Genealogical partitioning and phylogeography of Colpomenia peregrina (Scytosiphonaceae, Phaeophyceae), based on plastid rbcL and nuclear ribosomal DNA internal transcribed spacer sequences

Abstract

G.Y. Cho, S.M. Boo, W. Nelson and M.N. Clayton. 2005. Genealogical partitioning and phylogeography of Colpomenia peregrina (Scytosiphonaceae, Phaeophyceae), based on plastid rbcL and nuclear ribosomal DNA internal transcribed spacer sequences. Phycologia 44: 103–111.Colpomenia peregrina shows a large morphological variation, and two morphotypes have been described. We used the protein-coding plastid rbcL and the nuclear ribosomal internal transcribed spacer (ITS) region to investigate whether these morphotypes constitute distinct species and to explain the current distribution of the species. Here, we sequenced the rbcL gene from 38 specimens (32 C. peregrina and six putative relatives) and the ITS region from 33 specimens of C. peregrina, including an outgroup taxon. The C. peregrina specimens were variable, having up to 1.17% intraspecific divergence and nine haplotypes in the rbcL gene, and up to 11.01% intraspecific divergence and 21 haplotypes in the ITS region. Independent analyses of the rbcL and ITS data sets produced highly congruent but not identical results. Colpomenia peregrina is monophyletic, but is partitioned into two deeply divergent clades (‘lineage I’ and ‘lineage II’) that we interpret as different species. Lineage I consists of 27 specimens, in both rbcL and ITS data sets, and lineage II contains six specimens. Both lineages occur together in Australia, Korea, New Zealand and USA. Lineages I and II correspond to the epiphytic and epilithic forms, respectively, recognized by Clayton. Our rbcL and ITS data sets corroborate the recent anthropogenic dispersal event between the northwest Pacific and northeast Atlantic Oceans, and also suggest some natural dispersal events during the Pleistocene between the North and South Pacific Ocean.