Polypodium arcanum Maxon
Descripción
Rhizomes creeping, 4–7 mm diam.; rhizome scales white to reddish brown with reddish brown bases, deltate, with longattenuate often flexuous-contorted tips, denticulate, especially on the long tips, 4–6 X 1.5 mm, often with a few minute hairs on the scale surfaces; fronds (7–)15–40 cm long, distant; stipes 1⁄3–1⁄2 the frond length, stramineous to brown, glabrous; rachises glabrous except for rare long hairs 0.8–1 mm and rare, clavate brown hairs 0.1–0.3 mm, mostly in the axils of the pinnae; blades pinnatisect, oblong to oblong-deltate, 6–18 cm wide; rachises glabrous or with minute hairs, usually with a few small, contorted, hair-like, reduced scales at bases of proximal pinnae; pinnae 3–26 pairs, linear-deltate, equally dilated at base, 3–9 cm X 8–18 mm, acute to acuminate, laminae chartaceous, often reddish, especially near costules; margins serrulate to serrulatecrenulate; veins netted, generally with one row of areoles on each side of costae; sori round, medial, one row on each side of costae; sporangia with minute, inconspicuous to conspicuous hairs 0.1 mm.A
Forma de vida
EpífitaA
Distribución
México (país) EndémicoA
Elevación
1400 – 2550 mA
Tipo de vegetación
Bosque de neblina/mesófilo, Bosque de pino-encinoA
Categoría IUCN
No incluidaB
Categoría NOM-059-SEMARNAT-2010
No incluidaC
Discusión taxonómica
There is considerable variation in number of pinnae in P. arcanum, and this seems to be correlated with geography. Specimens from western Mexico (Michoacán, Jalisco, and southwestern Oaxaca) have (8–)12–26 pairs of pinnae whereas those to the east have (3–)4–8(–10) pairs. The former have been called P. plesiosorum var. bakeri based on pinna pair number (10–29 in P. plesiosorum), but clearly resemble P. arcanum in the conspicuous whitish (to tan) rhizome scales. We believe the rhizome scales are more consistent and taxonomically reliable in this group.
Polypodium arcanum is similar to P. eatonii, which occurs in Chiapas and Veracruz. The smaller scales, toothed pinna margins, narrower pinnae, and lack of cordate-clasping bases on the proximal pinnae distinguish P. arcanum. Polypodium arcanum is also very closely related to P. colpodes and P. plesiosorum, differing from the former in lacking dark stipes, and from the latter in having fewer pinnae (mostly 4–10 in the east and north, (12–26 in var. bakeri in the west) vs. 15–30(–39) in P. plesiosorum) and having larger, more spreading rhizome scales (vs. appressed and somewhat deciduous in P. plesiosorum). The blades are glabrous or with short minute hairs on the stipes and rachises and generally have sparse to rare small contorted reduced hair-like scales along the rachises at the bases of the proximal pinnae (Fig. 245K), reminiscent of the scale tips on the rhizomes of some specimens. The sporangia have short inconspicuous to conspicuous hairs 0.1 mm. Blades may have a reddish color when young.
Key to the Mexican Varieties of Polypodium arcanum
Stipes, rachises, and costae sparsely to moderately pubescent abaxially with hairs less than 0.1 mm; pinna pairs (5–)7–15; Hgo to Gto and Coah...............var. septentrionale
Stipes, rachises, and costae glabrous abaxially except for sparse to rare contorted hairs/reduced scales at the bases of proximal pinnae:
Pinna pairs (3–)4–8(–10); Oax to Gro and Hgo.....................................................var. arcanum
Pinna pairs 10–26; western Oax to Jal..................var. bakeri
Polypodium arcanum var. arcanum Maxon, Proc. Biol. Soc. Washington 51: 38. 1938
Var. arcanum is distinct by its few pinna pairs and southeastern distribution.
Distribution. Epiphytic in pine-oak forests; 1700–2550 m. Mexico.
Selected Specimens Examined. Gro (Calonico Soto 4531, FCME). Hgo (Gimate L. 1064, NY). Oax (Mickel 1174, 4054, NY). Pue (Marcks & Marcks 753, NY; Liebmann s.n. [Pl. Mex. 2598, Fl. Mex. 155, 156] C, GH, K; Purpus 2689, UC). Ver (Ventura A. 652, NY).
Polypodium arcanum var. bakeri (Davenp.) Mickel & Tejero, Acta Bot. Mex. 67: 84. 2004
Polypodium plesiosorum var. bakeri Davenp., Gard. & Forest 4(196): 556 (555-556). 1891
Differs from var. arcanum in having a greater number of pinnae (8–26 pairs) and a more western distribution.
Distribution. Mostly epiphytic on oaks in forests of pine and oak; 2100–2500 m. Mexico.
Selected Specimens Examined. Jal (Diaz Luna 5144, UC; Pérez-Rulfo T. 17167, UC). Mich (Beaman 2420, MEXU, UC; Rzedowski 2125, XAL, 3995, IEB, 45712, UAMIZ; Santos Martínez 2125, IEB, UAMIZ). Oax (Mickel 1174, ISC, UC, 3904, NY).
See var. arcanum for further discussion.
Polypodium arcanum var. septentrionale Mickel, Mem. New York Bot. Gard. 88: 482 (-483; f.245M-P). 2004. Type. Mexico. Queretaro: Mpio. Landa, 2.5 km al suroeste de El Aguacate, Rubio 1243 (holotype NY!).
A var. arcano laminis pilosis necnon distributione boreali diversa. (L., septentrionalis, northern, alluding to the more northern distribution of this variety).
Var. septentrionale differs from var. arcanum in having abaxial laminar hairs less than 0.1 mm, generally (5–)9–15 pinna pairs (vs. (3–)4–8(–10)), and a more northern distribution; 2n=74. From P. colpodes, var. septentrionale differs in the stramineous stipes and rachises.
Distribution. Epiphytic or occasionally on rocks in pine-oak or Liquidambar forests; 1400–1730 m. Mexico.
Specimens Examined. Coah (Marsh 1926, TEX). Gto (Carranza & Pérez 4649, IEB, NY). Hgo (Chase 7307, MICH; Clark 7023, NY; Dunn & Dunn 19063, NY; Pringle 13294, CAS, TEX). NL (Mueller & Mueller 965, US; Rodríguez L. 136, TEX). Qro (Carranza G. 2323, NY; González 1350, IEB, MEXU; González P. 352, NY; Herrera 121, MEXU; Rzedowski 46687b, NY; Zamudio & Carranza 6598, NY). Tam (Sharp et al. 52036, US). Tex-Mex border (Wright 758, 2178, NY).
A
Polypodium arcanum is similar to P. eatonii, which occurs in Chiapas and Veracruz. The smaller scales, toothed pinna margins, narrower pinnae, and lack of cordate-clasping bases on the proximal pinnae distinguish P. arcanum. Polypodium arcanum is also very closely related to P. colpodes and P. plesiosorum, differing from the former in lacking dark stipes, and from the latter in having fewer pinnae (mostly 4–10 in the east and north, (12–26 in var. bakeri in the west) vs. 15–30(–39) in P. plesiosorum) and having larger, more spreading rhizome scales (vs. appressed and somewhat deciduous in P. plesiosorum). The blades are glabrous or with short minute hairs on the stipes and rachises and generally have sparse to rare small contorted reduced hair-like scales along the rachises at the bases of the proximal pinnae (Fig. 245K), reminiscent of the scale tips on the rhizomes of some specimens. The sporangia have short inconspicuous to conspicuous hairs 0.1 mm. Blades may have a reddish color when young.
Key to the Mexican Varieties of Polypodium arcanum
Stipes, rachises, and costae sparsely to moderately pubescent abaxially with hairs less than 0.1 mm; pinna pairs (5–)7–15; Hgo to Gto and Coah...............var. septentrionale
Stipes, rachises, and costae glabrous abaxially except for sparse to rare contorted hairs/reduced scales at the bases of proximal pinnae:
Pinna pairs (3–)4–8(–10); Oax to Gro and Hgo.....................................................var. arcanum
Pinna pairs 10–26; western Oax to Jal..................var. bakeri
Polypodium arcanum var. arcanum Maxon, Proc. Biol. Soc. Washington 51: 38. 1938
Var. arcanum is distinct by its few pinna pairs and southeastern distribution.
Distribution. Epiphytic in pine-oak forests; 1700–2550 m. Mexico.
Selected Specimens Examined. Gro (Calonico Soto 4531, FCME). Hgo (Gimate L. 1064, NY). Oax (Mickel 1174, 4054, NY). Pue (Marcks & Marcks 753, NY; Liebmann s.n. [Pl. Mex. 2598, Fl. Mex. 155, 156] C, GH, K; Purpus 2689, UC). Ver (Ventura A. 652, NY).
Polypodium arcanum var. bakeri (Davenp.) Mickel & Tejero, Acta Bot. Mex. 67: 84. 2004
Polypodium plesiosorum var. bakeri Davenp., Gard. & Forest 4(196): 556 (555-556). 1891
Differs from var. arcanum in having a greater number of pinnae (8–26 pairs) and a more western distribution.
Distribution. Mostly epiphytic on oaks in forests of pine and oak; 2100–2500 m. Mexico.
Selected Specimens Examined. Jal (Diaz Luna 5144, UC; Pérez-Rulfo T. 17167, UC). Mich (Beaman 2420, MEXU, UC; Rzedowski 2125, XAL, 3995, IEB, 45712, UAMIZ; Santos Martínez 2125, IEB, UAMIZ). Oax (Mickel 1174, ISC, UC, 3904, NY).
See var. arcanum for further discussion.
Polypodium arcanum var. septentrionale Mickel, Mem. New York Bot. Gard. 88: 482 (-483; f.245M-P). 2004. Type. Mexico. Queretaro: Mpio. Landa, 2.5 km al suroeste de El Aguacate, Rubio 1243 (holotype NY!).
A var. arcano laminis pilosis necnon distributione boreali diversa. (L., septentrionalis, northern, alluding to the more northern distribution of this variety).
Var. septentrionale differs from var. arcanum in having abaxial laminar hairs less than 0.1 mm, generally (5–)9–15 pinna pairs (vs. (3–)4–8(–10)), and a more northern distribution; 2n=74. From P. colpodes, var. septentrionale differs in the stramineous stipes and rachises.
Distribution. Epiphytic or occasionally on rocks in pine-oak or Liquidambar forests; 1400–1730 m. Mexico.
Specimens Examined. Coah (Marsh 1926, TEX). Gto (Carranza & Pérez 4649, IEB, NY). Hgo (Chase 7307, MICH; Clark 7023, NY; Dunn & Dunn 19063, NY; Pringle 13294, CAS, TEX). NL (Mueller & Mueller 965, US; Rodríguez L. 136, TEX). Qro (Carranza G. 2323, NY; González 1350, IEB, MEXU; González P. 352, NY; Herrera 121, MEXU; Rzedowski 46687b, NY; Zamudio & Carranza 6598, NY). Tam (Sharp et al. 52036, US). Tex-Mex border (Wright 758, 2178, NY).
A