Boreotropical range expansion and long-distance dispersal explain two amphi-Pacific tropical disjunctions in Sabiaceae

Sabiaceae comprises three genera and ca. 80 species with an amphi-Pacific tropical disjunct distribution. It has been unclear whether the family is monophyletic, where the family belongs within the angiosperm phylogeny, and when and how is present-day disjunct distribution originated. To address these questions, we conducted a phylogenetic analysis of Sabiaceae with comprehensive sampling of the family and basal eudicots using six chloroplast DNA loci (atpB, rbcL, matK, ndhF, atpB- rbcL and trnL-trnF). Our results support the monophyly of Sabiaceae s. l. that includes three genera: Meliosma Blume, Ophiocaryon Endl. and Sabia Colebr. The placement of Sabiaceae as sister to Proteales receives moderate bootstrap support, and is corroborated by various alternative hypothesis tests. Within Sabiaceae, Ophiocaryon and Sabia were resolved as strongly supported clades, whereas Meliosma was paraphyletic with Ophiocaryon nested within it. The biogeographically disjunct accessions of Meliosma alba (which is alternatively known as Kingsboroughia alba (Schltdl.) Liebm.) sampled from southwestern China and Mexico form a monophyletic group. Molecular dating and ancestral area reconstruction suggest a Eurasian origin of Sabiaceae in the late Cretaceous and a boreotropical range expansion during Paleogene. Southward migrations were inferred from continental Eurasia to the Malesian region in Sabia and in the Asian Meliosma, and from Central America to South America in the Neotropical clade of Meliosma in response to climatic cooling after the late Miocene. A long distance dispersal from Central America to tropical Asia was suggested during the time at the Neogene and Quaternary boundary in Meliosma alba (now recognized as Kingsboroughia alba). Our results also support the recognition of Kingsboroughia Liebm. as a distinct genus to maintain the monophyly of each of the genera: Meliosma, Ophiocaryon and Sabia. Kingsboroughia along with Meliosma and Ophiocaryon constitutes the subfamily Meliosmoideae Mast., while Sabia is the sole genus of Sabioideae Y. W. Law & Y. F. Wu