Selaginella surucucusensis L.A. Goes & E.L.M. Assis, Kew Bull. 72: 40, 1. 2017.

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 surucucusensis L.A. Goes & E.L.M. Assis, Kew Bull. 72: 40, 1. 2017. Figures 5 , 19

Type.

Brazil. Roraima: Serra Surucucú, 26 Jan 1975, B.G.S. Ribeiro 15.189(616) (holotype: HRB-n.v.; isotypes: BHCB-n.v., HRB-n.v., MG!, NY!, RB!).

Description.

Plants terrestrial. Stems erect, stramineous, (25)35-75 cm tall, 1.2-3.0 mm diam., non-articulate, usually not flagelliform or infrequently so, stoloniferous, 3-branched, the terminal portion of the stems similar in shape to lateral branches (i.e., conform). Rhizophores axillary, ventral, dorsal, dorso-axillary, and seemingly lateral, borne on lower most part of stems and throughout stolons, filiform or stout, 0.2-1.0 mm diam. Leaves seemingly monomorphic and strongly appressed to the stem shortly before or after the first or second branches and without distinctive auricles, then heteromorphic throughout, chartaceous to coriaceous, upper surfaces shiny dark, brown-green (dark olive) to brownish (due to drying technique), seemingly smooth, lower surfaces shiny, yellowish green, dark olive to brown (due to drying technique), smooth. Lateral leaves on main stem after leaves become fully heteromorphic, distant, ascending to slightly spreading, ovate or ovate-oblong, 3.0-4.8 × 1.4-2.6 mm; bases rounded to truncate, glabrous, without auricles, acroscopic bases strongly overlapping stems, basiscopic bases free from stems; margins on upper and lower surfaces bordered by a narrow band comprised of greenish cells, the band 1-3 cells wide, the cells elongate, slightly sinuate-walled, and glabrous, on acroscopic margins dentate along proximal ¼, otherwise denticulate on distal ¾, on basiscopic margins entire along proximal ¾, otherwise sparsely denticulate distally; apices broadly acute to obtuse, tipped by 3-5 teeth; upper surfaces consisting of quadrangular to rectangular (jigsaw puzzle-like), sinuate-walled cells (often difficult to distinguish because of waxy deposits), many of these consisting of papillate idioblasts, comprising some sparse, elongate and papillate idioblasts, the papillae 4-11 in 1 or 2 rows on each cell lumen, without stomata; lower surfaces consisting of elongate, irregularly sinuate-walled cells (jigsaw puzzle-like) and of many elongate, straight-walled, papillate idioblasts, papillae 4-11 in 2 rows on each cell lumen, with stomata on 2-4 rows along central portion of midribs Median leaves on main stem after leaves fully heteromorphic, imbricate, ascending, ovate, ovate-elliptic, ovate-lanceolate to ovate-oblong, 1.7-4.2 × 0.8-2.8 mm; bases glabrous, oblique, truncate or asymmetric, inner bases rounded to truncate, outer bases auricled, the auricles ciliate with 3-14 short hairs; margins bordered continuously by a band of glabrous cells, the band 1-3 cells wide with the cells elongate, slightly sinuate-walled, glabrous, except for those on distal ⅓ of outer margins that are composed by a narrow hyaline band of idioblasts, the band 1-3 cells wide, the idioblasts straight-walled, and papillate, the papillae in one row, margins dentate to denticulate; apices acute, acuminate or aristate, each acumen or arista 0.1-0.6 mm long, tipped by 1-3 teeth; upper surfaces similar to those on upper surfaces of lateral leaves, except abundantly covered by quadrangular and elongate and papillate idioblasts, the papillae 4-32 in 1 or 2 rows on each cell lumen, with stomata in 1-5 rows along the midribs, lower surfaces comprising by elongate, irregularly sinuate-walled cells, (jigsaw puzzle-like), without idioblast and stomata. Axillary leaves on main stem after leaves fully heteromorphic ovate to ovate-lanceolate, 2.0-4.0 × 0.8-2.2 mm; bases rounded to slightly truncate, entire, without auricles; inner and outer margins as acroscopic margins of lateral leaves, denticulate throughout; apices broadly acute to obtuse, tipped by 1-4 teeth; both surfaces as lateral leaves. Strobili terminal on main stem and each branch tip, quadrangular, 0.5-4.0 cm. Sporophylls monomorphic, without a laminar flap, each with a slightly developed and glabrous keel along distal ¾ of the midrib, ovate to ovate-lanceolate, 0.8-1.2 × 0.4-0.7 mm; bases rounded; margins narrowly hyaline, 1 or 2 cells wide with the cells elongate, slightly sinuate-walled and glabrous, parallel to margins, denticulate throughout; apices shortly acuminate, the acumen 0.1-0.2 mm long, tipped by 1-3 teeth-like projections; dorsal sporophylls with upper surfaces green and cells as in median leaves, except for the half that overlaps the ventral sporophylls where the surfaces are greenish hyaline comprising elongate, slightly sinuate-walled cells, lower surfaces silvery green, comprised of elongate, sinuate-walled cells; ventral sporophylls with both surfaces hyaline, comprised of elongate, sinuate-walled cells and of papillate idioblasts. Megasporangia in two ventral rows; megaspores white, 240-310 µm diam., proximal faces rugulate-reticulate without an equatorial flange, the microstructure strongly echinate and perforate, distal faces reticulate the reticulae open (incomplete) to closed, each reticulum with low muri, the microstructure strongly echinate and perforate. Microsporangia in two dorsal rows; microspores orange, 23-27 µm diam., proximal faces rugulate, the microstructure echinate and granulate, distal faces capitate or baculate, the microstructure of capita or bacula and the rest of the surface echinate.

Additional specimen examined. Colombia. Amazonas: Río Miritiparaná, ca. 00°30'S, 70°40'W, 700 ft [213 m], 8 May 1952, Schultes & Cabrera 16471 (US [cited by Crabbe and Jermy (1973) as a paratype of S. palmiformis Alston ex Crabbe & Jermy]. Vaupés: Mpio. Carurú, Caño Carurú, Comunidad del Palmar, Cachivera Pacú, camino entre cachivera y sabana de Kuw (Kuvai), 01°14'47.0"N, 71°19'23.5"W, 270-430 m, 10 Sep 2013, Rodríguez et al. 7916 (NY). Venezuela. Amazonas: Depto. Atabapo, sector Norte de la Sierra Parima, cuenca alta del Río Matacuni, ca 20 km NNW de Shimada-Wochi, 03°59'N, 64°41'W, 1000-1500 m, 10 Nov 1983, Huber & Colchester 8430 (NY-2 sheets); Depto. Atures, E del Cerro Cuao, Caño Piedra, 75 km SE de Puerto Ayacucho, 05°05'N, 67°19'W, 1050 m, Sep 1989, Fernández et al. 6113 (NY), vicinity of and upstream from damsite, N side of Río Cataniapo, 45 km SE of Puerto Ayacucho, 05°35'N, 67°15'W, 100 m, 13 May 1980, Steyermark et al. 122394 (MO, UC); Cerro Marahuaca, 1000 m, 3 May 1949, Maguire & Maguire Jr. 29202 (NY, US); Cerro Sipapo ( Paráque), 3 km SW of Base Camp, 200 m, 8 Feb 1949, Maguire & Politi 28814 (NY, UC, US); Comision de Frontera, ca 0.5 km below Camp 3, 02°27'24"N, 63°56'W, 20 May 1972, Steyermark 106041 (NY); Serranía Batata, 2 km NE of Salto Colorado, Caño Colorado, 55 km SE of Puerto Ayacucho, 05°33'N, 67°08'W, 550 m, Sep 1989, Fernández et al. 6360 (MO, NY, US). Brazil. Roraima: Serra dos Surucucú, NE of mission station, 02°42-47'N, 63°33-36'W, 1000-1400 m, 17 Feb 1969, Prance et al. 9979 (F, INPA-image, NY, R, UC, US).

Habitat and distribution.

Selaginella surucucusensis grows on humid forest floors, creek- and riverbanks in lowland to montane tropical rainforests and in open scrub savanna on white sand at 200-1500 m. It was originally described from Serra dos Surucucú in the state of Roraima, Brazil. Nevertheless, its distribution range is here significantly expanded farther north- and northwestwards into the Amazon basin region to include Colombia and Venezuela. Moreover, it is here documented to be fertile from February to November.

Conservation status.

This species is widely distributed at low and high elevations in tropical rainforests of South America. Accordingly, it is considered of Least Concern (LC) based on IUCN (2012).

Discussion.

Despite the relatively recent publication of S. surucucusensis , with an originally limited, corroborated distribution range in Brazil provided by Góes-Neto et al. (2017), a number of specimens from Colombia and Venezuela are known and here newly documented. The study of these broader spectrum of specimens provides a better understanding of morphological characters (including mega- and microspores ornamentation features) of the species, expanded geographic circumscription, as well as of its presumed affinities. Consequently, an emended description for S. surucucusensis is provided, including a novel illustration.

Selaginella surucucusensis is characterized by its fern-like habit, non-articulate and usually not flagelliform or infrequently so, stoloniferous, 3-branched erect stems, each (25)35-75 cm tall and 1.2-3.0 mm in diam., with axillary, lateral, and dorsal to dorso-axillary rhizophores, which are borne on the lower most part of the stems and throughout stolons, each filiform or stout, 0.2-1.0 mm diam. In addition, the leaves on main stems are seemingly monomorphic and strongly appressed to stems, shortly below or above first stem branches and after this become fully heteromorphic, with median leaf upper surfaces covered with short-elongate or punctate, papillate idioblasts, and with a small or reduced, dentate outer auricle on outer bases, and lateral leaf with scattered, elongate, papillate idioblasts on lower surfaces. Furthermore, megaspores of this species are white, rugulate-reticulate on proximal faces without an equatorial flange and with strongly echinate and perforate microstructure, reticulate with open and closed reticulae formed by low muri and reticulate-granulose on distal faces with strongly echinate and perforate microstructure. Finally, microspores of this species are orange, echinate, rugulate, and granulate on proximal faces with punctate microstructure, capitate or baculate on distal faces with each caput or bacula and the rest of the surface with an echinate microstructure. In addition, the most examined specimens of S. surucucusensis have their leaf upper surfaces dark, brown-greenish to brownish, probably due to being fixed in alcohol.

Selaginella surucucusensis is morphologically somewhat similar to S. gioiae , from which it is set aside by the characters listed under the diagnosis and discussion of the latter. Furthermore, because of the fern-like habit and erect stems of S. surucucusensis most examined specimens were variously misidentified as S. anceps (C. Presl) C. Presl, S. amazonica Spring, S. mazaruniensis Jenm., S. oaxacana Spring or S. palmiformis . The short-elongate or punctate, papillate idioblasts on upper surfaces in median leaf of S. surucucusensis are somewhat similar to those of S. cuneata Mickel & Beitel from Mexico. Selaginella surucucusensis differs from S. cuneata by its ovate or ovate-oblong (vs. broadly ovate to ovate-orbicular) lateral leaves; median leaves bases (on main stems after first branches) oblique, truncate or asymmetric with the outer bases prominent (vs. slightly so) with (vs. without) an outer auricle, outer halves of leaf laminae at least ¼ to ½ wider (vs. twice as narrow) than inner halves, and margins of median and acroscopic margins of lateral leaves hyaline (vs. greenish).

Selaginella surucucusensis also appears morphologically close to S. oaxacana because both have median leaf with acuminate to short-aristate apices, narrowly hyaline and denticulate margins, outer basal auricles, and axillary, lateral, and dorsal rhizophores. Selaginella surucucusensis is set aside from S. oaxacana by its lateral leaf basiscopic bases rounded to adnate to the stems (vs. geniculate to auricled) and upper surfaces of the median leaves and sporophylls with short-elongate or punctate (vs. with long) idioblasts.

Selaginella surucucusensis differs from S. amazonica by its upper surfaces of leaf shiny, dark brown-green (vs. dark olive) to brownish (due to drying technique) and smooth (vs. dark brown and corrugate), with (vs. without) punctate or elongate idioblasts, median leaves above first branches ovate, ovate-elliptic, ovate-lanceolate to ovate-oblong (vs. broadly ovate to ovate-deltate) with (vs. lacking) an outer auricle, and lateral leaves shortly below or immediately above first branches ovate to ovate-oblong (vs. ovate-deltate). Selaginella surucucusensis is easily set aside from S. anceps by its leaf on main stems seemingly monomorphic and strongly appressed to the stem shortly before or after the first or second branches (vs. up to the third of fourth) branches, truncate and without (vs. with one or two, long, incurved, and ciliate) auricles. Likewise, S. surucucusensis is separated from S. mazaruniensis by its median leaf upper surfaces smooth (vs. corrugate), those above first branch with (vs. without) short-elongate or punctate, papillate idioblasts, with an outer (vs. lacking) auricle, and branches distinctly pinnate and conform (vs. usually flabelliform).

Crabbe and Jermy (1973: 141) cited one specimen here included in S. surucucusensis (Schultes & Cabrera 16471, US) as a paratype of S. palmiformis and Alston et al. (1981: 256) followed them. Both species are similar in having their median leaf bases with an outer, ciliate auricle. Nevertheless, in S. palmiformis the auricle is less prominent and covered only by 3-6 hairs. Selaginella surucucusensis further differs from S. palmiformis by its stems 3- (vs. 1- or 2-) branched, rounded when dry (vs. quadrangular) with the overall shape of proximal branches wider at base (vs. at middle) and rhombic-triangular to deltate-triangular (vs. elliptic or elliptic-lanceolate), leaves obviously heteromorphic above first or second (vs. usually at or above fourth) branches with upper surfaces having (vs. lacking conspicuous) short-elongate or punctate, and papillate idioblasts. It differs further from the latter by median leaf margins denticulate (vs. coarsely dentate), truncate (vs. often subcordate) axillary leaf bases, and ovate-lanceolate to ovate-oblong (vs. oblong) lateral leaves. Selaginella surucucusensis further differs from S. palmiformis by its median leaves on main stems after fully heteromorphic ovate, ovate-elliptic, ovate-lanceolate to ovate-oblong (vs. broadly ovate to ovate-deltate) with arcuate (vs. straight and almost central) midribs, outer halves of leaf laminae ca. ⅛ wider than inner halves (vs. both halves about the same width), and leaf bases evenly raised (vs. centrally ventricose).

Selaginella surucucusensis as well as S. altheae Valdespino are members of the " Selaginella flabellata group," and have similar microspore ornamentation but they diverge on their leaf shapes. Selaginella surucucusensis differs from S. altheae by its median leaf margins denticulate (vs. inner margins short ciliate along proximal ⅔, otherwise denticulate on distal ⅓ and outer margins entire along proximal ⅓, becoming short-ciliate along medial ⅓, otherwise denticulate on distal ⅓), with (vs. without) an outer basal auricle, and lacking marginal to submarginal stomata (vs. stomata present on proximal ¼ along outer margins), and lateral leaf acroscopic margins dentate along proximal ¼, otherwise denticulate on distal ¾ (vs. long-ciliate along proximal ½-¾, otherwise short-ciliate to dentate distally).

Finally, the presence of dorsal rhizophores in S. altheae , S. oaxacana , S. surucucusensis , and other members of the " Selaginella flabellata group" might eventually prove to be a morphological character that helps define this alliance. Nevertheless, dorsal rhizophores are also found in other heterophyllous Selaginella species such as S. psittacorhyncha ( Valdespino 2017b) within subg. Stachygynamdrum , where it has not been widely reported, and is characteristic of articulate species of subg. Gymnogynum s.l. ( Valdespino et al. 2018; Valdespino and López 2019), subg. Lepidophyllae ( Weststrand and Korall 2016), and homophyllous species classified in subg. Rupestrae ( Valdespino 1993a; Weststrand and Korall 2016). Consequently, it might well be that dorsal rhizophores are underreported in subg. Stachygynandrum and of wider occurrence in Selaginella or perhaps this feature has originated several times in different evolutionary lineages within the genus. Accordingly, the occurrence of dorsal rhizophores within Selaginella warrants further morphological, anatomical, molecular, and phylogenetic studies throughout species alliances to ascertain its evolutionary implications.

Figures

Figure 5. Distribution of Selaginella gioiae □, S. surucucusensis ▲, S. xanthoneura ●.

Figure 19. Selaginella surucucusensis A Habit, upper surface of stem B branch section, upper surface. C branch section, lower surface D branch section showing median leaves, upper surfaces E, F branch section showing axillary leaf (E) and lateral leaf (F), lower surfaces. A-F line drawing made from the isotype at NY. Illustration by Haruto Fukuda.