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NONADAPTIVE EVOLUTION OF MITOCHONDRIAL GENOME SIZE

Authors

  • Bastien Boussau,

    1. Department of Integrative Biology, University of California—Berkeley, 3060 Valley Life Sciences Building, Berkeley, California, 94720–3140
    2. Laboratoire de Biométrie et Biologie Evolutive, Université de Lyon, Université Lyon 1, CNRS, UMR5558, Villeurbanne, France
    3. E-mail: bastien.boussau@univ-lyon1.fr
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  • Jeremy M. Brown,

    1. Department of Integrative Biology, University of California—Berkeley, 3060 Valley Life Sciences Building, Berkeley, California, 94720–3140
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  • Matthew K. Fujita

    1. Museum of Comparative Zoology, Harvard University, 26 Oxford St., Cambridge, Massachusetts, 02138
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Abstract

Genomes vary greatly in size and complexity, and identifying the evolutionary forces that have generated this variation remains a major goal in biology. A controversial proposal is that most changes in genome size are initially deleterious and therefore are linked to episodes of decrease in effective population sizes. Support for this hypothesis comes from large-scale comparative analyses, but vanishes when phylogenetic nonindependence is taken into account. Another approach to test this hypothesis involves analyzing sequence evolution among clades where duplications have recently fixed. Here we show that episodes of fixation of duplications in mitochondrial genomes of the gecko Heteronotia binoei (two independent clades) and of mantellid frogs (five distinct branches) coincide with reductions in the ability of selection to purge slightly deleterious mutations. Our results support the idea that genome complexity can arise through nonadaptive processes in tetrapods.

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