint

Diving
Ducks
diving
limbs (animal)
ducks
limb
Extremities
phylogeny
phylogenetics
Oxyura
Phylogeny
Oceans and Seas
branches
topology
cytochrome
Oxyura leucocephala
substitution
Oxyura jamaicensis
amino acid
ecology

Keywords

  • Anatidae
  • Anseriformes
  • Behavior
  • Congruence analysis
  • Cytochrome b
  • Diving
  • Foraging ecology
  • Functional morphology
  • Oxyurinae

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics

Cite this

Data set incongruence and correlated character evolution : An example of functional convergence in the hind-limbs of stifftail diving ducks. / McCracken, Kevin; Harshman, John; Mcclellan, David A.; Afton, Alan D.

In: Systematic Biology, Vol. 48, No. 4, 12.1999, p. 683-714.

Research output: Contribution to journalArticle

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