Phylogeny and biogeography of Alangiaceae (Cornales) inferred from DNA sequences, morphology, and fossils

Abstract

Alangiaceae, in the basal Asterid clade Cornales, consists of only one genus, Alangium. The genus has approximately 24 species distributed mainly in tropical and subtropical regions of the Old World and is well represented in the Tertiary fossil record of the northern hemisphere. We conducted phylogenetic and biogeographic analyses for Alangium by integrating data from DNA sequences, morphology, and fossils to evaluate systematic and biogeographic hypotheses. The results largely agree with the traditional classification of four sections within the genus, and suggest sects. Conostigma and Rhytidandra are successive sister taxa to a clade containing sects. Marlea and Alangium. Our results also indicate that the widespread species A. chinense consists of at least two lineages meriting recognition as distinct species. Biogeographic analysis using DIVA and divergence time dating with the Bayesian method (MULTIDIVTIME) resolved the ancestor of Alangium as being in S.E. Asia in the Late Cretaceous. Several intercontinental migrations involving the margin of the Tethys seaway (TESW), the North Atlantic land bridge (NALB) or the Bering land bridge (BLB), and long-distance dispersals are suggested. The results support TESW for plant migration of thermophilic (including evergreen) taxa in the early Tertiary.