Evidence for both long-distance dispersal and isolation in the Southern Oceans: molecular phylogeny of Sophora sect Edwardsia (Fabaceae)

We examined the phylogenetic relationships within Sophora sect. Edwardsia using DNA sequences from the chloroplast trnQ-5′rps16 and trnHGUG-psbA intergenic spacers and the nuclear-encoded chloroplast-expressed glutamine synthetase gene. Sequences were analysed with median-joining networks and phylogenetic approaches. Low sequence diversity was detected, which is consistent with past genetic studies of the section. Chloroplast and nuclear sequences are shared across large geographic distances. The New Zealand species did not form a monophyletic group, nor did the species from Chile. However, species on some Pacific Islands (Lord Howe Island, Easter Island, Hawaii and French Polynesia) and Réunion Island in the Indian Ocean appear to have unique chloroplast haplotypes, indicating isolation. The S. chrysophylla chloroplast haplotype derives from the French Polynesian haplotype rather than S. denudata from Réunion Island, with which it shares morphological characters. In the nuclear phylogeny Sophora macrocarpa was sister to the remaining species that were sequenced in the section, a relationship that has been previously suggested from morphological analysis.