Polystichum Roth, Tent. Fl. Germ.

Kessler, Michael, Moran, Robbin C., Mickel, John T., Matos, Fernando B. & Smith, Alan R., 2018, Prodromus of a fern flora for Bolivia. XXXV. Dryopteridaceae, Phytotaxa 353 (1), pp. 448-450 : 448-450

Polystichum Roth, Tent. Fl. Germ. 3(1): 31, 69–70. 1800.

Polystichum is characterized by having stout, erect or suberect rhizomes, scaly axes, and round sori; most species also have spinulose blade margins and ultimate pinnae and/or pinnules that have a slightly elongated lobe (auricle) or segment on the acroscopic base.

The limits of the genus are still contentious, vis-à-vis certain Old World genera like Cyrtomium , and the relationship to neotropical Phanerophlebia is also close, although neither of these two genera occur in Bolivia. Beyond these affinities, Polystichum is related to the largely temperate genus Dryopteris ( Li & Lu 2006, Li et al. 2008, Liu et al. 2007, Schuettpelz & Pryer 2007). Among the related Bolivian genera, Dryopteris wallichiana is superficially similar, but has entire, nonspinulose pinnules, and the similar Arachniodes and Rumohra have creeping rhizomes and 3- to 4- pinnate blades. Polystichum is monophyletic ( Little & Barrington 2003, Li et al. 2008), with the neotropical species in turn representing a clade that diversified within approximately the last 15 million years ( Driscoll & Barrington 2007, McHenry & Barrington 2014).

The delimitation of individual species is difficult, and polyploidy has often obscured species boundaries ( Barrington 1995 a, b, Little & Barrington 2003, Perrie et al. 2003, Morero et al. 2015). The Andean species of Polystichum are badly in need of monographic study, involving fieldwork, chromosome counts, and molecular analyses ( Driscoll & Barrington 2007, Little & Barrington 2003, McHenry & Barrington 2014). To further complicate the situation, temperate and Central American species are known to hybridize ( Barrington 1985a, 1985b, 1985c, 1990, 2003). This also appears also to be the case in the Andes, but the evidence is scant, and based primarily on perceived morphological intermediacy and occasional spore malformation. More documentation and study (chromosome configurations at meiosis, molecular analyses, detailed character comparisons, field study in areas of sympatry, etc.) are needed to confirm these suspicions. Species delimitation is tentative, and not all specimens of Polystichum from Bolivia can at present be identified with confidence; some are possible hybrids, while others are seemingly distinct ecological forms known from insufficient material.

Polystichum is a genus of temperate and tropical montane regions with 360–400 species. There are about 27 species in the northern and central Andes ( Kessler et al. 2005, McHenry & Barrington 2014), nine in austral South America ( Morero et al. 2013), nine in central and eastern Brazil ( Condack et al. 2010), 31 in the Antilles ( Mickel 1997), and ca. 23 in Mesoamerica and Mexico ( Stolze 1981, Barrington 1995, Mickel & Smith 2004). With 21 species, nearly all different from those in Mexico and Mesoamaerica, Bolivia has the highest number of recognized species in any South American country, but this may reflect intense taxonomic ( Kessler et al. 2005) and ecological work in this area ( Soria & Kessler 2008), rather than a significant biogeographic pattern.