Phylogeny and historical biogeography of Anaxagorea (Annonaceae) using morphology and non-coding chloroplast sequence data

The Annonaceae are a pantropical angiosperm. family, in which Anaxagorea is sister to the rest of the family based on previous phylogenetic studies. Anaxagorea is the only genus of Annonaceae with a disjunct distribution in South and Central America and southeast Asia. Earlier arguments on the biogeographic history of Annonaceae led to the hypothesis of a Laurasian origin for Anaxagorea. A detailed phylogenetic study was conducted using 75 morphological characters and molecular sequences from the atpB-rbcL, psbA-trnH, and trnL-trnF spacer regions and the trnL intron. Molecular analyses alone do not support the monophyly of the Asian species, but the morphological and combined molecular and morphological analyses do. AN analyses place most Central American species in a clade, but none support an Asian-Central American clade. South American species form a basal grade, thereby refuting the hypothesis of a Laurasian origin for the genus and indicating instead a Gondwanan origin. Parsimony optimizations and DIVA reconstructions of biogeographic data indicate separate dispersals from South America to Central America and to Asia. Molecular age estimates indicate an Eocene origin for the genus. The clade containing the Asian and Central American species is dated to be younger than the Oligocene climatic deterioration, which reduces support for the North Atlantic land bridge as a dispersal route from South America to Asia.