Chloranthaceae is one of the earliest diverging angiosperm families and is comprised of approximately 75 species in four genera (Chloranthus, Sarcandra, Ascarina, and Hedyosmum). This family has received considerable attention because of its seemingly primitive morphology, disjunct tropical distribution in Asia and America, and extensive fossil record from the Early Cretaceous. In the present study, we reconstructed the phylogeny of Chloranthaceae based on a combined dataset of three plastid DNA regions and 56 species. We then estimated divergence times in the family using two relaxed molecular clock methods (BEAST and penalized likelihood). We focused on testing the influence of fossil taxa in calibrating the molecular phylogeny, and on assessing the current taxonomy of the family in light of the phylogenetic results. Our results indicate that most intrageneric divisions within Ascarina and Hedyosmum are not monophyletic. The results from the dating analysis suggest that the Hedyosmum-like fossil Asteropollis represents a stem lineage of Hedyosmum, as has been suggested previously from morphological analyses. In contrast, our results indicate that the Chloranthus-like fossil Chloranthistemon, previously suggested on morphological grounds to be a stem relative of Chloranthus, may, instead, belong to the branch leading to the clade Chloranthus+Sarcandra. The median crown ages of Chloranthus, Sarcandra, Ascarina, and Hedyosmum estimated in the BEAST analysis were 26.3, 9.5, 31.0 and 45.8 million years ago (Ma), respectively, whereas the divergence between Chloranthus and Sarcandra, the splitting of Ascarina with the former two genera, and Hedyosmum separating from the three genera were estimated to 63.8, 95.7 and 111.1 Ma. The present study sheds further light on the temporal evolution of Chloranthaceae and exemplifies how molecular dating analyses may be used to explore alternative phylogenetic placements of fossil taxa.

This study analyses the pollination systems and biogeography of three allopatric species of Schisandra (Section Euschisandra) consisting of S. glabra (North America), S. bicolor (China), and S. repanda (Japan); the clade is delimited in a phylogenetic tree of Schisandraceae constructed with nuclear and plastid genes. The male and female flowers of these species have similar floral structures, but exhibit different pollination systems. At the base of the clade, S. glabra is pollinated by a wide variety of beetles and flies in a generalist pollination system that also includes floral heat and the use of male and female flowers as brood sites for insects. In Asia, however, S. bicolor and S. repanda are pollinated exclusively by one or two different species of gall midges (Resseliella spp.) in a specialist pollination system. In this system only female, pollen-eating gall midges pollinate the flowers and breed on nearby spiderwebs. The gall midge pollination system is specialized and derived from the generalist system in S. glabra, and basal in the clade. Pollen is the main floral resource, and we hypothesize it is exploited to enrich eggs, and as a result species of gall midges could increase reproductive fitness by feeding on a single dependable food source. Subsequently the life cycles of the plants and insects evolved into a tight association in old stable plant communities in the Sino-Japanese flora. Divergence times for the plant species are presented and correlated with past distributions and migration routes.