Pelazoneuron

Kessler, Michael, Smith, Alan R., Øllgaard, Benjamin, Matos, Fernando B. & Moran, Robbin C., 2023, Prodromus of a fern flora of Bolivia. XLII. Update I., Phytotaxa 630 (3), pp. 183-210 : 205-206

Pelazoneuron

As a result of recent studies by Fawcett & Smith (2021), as well as phylogenetic studies by Fawcett et al. (2021), the family Thelypteridaceae has received a new classification, which impacts the classification of species previously placed in Christella by Smith & Kessler (2017). Holttum (1974) described Christella sect. Pelazoneuron in his treatment of the Thelypteridaceae of Africa and considered most African species of Christella to belong to this section, in addition also to many neotropical species (unnamed by Holttum); he selected one of these, Christella patens , as the type of his section. Molecular data suggest that Pelazoneuron is rather distantly related to Christella ( Smith & Cranfill 2002, Almeida et al. 2016, Patel et al. 2019, Fawcett & Smith 2021, Fawcett et al. 2021). Pelazoneuron , as newly defined, is an exclusively American genus of 16 species, four of which occur in Bolivia. Characters distinguishing Pelazoneuron from Christella and most other New World genera in the family include having the lowermost veins from adjacent segments connivent at an acute angle at the sinuses (vs. united at an obtuse angle below the sinus and with an excurrent vein to the sinus) and in having the proximal pinnae the longest, or nearly so. Pelazoneuron differs from many other cyclosoroid genera (in the Neotropics including Amblovenatum , Cyclosorus , Goniopteris , Meniscium, Stegnogramm a, and Steiropteris ) in one or often more of the following characteristics: lack of protruding aerophores at pinna bases; relatively large, ± persistent indusia; lack of areolate venation and included veinlets; monomorphic fronds; lack of laminar buds; lack of sessile, resinous glands on veins and laminar tissue; generally long-creeping rhizomes; and somewhat weedy nature in semi-open habitats.

All known species of Pelazoneuron , except of one species naturalized in Spain and East Africa, are restricted to the New World tropics and subtropics, from the southern U.S.A. through the Antilles, Mexico, Central America, and South America to northern Argentina, Paraguay, Uruguay, and Bolivia ( Smith 1971). Most species are at least locally common, if not weedy, and occur at low to middle elevations, to ca. 2600 m in the tropics, and are found along roadsides, trails, ditches, ravines, and limestone outcrops, often in slightly disturbed, somewhat open places.

Other neotropical genera in the family ( Amauropelta , Cyclosorus , Goniopteris , Meniscium , Stegnogramma , and Steiropteris ) are distantly related to Pelazoneuron , which is sister to a large clade that includes predominantly paleotropical genera (Fawcett et al. 2021). Our circumscription of New World Pelazoneuron is largely as treated by Smith (1971) as Thelypteris sect. Cyclosorus , with the exclusion of a few species now placed in other genera: three are included in Christella ( C. conspersa , C. dentata , C. hispidula ), one in Cyclosorus s.s. ( C. interruptus ), and another, the widely naturalized Thelypteris opulenta , is now placed in the paleotropical genus Amblovenatum . All of the American species now placed in Christella , Cyclosorus , and Amblovenatum have the lowermost veins from adjacent segments truly united at an obtuse angle below the sinuses, producing an excurrent vein from this union that runs to the sinus, a condition largely absent in Pelazoneuron .

The following new combinations have now been made to accommodate the species of Pelazoneuron in Bolivia. The key distinguishing them is adapted from Kessler & Smith (2017):

1 Rhizomes suberect to erect, hidden by old leaf bases; proximal pinnae often auriculate at acroscopic bases ................................ 2

- Rhizomes creeping, readily visible; proximal pinnae not auriculate ............................................................................................... 3

2 Blades adaxially glabrous on costules and veins; petiole base scales tan, ovate to ovate-lanceolate, glabrous or nearly so, dull ..... .............................................................................................................................................................................................. P. patens

- Blades adaxially hairy on costules and veins; petiole base scales brown, lanceolate, pubescent, shining ...................... P. schizotis

3 Costal hairs ca. 0.1. 2 mm long, moderately dense; costal scales relatively few ........................................................... P. abruptum

- Costal hairs mostly> 0.2 mm long, dense; costal scales numerous ..................................................................................... P. clivale