Amauropelta Kunze, Farrnkräuter

Smith, Alan R. & Kessler, Michael, 2017, Prodromus of a fern flora for Bolivia. XXX. Thelypteridaceae, Phytotaxa 331 (1), pp. 1-34 : 3

Amauropelta Kunze, Farrnkräuter 1: 86. 1843.

= Thelypteris subg. Amauropelta (Kunze) A.R.Sm., Amer. Fern J. 63: 121. 1973.

= Parathelypteris H.Ito, Acta Phytotax. Sin. 8(4): 300–301. 1963.

= Thelypteris subg. Parathelypteris (H.Ito) R.M.Tryon & A.F.Tryon, Rhodora 84: 128. 1982.

This genus is characterized by 1-pinnate-pinnatifid or 2-pinnate laminae (rarely 1-pinnate, then pinnae <15 mm long) with one to usually many pairs of gradually reduced proximal pinnae (the lowest auriculiform or glanduliform), and free veins, those from adjacent segments meeting the margin above the sinuses (rarely at the sinuses) of pinnatifid pinnae; x = 29 (many spp. counted). Some species groups are in need of monographic revision. Not all specimens can be reliably determined; it is also likely that many species, some known only from sterile and/or fragmentary material, remain to be described. A sectional classification of Amauropelta ( Smith 1974) , based on morphological characters, e.g., rhizome habit, aerophores, presence/absence of glands, hair type, attenuation of blade base, and indusial presence/ absence, appears to need modifications. Attempts to confirm this, using molecular data, have so far been unsuccessful, possibly due to insufficient sampling .

Amauropelta is the most common and widespread genus of Thelypteridaceae in the neotropics, with over 200 species there, also with a few species in Africa, Madagascar, the Mascarene Islands, Sri Lanka, and Polynesia (one in Hawaii). The genus is most closely related to several Old World genera: Coryphopteris Holttum , Metathelypteris (H.Itô) Ching , and Parathelypteris (H.Ito) Ching ( Almeida et al. 2016). The north-temperate genus Parathelypteris , comprising about 15 species, is now thought to be polyphyletic ( He & Zhang 2012, Almeida et al. 2016) and differs mainly by having long-creeping, narrow rhizomes and different base chromosome numbers (x = 27, 31); part of Parathelypteris , including the type, appears basal to Amauropelta ( Almeida et al. 2016) , and we include it within Amauropelta .

Twenty of the 54 species of Amauropelta in Bolivia are known from three or fewer collections; eight species are known only from the Bolivian types. Clearly , the genus is under-collected, not only in Bolivia but throughout its range, and collectors often pass them by, because of general similarity to other, sometimes common or weedy species of Amauropelta . This is a taxonomically difficult group, still in need of much more study, throughout the American tropics, including Bolivia .

Characters useful for the identification of Amauropelta spp. include: rhizome habit (creeping to suberect or erect); rhizome apex and stipe base scale morphology; blade base (number of reduced pinnae, whether gradually or abruptly diminishing); pinna lobing (entire, shallowly, or deeply pinnatifid) and size; veins per segment; aerophores (presence or absence, tuberculiform vs. elongate/peglike); indument (hairs and scales) on the blades (present or absent, scale color, clathrate or not, hair length, whether single-celled or septate, hooked or straight, spreading vs. adpressed, clustered or not); laminar and indusial glands (present or absent, color, form – short-stipitate or sessile); soral shape (round vs. oblong) and position (inframedial to submarginal; indusia (present or absent, as well as size); sporangial indument (setulose or not).