The exotic species Pteris ensiformis (Pteridaceae) in South America: an aproach to naturalization process

Abstract Pteris has numerous representatives of Asian and Oceanic origin naturalized in America, some of them recognized as invasive weeds. Pteris ensiformis was introduced in America in the middle of the 19th century and subsequently naturalized in USA and Central America, but the records of its distribution in South America are isolated and the establishment or naturalization of the populations is unclear. As part of a broader study whose objective is to review the diversity of ferns and lycophytes in the Paranaense forest P. ensiformis was found for the first time in Argentina. In addition to describing, illustrating, and distinguishing the species from other species of the genus in the country, we review the distribution of P. ensiformis in South America comparing herbarium collections and iNaturalist observations, a citizen science platform. Additionally, a status for the species is proposed or suggested in each country where it is registered according to its stage of the naturalization process.