Population and microclimate studies of the American hart's-tongue fern (Asplenium scolopendrium var. americanum (fern.) Kartesz & Ghandi) in central New York

The American hart's-tongue fern (Asplenium scolopendrium var. americanum) is a climatically sensitive, federally-listed (threatened) evergreen fern. New York contains the largest population of American hart's-tongue fern in the United States. This research updated available census data, used count-based population viability analysis to simulate extinction risk, investigated long-term population trends, described microclimate within American hart's-tongue fern habitats, and tested the effect of climate on sporophyte distribution. Censuses in 2011 and 2012 showed that the population recovered after a significant decline observed in 2002. Extinction risk and long term trends varied between individual occurrences. American hart's-tongue fern habitats had significantly different microclimates than surrounding areas. Daily temperature ranges, daily minimum temperatures, and days with freezing temperatures were significantly correlated with sporophyte distribution within habitats. Future studies will be required to investigate links between microclimate and extinction risk, and to predict climate change impacts to this species.