Two new species of Selaginella (i.e. S. ayitiensis and S. brigitteana) from Hispaniola Island are described. Illustrations are provided for both new species and their affinities are discussed. Selaginella ayitiensis was collected in the Massif de la Hotte, Haiti, and is characterized by its long-creeping stems, corrugate to bumpy leaf upper surfaces, broadly acute to obtuse or apiculate median leaf apices, and white megaspores. It is morphologically related to the “Selaginella flexuosa group”. Selaginella ayitiensis differs chiefly from S. denudata and S. krugii (the only two other members of the “Selaginella flexuosa group” in the Greater and Lesser Antilles) by the shape of the median and lateral leaves apices. Selaginella brigitteana is known from different localities in the Dominican Republic and Haiti; it can be distinguished by its long-creeping, 2–4-branched stems, coriaceous leaves with the upper surfaces glossy, the median leaves with broadly hyaline, long-ciliate margins, and short-acuminate apices tipped by 2 or 3 cilia, and light yellow to cream megaspores. Selaginella brigitteana differs from S. leonardii, with which it has been confused in the past, by its broadly ovate median leaves with rounded, non-auriculate, and glabrous outer bases, submarginal and marginal stomata along proximal ½ of outer halves of the laminae, and with the upper surfaces glossy, comprising rounded and rectangular to elongate cells, many of which are papillate.
Alston (1952) prepared the only comprehensive revision of Selaginella in the Greater and Lesser Antilles presently available. It includes a key to species, synonymy, distribution and exsiccatae for each taxon, but provides no taxon descriptions. Since that work, Greater and Lesser Antilles Selaginella species were treated in geographically defined floristic accounts that include species descriptions such as those of Jamaica (Proctor 1985) and Puerto Rico and the Virgin Islands (Proctor 1989). More recently, new species of Selaginella were added for Cuba either in the context of putative species group reports (i.e. Caluff & Shelton 2003, 2009) or as independent taxa (Shelton & Caluff 2003; Caluff & Shelton 2014; Valdespino & al. 2014). Within the Greater and Lesser Antilles, Hispaniola Island is the second largest island of the region and its Selaginella flora has received slight attention over the more than six decades since Alston (1952) recognized 13 species to be present there. Recently, though, Caluff & Shelton (2015) reported a second collection of S. fuertesii Hieron., a little-known endemic, articulate species, from the Dominican Republic.
In connection with the IX Latin American Botanical Congress held in Santo Domingo, Dominican Republic in 2006, my colleagues John Pruski and Rosa Ortíz (MO), Rita Besana and I conducted fieldwork in the central mountainous region of that country and collected an intriguing Selaginella species along wet road banks. Further examination of that collection and revision of additional herbarium specimens representing species from the Greater and Lesser Antilles, as well as relevant published taxonomic literature on Selaginella, has revealed it to be an undescribed species and has revealed an additional new taxon from Hispaniola. Accordingly, herein they are formally named and established as S. ayitiensis Valdespino from Haiti and S. brigitteana Valdespino from Dominican Republic and Haiti.
Material and methods
This study is based on examination of herbarium specimens from B, F, GH, JBSD, MO, NY, PMA, UC and US (herbarium codes follow Thiers 2019+) and fieldwork conducted in 2006 in La Vega province, Dominican Republic. Samples for Scanning Electron Microscopy (SEM) to document upper and lower surfaces of stem sections and leaves, and to determine sculpturing patterns and diameter of the spores of the new taxa and possible related species were taken from selected representative herbarium specimens. SEM samples were prepared following standard techniques as described by Valdespino (1995) and Valdespino & al. (2014) and were examined and imaged at different magnifications using a Zeiss Model Evo 40 at 10–15 kV. Digitized SEM images were post-processed with Adobe Photoshop and assembled according to species in multipart figures.
Descriptions of the new species follow the pattern and methods utilized by Valdespino (2017) and Valdespino & al. (2014, 2018), complemented by terminology found in general botanical glossaries (e.g. Beentje 2016) and those specialized for pollen and spores (e.g. Punt & al. 2007; Halbritter & al. 2018). Furthermore, when describing cell surface projections the terms “mammilla (pl. mammillae) / mammillate (with mamillae)” and “papilla (pl. papillae) / papillate (with papillae)” regardless of their composition and consistency may be considered equivalent. Therefore, herein these structures are defined as a nipple-shaped structure or single, discrete, round and small, nipple-like, cell surface projection, where the “mammilla” is less than 1 µm in diam., while the “papilla” is usually 1–2 µm in diam. Finally, the conservation status was assessed according to the IUCN Red List categories and criteria version 3.1, second edition (IUCN 2012).
Results and Discussion
Holotype: Haiti, Dept. Sud-Grand'Anse, Massif de la Hotte, Geffrard, 18 km N of Camp Perrin, on road to Beaumont and Jerémié, [c. 18°23′N, 73°48′W], 850 m, 11 Mar 1983, J. Mickel, T. Zanoni, M. Mejía & J. Pimentel 9308 (NY!; isotype: PMA!).
Diagnosis — Selaginella ayitiensis resembles S. denudata (Willd.) Spring but differs from it by its median leaf apices broadly acute to obtuse or apiculate, in latter case each apiculum 0.05–0.1 mm long (vs short-aristate, each arista ¼–⅓ the length of the leaf lamina, 0.2–0.4 mm long), lateral leaf apices obtuse (vs acute), and ventral (vs axillary) rhizophores, which are filiform, each 0.1–0.3 mm in diam. (vs stout, each 0.6–1.5 mm in diam.).
Description — Plants terrestrial or epipetric. Stems long-creeping, stramineous, 6–15 cm long, 0.3–0.5 mm in diam., non-articulate, not flagelliform or stoloniferous, 2- or 3-branched. Rhizophores ventral, throughout stems, filiform, 0.1–0.3 mm in diam. Leaves dimorphic, chartaceous, both surfaces glabrous, upper surfaces green and corrugate to bumpy, lower surfaces silvery green and smooth or slightly corrugate on lateral leaves. Lateral leaves distant, ascending, ovate, broadly ovate or ovate-elliptic, 1–2.5 × 0.7–1.5 mm; bases rounded, acroscopic bases overlapping stems, basiscopic bases free from stems; acroscopic margins on upper surfaces narrowly hyaline along proximal ½ or throughout and comprising an obscure band 2–4 cells wide, each cell elongate and papillate, idioblast-like, papillae in one row on each cell lumen, or greenish along distal ½ and comprising rounded to rectangular, sinuate-walled cells, dentate to serrulate, basiscopic margins on upper surfaces greenish and comprising rounded to rectangular, sinuate-walled cells, entire along proximal , otherwise sparsely dentate distally, margins on lower surfaces hyaline and comprising a band 2–4 cells wide, cells elongate and papillate, idioblast-like, papillae in one row on each cell lumen; apices obtuse, tipped by 1–4 teeth; upper surfaces consisting of rounded, rectangular to elongate or irregular, sinuate-walled cells, some laevigate and others papillate, papillae 8–25 on each cell lumen, without idioblasts or stomata, lower surfaces consisting of elongate, sinuate-walled cells, some laevigate and others papillate, idioblast-like, papillae 30–65 in 2 rows on each cell lumen, with stomata in 2–4 rows along central portion of midribs. Median leaves distant to slightly imbricate, ascending, broadly obovate, broadly ovate-oblong or broadly ovate-elliptic, 1–1.4 × 0.5–0.8 mm; bases oblique, inner bases rounded to truncate, outer bases rounded, ventricose; inner margins narrowly hyaline and comprising a band of 2 or 3 cells wide, each cell elongate and papillate, idioblast-like, papillae in one row on each cell lumen, dentate, outer margins conspicuously hyaline along distal ½ and obscurely so (because margins folding inward) on proximal ½ and comprising a band 2–4(–6) cells wide, cells as in inner margins; apices broadly acute to obtuse or apiculate, if latter, apiculae 0.05–0.1 mm long and often breaking off; both surfaces without idioblasts, upper surfaces consisting of rounded, rectangular to elongate or irregular, sinuate-walled cells, some laevigate, most papillate, papillae 8–25 over each cell lumen, with stomata in 1–3 rows along distal ¾ of midribs, lower surfaces consisting of elongate, sinuate-walled, laevigate cells, except for those on incurved, outer submarginal to marginal region along proximal ¼, where cells are elongate, sinuate-walled and papillate, papillae 15–35 in 1 or 2 rows over each cell lumen, without stomata or few submarginal on incurved portion of outer margins and bases. Axillary leaves similar to lateral leaves or oblong-elliptic, with both margins hyaline and dentate. Strobili terminal and single on branch tips, quadrangular, 2.5–15 mm long. Sporophylls monomorphic, without a laminar flap, ovate, 0.8–1.2 × 0.4–0.7 mm, with a slightly developed keel distally on upper surfaces along midribs; bases rounded; margins hyaline, dentate; apices acute; dorsal sporophylls upper surfaces green with cells as in median leaves, except for halves that overlap ventral sporophylls, where they are hyaline and have elongate, slightly sinuate-walled cells, lower surfaces greenish-hyaline consisting of elongate, sinuate-walled cells; ventral sporophylls with both surfaces hyaline to greenish-hyaline, consisting of elongate, sinuate-walled cells. Megasporangia on proximal ½ of two ventral rows; megaspore white, rugulate and slightly reticulate marginally on proximal faces with granulate-foveolate microstructure, reticulate with open reticulae on distal faces with granulate-echinate microstructure, 230–280 µm in diam. Microsporangia in two dorsal rows and on distal ½ of two ventral rows; microspores deep orange, granulate-rugulate on proximal faces, capitate or baculate (if tips broken off) on distal faces, with echinulate microstructure on both faces, 25–30 µm in diam.
Distribution and ecology — Selaginella ayitiensis is known only from the type collection made in Geffrard in the vicinity of the Massif de la Hotte in Haiti, where it may be a local endemic; it grows on limestone rocks at c. 850 m.
Conservation status — Selaginella ayitiensis seems to be an element of remnant patches of primary to secondary, wet, limestone forests in and around the Massif de la Hotte in Haiti, which is an important centre of plant endemism and dispersal and one of the most biologically diverse regions of Hispaniola (Judd 1986; Peguero & al. 2006). This region is highly threatened by human encroachment resulting in vegetation loss due to the expansion of subsistence agriculture, harvest of wood for diverse uses (e.g. construction and charcoal production), and small-scale ranching (Judd 1986; Peguero & al. 2006). Based on these threats, S. ayitiensis is considered Endangered; EN A1c; B2ab(i–iv).
Etymology — The species epithet derives from the aboriginal Taino word “Ayiti”, meaning land of the high mountains, which was one of the pre-Columbian names for Hispaniola and that is still used in Haitian creole to refer to the country of Haiti.
Remarks — Selaginella ayitiensis is characterized by its long-creeping stems, corrugate to bumpy leaf upper surfaces, broadly acute to obtuse or apiculate median leaf apices, and white megaspores. Some of these features are also shared with a group of Neotropical species of Selaginella, here informally called the “Selaginella flexuosa group”, which includes S. alampeta M. Kessler & A. R. Sm., S. barnebyana Valdespino, S. chiapensis A. R. Sm., S. corrugis Mickel & Beitel, S. denudata, S. flexuosa Spring, S. guatemalensis Baker, S. huehuetenangensis Hieron., S. idiospora Alston, S. krugii Hieron., S. macrostachya (Spring) Spring and S. subrugosa Mickel & Beitel. All these taxa, except S. denudata and S. krugii, are restricted to the mainland of the Neotropics and have acuminate to long-aristate median leaf apices, except for S. corrugis that could have apiculate median leaf apices as in the newly described S. ayitiensis. Selaginella ayitiensis, however, is a more robust plant than S. corrugis and has larger median leaves, 1–1.4 × 0.5–0.8 mm (vs 0.4–0.6 × 0.2–0.4 mm). In the Greater and Lesser Antilles region, S. denudata from Jamaica and S. krugii from Puerto Rico are morphologically close (including also having white megaspores) to S. ayitiensis. In fact, S. ayitiensis will key out to S. denudata in Alston (1952) but the former differs from the latter by the characters listed under the diagnosis and by having broadly obovate, broadly ovate-oblong or broadly ovate-elliptic (vs elliptic) median leaves with the upper surfaces of the apices glabrous (vs with tooth-like projections on aristae), and hyaline (vs greenish) basiscopic margins on lower surfaces of lateral leaves, composed of elongate and papillate cells (vs cells without papillae). Selaginella ayitiensis is set aside from S. krugii by its median leaf apices broadly acute to obtuse or apiculate, if the latter, apiculae 0.05–0.1 mm long (vs apices long-aristate, arista at least or more the length of the leaf lamina, each 1.5–2 mm long) with the upper surfaces glabrous (vs with tooth-like projections on upper surfaces of aristae), and dentate (vs short-ciliate) margins, obtuse (vs acute) lateral leaves, and filiform (vs stout) rhizophores, each 0.1–0.3 mm (vs 0.4–1.2 mm) in diam.
Holotype: Dominican Republic, La Vega, Cordillera Central, along DR Carretera Secundaria 12, c. 3 km E of El Río on road to Arroyo Prieto, c. 23 km E of Constanza, 19°01′N, 70°31′W, 1150 m, 25 Jun 2006, J. Pruski, R. Ortíz, I. Valdespino & R. Besana 4045 (PMA!; isotypes: B!, JBSD!, MO!, NY!, UC!, US!).
Diagnosis — Selaginella brigitteana differs from S. leonardii O. C. Schmidt by its 2–4- (vs 1- or 2-) branched stems, broadly ovate (vs ovate-oblong to ovate-deltate) median leaves with the outer bases rounded, slightly prominent, non-auriculate and glabrous (vs with a prominent, distinct, linear, terete and hirsute outer auricle that curves inward towards the stems), upper surfaces with some cell lumina papillate (vs papillate and mammillate), and with (vs without) submarginal stomata on upper surfaces along proximal ½ of outer halves, and leaves upper surfaces glossy (vs dull) comprising rounded and rectangular to elongate (vs quadrangular to rectangular) cells.
Description — Plants terrestrial or epipetric. Stems creeping, stramineous, 10–35 cm long, 0.3–1 mm in diam., non-articulate, not flagelliform or stoloniferous, 2–4-branched. Rhizophores axillary-ventral, throughout stem, filiform, 0.1–0.3 mm in diam. Leaves dimorphic, chartaceous, both surfaces glabrous, upper surfaces green, smooth or slightly corrugate, and glossy, lower surfaces silvery green, smooth, slightly glossy. Lateral leaves distant or slightly imbricate at branches, ascending, ovate or ovate-deltate, 1–2.5 × 0.7–1.5 mm; bases rounded to subcordate, acroscopic bases overlapping stems, basiscopic bases free from stems; acroscopic margins on upper surfaces hyaline along proximal and comprising a band 3–6 cells wide, cells elongate and papillate, idioblast-like, papillae in one row over each cell lumen, otherwise greenish on distal distally and comprising rounded to rectangular, sinuate-walled cells, long-ciliate along proximal ⅔–¾, otherwise short-ciliate on distal ¼–⅓, basiscopic margins on upper surfaces greenish and comprising rounded to rectangular and elongate, sinuate-walled cells, both margins on lower surfaces as in acroscopic margins, long-ciliate along proximal ¼–⅓, otherwise short-ciliate distally; apices acute, tipped by 1–3 short cilia; upper surfaces consisting of rounded to rectangular, sinuate-walled cells, some of these cells laevigate, others papillate, papillae 10–35 over each cell lumen, without idioblasts, with some marginal stomata on distal ⅓ of acroscopic and basiscopic margins and along proximal ⅓ of basiscopic margins, lower surfaces consisting of elongate, sinuate-walled cells, some of these papillate and idioblast-like, papillae in 2 or 3 rows over each cell lumen, with stomata in 1–4 rows along central –4/6 portion of midribs. Median leaves distant or slightly imbricate at branches, ascending, broadly ovate, 1.1–1.5 × 0.5–1.3 mm; bases oblique or subcordate, inner bases rounded to truncate, outer bases rounded or both bases rounded; inner margins hyaline and comprising a band 2–4 cells wide, cells elongate and papillate, idioblast-like, papillae in one or occasionally two rows over each cell lumen, long-ciliate, outer margins green along proximal ⅓–½ and comprising rounded to rectangular, sinuate-walled cells, long-ciliate throughout or long-ciliate near bases and becoming entire up to proximal ½ and then long-ciliate along distal ½, greenish along proximal ⅓–½ and comprising obscurely rectangular to elongate cells, hyaline along distal ½– and comprising a band 2–4 cells wide, cells as in inner margins, long-ciliate along distal ½–⅔; apices short-acuminate to short-aristate, each acumen or arista hyaline and 0.1–0.4 mm long, tipped by 1–3 often divergent cilia; both surfaces without idioblasts, upper surfaces consisting of rounded and rectangular to elongate, sinuate-walled cells, some of these laevigate or papillate, others elongate, sinuate-walled and papillate, idioblast-like, papillae 10–35 over each cell lumen, with stomata in 2 or 3 rows on distal ½ along midribs and submarginal and marginal along proximal ½ of outer halves of lamina, lower surfaces laevigate, consisting of elongate, sinuate-walled cells, without stomata. Axillary leaves shape, bases, margins (except for both margins long-ciliate) and apices similar to lateral leaves. Strobili terminal, single on branch tips, quadrangular, 2.5–15 mm long. Sporophylls monomorphic, without a laminar flap, ovate, 0.8–1.2 × 0.4–0.7 mm, with a slightly developed keel distally along midribs on upper surfaces; bases rounded; margins hyaline, dentate; apices acute; dorsal sporophylls with upper surfaces green with cells as in median leaves, except for halves that overlap ventral sporophylls where cells are hyaline, elongate, slightly sinuate-walled, lower surfaces greenish-hyaline, composed of elongate, sinuate-walled cells; ventral sporophylls with both surfaces hyaline to greenish, composed of elongate, sinuate-walled cells. Megasporangia in two ventral rows; megaspores light yellow to cream, rugulate-reticulate on proximal and distal faces with verrucate, echinulate and perforate microstructure, 320–360 µm in diam. Microsporangia in two dorsal rows; microspores deep orange, slightly rugulate to smooth on proximal and distal faces, 25–40 µm in diam.
Distribution and ecology — This species grows in see-pages on steep roadside banks, limestone rocks or clay soil in humid broad-leaved forests at 300–2140 m; it is known from the Massif de la Selle in southeastern Haiti and in the central and northeastern mountainous region of the Dominican Republic.
Conservation status — This species has a wide distribution in Hispaniola and may be more common than here recorded. However, the localities where it has been collected are imperilled do to human encroachment into natural forest remnants, resulting in increased deforestation. Therefore, according to IUCN (2012) categories and criteria, it is tentatively considered Vulnerable: VU A1c; B1ab(iii).
Eponomy — Selaginella brigitteana is dedicated to my colleague and friend Brigitte Zimmer (b. 1943) from the Botanic Garden and Botanical Museum Berlin; a specialist on Adiantum and whose skilled dedication to the curation, including databasing and imaging of the lycophyte and fern collections at B has been outstanding, thereby making systematic and taxonomic studies on these groups more accessible and efficient for pteridologists.
Remarks — Selaginella brigitteana is distinguished by its long-creeping, 2–4-branched stems, glossy and chartaceous leaves, broadly hyaline and long-ciliate median leaves tipped by a short acumen or short arista tipped by 1–3 often divergent cilia, with leaf laminae upper surfaces with some cell lumina papillate. It may be confused with S. leonardii and S. plumieri Hieron., both also found in Hispaniola. In fact, Caluff & Shelton (2009) cited two of the paratypes of this new taxon (i.e. Abbott 2137 and Judd & al. 4467) under S. leonardii. Selaginella brigitteana differs from S. leonardii by the characters of median leaves overall laminae and outer bases shape, and upper surface cell types and stomata distribution listed under the diagnosis. It is separated from S. plumieri, which is an ill-defined species, by its short-acuminate to short-aristate (vs long-aristate) median leaf apices, the acumen or arista hyaline (vs the arista greenish) and 1/12 (vs ½ or more) the length of the leaf laminae, each 0.1–0.4 (vs 0.5–1) mm long, tipped by 1–3 often divergent cilia (vs tipped by teeth), outer margins long-ciliate near bases (vs entire), and lateral leaf apices acute (vs acuminate).
Additional specimens examined (paratypes) — Haiti: Dép. Ouest, Port-au-Prince, Massif de la Selle, near Roberjot, northern slope of Morne Cabaio, 1700 m, 28 Aug 1924, Ekman H1691 (B, F, GH, US); Parc National Morne La Visite, ravine of Riviere Blanche, W of point where crossed by road from Seguin to Furcy, SW of Park Headquarter, 1700–1800 m, 10 May 1984, Judd & al. 4467 (NY, S n.v.). — Dominican Republic: La Vega, between Constanza and main highway Santo Domingo–Santiago, c. 300 m, 21 Dec 1964, Jones & Norris 1011 (NY); Cordillera Central, Constanza, Río del Medio, c. 1150 m, 28 Oct 1929, Ekman H13952 (B, GH, U); Arroyo La Sal, SE of town of La Sal, between Loma La Sal and Loma La Golondrina, 19°03.5′N, 70°34′W, 14 Apr 1982, Zanoni & al. 20040 (NY); Loma La Golondrina, S of Jarabacoa, near La Sal, Paso Bajito, 19°04′N, 70°33′W, 2 Jul 1986, Zanoni & al. 36763 (NY); 13.3 km N of El Río and 10 km from La Sal and la Palma towns, 19°04′N, 70°34′W, 3000–3300 ft [914–1006 m], 29 Apr 1982, Zanoni & al. 20293 (NY); 12 km road Duarte (Santo Domingo–Santiago), on road to El Río and Constanza, Casabito, valley of Río Jalubey, 19°03′N, 70°30′W, 900 m, 2 Sep 1982, Zanoni & al. 23024 (NY); 4 km W of La Culata de Constanza, Loma El Campanario, 18°57′N, 70°48′W, 1800–2140 m, 8 Sep 1982, Zanoni & al. 23247 (NY); Subida al Casabito, Bonao, 600–700 m, 4 May 1975, Liogier & Liogier 22868 (NY 2 sheets); Reserva Científica Ebano Verde, sendero (nuevo) de El Cajón (ladera de Loma La Sal), en ladera Norte Loma La Sal a Río Camú, 19°04′N, 70°33′W, 1200–1300 m, 6 May 1992, Zanoni & al. 45759 (NY); cima de Loma La Sal, 19°04′N, 70°34′W, 1350–1440 m, 27 May 1992, Zanoni & al. 45970 (NY); Pacificador [Duarte], vicinity of San Francisco de Macorís, 400–1000 m, Abbott 2137 (B, BM n.v., GH).
I thank the curators of the cited herbaria who made collections available. I am particularly grateful to my friends John Pruski, Rosa Ortega and Rita Besana for their companionship during our botanizing in the Dominican Republic, and the IX Latin American Botanical Congress organizers and the Ministry of Environment of the Dominican Republic for facilitating collecting permits within the framework of the Congress. I would also like to thank the Smithsonian Tropical Research Institute (STRI) in Panama for access to its SEM facilities, as well as the New York Botanical Garden and the Botanic Garden and Botanical Museum Berlin and their staff for granting access to their research facilities during my visits there. The offices of the Dean of the Faculty of Natural and Exact Sciences and Technology and the Vice-president for Research and Graduate Programs of the University of Panama and the National Research System (Sistema Nacional de Investigation, SNI) of Panama provided further support for this research. I am most indebted to Brigitte Zimmer and Robbin Moran who hosted me during my visits to B and NY, respectively, Mr Jorge Ceballos at STRI for providing valuable assistance with the SEM, and Mr Pedro Argudo in helping prepare figures. My gratitude also extends to Chris Gioia who read and corrected the English on an early draft of this paper and also provided endless encouragement throughout my research on Selaginella. Finally, I am grateful to Nicholas Turland, editor of Willdenowia, and three anonymous reviewers for helpful comments on the manuscript.