Evolution and phylogeography of Halimeda section Halimeda (Bryopsidales, Chlorophyta) |
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Authors: | Verbruggen Heroen Clerck Olivier De Schils Tom Kooistra Wiebe H C F Coppejans Eric |
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Institution: | Phycology Research Group and Center for Molecular Phylogenetics and Evolution, Ghent University, Krijgslaan 281 (S8), B-9000 Gent, Belgium. heroen.verbruggen@ugent.be |
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Abstract: | Nuclear ribosomal and plastid DNA sequences of specimens belonging to section Halimeda of the pantropical green seaweed genus Halimeda show that the group under scrutiny contains many more genetically delineable species than those recognized by classical taxonomy. Discordances between phylograms inferred from nuclear and plastid DNA sequences suggest that reticulate evolution has been involved in speciation within the clade. Nonetheless, our data do not allow ruling out certain alternative explanations for the discordances. Several pseudo-cryptic species are restricted to the margins of the generic distribution range. In a clade of H. cuneata sibling species from widely separated subtropical localities in the Indian Ocean, the South African sibling branches off first, leaving the Arabian and West Australian species as closest relatives. We hypothesize that geographic isolation of the siblings may have taken place following Pleistocene or Pliocene periods of climatic cooling during which subtropical species occupied larger distribution ranges. A more basal separation of Atlantic, Indo-Pacific, and Mediterranean species indicates vicariance. The alternative events that could have caused this vicariance are discussed. |
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Keywords: | Biogeography Chlorophyta Evolution Halimeda Incomplete lineage sorting Indian ocean Marine speciation Phylogeny Reticulate evolution |
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