Reticulate evolution of the Daphnia pulex complex as revealed by nuclear markers

Authors

  • ROLAND VERGILINO,

    1. Département de Biologie, Centre d’Études Nordiques, Université du Québec à Rimouski, Québec, Canada G5L 3A1
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  • SILVIA MARKOVA,

    1. Département de Biologie, Centre d’Études Nordiques, Université du Québec à Rimouski, Québec, Canada G5L 3A1
    2. Institute of Animal Physiology and Genetics, Department of Vertebrate Evolutionary Biology and Genetics, Academy of Sciences of the Czech Republic, 277 21 Libechov Czech Republic
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  • MARC VENTURA,

    1. Spanish Research Council CSIC, Ctr Adv Studies Blanes CEAB, Biodiversity and Biogeodynamics Grp, Blanes 17300, Girona, Catalonia, Spain
    2. Institut de la Recerca de l'Aigua. Universitat de Barcelona, Av. Diagonal 684, 08034-Barcelona, Catalonia, Spain
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  • MARINA MANCA,

    1. CNR Istituto per lo Studio degli Ecosistemi, largo Tonolli 50, 28922 Verbania, Italy
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  • FRANCE DUFRESNE

    1. Département de Biologie, Centre d’Études Nordiques, Université du Québec à Rimouski, Québec, Canada G5L 3A1
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France Dufresne, Fax: 418 724 1849; E-mail: France_dufresne@uqar.qc.ca

Abstract

The study of species complexes is of particular interest to understand how evolutionary young species maintain genomic integrity. The Daphnia pulex complex has been intensively studied as it includes species that dominate freshwater environments in the Northern hemisphere and as it is the sole North American complex that shows transitions to obligate parthenogenesis. Past studies using mitochondrial markers have revealed the presence of 10 distinct lineages in the complex. This study is the first to examine genetic relationships among seven species of the complex at nuclear markers (nine microsatellite loci and one protein-coding gene). Clones belonging to the seven species of the Daphnia pulex complex were characterized at the mitochondrial NADH dehydrogenase (ND5) gene and at the Lactate dehydrogenase (LDH) locus. K-means, principal coordinate analyses and phylogenetic network analyses on the microsatellite data all separated European D. pulicaria, D. tenebrosa, North American D. pulex, D. pulicaria and their hybrids into distinct clusters. The hybrid cluster was composed of diploid and polyploid hybrids with D. pulex mitochondria and some clones with D. pulicaria mitochondria. By contrast, the phylogeny of the D. pulex complex using Rab4 was not well resolved but still showed clusters consisting mostly of D. pulex alleles and others of D. pulicaria alleles. Incomplete lineage sorting and hybridization may obscure genetic relationships at this locus. This study shows that hybridization and introgression have played an important role in the evolution of this complex.

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