Selaginella rostrata Valdespino, 2020

Valdespino, Ivan A., 2020, Taxonomic innovations in South American Selaginella (Selaginellaceae, Lycopodiophyta): description of five new species and an additional range extension, PhytoKeys 159, pp. 71-113 : 71

Selaginella rostrata Valdespino sp. nov. Figures 9 , 13

Diagnosis.

Selaginella rostrata differs from S. microdonta by its broadly ovate to ovate-deltate (vs. ovate to ovate-lanceolate) median leaves that are wider at middle (vs. at base) of the laminae, with cordate to subcordate (vs. oblique) bases, hyaline (vs. greenish to weakly hyaline) inner margins, strongly beveled (vs. plane or weakly beveled) apices in profile that are long-aristate (vs. acute to attenuate), the arista (0.06)0.1-0.2 mm long (vs. apices less than 0.05 mm long), usually tipped by one to three teeth (vs. bluntly tipped or tipped by one teeth).

Type.

Venezuela. Bolívar: Piar, Ptari-tepui, steep forested slopes at base of first line of sandstone bluff, on south-facing part, E of "Cave Rock," 2130 m, 4 Nov 1944, J.A. Steyermark 59836 (holotype: NY!; isotypes: BM-n.v., F!, MO!, US!).

Description.

Plants epipetric or terrestrial, ribbon-like, with leafy liverwort habit. Stems creeping, stramineous, 3-10 cm long, (0.1)0.18-0.34 mm diam., non-articulate, not flagelliform, non-stoloniferous, 1- or 2-branched, the lateral branches resulting from division of the main stem usually becomes arrested. Rhizophores axillary and subdorsal, borne throughout stems, 0.08-0.12 mm diam. Leaves heteromorphic throughout, chartaceous to thin-coriaceous, upper surfaces green or light-brown when old or due to dying process, lower surfaces silvery green or light-brown when old or due to dying process. Lateral leaves distant, ascending to slightly perpendicular to stems, broadly elliptic to broadly ovate, 0.7-2.0 × 0.4-1.4 mm; bases rounded to round-truncate, glabrous, acroscopic bases overlapping stems, basiscopic bases free from stems; acroscopic margins on upper surfaces greenish or weekly hyaline along proximal ½, otherwise greenish on distal ½, composed of quadrangular to rounded cells, basiscopic margins on upper surfaces greenish, bordered by quadrangular to rounded cells, margins on lower surfaces continuously bordered by a hyaline band comprised of idioblasts, the band 3-15 cells wide, the idioblasts elongate, straight-walled, and papillate, the papillae in a single row over each cell lumen, acroscopic margins dentate to denticulate throughout or denticulate along proximal ⅓- ½ and entire distally, basiscopic margins sparsely denticulate or entire throughout; apices obtuse to rounded, occasionally tipped by a caducous short or tooth-like hair; upper surfaces glabrous, comprising rounded to irregularly, sinuate-walled, laevigate cells, without idioblasts or stomata; lower surfaces comprising elongate, slightly sinuate-walled cells, without idioblasts, with stomata in 1-3 rows along midribs. Median leaves slightly imbricate to distant, ascending, ovate to ovate-deltate with the inner halves of the leaf lamina ⅛- ¼ wider than the outer halves, 0.6-1.5 × 0.4-1.0 mm; bases glabrous, cordate to subcordate, without auricles; margins bordered continuously by a hyaline band comprised of idioblasts, the band 2-5 cells wide, the idioblasts, elongate, straight-walled, and papillate, the papillae on one row on each cell lumen, denticulate throughout or entire along proximal ½ and denticulate along distal ½; apices keeled, long-acuminate to long-aristate, the acumen or arista denticulate, ⅓- ¼ the length of the laminae, each (0.06-)0.1-0.2 mm long, usually tipped by one to three teeth; upper surfaces similar to lateral leaves upper surfaces, without idioblasts, with stomata in 1 or 2 rows restricted to distal ⅓ along the keel; lower surfaces similar to lower surfaces of lateral leaves, without idioblasts or stomata. Axillary leaves shape (except, occasionally oblong), size, bases, margins, apices and leaf surfaces similar to lateral leaves. Strobili terminal, single or dichotomous at branch tips, loosely quadrangular to slightly dorsiventral flattened, 2-12 mm long. Sporophylls slightly heteromorphic, broadly ovate to ovate-lanceolate (ventral sporophylls more broadly ovate and slightly shorter, dorsal sporophylls usually ovate-lanceolate and slightly larger), with a strongly developed keel along midrib, the keel glabrous, 1.0-1.3 × 0.5-0.9 mm; bases rounded; margins bordered by a hyaline band similar to that of the median leaves, dentate; dorsal sporophylls spreading, strongly keeled along midribs and especially near apices, the keel glabrous; apices acute to short-acuminate and beveled in profile and abruptly ending in a short, tooth-like cilia, the cilia often caducous; upper surfaces green and cells as in median leaves, except for the half that overlaps the ventral sporophylls where the surfaces are hyaline composed of idioblasts similar to those of the median leaves margins, lower surfaces hyaline and comprising elongate, sinuate-walled cells; ventral sporophylls ascending, slightly keeled along midribs, the keel glabrous; apices acute to short-acuminate, not beveled in profile and usually ending in a short cusp; upper and lower surfaces hyaline, comprised of idioblasts similar to those of the median leaves margins. Megasporangia along two ventral rows; megaspores lemon yellow, 200-220 µm diam., proximal faces rugulate-reticulate with a well-developed equatorial flange, the microstructure echinate and perforate, distal faces reticulate, the reticulae open (incomplete) to closed, the microstructure granulose and perforate; microsporangia on two dorsal rows; micropores light-orange, 30-35 µm diam., proximal and distal faces gemmate, the microstructure granulose.

Habitat and distribution.

Selaginella rostrata grow on wet and mossy sandstone bluffs, near damp stream banks, and at the base of waterfalls in mountainous tropical rainforests at 1000-2130 m. It has been found on several tepuis of the Guiana Highland in the state of Bolívar, Venezuela.

Etymology.

The specific epithet derives from the Latin " rostratum," meaning beaked, and refers to the keeled/beaked median leaf and dorsal sporophyll apices.

Conservation status.

Selaginella rostrata is known from several collections made over a time span of more than fifty years from mid-to-late twentieth century at different localities in the Guiana Highland region of Venezuela, some of which are adjacent to the neighboring country of Guyana. This suggests an overall wide distribution. Unfortunately, the paucity of more recent collections due, in part, to a decline in botanical exploration in the aforementioned areas, does not allow for an accurate conservation assessment. Consequently, this new species is considered Data Deficient (DD) based on IUCN (2012).

Additional specimens examined (paratypes).

Venezuela. Bolívar: Altiplanicie of Auyan-tepui, SW sector, 05°48.02'N, 62°33.82'W, ca. 1850 m, 23-25 Apr 1996, Anderson 13880 (MO, NY), Auyan-tepui, 1660 m, 12 May 1964, Steyermark 93788 (US), 1820 m, 13 May 1964, Steyermark 93871 (GH, K, NY, US), 2100 m, 17 May 1964, Steyermark 94074 (NY, US), 1850 m, Dec 1937-Jan 1938, Tate 1271 (NY); Cerro Venamo, 1100 m, 21 Apr 1960, Steyermak & Nilsson 439 (NY, US-2 sheets), 1400-1450 m, 1 Jan 1964, Steyermark et al. 92528 (GH, U, US), 1500 m, 2 Jan 1964, Steyermark et al. 92588 (GH, U p.p., US, VEN), Steyermark et al. 92588-A (U p.p.), 1400-1500 m, 3 Jan 1964, Steyermark et al. 92626 (US); Heres, Cerro Marutani, 03°50'N, 62°15'W, 1200 m, 11-14 Jan 1981, Steyetmark et al. 123925 (GH, MO, NY), 1000-1050 m, 11-14 Jan 1981, Steyermark et al. 124067 (GH, MO, NY); Meseta de Jáua, Cerro Jáua, 60 km NE Sanidad del Río Kanarakuni Camp, 04°45'N, 64°26'W, 1922-2100 m, 22-27 Mar 1967, Steyermark 98018 (US), Steyermark 98116 (US), Steyermark 98120 (US); Piar, Amaruay-tepui, 05°54'N, 62°15'W, 700-810 m, 27 Apr 1986, Liesner & Holst 20424 p.p. [mixed coll. 20424a] (MO, UC), Ptari-tepui, 2130 m, 4 Nov 1944, Steyermark 59836 (F, MO, NY, US); Torono-tepui, Chimantá Massif, 1880-1970 m, 27 Feb 1955, Steyermark & Wurdack 1181 (F, NY, UC, US).

Discussion.

Selaginella rostrata is characterized by its creeping, ribbon-like, leafy liverwort habit, median leaf ovate to ovate-deltate, with inner halves of leaf laminae ⅛- ¼ wider than outer halves, margins continuously bordered by a hyaline band of idioblasts, each band 2-5 cells wide, the idioblasts elongate, straight-walled, and papillate, and dentate to denticulate, and apices strongly keeled, long-acuminate to long-aristate, the acumen or arista denticulate, ¼ -⅓ the length of the laminae, each (0.06)0.1-0.2 mm long, each usually tipped by one to three teeth. Selaginella rostrata its further defined by lateral leaf broadly elliptic to broadly ovate with obtuse to rounded apices, which occasionally are tipped by a caducous short or tooth-like hair, and sporophylls (especially dorsal sporophylls) conspicuously keeled (i.e., carinate) along midribs, and with apices acute with those of dorsal sporophylls apiculate ending on a single tooth-like, short hair, and stomata along midribs and keeled apices.

Selaginella rostrata is morphologically close to a species group that I informally call the " S. microdonta group," and in particular to the latter species and S. neblinae . Selaginella rostrata can be distinguished from S. microdonta , which may still need to be further circumscribed, by the characters listed in the diagnosis and its median leaf with inner halves of leaf laminae ⅛- ¼ wider than outer haves (vs. inner and outer halves of leaf laminae about the same width or inner halves ⅛ narrower than outer halves). Selaginella rostrata further differs from S. microdonta by its acroscopic lateral leaf margins dentate to denticulate throughout or denticulate along the proximal ⅓- ½, and entire distally, and basiscopic margins sparsely denticulate or entire (vs. acroscopic and basiscopic margins serrate). Furthermore, S. rostrata is also set aside from S. neblinae by its broadly elliptic to broadly ovate (vs. ovate-lanceolate) lateral leaves, with obtuse to rounded (vs. long attenuate to acuminate) apices, each occasionally tipped by a caducous short or tooth-like hair (vs. hair or teeth absent), and median leaf apices acuminate to long-aristate, each acumen or aristae ¼ -⅓ (vs. ½) the length of the laminae, and margins conspicuously hyaline (vs. greenish).

Selaginella microdonta , S. rostrata , and S. neblinae along with S. breweriana , S. cardiophylla , S. hemicardia , and S. valdepilosa are part of the S. microdonta group. The relationship of the " S. valdepilosa group" still needs to be ascertained by phylogenetic methods but an initial hypothesis would suggest that S. breweriana and S. neblinae seem to be sister species, whereas S. cardiophylla and S. rostrata form another putative sister alliance that in turn is sister to a S. microdonta and S. hemicardia alliance, to which probably S. valdepilosa also belongs to as an offshoot that is most distinct by its leaves and sporophylls densely, long-ciliate.

Interestingly and as part of this study, it was observed that branches of S. rostrata can become arrested at branch forks giving the species a ribbon-like, leafy liverwort resemblance. Valdespino (1992) previously reported this condition as resting branches in S. hemicardia . Furthermore, as a result of the undeveloped branches, rhizophores in both species are seemingly subdorsal.

Additionally, one paratype collection here cited (i.e., Lierner & Holsts 20424 p.p. at MO and UC) represents mixed gatherings, which I identified as a = S. rostrata and b = S. tuberculata , while two other collections (Steyermark et al. 92588 p.p. at U, and Steyermark et al. 92588-A p.p at U) are also mixed gatherings, which I identified as a = S. rostrata and b = S. cardiophylla ). Selaginella tuberculata also has a leafy, liverwort habit and creeping stems and might eventually prove to be part of the " S. microdonta group," but it is distinct from the rest of species here included in that alliance by its acroscopic lateral leaves margins long-ciliate along the proximal ¼ -⅓ with upper surfaces puberulent along the basiscopic halves and towards the apices as well as occasionally also distally along the acroscopic halves.

Finally, to help identify species in the " S. microdonta group" a key is provided below, which summarizes distinguishing characters among taxa in this alliance.

Figures

Figure 9. Distribution of Selaginella papillosa *, S. pubimarginata ◊, S. rostrata ■.

Figure 13. Selaginella rostrata Valdespino. A Section of upper surface of stem showing median and lateral leaves B median leaf, upper surface C section of lower surface of stem showing lateral and median leaves D lateral leaf, lower surface E megaspore, proximal face F detail of megaspore, proximal face G megaspore, distal face H detail of megaspore, distal face. A-H taken from the holotype.