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New and Noteworthy Epiphytic Ferns from the Urban Forests of Coastal Southern California, U.S.A.

Davallia solida (G. Forst.) Sw. (Davalliaceae), Phlebodium aureum (L.) J. Sm. (Polypodiaceae), Phlebodium pseudoaureum (Cav.) Lellinger (Polypodiaceae), and Rumohra adiantiformis (G. Forst.) Ching (Dryopteridaceae) are epiphytic ferns native to the subtropical and tropical regions primarily of the Southern Hemisphere. These cultivated ornamental ferns are reported here for the first time growing without direct human assistance in the urban forests of coastal southern California. Sphaeropteris cooperi (Hook. ex Muell.) R.M. Tryon (Cyatheaceae), a popular ornamental tree fern native to the subtropical rainforests of eastern Australia, has naturalized on the rocky cliffs of Santa Catalina Island, southern California. We report the first documented mainland occurrences of this species growing as an epiphyte in coastal urban southern California. The known epiphytic occurrences documented for Nephrolepis cordifolia (L.) C. Presl (Nephrolepidaceae) and Psilotum nudum (L.) P. Beauv. (Psilotaceae) for the urban forests are also provided. Apparently for the first time in California or elsewhere, we report the known epiphytic occurrences of Cyrtomium falcatum (L.f.) C. Presl (Dryopteridaceae). Our findings suggest the southern California coastal urban forest environment promotes the dispersal and establishment of non-native epiphytes by facilitating interactions between cultivated phorophytes and several epiphytic ferns escaping cultivation. The ferns have been introduced by horticulture and escaped from gardens, events that represent an important colonization pathway for the invasion of southern California’s urban forests. We hope that our findings will stimulate discourse and motivate others to study further the epiphytic ferns of California and other Mediterranean climate regions around the world.