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Speciation reversal and biodiversity dynamics with hybridization in changing environments

Authors

  • OLE SEEHAUSEN,

    1. Center of Ecology, Evolution & Biogeochemistry, Swiss Institute for Environmental Sciences and Technology (EAWAG ), Seestrasse 79, 6047 Kastanienbaum, Switzerland,
    2. Institute of Zoology, University of Bern, Baltzerstrasse 6, 3012 Bern, Switzerland,
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  • GAKU TAKIMOTO,

    1. Center of Ecology, Evolution & Biogeochemistry, Swiss Institute for Environmental Sciences and Technology (EAWAG ), Seestrasse 79, 6047 Kastanienbaum, Switzerland,
    2. Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT 06511, USA,
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  • DENIS ROY,

    1. Center of Ecology, Evolution & Biogeochemistry, Swiss Institute for Environmental Sciences and Technology (EAWAG ), Seestrasse 79, 6047 Kastanienbaum, Switzerland,
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  • JUKKA JOKELA

    1. Center of Ecology, Evolution & Biogeochemistry, Swiss Institute for Environmental Sciences and Technology (EAWAG ), Seestrasse 79, 6047 Kastanienbaum, Switzerland,
    2. Institute of Integrative Biology, ETH-Zürich, Überlandstrasse 133, 8600 Dübendorf, Switzerland
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  • Ole Seehausen and Gaku Takimoto contributed equally to the work (authorship in alphabetical order).

Ole Seehausen, Fax: +41 41 349 21 68, E-mail: ole.seehausen@eawag.ch,GakuTakimoto,Email: gaku@bio.sci.toho-u.ac.jp

Abstract

A considerable fraction of the world's biodiversity is of recent evolutionary origin and has evolved as a by-product of, and is maintained by, divergent adaptation in heterogeneous environments. Conservationists have paid attention to genetic homogenization caused by human-induced translocations (e.g. biological invasions and stocking), and to the importance of environmental heterogeneity for the ecological coexistence of species. However, far less attention has been paid to the consequences of loss of environmental heterogeneity to the genetic coexistence of sympatric species. Our review of empirical observations and our theoretical considerations on the causes and consequences of interspecific hybridization suggest that a loss of environmental heterogeneity causes a loss of biodiversity through increased genetic admixture, effectively reversing speciation. Loss of heterogeneity relaxes divergent selection and removes ecological barriers to gene flow between divergently adapted species, promoting interspecific introgressive hybridization. Since heterogeneity of natural environments is rapidly deteriorating in most biomes, the evolutionary ecology of speciation reversal ought to be fully integrated into conservation biology.

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