Selaginella willdenowii (Desv.) Baker (Selaginellaceae) first record from Sitakundo Ecopark, Chattogram, for the vascular plant of Bangladesh

The present study provides the new distributional records of Selaginella willdenowii (Desv.) Baker in the Sitakundo Ecopark, located in Chattogram, Bangladesh. This is the first record of the ridges naturally found on limestone rocks and waterfalls. An updated nomenclature, important synonym, description, ecology, specimen examined, and geographic distribution are provided along with a detailed overview and pictures.


INTRODUCTION
The Peacock fern (Selaginella willdenowii) is a vascular plant species in the family Selaginellaceae.Selaginellaceae, a cosmopolitan family including a sole genus (Selaginella) and seven subgenera Weststrand and Korall, (2016), are the most species-rich family in extant lycophytes and estimated to have about 600-800 species (Valdespino, 2015;Zhou and Zhang, 2015).Selaginella is also known as spike moss or club mosses.The rhizophore in Selaginella is a unique kind of rootbearing organ, a positive gravitropic leafless cylinder without typical root traits such as a root cap (RC) and root hairs (Mello et al., 2019).It corresponds to a group of early vascular plants with an important place in evolutionary history (Kang et al., 2020).They belong to the Lycopodiophyta division, the oldest lineage of vascular plants on Earth (Weng and Noel, 2013).There are more than 700 Selaginella species distributed worldwide, in a diverse range of habitats, from deserts to tropical rainforests and mountainous regions.
Like other Selaginallales, they are sometimes included in a paraphyletic group called the "fern allies" and not a true fern, it is a type of moss.Peacock fern is a great little terrarium plant, known for its striking blue color.Selaginella occurs mostly in the world's tropical regions, with a handful of species to be found in the arctic-alpine zones of both hemispheres.In Bangladesh, seven species from the genus Selaginella have been previously documented.These species include Author Affiliation: 1 Plant researcher, RDA Campus, Bogura, Bangladesh 2 Lab. of Medicinal Plant Resources, Department of Crop Botany, Bangladesh Agricultural University, Mymensingh, Bangladesh (Sw.) Spring, S. microphylla (Kunth) Spring, S. tenuissima Fée, S. myosurus (Sw.)Alston and S. repanda (Desv.)Spring.It has no data on the occurrence of Peacock ginger (Selaginella willdenowii) in Bangladesh in previously published literature.During a botanical exploration of Sitakundo Ecopark in Chattogram, Bangladesh, a species was found to have abundant populations.Therefore, we report it as the country's newly recorded Selaginella species.

MATERIALS AND METHODS
The present research work was conducted in Sitakunda Ecopark and the adjacent Botanical Garden is located along the Dhaka-Chattogram highway in Sitakunda upazila of Chattogram district.The eco-park is located between 2236 to 2239 North latitude and 9140 to 9142 East longitude and about 15 to 65m above mean sea level.The park is bordered by Mirsarai upazila to the north, Pahartali to the south, the Sandwip canal and the Bay of Bengal to the west, and Fatikchari to the east.During the documentation of the biodiversity of Sitakunda Eco -park, a plant is observed in stream bank areas on exposed rock.The place is mostly shady and wet.Along with the stream bank, the plant is also found in exposed rock with little cover of soil.The plant was collected and identified as Selaginella willdenowii.The voucher specimens were poisoned, dried, prepared and deposited at the herbarium for future reference.
Median leaves falcate-lanceolate or oblique-ovate, 2.4-2.7 × 0.9-1.3mm; base auriculate, outer auricle larger than inner; margins transparent, entire; apex obtuse.Strobili (Spore bearing parts) are produced at the tips (Figure 1c, g).Solitary, 0.5-2 cm; sporophylls monomorphic, cordate to ovate-deltate, base glabrous, margins green, entire, apex slightly cuspidate.Iridescent fronds look like blue-green and pinkish hues (Figure 1e).Sometimes all leaves are green depending on light, soil & water flows (Figure 1f).The presence of iridescent blue color in the leaves of Selaginella willdenowii indicates the presence of a layered lamellar structure within the upper cuticle of these iridescent leaves.The blue iridescence is achieved through the utilization of multi-layer structures.There are blue and green leaves from the same plant indicating that the loss of the blue iridescence corresponds to a loss of the multi-layer structure.These blue-green colors indicate the color of blue Peacock.

Ecology
Like the waterfall rocks or stony riverside (Figure 1b), having low light and moist conditions, limestone rock.Some fern species found this type of limestone mixed soil, rich in calcium carbonate and tropical rainforest weather.

Key identifying characters
This fern is easily identified by its iridescent, metallic bluish-green fronds.When viewed at different angles, hues of green and blue.

Specimen examined
Selaginella willdenowii grows on the limestone rocks at the side of a small waterfall at Chandranath Hill at Sitakunda Eco Park.
Discuss the sample plant matching with the Peacock (Mayur fern).

Figure 1 a
Figure 1 a.Iridescent leaves b.The muddy leaves showing the hilly river soil c.Close tips of fern d.Average size e.Blue-greenpink-hues f.Sometimes green g.Strobilus showing on the tips of upper branches h.Illustration with Scale