New perspectives on the pollination biology of basal angiosperms

Coleoptera and Diptera are the primary pollinators of extant basal angiosperms (wind pollination is rare); lineages of these insects were established by the Late Jurassic. Contemporary examples of insect pollination of nonangiosperm plants are present in Gnetales (flies, moths) and Cycadales (beetles). The breeding systems of extant basal angiosperms are dominated by bisexual, protogynous, fragrant flowers that may form chambers in the female phase. Floral thermogenesis is widely distributed throughout the extant basal angiosperms (Nymphaeaceae, Illiciaceae, Aristolochiaceae, Magnoliaceae, and Annonaceae), into the basal monocots (Araceae) and extends into the advanced monocots (Arecaceae and Cyclanthaceae) and eudicots (only one family, Nelumbonaceae). The cycads are the only other plant group with heat-producing reproductive structures (male and female cones). Flower temperatures of thermogenic plants are in the range required by endothermic insects for purposes of mating and flight, and it is hypothesized that floral heat is a direct energy reward to insects (a resource). Floral fragrance and heat played major roles in early plant reproductive systems, and fragrance could signal not only food and sex but also heat.