Selaginella trygonoides Valdespino, 2015

Valdespino, Ivan A., 2015, Novelties in Selaginella (Selaginellaceae - Lycopodiophyta), with emphasis on Brazilian species, PhytoKeys 57, pp. 93-133 : 103-105

Selaginella trygonoides Valdespino sp. nov. Figures 11 , 12

Diagnosis.

Selaginella trygonoides differs from the similar Selaginella glazioviana Hieron. by having the upper surfaces of the leaves dull (vs. shiny due to thick waxy deposits covering cell walls), median leaf margins short-ciliate (vs. entire to denticulate) with the arista ½ (vs. usually ¼ -⅓) the length of the lamina, and lateral leaves acuminate (vs. broadly acute to acute).

Type.

BRAZIL. Minas Gerais: Serra do Azeite, Pocrane, 19°30'12"S, 41°37'47"W, 300 m, 1 Jun 2009, T.E. Almeida, D.T. Souza & M.M.T. Cota 1994 (holotype: PMA! [PMA103371]; isotype: BHCB [BHCB130573]-n.v.).

Description.

Plants terrestrial or epipetric. Stems ascending to erect, stramineous, 3-5 cm long, 0.2-0.5 mm diam., non-articulate, not flagelliform or stoloniferous, 1- or 2-branched. Rhizophores axillary, borne on proximal ¼-½ of stems, filiform, 0.1 or 0.2 mm diam. Leaves heteromorphic throughout, chartaceous, both surfaces glabrous, upper surfaces green, lower surfaces silvery green. Lateral leaves spreading or ascending, ovate-deltate or ovate-elliptic, 1.5-2.2 × 0.8-1.1 mm; bases rounded, acroscopic bases strongly overlapping stems, basiscopic bases free from stems; acroscopic margins 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, short-ciliate along proximal ½, otherwise dentate distally; basiscopic margins on upper surfaces greenish comprising quadrangular, sinuate-walled, glabrous and papillate cells, on lower surfaces broadly hyaline in a band 2-6 cells wide with the cells as along acroscopic margins, dentate to denticulate throughout; apices acuminate, each acumen 0.1 or 0.2 mm, variously tipped by 1-3 teeth; upper surfaces comprising rounded or quadrangular, sinuate-walled cells, some of these covered by 3-11 papillae, without idioblasts or stomata, lower surfaces comprising elongate, sinuate-walled cells, with few of these papillate and idioblast-like on both sides of the midribs, papillae in 1 row over each cell lumen, with stomata in 2 or 3 rows along midribs and throughout acroscopic half of the lamina. Median leaves imbricate or distant, ascending, broadly ovate-elliptic, 0.8-1.2 × 0.5-0.9 mm; bases rounded to slightly oblique; margins broadly hyaline in a band 3-7 cells wide, the cells elongate, straight-walled and papillate parallel to margins, papillae in 1 row over each cell lumen, short-ciliate throughout or along proximal ⅔ and dentate distally; apices long-aristate, each arista 0.4-0.6 mm, denticulate on upper surfaces, tipped by 1-3 teeth; both surfaces with out idioblasts, upper surfaces comprising rounded or quadrangular, sinuate-walled cells, many of these covered by 4-14 papillae, with stomata in 4 rows along midribs, few scattered throughout inner halves and on margins of outer halves of the laminae, lower surfaces comprising elongate, sinuate-walled cells, without stomata. Axillary leaves similar to lateral leaves, except for both margins hyaline and short-ciliate along proximal ½ and distally dentate. Strobili terminal on branch tips, loosely quadrangular, 0.5-1.0 cm. Sporophylls monomorphic to subdimorphic, without a laminar flap, each with a strongly developed and dentate keel along midribs, ovate to ovate-lanceolate, 0.9-1.2 × 0.4-0.6 mm; bases rounded; margins broadly hyaline (this more obviously so on dorsal sporophylls), short-ciliate or dentate on ventral sporophylls; apices acuminate to short-aristate, each acumen (arista) 0.2-0.4 mm with margins dentate and tipped by 1 or 2 teeth; dorsal sporophylls with upper surfaces green and cells as in median leaves, including stomata, 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 yellow, mostly immature, rugulate-reticulate on proximal faces with a prominent equatorial flange, reticulate on distal faces, microstructure not determined, ca. 200 µm. Microsporangia in 2 dorsal rows; microspores light orange, ornamentation and microstructure not determined.

Habitat and distribution.

Selaginella trygonoides is known only from the state of Minas Gerais, Brazil, where it may be endemic. It grows on creek banks in Gallery forests or Atlantic semi-deciduous forests vegetation at 185-300 m.

Etymology.

The specific epithet is derived from the Latin " trigon / trygonus ", meaning stingray; it alludes to the shape of the median leaf, which resembles these marine fish.

Conservation status.

Selaginella trygonoides is known only from two collections made within or nearby populated areas; most likely it is subjected to anthropomorphic pressures. Thus, I tentatively consider it Vulnerable (VU).

Additional specimen examined

(paratype). BRAZIL. Minas Gerais: Santa Rita do Itueto, Região da Cachoeira do Pontão, 19°24'52"S, 41°22'45"W, 185 m, 27 May 2009, Almeida et al. 1960 (BHCB-n.v., PMA).

Discussion.

Selaginella trygonoides is morphologically close to Selaginella glazioviana , but it is distinguished from the latter by the characters of leaf surfaces and apex type, as well as median leaf marginal projections, as discussed in the diagnosis. In addition, Selaginella trygonoides grows in lowland vegetation at 185-300 m, whereas Selaginella glazioviana is found in montane vegetation at 900-1600 m. Selaginella glazioviana was thought to be conspecific with Selaginella erectifolia Spring by Alston (1936), Reed (1965-1966), and Alston et al. (1981), but I consider these taxa to be distinct species (see discussion under Selaginella glazioviana ). Selaginella trygonoides differs from Selaginella erectifolia by its lateral leaves ovate-deltate (vs. ovate) with the acroscopic margins short-ciliate along proximal ½ (vs. dentate) and apices acuminate (vs. acute), the median leaves with short-ciliate (vs. dentate) margins, apices long-aristate (vs. short-aristate) with each arista ½ (vs. ¼) the length of the lamina, the upper surface with (vs. lacking) stomata on the inner half of the leaf lamina and some cells with the lumen covered by 4-8 (vs. 14-25) papillae.

Another collection, Almeida & Souza 336 (PMA!), gathered in the same general locality of Selaginella trygonoides , is provisionally referred to Selaginella decomposita Spring. This collection is similar to Selaginella trygonoides in having lateral leaves acuminate and median leaves aristate; however it differs by its prostrate to ascending habit, stems to 3-branched, dorsal and ventro-axillary rhizophores, shiny leaves, median leaves dentate throughout with prominent outer bases, lateral leaves ovate-oblong to oblong, and axillary leaves ovate-lanceolate to ovate-elliptic.

Figures

Figure 11. Selaginella trygonoides Valdespino. A Section of upper surface of stem B Upper surface of median leaf; note submarginal stomata (a) on inner half of the lamina C Close-up of inner margin of median leaf, upper surface; note submarginal stomata (a) D Close-up of median leaf upper surface; note papillae on cell lumen E Upper surface of median leaf; note submarginal stomata on inner half of the lamina F Close-up of base, portion of inner margin and inner half of lamina (note stomata), and portion of outer margin and outer half of lamina of median leaf, upper surface G Upper surface of lateral leaf and portion of median leaves, upper surface H Close-up of distal portion and apex of lateral leaf, upper surface. A-H taken from the holotype, Almeida et al. 1994 (PMA).

Figure 12. Selaginella trygonoides Valdespino. A Section of lower surface of stem B Lower surface of lateral leaf C Close-up of base and proximal portion of lateral leaf, lower surface; note marginal stomata (a) D Close-up of distal portion and apex of lateral leaf, lower surface E Lower surface of axillary leaf and portions of lateral leaves F Upper surface of lateral leaf G Close-up of base and proximal portion of lateral leaf, upper surface H Close-up of distal portion and apex of lateral leaf, upper surface; note marginal stoma (a). A-H taken from the holotype, Almeida et al. 1994 (PMA).