Chascolytrum serranum L.N.Silva, 2020

Da Silva, Leonardo N., Saarela, Jeffery M., Sokoloff, Paul C., Essi, Liliana & De Souza-Chies, Tatiana T., 2020, Chascolytrum serranum (Poaceae: Pooideae: Poeae: Calothecinae), a new microendemic species from Campos de Cima da Serra, southern Brazil, Phytotaxa 435 (1), pp. 41-49 : 42-46

Chascolytrum serranum L.N.Silva , sp. nov.

Type:— BRAZIL. Rio Grande do Sul: Cambará do Sul, Parque Nacional da Serra Geral, road to Cânion Fortaleza , swamp, 29°04’02.70”S, 50°02’28.70”W, 1022 m, 5 December 2017, L.N. da Silva, R. Oliveira, R. Marchioretto & A. Christ 1067 (holotype ICN! , isotypes CAN! , RB! , US! ). ( Figs 1 , 2 , 3I‒L ).

Diagnosis:—Similar to Chascolytrum ambiguum and C. juergensii var. angustilemma due to the narrow lemmas (up to 1.5 mm wide), but distinguished by having paleas more than 2/3 the length of the lemmas (vs. paleas less than 2/3 the length of the lemmas in C. ambiguum and C. juergensii var. angustilemma ), puberulous paleas (vs. glabrous paleas in C. ambiguum ), and glabrous and smooth lemmas (vs. strigose lemmas in C. juergensii var. angustilemma ).

Description: —Perennial, caespitose, 55–87 cm tall, basal internodes of the culms not thickened, basal innovations extravaginal. Leaf sheaths glabrous, open, margins not overlapping; ligules 2.6–4.8 mm long, membranous, apex obtuse to truncate; leaf blades 9.5–18 × 0.2–0.6 cm, linear-lanceolate, apex acute, glabrous on both surfaces. Panicle open to contracted, erect, 8.5–16 cm long, pedicels scabrous. Spikelets 4–8–flowered, 4.5–7 × 2–4 mm, laterally compressed, elliptic-lanceolate to lanceolate, florets imbricate, loose at maturity. Glumes herbaceous, naviculate, glabrous, 3-nerved, nerves free, midveins scabrous distally, subequal, muticous, apices acute; lower glumes 2.5–3.2 × 0.6–0.8 mm; upper glumes 2.8–3.7 × 0.7–1.2 mm. Lemmas herbaceous, lanceolate to linear-lanceolate, laterally compressed, gibbous back not distinct from the margins, 3–5–nerved, glabrous, smooth, apex acute, muticous, margins glabrous, flat to slightly involute, base attenuate, without oil glands; lower lemma 3.3–4.1 × 1–1.4 mm. Paleas lanceolate or linear-lanceolate, membranous, puberulous between the keels, keels ciliate; lower palea 2.6–3.6 × 0.8–1.1 mm. Lodicules linear-lanceolate, stamens 1. Caryopsis ellipsoid or elliptic-lanceoloid, 1–1.4 mm, hilum linear.

Etymology:— The specific epithet highlights the area of occurrence of the new species, referring to the locality within Serra Geral National Park where the species is most frequent. The park is located in the Southern Brazilian Highlands where the vegetation is a mosaic of grasslands and Araucaria angustifolia ( Bertoloni 1819: 411) Kuntze (1898: 375) forest (IBGE 2004, Overbeck et al. 2007), a region also called Campos de Cima da Serra ( Iganci et al. 2011). Also, the human population living in this area is colloquially known as “ serranos ” (in Portuguese).

Phenology:— Specimens were collected with flowers and fruits in December.

Distribution and habitat:— The new species is known only from a restricted geographic area: the surroundings of and within Serra Geral National Park, municipality of Cambará do Sul, Rio Grande do Sul, Brazil, at around 1000 m elevation ( Fig. 4 ), inhabiting river banks or swamps ( Fig. 2A, C, D ). Only five populations are currently known, four of them recorded within the park and located less than 5 km from one another.

Conservation status: — Chascolytrum serranum has a restricted geographic distribution, with an extent of occurrence (EOO) and area of occupancy (AOO) of 5.34 km 2 and 12 km 2, respectively. Fewer than five locations are known for the species. Although the species is often recorded within a conservation unit (Serra Geral National Park), populations outside the park may be threatened due to the loss and reduction of habitat quality, especially due to silviculture of pine species. Thus, according to the IUCN Red List guidelines ( IUCN 2017), Chascolytrum serranum should be considered Endangered (EN) [B2ab(iii)].

Additional specimens examined (paratypes): — BRAZIL. Rio Grande do Sul: Cambará do Sul, Parque Nacional da Serra Geral, road to Cânion Fortaleza , swamp, 29°04’02.70”S, 50°02’28.70”W, 1022 m, 17 December 2018, L.N. da Silva et al. 1129 ( CAN, ICN, RB, K) ; in wet and peaty grassland, at the riverbank of Arroio Segredo , 29°04’47.10”S, 49°59’17.00”W, 994 m, 17 December 2018, L.N. da Silva et al. 1132 ( CAN, ICN, RB, US) ; trail to Fortaleza , riverbank, 29°04’01.60”S, 49°57’45.50”W, 1026 m, 17 December 2018, L.N. da Silva et al. 1137 ( CAN, ICN, RB, SMDB) ; riverbank of Cachoeira do Tigre Preto , 29°04’21.40”S, 49°59’18.70”W, 1001 m, 17 December 2018, L.N. da Silva et al. 1138 ( CAN, ICN, K, US) ; 29°03’43.90”S, 49°57’23.70”W, 1 December 2003, L. Essi, A. Guglieri & S. Hefler 135, 136 ( ICN) .

Comments:— Chascolytrum serranum belongs to C. sect. Hildaea ( da Silva et al., 2020), and is morphologically similar to C. ambiguum and C. juergensii var. angustilemma by having narrow lemmas that are at least 2.5 times longer than wide. It differs from C. ambiguum by having puberulous paleas ( Fig. 1C ) (vs. glabrous paleas in C. ambiguum ) and from C. juergensii var. angustilemma by having glabrous and smooth lemmas ( Fig. 1D ) (vs. strigose lemmas in C. juergensii var. angustilemma ).

Chascolytrum ambiguum is distributed further northeast in Rio Grande do Sul than C. serranum , extending to the highlands of Santa Catarina, up to Rio de Janeiro and Minas Gerais, inhabiting rock cliffs and rocky grasslands over 1200 m elevation ( Essi et al. 2017, Essi & da Silva 2018). Conversely, C. serranum is restricted to the Serra Geral National Park and surroundings, in Rio Grande do Sul, inhabiting river banks or swamps, at around 1000 m elevation. Chascolytrum juergensii var. angustilemma is widespread in Serra Geral National Park, but inhabits open grasslands or edges of Araucaria angustifolia forests ( Essi et al. 2010). Despite their distinct habitats, C. serranum and C. juergensii var. angustilemma are difficult to distinguish in the field. However, the panicles of C. serranum are usually more delicate than those of C. juergensii var. angustilemma and its spikelets are usually purplish and shiny ( Fig. 2B ), whereas the spikelets of C. juergensii var. angustilemma are usually greenish and dull.

Essi et al. (2010) cited two specimens (L. Essi, A. Guglieri & S. Hefler 135, 136, ICN) as paratypes of C. juergensii var. angustilemma . However, the description of C. juergensii var. angustilemma ( Essi et al. 2010) only mentioned pilose lemmas (hereafter treated as strigose) for the taxon, and these two specimens are distinct by having glabrous and smooth lemmas. We include them here in C. serranum , as paratypes. Their exclusion from C. juergensii var. angustilemma does not affect its circumscription.

Micromorphology of the upper anthecium/floret:— Our micromorphological examination of the lemmas and paleas revealed additional characters that distinguish the new species from its congeners. Lemmas of Chascolytrum serranum are glabrous and smooth, without prickles ( Fig. 3I–J ), whereas the lemmas of C. ambiguum are glabrous and scabrous, possessing small prickles on the back and larger ones on the margins and apex ( Fig. 3A‒B ). Conversely, the lemmas of C. juergensii var. angustilemma are strigose and slightly scabrous due to the presence of prickles and hairs densely covering the lemma back, and short prickles distributed towards the margins and apex ( Fig. 3E‒F ). The palea of C. serranum has a combination of short and sparse prickles and hairs on the back and margins ( Fig. 3K‒L ), the palea of C. juergensii var. angustilemma has short and dense prickles and sparse hairs on the back and margins ( Fig. 3G‒H ), and the palea of C. ambiguum has only short and sparse prickles on the back and hairs restricted the margins ( Fig. 3C‒D ). The comparison of macro and micromorphological characters among the three taxa is also presented in Table 1 .

Discovery of this new species raises the number of species in C. sect. Hildaea to six and increases the number of species in Chascolytrum to 24.

Figures

FIGURE 1. Chascolytrum serranum. A. Habit. B. Spikelet, lateral view. C. Palea, dorsal view. D. Lemma, lateral view. Drawn from the holotype (L.N. da Silva et al. 1067, ICN) by Rafaella M. Marchioretto.

FIGURE 2. Chascolytrum serranum. A. Habit of C. serranum. B. Detail of the panicle, showing the purplish and shiny spikelets. C. Habitat of C. serranum, in the Serra Geral National Park, near to “Arroio Segredo”. D. Habitat of C. serranum, in the Serra Geral National Park, near to “Cachoeira do Tigre Preto”. (Photos by L.N. da Silva)

FIGURE 3. Micromorphological features of the floret of Chascolytrum serranum and related species. A‒D. C. ambiguum. A. Lemma, lateral view. B. Detail of the lemma surface. C. Palea, dorsal view. D. Detail of the palea surface. E‒H. C. juergensii var. angustilemma. E. Lemma, lateral view. F. Detail of the lemma surface. G. Palea, dorsal view. H. Detail of the palea surface. I‒L. C. serranum. I. Lemma, lateral view. J. Detail of the lemma surface. K. Palea, dorsal view. L. Detail of the palea surface. (A–D from L.N. da Silva 1025, ICN; E–H from L.N. da Silva 1054, ICN; I–L from L.N. da Silva 1067, ICN).

FIGURE 4. Geographic distribution of Chascolytrum serranum (star).