On the Spread of Five Nonnative Ferns in Georgia

Abstract. Compared to most other groups of vascular plants, ferns have been neglected with respect to the potential for nonnative species to invade native plant communities and displace native species. Targeted collecting in the Piedmont of northeast Georgia uncovered five nonnative ferns that represent range extensions or provide clear confirmation of naturalization. Examination of herbarium specimens from Georgia revealed that some earlier records, as well as some overlooked records, were based on misidentifications. The species involved (Cyrtomium fortunei, Deparia petersenii, Dryopteris erythrosora, Macrothelypteris torresiana, and Pteris multifida) are all introductions from temperate regions in East Asia and represent escapes from cultivation. Study of Georgia collections held in herbaria from throughout the Southeast allowed determination of the first appearance and subsequent range expansion of the five species over time. These data and information about mating systems, ploidy level, and ecological requirements of each species allowed inferences to be made about their probable spread in the future, including effects of climate change.