Selaginella mucronata G. Heringer, Salino & Valdespino, 2015

Valdespino, Ivan A., Heringer, Gustavo, Salino, Alexandre, Goes-Neto, Luiz A. de Araujo & Ceballos, Jorge, 2015, Seven new species of Selaginella subg. Stachygynandrum (Selaginellaceae) from Brazil and new synonyms for the genus, PhytoKeys 50, pp. 61-99 : 69-72

Selaginella mucronata G. Heringer, Salino & Valdespino sp. nov. Figures 8 , 9

Diagnosis.

Selaginella mucronata seems morphologically related to Selaginella jungermannioides but differs from it in having the upper surfaces of the leaves slightly rugose (vs. smooth), lateral leaves with the basiscopic margins entire to serrulate distally (vs. basiscopic margins long-ciliate along proximal ⅛, otherwise entire), median leaf bases rounded (vs. oblique with a slightly developed outer lobe), and margins hyaline (vs. greenish) and long-ciliate throughout (vs. inner margins denticulate and outer margins sparingly long-ciliate along proximal ⅓, otherwise denticulate).

Type.

BRAZIL. Espírito Santo: Castelo, Parque Estadual do Forno Grande, [20°32'29"S, 41°07'17"W], [1200 m], 28 Jun 2008, A. Salino, G. Heringer & V.A.O. Dittrich 13686 (holotype: BHCB!; isotype: PMA-fragment!).

Description.

Plants epipetric. Stems creeping, stramineous, 5.5-8.0 cm long, 0.4-0.8 mm diam., exarticulate, not flagelliform or stoloniferous, 1- or 2-branched. Rhizophores ventral, axillary or dorsal, borne throughout stems, filiform, 0.1-0.2 mm diam. Leaves heteromorphic throughout, membranaceous to chartaceous, both surfaces glabrous, upper surfaces green, lower surfaces silvery green. Lateral leaves imbricate or distant, spreading, broadly ovate to ovate-oblong, 2.5-4.0 × 1.3-2.3 mm; bases rounded or hemicordate, acroscopic bases strongly overlapping stems, basiscopic bases free from stems; acroscopic margins greenish or hyaline in band 2-4 cells wide, the cells elongate and papillate parallel to margins, papillae in 1 row over each cell lumen, long-ciliate along proximal ½ -⅔ and serrulate to entire distally, basiscopic margins greenish or narrowly hyaline in a band 1 or 2 cells wide, the cells as along acroscopic margins, entire or entire along proximal ¾ and serrulate along distal ¼, apices mucronate or obtuse, tipped by 2 or 3 teeth; upper surfaces comprising rounded to quadrangular, sinuate-walled cells, most of these covered by 5-10 papillae, without idioblasts or stomata, lower surfaces comprising elongate, sinuate-walled cells, few of these papillate and idioblast-like, papillae in 1 row over each cell lumen, with stomata in 2 or 3 rows along midribs. Median leaves imbricate (especially at stem and branch apices), ascending, orbiculate to broadly elliptic, 1.4-2.6 × 1.1-2.1 mm; bases rounded; margins hyaline in a band 1-3 cells wide, the cells elongate and papillate parallel to margins, long-ciliate throughout; apices mucronate or infrequently acute, each mucro 0.14-0.16 mm, ending in 1-3 teeth; both surfaces without idioblasts, upper surfaces comprising rounded to quadrangular, sinuate-walled cells, many of these covered by 5-10 papillae, with stomata throughout the laminae and some near submarginal region of the outer bases, lower surfaces comprising elongate, sinuate-walled cells, without stomata. Axillary leaves ovate or slightly cordiform, bases rounded or cordate, margins and apices similar to lateral leaves. Strobili terminal on branch tips, compact, quadrangular, 4.0-7.0 mm. Sporophylls monomorphic to slightly dimorphic, without a laminar flap, ovate to lanceolate, 1.3-1.9 × 0.7-0.9 mm, each with or without a slightly developed denticulate keel along distal ½ of the midribs; bases rounded; margins narrowly hyaline, serrulate to short-ciliate; apices acute, tipped by 1-3 teeth; dorsal sporophylls with upper surfaces green and cells as in median leaves, except for the half that overlaps the ventral sporophylls, there hyaline and with elongate, papillate, and slightly sinuate-walled cells, lower surfaces silvery green and comprising elongate, sinuate-walled cells; ventral sporophylls with both surfaces silvery green and comprising elongate, sinuate-walled cells. Megasporangia in 2 ventral rows; megaspores creamy or light yellow, most observed immature, reticulate to reticulate-rugulate on proximal faces, reticulate on distal faces, with perforate microstructure on both faces, 200-230 µm. Microsporangia in 2 dorsal rows; microspores orange, psilate-rugulate on proximal faces, capitate or baculate (if apices of projected elements broken off) [Fig. 9E, G, H ] on distal faces, with granulate microstructure on both faces, 20-27 μm diam.

Habitat and distribution.

Selaginella mucronata is known only from the type collection from Parque Estadual do Forno Grande, state of Espírito Santo, growing on rocks in understory of Atlantic Rainforest vegetation at 1200 m. It could be considered a local endemic given its limited distribution and the vegetational type.

Etymology.

The epithet mucronata refers to the apices of the median leaves.

Conservation status.

The paucity of data available does not allow an assessment of abundance and possible threats to this species and, thus, we assign to it a Data Deficient (DD) conservation assessment according to IUCN (2012) categories and criteria.

Discussion.

Selaginella mucronata belongs to subg. Stachygynandrum and is characterized by its creeping habit, orbicular to broadly elliptic, long-ciliate, mucronate or infrequently acute median leaves with stomata distributed throughout the upper surfaces (Fig. 8A-C ). Selaginella mucronata seems to be morphologically most similar to Selaginella jungermannioides ; however, the characters of leaf texture, margin type, and shape of median leaf bases discussed in the diagnosis distinguish these two species. Selaginella mucronata could be confused with Selaginella crinita , another member of the " Selaginella jungermannioides group," which see for discussion.

The upper surfaces of Selaginella mucronata may be slightly corrugate (Fig. 8A-C ), perhaps as a drying artifact, and because of this and its creeping habit it could be confused, among other Brazilian species, with Selaginella flexuosa Spring and Selaginella macrostachya (Spring) Spring. Selaginella mucronata differs chiefly from those two species in having the apices of median leaves mucronate or acute (vs. long-aristate) with each acumen 1/10-1/16 (vs. arista ¼-¾) the length of the leaf lamina. Additionally, Selaginella mucronata differs from Selaginella flexuosa by acroscopic margins of lateral leaves long-ciliate along proximal ½ -2/3 and serrulate to entire distally (vs. denticulate along proximal ¼-½, otherwise entire distally) and the margins of the median and axillary leaves ciliate (vs. serrulate). It is further distinguished from Selaginella macrostachya by its orbiculate to broadly elliptic (vs. cordate) median leaves with the outer bases glabrous (vs. tufted with short hairs) and lateral leaves with upper surfaces near basiscopic margins glabrous (vs. often with short, tooth-like hairs).

Figures

Figure 8. Selaginella mucronata G. Heringer, Salino & Valdespino. A Section of upper surface of stem B Upper surface of median leaf C Close-up of upper surface of median leaf D Lower surface of median leaf E Section of lower surface of stem F Close-up of lower surface of lateral leaf A-F taken from isotype, Salino et al. 13686 (PMA).

Figure 9. Selaginella mucronata G. Heringer, Salino & Valdespino. A Megaspore proximal face B Close-up of megaspore proximal face surface C Megaspore distal face D Close-up of megaspore distal face surface E Microspore proximal face F Close-up of microspore proximal face surface G Microspore distal face H Close-up of microspore distal face surface A-H taken from isotype, Salino et al. 13686 (PMA).