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.
Pollination systems, biogeography, and divergence times of three allopatric species of Schisandra in north America, China, and Japan
Year: 2011
