Selaginella ayitiensis and S. brigitteana (Selaginellaceae): two new species from Hispaniola Island

Abstract: 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.


Introduction
prepared the only comprehensive revision of Selaginella in the Greater and Lesser Antilles presently available. It includes a key to species, synonymy, distribu-tion 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 72 Valdespino: Selaginella ayitiensis and S. brigitteana from Hispaniola Island 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. , 2009 or as independent taxa 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. (2014Valdespino & al. ( , 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. papil lae) / papillate (with papillae)" regardless of their com-position and consistency may be considered equivalent. Therefore, herein these structures are defined as a nippleshaped 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).
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 flexu osa 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. flexuo sa Spring, S. guatemalensis Baker, S. huehuete nangensis Hieron., S. idiospora Alston, S. krugii Hieron., S. mac rostachya (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. cor rugis 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 ayitien sis 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 ⅔ or more the length of the leaf lamina, each 1.5 -2 mm long) with the upper surfaces glabrous (vs with tooth-76 Valdespino: Selaginella ayitiensis and S. brigitteana from Hispaniola Island 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. Valdespino, sp. nov 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.
Distribution and ecology -This species grows in seepages 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 77 Willdenowia 49 -2019  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 sur faces 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).