Population dynamics and reproductive ecology of the gynodioecious prairie species Lobelia spicata Lam. (Campanulaceae)

The breeding system of a plant species describes not only gender distribution among plant morphs (gender system), but can also include pollination type, floral compatibility, and pollination syndrome. Since breeding system traits are likely to be genetically inherited, predictions about evolutionary relationships within a family or genus can be made by examining variation in breeding system dynamics. In this literature review, the classification of and phylogenetic relationships within Lobelia L. were examined to determine the closest relatives of Lobelia spicata Lam. (Campanulaceae), a gynodioecious prairie species. Breeding system distribution was assessed for Lobelia overall, and patterns of variation in pollination type, floral compatibility and pollination syndrome were reviewed for the closest relatives of L. spicata. The classification of Lobelia has undergone multiple transformations throughout history, but the most recent system divides the genus into 18 sections based on phenotypic characters, biogeographical patterns and molecular phylogenies. L. spicata is grouped with the 21 other eastern North American species into Lobelia section Lobelia. Members of Lobelia are exclusively synoecious with the exception of section Hypsela, which contains dioecious species, and section Lobelia, which contains two gynodioecious species including L. spicata. For L. spicata’s closest relatives in Lobelia section Lobelia, only 6 species out of 22 have had data on pollination type and floral compatibility collected, and among those species the combinations are highly variable. Further, 21 of the 22 species (e.g. L. spicata) are insect-pollinated with white, blue or purple corollas. L. cardinalis is the only species exhibiting an avian pollination syndrome, most likely due to its large, red flowers. The construction of comprehensive, molecular-based phylogenies for the North American Lobelia as well as additional research on individual Lobelia species will increase understanding of breeding system evolution within the genus.