Selaginella monticola Valdespino, 2015

Valdespino, Iván A., 2015, Lectotypification of Selaginella tenuissima and S. papagaiensis (Selaginellaceae) with the description of S. monticola, Phytotaxa 233 (2), pp. 153-165 : 154-156

Selaginella monticola Valdespino , sp. nov. ( Fig. 1 )

Selaginella monticola is morphologically very similar to S. tenuissima because of its creeping to prostrate habit and median leaves cordiform and long-aristate, but differs in its lateral leaves with usually obtuse, rounded to truncate [ Fig. 1A, E–G ] or in juvenile plants apiculate apices (vs. acute, broadly acute [ Fig. 2A, E ] in S. tenuissima ), each variously tipped by 1–3 cilia (vs. entire) and, median leaf margins hyaline (vs. greenish) in a band of 2–5 elongate, straight-walled, and papillate cells [ Fig. 1A –D-1] (vs. comprising quadrangular, sinuate-walled, and glabrous cells [ Fig. 2A–C ]), long-ciliate throughout [ Fig. 1B ] (vs. dentate to short-ciliate mostly along distal ⅓ [ Fig. 2B ]), cilia (44–)53–120 [ Fig. 1B –D-1] (vs. 9–47 [ Fig. 2B, D ]) μm long, and with the upper surfaces of the cells usually covered by (6–)8–16 [ Fig. 1C , D-1] (vs. 2–9 [ Fig. 2D ]) papillae and with stomata distributed along the midribs and on the inner half of the laminae [ Fig. 1A–C ] (vs. stomata only along the midribs [ Fig. 2A, B ]).

Type:— BRAZIL. São Paulo: Parque Estadual da Serra do Mar, [Mpio. Cunha], Núcleo Cunha, [ca. 1000 m], 18 December 1996, Salino 2980 (holotype NY!, isotypes BHCB n.v., PMA!).

Plants terrestrial. Stems prostrate or pendulous, stramineous, to 14 cm long, 0.2–0.7 mm diam., exarticulate, not flagelliform or stoloniferous, 1- or 2-branched. Rhizophores axillary or dorsal, borne throughout stems, filiform, 0.1– 0.2 mm diam. Leaves heteromorphic throughout, chartaceous, both surfaces glabrous, upper surfaces green, lower surfaces silvery green. Lateral leaves imbricate, spreading, broadly ovate, broadly ovate-oblong or orbicular, 1.2–2.0 × 0.9–1.4 mm; bases rounded, acroscopic bases slightly overlapping stems, basiscopic bases free from stems; acroscopic margins on upper surfaces greenish in a band 1–3 cell wide, the cells quadrangular or shortly elongate, sinuate-walled and glabrous, parallel to margins, on lower surfaces greenish in a band 1–3 cell wide, the cells elongate, sinuate-walled and glabrous, parallel to margins or hyaline in a band 2–6 cells wide, the cells elongate, straight-walled and papillate, parallel to margins, the papillae in 1 row over each cell lumen, short-ciliate throughout or short-ciliate along proximal ⅔ and denticulate on distal ⅓; basiscopic margins on upper surfaces as along upper surfaces of acroscopic margins, on lower surfaces greenish throughout in a band 1–3 cell wide, the cells elongate, sinuate-walled and glabrous, parallel to margins or basiscopic margins greenish along central ½ in a band 1–3 cell wide, the cells elongate, sinuate-walled and glabrous, parallel to margins and with the proximal and distal ¼ slightly hyaline in a band 1–3 cells wide, the cells elongate, straight-walled and papillate, parallel to margins, the papillae in 1 row over each cell lumen, short-ciliate throughout or only along proximal ⅔ and serrate on distal ⅓; apices usually obtuse, rounded to truncate or in juvenile plants apiculate and variously tipped by 1–3 cilia; upper surfaces comprising quadrangular to rounded, sinuate-walled cells, many of these covered by (6–)8–16 papillae, without idioblasts or stomata, lower surfaces comprising elongate, sinuate-walled cells, with some of these papillate and idioblast-like on both sides of the midribs and especially often at the proximal portion of the laminae, papillae in 1 or 2 rows over each cell lumen, with stomata in 2 or 3 rows along distal ¾ of the midribs where cells are shortly elongate and sinuate-walled, as well as some stomata along acroscopic and basiscopic margins. Median leaves imbricate, ascending, cordiform, 0.7–1.0 × 0.6–1.0 mm; bases cordate; margins on both surfaces hyaline in a band 2–5 cells wide, the cells elongate, straight-walled and papillate, parallel to margins, papillae in 1 or 2 rows over each cell lumen, long-ciliate throughout, cilia (44–)53–120 μm long; apices abruptly tapering into a long-arista, each arista (0.2–) 0.3–0.5 mm long, tipped by 1–3 cilia; both surfaces without idioblasts, upper surfaces comprising quadrangular to rounded, sinuate-walled cells covered by (6–)8–16 papillae, with stomata in 1 or 2 rows along distal ¾ of the midribs and with a few on submarginal to marginal portion of inner half of the laminae, lower surfaces of elongate, sinuate-walled cells, without stomata. Axillary leaves narrowly oblong to oblong, otherwise similar to lateral leaves. Strobili terminal on branch tips, compact, mostly quadrangular, 3.0–6.0 mm long. Sporophylls monomorphic, without a laminar flap, ovate to broadly ovate, 1.0–1.3 × 0.6–1.0 mm, each with a strongly developed and dentate midrib keel; bases rounded; margins broadly hyaline, more obviously so on dorsal sporophylls, short-ciliate; apices long-aristate, each arista 0.3–0.6 mm long with margins dentate and tipped by 1–2 cilia; dorsal sporophylls with upper surfaces green and cells as in median leaves, lower surfaces silvery green and comprising elongate, sinuate-walled cells; ventral sporophylls with both surfaces hyaline, comprising elongate, sinuate-walled cells. Megasporangia in 2 ventral rows; megaspores whitish to creamy, rugulate-reticulate on proximal face with a prominent equatorial flange, reticulate on distal face, ca. 200 μm diam. (based on immature material). Microsporangia in 2 dorsal rows; microspores light orange, not measured.

Habitat and distribution:— Selaginella monticola is known from the states of Minas Gerais and São Paulo in Brazil, where it seems to be endemic. It grows on riverbanks within the Atlantic Rainforest vegetation in the Serra do Mar and Serra do Carapaó mountain ranges at 1000–2193 m.

Etymology:—From Latin monticola , mountain-dweller, in reference to the species growing in mountains.

Conservation status:—Additional in situ and herbarium specimen research is needed to ascertain distributional range, abundance, and possible threats to this species. High levels of tourist visitation to its currently known habitat may threaten it. Nevertheless, since its current occurrences are within relatively well-protected areas, Selaginella monticola is tentatively considered of Least Concern (LC), according to IUCN (2012) categories and criteria.

Additional Specimens Examined (Paratypes): — BRAZIL. Minas Gerais: Alto Carapaó, Parque Nacional do Carapaó, Terreirão , 20°25’00.3”S, 41°49’17.6”W, 2193 m, 3 March 2010, Heringer et al. 231 ( BHCB n.v., PMA), Serra do Carapaó , Rio Domingos , 1900 m, October 1941, Brade 17108 ( RB) ; In Serra Negra, inter Lima Duarte et Rio Preto , Magalhães s.n. In Herb. Com. Geog. et Geol. Civitatis Minas Geraes No. 2603 ( R [as Herb. Silveira No. 157]) .

Discussion:— Selaginella monticola is a pseudo-cryptic species characterized by its creeping to prostrate habit, rhizophores axillary and dorsal, median leaves cordiform with margins long-ciliate [(44–)53–120 μm], long-aristate apices, as well as lateral leaves with usually obtuse, rounded to truncate apices ( Fig. 1A–H ). Its heteromorphic leaves, monomorphic sporophylls, and quadrangular strobili indicate it is a member of subg. Stachygynandrum according to Jermy’s (1986, 1990) subgeneric classification. Selaginella monticola is morphologically close to S. tenuissima and, as previously discussed, until now it was considered part of the latter as a broadly circumscribed taxon. Nevertheless, detailed comparative study of leaf epidermal surfaces and marginal projections using finer morphological analysis techniques (i.e., SEM) unveiled consistent micromorphological characters that, as described in the diagnosis, support the segregation of a new taxon. In addition, S. monticola seems to be adapted to more humid habitat than S. tenuissima and has submarginal stomata on the inner half on the upper surfaces of dorsal sporophylls ( Fig. 1 D-2) and more obviously short-ciliate lateral leaves margins ( Fig. 1F ). These results emphasize the need to apply more detailed comparative analysis of (micro-) morphological features in the genus Selaginella to ascertain its diversity, which in this case allows a pseudo-cryptic species to be proposed in the sense reviewed by Sáez & Lozano (2005) and Lajus et al. (2015).

Figures

FIGURE 1. SEM micrographs of stem sections, leaves, and strobilus of Selaginella monticola (Salino 2980, PMA). A. Upper surface of stem. B. Upper surface of median leaves; note stomata along midribs and on inner half of laminae (a), and marginal, elongate, straightwalled and papillate cells (b). C. Close-up of median leaf inner half of lamina, upper surface; note stomata (a), and marginal, elongate, straight-walled and papillate cells (b). D-1. Close-up of portion of outer half of median leaf, upper surface; note papillate, roundish to quadrangular cells, marginal, elongate, straight-walled and papillate cells (b), and marginal cilia. D-2. Upper surface of strobilus; note stomata (a) on inner half of sporophylls laminae, and marginal, elongate, straight-walled and papillate cells (b). E. Lower surface of stem section; note axillary rhizophores. F. Lower surface of lateral leaf. G. Close-up distal portion and apex of lateral leaf, lower surface; note stomata along midrib, elongate, sinuate-walled cells, and elongate, papillate cells. H. Close-up of proximal portion and base of lateral leaf, lower surface; note stomata along midrib, elongate, sinuate-walled cells, and elongate, papillate cells.

FIGURE 2. SEM micrographs of stem section and leaves of Selaginella tenuissima (Brade 9662, R). A. Upper surface of stem. B. Upper surface of median leaves. C. Close-up of apex of median leaf. D. Close-up of distal portion of inner half of median leaf lamina, upper surface. E. Lower surfaces of lateral leaf and of proximal portion of median leaf outer half; note marginal stomata (a). F. Close-up of proximal portion and margin of acroscopic half of lateral leaf lamina, lower surface.