Selaginella pellucidopunctata Valdespino, 2015

Valdespino, Ivan A., 2015, Novelties in Selaginella (Selaginellaceae - Lycopodiophyta), with emphasis on Brazilian species, PhytoKeys 57, pp. 93-133 : 99

Selaginella pellucidopunctata Valdespino sp. nov. Figures 7 , 8 , 9

Diagnosis.

Selaginella pellucidopunctata differs from the similar Selaginella muscosa Spring by its median leaves elliptic or ovate-lanceolate (vs. broadly ovate to cordate), lateral leaves with the upper surfaces with few submarginal prickle- or tooth-like projections on basiscopic halves near basiscopic margins (vs. upper surfaces glabrous), with the acroscopic margins ciliate along proximal ½ (vs. denticulate throughout), axillary leaves ovate to broadly ovate (vs. broadly ovate or cordate), and megaspores deep yellow (vs. light yellow).

Type.

BRAZIL. Alagoas: Mpio. Ibateguara, Engenho Coimbra, Grota do Vargão, [ca. 09°00'02"S, 35°51'12"W], [ca. 500 m], 12 Nov 2001, M. Oliveira 1094 (holotype: UFP! [UFP 39685]; isotype: PMA! [PMA103269]).

Description.

Plants terrestrial or epipetric. Stems ascending to erect, stramineous, 9-13 cm long, 0.4-0.7 mm diam., non-articulate, not flagelliform, shortly stoloniferous, 2-3-branched. Rhizophores axillary, borne on proximal ⅛- ¼ of stems, filiform, 0.1-0.3 mm diam. Leaves heteromorphic throughout, membranaceous, both surfaces glabrous, upper surfaces green, lower surfaces silvery green. Lateral leaves spreading or slightly ascending, ovate to broadly ovate, 2.0-2.4 × 1.0-1.3 mm; bases rounded to almost semicordate, acroscopic bases strongly overlapping stems, basiscopic bases free from stems; acroscopic margins narrowly to broadly hyaline in a band 2-6 cells wide with the cells elongate, straight-walled and papillate parallel to margins, papillae in 1 row over each cell lumen, ciliate along proximal ½, otherwise dentate distally, basiscopic margins on upper surfaces greenish, comprising rounded or quadrangular, sinuate-walled cells, on lower surfaces narrowly to broadly hyaline in a band 2-4 cells wide with the cells as along acroscopic margins, denticulate throughout; apices acute to short-acuminate, each acumen 0.05-0.1 mm, variously tipped by 1-3 cilia; upper surfaces comprising rounded or quadrangular, sinuate-walled cells, some of these, particularly along submarginal and distal regions of the laminae, covered by 12-30 papillae, without idioblasts and with stomata along proximal ½ of basiscopic margins, lower surfaces comprising elongate, sinuate-walled cells, without conspicuous idioblasts (when viewed with stereomicroscope, EM) or these conspicuous (when viewed with SEM) and papillate on both sides of midribs, papillae in 1 or 2 rows over each cell lumen, with stomata in 2 or 3 rows along midribs and throughout acroscopic halves of the laminae. Median leaves distant, ascending, elliptic or ovate-lanceolate, 1.0-1.4 × 0.5-0.7 mm; bases rounded to slightly oblique; margins broadly hyaline in a band 1-7 cells wide, the cells elongate, straight-walled and papillate parallel to margins, papillae in 1 or 2 rows over each cell lumen, short-ciliate throughout or along proximal ⅔ and dentate distally or dentate throughout; apices long-aristate, each arista 0.5-0.7 mm, denticulate on upper surfaces, tipped by 1-3 cilia; both surfaces without idioblasts, upper surfaces comprising quadrangular or rounded, sinuate-walled cells, many of these covered by 7-20 papillae, with stomata in 4 rows along midribs, few stomata along proximal ¼ of outer margins, lower surfaces comprising elongate, sinuate-walled cells, without stomata. Axillary leaves similar to lateral leaves, except for both margins hyaline and long-ciliate along proximal ½, distally dentate. Strobili terminal on branch tips, dorsiventral, 0.2-1.0 cm. Sporophylls dimorphic; dorsal sporophylls spreading, with an adaxial laminar flap, each with a strongly developed and dentate keel along midribs, narrowly ovate to ovate-lanceolate, 1.5-1.8 × 0.5-0.7 mm; bases rounded; margins broadly hyaline, dentate to denticulate; apices acuminate, each acumen 0.1 or 0.2 mm with margins dentate and tipped by 2-4 teeth; upper surfaces green and cells as in median leaves, including many stomata, except for the half that overlaps the ventral sporophylls where the surfaces are hyaline with elongate, sinuate-walled cells, lower surfaces silvery green and comprising elongate, sinuate-walled cells; ventral sporophylls ascending, without a laminar flap, each with a slightly developed and dentate keel along midribs, ovate to ovate-lanceolate, 1.0-1.2 × 0.4-0.6 mm; bases rounded; margins broadly hyaline, dentate to denticulate; apices long-acuminate, each acumen 0.2 or 0.3 mm with margins dentate and tipped by 2-4 teeth; both surfaces hyaline, comprising elongate, straight-walled cells and papillate idioblasts. Megasporangia in 2 ventral rows; megaspores yellow, rugulate-reticulate on proximal faces with a prominent equatorial flange, reticulate on distal faces, with granulate-echinulate and perforate microstructure on both faces (Fig. 9A-D ), 250-280 µm. Microsporangia in 2 dorsal rows; microspores orange, rugulate-echinulate on proximal faces, capitate on distal faces, with echinulate microstructure on both faces (Fig. 9E-H ), 27-35 µm.

Habitat and distribution.

Selaginella pellucidopunctata grows along stream banks or near bushes in flagstones of inselbergs in the Atlantic semi-deciduous forest vegetation at 300-650 m. It is known only from the states of Alagoas and Pernambuco in Brazil.

Etymology.

The specific epithet is derived from the Latin pellucidus, meaning translucent, and punctatus, dotted; this alludes to many, conspicuous stomata on the greenish upper surfaces of dorsal sporophylls that resemble translucent dots.

Conservation status.

Given that few collections are available, I cannot provide a definitive conservation status assessment of Selaginella pellucidopunctata . Nevertheless, this species occurs in one of the most critically endangered ecoregions of Brazil, the Atlantic Pernambuco interior forest of Northeaster, which is highly deforested with only five percent of the original vegetation present ( WWF 2015). Therefore, Selaginella pellucidopunctata is preliminarily considered Endangered (En).

Additional specimens examined

(paratypes). BRAZIL. Alagoas: Mpio. Ibateguara, Usina Serra Grande, Engenho Coimbra, [ca. 09°00'02"S, 35°51'12"S], [ca. 500 m], 15 Oct 2003, Pietrobom et al. 5637 (UFP, PMA); Mpio. São José da Lage, Usina Serra Grande, 08°59'42.4"S, 36°07'28.9"W, ca. 380-415 m, 8 Feb 2001, Pietrobom & Santiago 4807 (UFP, PMA). Pernambuco: Mpio. Jaqueira, Usina, Colônia, 08°04'15"S, 35°50'13"W, ca. 650 m, 17 Oct 2001, Lopes & Pietrobom 350 (RB-image, UFP-n.v.), 08°43'21.1"S, 35°50'22.1"W, ca. 545 m, 20 May 2002, Lopes, 593 (RB-image, UFP-n.v.); Mpio. Timbaúba, Complexo da Serra do Mascarnhas, Usina Cruangi, Engenho Água Azul, ca. 07°36'31.5"S, 35°22'42.9"W, ca. 304-394 m, 13 Nov 2000, Pietrobom et al. 4646 (UFP, PMA).

Discussion.

Among Brazilian Selaginella , Selaginella pellucidopunctata most resembles Selaginella muscosa . They differ most noticeably by the characters of the median leaf shape and the projections on the upper surfaces and margins of the lateral leaves, as discussed in the Diagnosis. In addition, the leaf surfaces of Selaginella pellucidopunctata , when viewed with EM, seem to lack (vs. exhibit) conspicuous idioblasts. However, idioblasts are seen on SEM images of the lower surfaces of lateral leaves of Selaginella pellucidopunctata .

One specimen, Lopes & Pietrobom 350 at RB ([RB 375875]-image!) is identified as Selaginella arenaria Baker, a synonym of Selaginella brevifolia Baker ( Valdespino 2015c), which is a species characterized by its lateral leaves with the upper surfaces hispidulous with prickle- or tooth-like projections usually found submarginally, marginally, and apically along the basiscopic halves of the laminae, and with conspicuous, straw-colored midribs. Another specimen, Lopes 593 at RB ([RB 375877]-image!) is identified as Selaginella tenuissima Fée, which is a creeping to prostrate species with usually cordate median leaves.

Figures

Figure 7. Selaginella pellucidopunctata Valdespino. A Section of upper surface of stem B Upper surface of median leaf C Close-up of base and proximal portion of median leaf, upper surface; note marginal stoma (a) on outer margin D Close-up of median leaf, distal region, upper surface E Close-up of apex of median leaf, upper and lower surfaces; note marginal stoma (a) on basiscopic margin of lateral leaf, upper surface F Upper surface of lateral leaf; note marginal stoma (a) on basiscopic margin and submarginal tooth (b) G Close-up of base and proximal portion of lateral leaf, upper surface; note marginal stoma (a) on basiscopic margin H Close-up of distal portion and apex of lateral leaf, upper surface; note submarginal tooth (b). A-H taken from the isotype, Oliveira 1094 (PMA).

Figure 8. Selaginella pellucidopunctata Valdespino. A Section of lower surface of stem B Lower surface of lateral leaf C Close-up of distal portion and apex of lateral leaf, lower surface; note elongate, straight-walled, and papillate cells (idioblasts) D Close-up of lateral leaf, lower surface; note elongate, straight-walled, and papillate cells (idioblasts) E Strobilus, upper surface; note dorsal (Ds) and ventral (Vs) sporophyll F Dorsal sporophylls, adaxial- (F- 1) and abaxial surfaces (F- 2); note acroscopic margin (Ma) and basiscopic margin (Mb), this usually referred to as laminar flap (lf), stomata (a) throughout lamina and midrib, as well as tooth-like projections (b) on midrib and lamina, abaxial (upper) surface, marginal tooth projections (c), and ligule (d) G Strobilus, lower surface; note dorsal- (Ds) and ventral (Vs) sporophyll H Ventral sporophyll, adaxial (lower) surface. A-H taken from the isotype, Oliveira 1094 (PMA).

Figure 9. Selaginella pellucidopunctata Valdespino. A Megaspore, proximal face B Close-up of megaspore, proximal face C Megaspore, distal face D Close-up of megaspore, distal face E Microspore, proximal face F Close-up of microspore, proximal face G Microspore, distal face H Close-up of microspore, distal face. A - H taken from the isotype, Oliveira 1094 (PMA).