Evolution of nuclear rDNA ITSsequences in the Cladophora albida/sericea clade (Chlorophyta)

F.T. Bakker, J.L. Olsen, W.T. Stam

    Research output: Contribution to journalArticleAcademicpeer-review

    100 Citations (Scopus)

    Abstract

    Ribosomal DNA ITS sequences were compared among 13 different species and biogeographic isolates from the monophyletic albida/sericea clade in the green algal genus Cladophora. Six distinct ITS sequence types were found, characterized by multiple insertions and deletions and high levels of nucleotide substitution. Conserved domains within the ITS regions indicate the presence of ITS secondary structure. Low transition/transversion ratios among the six types and nearly symmetrical tree-length frequency distributions indicate some saturation, and low phylogenetic signal. Although branching order among five of the six ITS sequence types could not be resolved, estimates of ITS sequence divergence as compared with 18S divergence in a subset of the taxa suggests that the origin of the different ITS types is probably in the mid-Miocene (12 Ma ago) but that biogeographic isolates within a single ITS type (including both Pacific and Atlantic representatives) have probably dispersed on a time scale of thousands rather than millions of years.
    Original languageEnglish
    Pages (from-to)640-651
    JournalJournal of Molecular Evolution
    Volume40
    Issue number6
    DOIs
    Publication statusPublished - 1995

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