phymatosorus longissimus (bl.) pic. serm. (polypodiaceae): rediscovered in taiwan

The fern, Phymatosorus longissimus (Bl.) Pic. Serm., was believed to be locally extinct in Taiwan. However, we recently rediscovered this species in Mudan, Pingtung County and Lanyu Island, Taitung County of Taiwan. The species has currently been found in wetlands neighboring cultivated fields. These habitats are prone to the disturbance of human activities, which may lead to another future extinction of the species in Taiwan. Based on the IUCN criteria, we proposed Phymatosorus longissimus (Bl.) Pic. Serm. To be a critically endangered species in Taiwan. We also discussed the taxonomy and the distribution of this species.