Pariana caxiuanensis K.N.L. Dias, F.M. Ferreira

Dias, Kauê Nicolas Lindoso, Ferreira, Fabrício Moreira & Viana, Pedro Lage, 2021, Pariana caxiuanensis (Parianinae, Poaceae): a new species of an enigmatic genus of herbaceous bamboos from the Brazilian Amazon, Phytotaxa 510 (2), pp. 171-178 : 172-176

Pariana caxiuanensis K.N.L. Dias, F.M. Ferreira & P.L. Viana, sp. nov. ( Figs 1–3 )

Type:— BRAZIL. Pará state: Melgaço, Caxiuanã National Forest , Ferreira Penna Scientific Station , trail to igarapé Tijucaquara , 01°44’13.37”S, 51°29’57.78”W, 14 March 2019, K. N. L . Dias & C. A. Souza 605 (holotype MG!; isotypes HUEFS!, INPA!, MG!, RB!) .

Similar to Pariana intermedia Döll and Pariana interrupta Tutin , it differs by having pistilate terminal spikelets (vs. sterile in both species), dimorphic flowering culms, either with fewer blades than the sterile ones or sometimes bladeless (vs. flowering culms isomorphic), and large ligules (2.5–4 mm long) (vs. 2–3 mm in P. intermedia and 1–1.2 mm in P. interrupta ).

Plants 22–43.5 cm tall, rhizomatous, caespitose, perennial; flowering culms clearly morphologically distinct from the vegetative culms; vegetative culms erect to arching, internodes 4.1–11 × 0.2–0.3 cm, glabrous, callus below the nodes present, nodes dark brown, glabrous, compressed, leaves clustered at the apex; fertile culms dimorphic, leafy or bladeless (only sheaths present), if leafy then with ca. 5 developed blades, erect to arching, internodes 4–10 × 0.2–0.3 cm, glabrous, callus below the nodes present, nodes dark brown, glabrous, compressed, leaves clustered at the apex. Leaf sheaths shorter than the internodes at the base of the culm, becoming imbricate toward the apex, glabrous to glabrate toward the apex, striate, strongly purple; fimbriae rarely present, if so then 2, erect, ca. 12 mm long, scabrous to smooth; ligules membranous, 2.5–4 mm long, truncate; pseudopetioles 3–6 mm long, glabrous on both sides; blades ovate to elliptical, 10.3–15.7 × 2.8–4.7 cm, apex acuminate, base rounded, slightly asymmetrical, indurate, adaxial side smooth, abaxial side scabrous and strongly glaucous, margins smooth. Synflorescences erect to pendulous, 9–15 cm long, of 13–15 whorls, whorls 10.7 × 5 mm, rachis smooth and glabrous, callus 2 × 2 mm. Staminate spikelets ca. 5 × 2–2.5 mm, lanceolate; glumes ca. 3 mm long, margins ciliate, apex acuminate, surface glabrous, 2-nerved; lemma pubescent to hirsute, 3-nerved, acute; palea 5–6-nerved, pubescent toward the apex; lodicules not observed; pedicels villous to pubescent, ca. 5.7 mm long; stamens ca. 10. Pistillate spikelets ca. 6 × 3 mm, lanceolate; glumes subequal, pubescent, apex apiculate, 3-nerved, margins ciliate; floret indurate, 5.2 × 3 mm, glabrous; lemma 3-nerved, acuminate to apiculate, nerves inconspicuous; palea acuminate, 3-nerved; lodicules 3, symmetrical, the two prior flabellate, ciliate at the apex, ca. 1 mm long, the back one lanceolate, hyaline, ca. 2 mm long; staminodes present; caryopsis ellipsoid, ca. 3.5 × 2.5 mm, glabrous, brown, surface rough; styles 2, stigmas plumose; staminodes absent. Terminal spikelet pistillate, ca. 9.5 × 2–3 mm, lanceolate; glumes 2, subequal, glabrate, acuminate, 6-nerved; floret cartilaginous, lanceolate, ca. 6.2 mm long, rotated 90 o; lemma glabrous, glabrate towards the apex, 5-nerved; palea glabrous, glabrate towards the apex, 4-nerved; lodicules 3, symmetrical, the anterior pair flabellate, ciliate at the apex, 1.5–2 mm long, the posterior one lanceolate, hyaline, 1.2–2 mm long; ovary 2.5–3 × 1 mm; caryopsis not observed; styles 2, stigmas plumose; staminodes 6.

Etymology: —The epithet refers the type locality, where the species was found, at the Caxiuanã National Forest.

Distribution and habitat:— Pariana caxiuanensis is currently only known from the type locality, in Caxiuanã National Forest, Pará state, Brazil ( Fig. 3 ). The species was collected in two locations, on the Arauá and Tijucaquara igarapés trails. It occurs along the edges of trails and in the understory of dense forests, exclusively in non-flooded (Terra Firme) forests.

IUCN Red List category:— Two distinct populations with about 100 individuals each were found to date, at the Caxiuanã National Forest, far removed from anthropogenic impacts and exploration. The estimated EOO for the species is 1.117 km 2,and the estimated AOO is 8.000 km 2. The area belongs to a federal government conservation unit, which is a sustainable use forest. Therefore, due to the lack of threats to known populations, this new species should be considered Least Concern (LC) according to the IUCN (2019) categories and criteria.

Taxonomic notes:— Based on the fertile culm morphology (usually leafy) and on the position of the lodicules (symmetrically arranged), the new species fits in Pariana sect. Foliosae sensu Tutin (1936) and Hollowell (1987). Some species of this group may eventually have flowering culms without well-developed blades, a typical feature of species of the P. sect. Nudicaules Tutin (1936: 341) and P. sect. Graciles Tutin (1936: 341). Although Ferreira et al. (2019) has carried out a phylogenetic analysis with the subtribe, it was not possible to test this classification due to insufficient sampling in Pariana , since focus of that study was Eremitis . However, a more comprehensive phylogeny study focusing on Pariana , is in preparation (F.M. Ferreira, in prep.) in which the circumscription of the sections proposed by Tutin and Hollowell are going to be tested.

Pariana caxiuanensis can be distinguished from the other species of the genus by having the flowering culms with few leaf blades or sometimes just bladeless sheaths ( Figs. 1A, 1B , 2B and 2C ), larger ligules (2.5–4 mm long) ( Figs. 1C and 2E ) and pubescent to hirsute synflorescences ( Fig. 1D ). The new species and P. intermedia Döll in Martius (1877: 337) share the presence of dimorphic flowering culms. However, P. caxiuanensis can be differentiated from P. intermedia by its pistillate terminal spikelet ( Fig. 1F ) (vs. reduced and sterile in P. intermedia ), leaf sheaths without fimbriae or with only a few (vs. clearly fimbriate), and by the arrangement of the whorls in the inflorescence [pedicels of staminate spikelets covered about halfway by the staminate spikelets of the preceding whorl in P. caxiuanensis ( Fig. 1D ) vs. pedicels of staminate spikelets completely covered by staminate spikelets of the preceding whorl in P. intermedia ]. Pariana caxiuanensis is also similar to Pariana interrupta Tutin (1936: 348) due to the synflorescence with whorls loosely arranged (pedicels of staminate spikelets visible in the synflorescence, not hidden by staminate spikelets of the preceding whorl) and long pseudopetioles (ca. 4 mm). However, P. caxiuanensis has clearly dimorphic culms (vs. sterile and flowering culms relatively similar in P interrupta ), broadly ovate leaf blades of the flowering culms (vs. leaf blades of the flowering culm lanceolate), and pedicels of the staminate spikelets partially covered by staminate spikelets of the preceding whorl (vs. pedicels of staminate spikelets completely visible in the synflorescence). Along with this, the terminal spikelet of P. interrupta is sterile, as in P. intermedia , differing from the pistillate terminal spikelet of P. caxiuanensis . The three species distribution is sympatric, and they occur in the Caxiuanã National Forest. More details on the similarities and differences between the three species are presented in Table 1.

Additional specimens examined (paratypes):— BRAZIL. Pará: Melgaço, Caxiuanã National Forest, Ferreira Penna Scientific Station , trail to igarapé Tijucaquara , 01°44’13.37”S, 51°29’57.78”W, 15 June 2018, Dias, Afonso & Souza 403 ( MG) ; Dias, Afonso & Souza 404 (IAN); Dias, Afonso & Souza 405 (HSTM); Dias, Afonso & Souza 407 (HUEFS); Dias, Afonso & Souza 408 (HAMAB); 01°44’13.68”S, 51°29’59.05”W, 15 June 2018, Dias, Afonso & Souza 410 ( INPA) ; Dias, Afonso & Souza 412 (IAN); Dias, Afonso & Souza 413 (HSTM); Dias, Afonso & Souza 416 (INPA); Dias, Afonso & Souza 417 (MG); Dias, Afonso & Souza 421 (HUEFS); Dias, Afonso & Souza 422 (HAMAB); 01°44’13.63”S, 51°29’59.82”W, 15 June 2018, Dias, Afonso & Souza 423 ( MG) ; Dias & Souza 603 ( MG) ; Dias & Souza 604 ( MG) ; trail to igarapé Arauá , 01°45’57.8”S, 51°31’24.7”W, 14 March 2019, Dias & Souza 610 ( INPA) .

Figures

FIGURE 1. Illustration of Pariana caxiuanensis: A: habit with the flowering culm leafy; B: habit with the flowering culm bladeless; C: leaf sheath apex showing the large ligule and the lunar mark; D: part of synflorescence showing the pedicels of staminate spikelets partially hidden by spikelets of the preceding whorl. E: whorl; F: distal-most whorl of synflorescence and terminal spikelet (pistillate). Illustrations: K.N.L. Dias.

FIGURE 2. Pariana caxiuanensis: A: habit; B: leafy flowering culm; C: bladeless flowering culm (arrow); D: synflorescence; E: leaf sheath apex showing the large ligule (arrow); F: whorl; G: open whorl showing the pistillate spikelet (arrow). Photos: E.A.L. Afonso: B and C; K.N.L. Dias: A, D, E, F and G.

FIGURE 3. Distribution map of Pariana caxiuanensis (yellow triangles) in the Caxiuanã National Forest, Pará state, Brazil.