TY - JOUR
T1 - Data set incongruence and correlated character evolution
T2 - An example of functional convergence in the hind-limbs of stifftail diving ducks
AU - Mccracken, Kevin G.
AU - Harshman, John
AU - Mcclellan, David A.
AU - Afton, Alan D.
N1 - Funding Information:
ACKNOWLEDGMENTS Wear particue lalyrgrattoCeleaf JoursnFlr,e d e Sheldon, Mike Sorenson, Mike Stine, and Linda Whit- tingham for their laboratory support; Van Rsene, m Donna Dittmann,andSteve Cadiff rfr oactcmoue-ss seum skins and genetcir ercss; eBoarLudi vfroezey supplying his morphologilcd aastandeaTt o;y,Pn hyll, Sam, and Heidi Bartram for their hospitality on Kan- garoo Island. Les Christidis, Melisa sCunningham, TeryrDennis, Jef DiMfatteo, Mike Gaunt, BazHu hesg, Ali Lubbock, Mike Lubbock, Anthony MaGuire, David Paton, Graham Rowe, Esther Signe, anrd many others faitcaciletlocltieonodA f f, AruisctaardnnEar -ulian, asinatissues. Josie Babin, John Bates, Des Calalhan,g AmyDriskellP, r eFutel,lB aHaughzsagWe ,ir lmlia Johnson, Janet K,Je eayrKr eian,mrFrankchMcKinm- ney, Richard Olmstead, P. J. Pry,eJ. Vr. Remsen, Fred Sheldon, and Mark Weeat sptnreovdlvual ceiado-bm ments on the manuscript. Institutional and financial support for this project werep rd obytvehUi ivdr-nee sity of Adelae; iSduoAtthruaNa stlniioPaasrla dkn Willie dfSerMvniscieonDeta;rtaemnt pofNe aatl ur Resources; Louisiaa nCopoeFrhaias tnWiivldedel if ReseracUnit; hLuoiDsiaeenponWaaiftll f rediatd mn Fisheries; Louisiana State UnivrsityeSchool of Forestry, Willie, dfand Fisheries, Museum of Natural Science, College of Agricultreu, Ariculturgal Center; Louisiana State Board of Regents; NSF/LaSER grant 19–99-ADP-02;62 and grant fromSigma Xi.
PY - 1999/12
Y1 - 1999/12
N2 - 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.
AB - 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.
KW - Anatidae
KW - Anseriformes
KW - Behavior
KW - Congruence analysis
KW - Cytochrome b
KW - Diving
KW - Foraging ecology
KW - Functional morphology
KW - Oxyurinae
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U2 - 10.1080/106351599259979
DO - 10.1080/106351599259979
M3 - Article
C2 - 12066296
AN - SCOPUS:0033278652
VL - 48
SP - 683
EP - 714
JO - Systematic Biology
JF - Systematic Biology
SN - 1063-5157
IS - 4
ER -