Evolution of Insular Pacific Pittosporum (Pittosporaceae): Origin of the Hawaiian Radiation

We investigated the origin of Hawaiian Pittosporum and their relationship to other South Pacific Pittosporum species using internal transcribed spacer sequences of nuclear ribosomal DNA. We performed both maximum-parsimony and maximum-likelihood analyses, which produced congruent results. Sequence d...

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Bibliographic Details
Published in:Molecular phylogenetics and evolution 2002-01, Vol.22 (1), p.31-42
Main Authors: Gemmill, C.E.C., Allan, G.J., Wagner, W.L., Zimmer, E.A.
Format: Article
Language:English
Subjects:
Base Sequence
DNA, Plant - genetics
DNA, Ribosomal Spacer - genetics
Evolution, Molecular
Hawaii
Magnoliopsida - classification
Magnoliopsida - genetics
Phylogeny
Species Specificity
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Summary:We investigated the origin of Hawaiian Pittosporum and their relationship to other South Pacific Pittosporum species using internal transcribed spacer sequences of nuclear ribosomal DNA. We performed both maximum-parsimony and maximum-likelihood analyses, which produced congruent results. Sequence divergence was 0.0% between Hawaiian members of Pittosporum. These taxa formed a strongly supported clade, suggesting a single colonization event followed by phyletic radiation. Sister to the Hawaiian clade were two South Pacific species, P. yunckeri from Tonga and P. rhytidocarpum from Fiji. This result presents convincing evidence for a South Pacific origin of Hawaiian Pittosporum. Our results also identify a monophyletic group comprising three species representing the Fijian Province and East Polynesia, two introductions onto New Caledonia, and at least one (but possibly two) introduction(s) onto New Zealand. Whether the New Zealand taxa form a monophyletic group is unclear from these data. Previous morphologically based hypotheses, however, suggest the presence of four different lineages occupying New Zealand. The nonmonophyly of the New Caledonian species was not surprising based on the extent of their morphological diversity. Although this latter result is not strongly supported, these species are morphologically complex and are currently the subject of taxonomic revision and molecular systematic analyses.
ISSN:1055-7903
1095-9513
DOI:10.1006/mpev.2001.1019