Pteridium esculentum subsp. arachnoideum

Schwartsburd, Pedro B., Yañez, Agustina & Prado, Jefferson, 2018, Formal recognition of six subordinate taxa within the South American bracken fern, Pteridium esculentum (P. esculentum subsp. arachnoideum s. l. - Dennstaedtiaceae), based on morphology and geography, Phytotaxa 333 (1), pp. 22-40 : 37

4. Pteridium esculentum subsp. arachnoideum × Pteridium esculentum subsp. campestre ( Figs. 5F–H , 7 )

Plants probably forming small thickets. Rhizomes long-creeping. Fronds to 3 m long; petioles proximally with epipetiolar roots; laminae proximally 3-pinnate-pinnatifid; pinnae and pinnules distally with free lobes between the segments; compound distal segments equilateral, regularly dissected, caudate at apex; simple distal segments linear, to 2.5(–3) cm long; costae abaxially with reddish catenate hairs, 5–7-celled, 0.3–0.5 mm long, adaxially glabrous; costules abaxially with reddish catenate hairs, adaxially glabrous; veins abaxially strigose, with stiff, acicular hairs, 0.2–0.3 mm long, adaxially glabro us; laminar tissue between the veins abaxially with farinaceous appearance, not visible, totally covered by gnarled hairs, adaxially glabrous; laminar margins regularly transformed into pseudo-indusia; pseudo-indusia glabrous.

Distribution and ecology: — Venezuela, Guyana, and Brazil; from 150 m to 1950 m ( Fig. 7 ).

Specimens examined:— VENEZUELA. Amazonas: Río Negro , 1°57’N, 67°00’W, 150 m, 22 February 1989, G. Aymard et al. 7376 (US) ; Atabapo, 04°34’N, 65°31’W, 590 m, February 1992, A. Chaviel 189 (US). Bolivar: Meseta del Jaua, Cerro Jaua, 4°48’50”N, 64°34’10”W, 1850–1920 m, 4 March 1974, J. A. Steyermark et al. 109770 ( US).— GUYANA. Cuyuni-Mazaruni: Bartica-Potaro Road , 6 miles south of Bartica , 9 April 1956, J. R. Ramsammy 28 (US).— BRAZIL. Pernambuco: Timbaúba , Eng. Xixá, 22 May 1992, I. C. L. Barros et al. s.n. (PEUFR-21053) .

Bahia: Chapada Diamantina, Morro do Chapéu, 11°35’28”S, 41°12’27”W, 15 March 2008, M. L. Guedes et al. 14217 ( ALCB, VIC-frag.) ; Morro do Chapéu, Marrão, Mata de Grotão , 11°35’S, 41°12’W, 5 May 2007, J. L. Ferreira & F. R. Nonato 81 (HUEFS-on 2 sheets) ; Mucugê, Unidade de Manejo Sustentável Piabinha , 12°59’33”S, 41°20’30”W, 930 m, 12 January 1997, A. S. Conceição et al., UMS 206 ( HRB) .

Notes:— This putative hybrid between Pteridium esculentum subsp. arachnoideum and P. esculentum subsp. campestre occurs in places of sympatry ( Fig. 7 ) and has intermediate morphology between the parents. It has the unique laminar indument of subsp. campestre (i.e., veins abaxially strigose, with stiff, acicular hairs, laminar tissue between veins fully covered with gnarled hairs), and the laminar architecture similar to subsp. arachnoideum : free lobes between the ultimate segments, compound distal segments with caudate apex, and simple distal segments to 2.5(–3) cm long ( Figs. 5F–H ; see also Figs. 1A–F ).

Figures

FIGURE 1. A–C. Pteridium esculentum subsp. campestre: A. pinnule (Nonato 927), B. segment, abaxially (Schwartsburd 2411), C. segment, cross section, abaxial side up, showing strigose veins, with stiff, acicular hairs, and laminar tissue between the veins with farinaceous appearance, fully covered with gnarled hairs (Schwartsburd 2411), D–F. Pteridium esculentum subsp. arachnoideum var. arachnoideum: D. pinnule (Schwartsburd 2490), E. segment, abaxially (Schwartsburd 2490), F. segment, cross section, abaxial side up, showing serieceous veins, with lax, arachnoid hairs, and glabrous laminar tissue between the veins (Schwartsburd 2490). “s.d.s.”: simple distal segments, “c.d.s.”: compound distal segments. Drawn by R. Pinto, reproduced from Schwartsburd et al. (Phytotaxa 170(2): 105. 2014).

FIGURE 5. A–F. Pteridium esculentum subsp. arachnoideum var. paedomorficum: A. pinnae (Schwartsburd 3844), B. segment, abaxially (Schwartsburd 3844), C. segment, cross section, abaxial side up, showing sericeous veins, with with lax, arachnoid hairs, and glabrous laminar tissue between the veins (Schwartsburd 3844), D. segment, abaxially (Schwartsburd 3844), E. segment, cross section, abaxial side up, showing veins with setose hairs, and glabrous laminar tissue between the veins, F–H. Pteridium esculentum subsp. arachnoideum × P. esculentum subsp. campestre: F. pinnule (Fay 2413), G. segment, abaxially (Guedes 14217), H. segment, cross section, abaxial side up, showing strigose veins, with with stiff, acicular hairs, and laminar tissue between the veins with farinaceous appearance, fully covered by gnarled hairs (Guedes 14217). Drawn by R. Pinto.

FIGURE 7. Distribution of Pteridium esculentum subsp. arachnoideum (red circles), P. esculentum subsp. campestre (green circles), and P. esculentum subsp. arachnoideum × P. esculentum subsp. campestre (gray circles) in South America.