Ann. Bot. Fennici 49: 67–74 ISSN 0003-3847 (print) ISSN 1797-2442 (online) Helsinki 26 April 2012 © Finnish Zoological and Botanical Publishing Board 2012 Polystichum perpusillum (sect. Haplopolystichum, Dryopteridaceae), a new fern species from Guizhou, China Li-Bing Zhang1 & Hai He2,* 1) Chengdu Institute of Biology, Chinese Academy of Sciences, P.O. Box 416, Chengdu, Sichuan 610041, China; and Missouri Botanical Garden, P.O. Box 299, St. Louis, Missouri 63166-0299, USA 2) College of Life Sciences, Chongqing Normal University, Shapingba, Chongqing 400047, China (*corresponding author’s e-mail:
[email protected]) Received 20 Dec. 2010, final version received 23 Mar. 2011, accepted 24 Mar. 2011 Zhang, L. B. & He, H. 2012: Polystichum perpusillum (sect. Haplopolystichum, Dryopteridaceae), a new fern species from Guizhou, China. — Ann. Bot. Fennici 49: 67–74. Polystichum perpusillum L.B. Zhang & H. He, a new fern species of Polystichum sect. Haplopolystichum (Dryopteridaceae), is described and illustrated from the entrance to a karst cave in southern Guizhou, China. A phylogenetic analysis based on the chlo- roplast trnL-F sequences shows that it is phylogenetically isolated in the section with no close relatives. Morphologically, it is similar to P. minutissimum, but P. perpusillum has an acute lamina apex, up to 12 pairs of pinnae per lamina, and deltoid-ovate or ovate-lanceolate rachis scales, while P. minutissimum has a round lamina apex, 5–8 pairs of pinnae per lamina, and subulate or linear rachis scales. Polystichum perpusil- lum has a granulate sculpture with verrucae on its perispore, a sculpture rare in the genus. The species is considered to be critically endangered.