Directional asymmetry of long-distance dispersal and colonization could mislead reconstructions of biogeography

Cook, Lyn G. and Crisp, Michael D. (2005) Directional asymmetry of long-distance dispersal and colonization could mislead reconstructions of biogeography. Journal of Biogeography, 32 5: 741-754. doi:10.1111/j.1365-2699.2005.01261.x

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Author Cook, Lyn G.
Crisp, Michael D.
Title Directional asymmetry of long-distance dispersal and colonization could mislead reconstructions of biogeography
Journal name Journal of Biogeography   Check publisher's open access policy
ISSN 0305-0270
Publication date 2005-05
Sub-type Critical review of research, literature review, critical commentary
DOI 10.1111/j.1365-2699.2005.01261.x
Volume 32
Issue 5
Start page 741
End page 754
Total pages 14
Editor David Bellwood
Robert J. Whittaker
Place of publication Oxford, U.K
Publisher Blackwell Publishing
Language eng
Subject 0406 Physical Geography and Environmental Geoscience
Formatted abstract
Aim  Phylogenies are increasingly being used to attempt to answer biogeographical questions. However, a reliance on tree topology alone has emerged without consideration of earth processes or the biology of the organisms in question. Most ancestral-state optimization methods have inherent problems, including failure to take account of asymmetry, such as unequal probabilities of losses and gains, and the lack of use of independent cost estimates. Here we discuss what we perceive as shortcomings in most current tree-based biogeography interpretation methods and show that consideration of processes and their likelihoods can turn the conventional biogeographical interpretation on its head.

Location  Southern hemisphere focus but applicable world-wide.

Methods  The logic of existing methods is reviewed with respect to their adequacy in modelling processes such as geographical mode of speciation and likelihood of dispersal, including directional bias. Published reconstructions of dispersal of three plant taxa between Australia and New Zealand were re-analysed using standard parsimony and maximum likelihood (ML) methods with rate matrices to model expected asymmetry of dispersal.

Results  Few studies to date incorporate asymmetric dispersal rate matrices or question the simplistic assumption of equal costs. Even when they do, cost matrices typically are not derived independently of tree topology. Asymmetrical dispersal between Australia and New Zealand could be reconstructed using parsimony but not with ML.

Main conclusions  The inadequacy of current models has important consequences for our interpretation of southern hemisphere biogeography, particularly in relation to dispersal. For example, if repeated directional dispersals and colonization in the direction of prevailing winds have occurred, with intervening periods of speciation, then there is no need to infer dispersals against those winds. Failure to take account of directionality and other biases in reconstruction methods has implications beyond the simple misinterpretation of the biogeography of a taxonomic group, such as calibration of molecular clocks, the dating of vicariance events, and the prioritization of areas for conservation.
© 2005 Blackwell Publishing Ltd.
Keyword Ecology
Geography, Physical
Ancestral areas
Antarctic circumpolar current
Directional dispersal
Maximum likelihood
Maximum parsimony
New Zealand
Southern hemisphere
Trait optimization
West-wind drift
Ancestral character states
New-zealand flora
Historical biogeography
Transoceanic dispersal
Molecular evidence
Intercontinental disjunctions
Conservation priorities
Vicariance biogeography
Pacific biogeography
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ
Additional Notes This document is a journal review.

Document type: Journal Article
Sub-type: Critical review of research, literature review, critical commentary
Collections: Excellence in Research Australia (ERA) - Collection
School of Biological Sciences Publications
Ecology Centre Publications
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Citation counts: TR Web of Science Citation Count  Cited 109 times in Thomson Reuters Web of Science Article | Citations
Scopus Citation Count Cited 109 times in Scopus Article | Citations
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Created: Mon, 13 Aug 2007, 15:10:58 EST