Danaea opaca Keskiniva & Tuomisto, 2024

Keskiniva, Venni & Tuomisto, Hanna, 2024, Danaea (Marattiaceae) keeps diversifying, part 1: eighteen new species, Willdenowia 53 (3), pp. 173-228 : 205-209

11. Danaea opaca Keskiniva & Tuomisto , sp. nov. (D. subg. Arthrodanaea ) – Fig. 22, 23.

Holotype: Brazil, Amazonas , Río Juruá, 7 km N from town of Itamarati, 06°23'S, 68°16'W, 150 m, 10 Apr 2012, Tuomisto 16130 ( SP!; isotypes: TUR! (mounted on 2 sheets), UC!, Z!).

Diagnosis — Similar to Danaea bipinnata Tuomisto , but differing in fertile pinnae lanceolate (vs elliptic); sterile pinnae parallel-sided (vs elliptic); pinnae dull and pale bluish green adaxially when fresh (vs shiny and dark green); genetically differing in locations 326 (T vs C) of rbcL reference sequence; 32 (A vs G), 679 (C vs A) of trnL-F reference sequence; 413 (G vs T), 435 (G vs A), 707 (T vs G) of rpl32 reference sequence.

Description — Rhizomes erect, leaves and roots radially arranged, when fresh 1.5–3.0 cm in diam., when dry 1.0– 2.0 cm in diam., to 10 cm long. Sterile leaves 34–66 cm long; petioles 14–34 cm long, with 0–1(–2) nodes, not winged; laminae 20–32 × 16–27 cm, obovate to oblong, imparipinnate, distal pinnae usually smallest, 4–6(–7) pinna-pairs, medial pinnae 2.8–4.5 cm apart, pinnae colour dark brown when dried, often with a slightly paler zone along midvein, rather pale bluish green when fresh with a lighter yellowish zone along midvein, texture thin, rachises winged in distal part of lamina, wings to 0.2–1.0 mm wide; terminal pinnae 6.5–15 × 2.1–3.6 cm, lanceolate, bases acute, apices 1.0– 2.1 cm long, acuminate, margins of apices entire to (slightly) sinuate; largest lateral pinnae 10.6–16 × 2.7–4 cm, 3.3–5.0 times as long as wide without apex, parallel-sided, bases symmetrical (obtuse to acute) or asymmetrical (obtuse proximally, acute distally), apices 1.5–2.4 cm long, acuminate to attenuate, margins of apices entire to sinuate (to crenulate at shoulder of pinna); veins 10–12 per cm, usually mostly paired at costa, sometimes mostly simple. Fertile leaves 42–67 cm long; petioles 28–42 cm long, not nodose (only two seen); laminae 15–25 × 5–12 cm, (long-)oblong or lanceolate, imparipinnate, distal pinnae smallest, 5–7 pinna-pairs; terminal pinnae 3.1– 4.2 × 0.7–0.9 cm, lanceolate, bases acute, apices acuminate; largest lateral pinnae 4.2–8.5 × 0.7–1.2 cm, lanceolate, bases asymmetrical (obtuse proximally, acute distally), apices 0.3–1.0 cm long, attenuate to acuminate (or acute). Juveniles with terminal pinnae oblong to obovate or lanceolate, larger than lateral ones, lateral pinnae elliptic, largest simple juvenile 12 cm long, smallest pinnate juvenile 8.5 cm long.

Distribution and habitat — Danaea opaca has been found only in non-inundated rainforests along the Río Juruá in Amazonas, Brazil, from 90 to 550 m. Fig. 15.

Conservation status — We place Danaea opaca in the Least Concern (LC) category ( IUCN 2012). It has an Area of occupancy of 24 km 2, which corresponds to the EN category, and an Extent of occurrence of 16,155 km 2, which corresponds to the VU category, and is known from only seven collections. However, its forest habitat is continuous over a large area, and two of the specimens were gathered in a protected area (Reserva Extrativista do Médio Juruá). There appears to be no imminent threat to all its subpopulations.

Etymology — Danaea opaca is named after the colour of its leaves in the field: they are dull bluish green in comparison with those of D. bipinnata , whose leaves are glossy dark green.

Remarks — We separate Danaea opaca from D. bipinnata based on both morphological and genetic evidence. In the field the two co-occur and can be separated by their colour, as the pinnae of D. opaca are dull and relatively light bluish green adaxially with the centre often yellowish and paler than the margins, whereas the pinnae of D. bipinnata are glossy dark green. Both species can obtain a uniformly dark brown colour when dried, but often the adaxial side of D. opaca retains a paler zone around the midvein, whereas D. bipinnata develops a darker zone around the midvein. The sterile pinnae of D. opaca are parallel-sided and the fertile pinnae lanceolate (vs both elliptic in D. bipinnata ) with an abruptly tapering bases (vs gradually tapering) and short apices that can be attenuate or acute (vs usually long-acuminate).

In the field, Danaea opaca can easily be separated from the sympatric D. leprieurii by its bluish to greyish green laminar colour with a paler zone around the midvein of pinnae (vs concolorous yellowish green in D. leprieurii ). Furthermore, D. opaca typically has fewer nodes on petioles (usually 0–1 vs 2–3), longer leaves (34–66 cm vs 18–38 cm long), a more elongated lamina shape (vs often almost as wide as long), and larger lateral pinnae (10.6–16 × 2.7–4 cm vs 6–10 × 1.4–2.8 cm).

Danaea opaca differs from D. lingua-cervina Christenh. & Tuomisto , D. trifoliata Rchb. ex Kunze , and D. ulei Christ by its shorter terminal pinnae (6.5–15 cm vs 16–26 cm in D. lingua-cervina , 16–33 cm in D. trifoliata and 18–32 cm in D. ulei ) that are usually shorter than the second lateral pinnae distally (vs terminal pinnae usually longest), and by having generally more pinna-pairs (4–6(–7) vs 0–4 pinna-pairs in D. lingua-cervina and D. trifoliata , 2–4 in D. ulei ). In addition, D. opaca differs from D. ulei in its generally smaller size (sterile leaves 34–66 cm vs 45–92 cm, largest lateral sterile pinnae 11– 16 cm vs 16–21 cm), and usually thinner laminar texture. Danaea opaca develops pinnate leaves at a smaller size than D. lingua-cervina and D. trifoliata (simple leaves do not exceed 13 cm in length vs simple leaves may become 40 cm long in D. lingua-cervina and 54 cm long in D. trifoliata ).

Fertile specimens of Danaea alansmithii Tuomisto & Keskiniva are readily separated from D. opaca by the elliptic (vs lanceolate) fertile pinnae that are larger (8.5–15 × 1.4–2.6 cm vs 4.2–8.5 × 0.7–1.2 cm), have a sterile zone of 1–4 mm on each side of the costa (vs no sterile zone), and are thinner due to slender and widely spaced synangia. Danaea opaca tends to have more pinnae than D. alansmithii (4–6(–7) vs 3–5 sterile pinna-pairs, 5–7 vs 3–4 fertile pinna-pairs). In addition, dried leaves of D. alansmithii have a reddish brown tint (vs greenish brown rather than reddish) and are uniform in colour (vs often lighter near the midvein).

Danaea opaca differs from D. arbuscula Christenh. & Tuomisto in pinna shape (sterile pinnae parallel-sided and fertile pinnae lanceolate vs both usually elliptic), generally smaller size (sterile leaves to 66 cm vs to 90 cm long, lateral pinnae to 16 × 4 cm vs to 22 × 5 cm), and especially in smaller fertile pinnae (4.2–8.5 × 0.7– 1.2 cm vs 8–18 × 1.6–4.0 cm). In addition, D. arbuscula often has a thicker laminar texture and its rhizomes can exceed a meter (vs to 10 cm long in D. opaca ). Danaea arbuscula is a montane species mostly found in Colombia, Venezuela, Ecuador, and northern Peru above 500 m, whereas D. opaca has been found only in the lowlands of Brazilian Amazonia.

Danaea geniculata Raddi has a more eastern distribution than D. opaca in the Atlantic coast of Brazil and in French Guiana. It can have fertile pinnae with a similarly lanceolate shape as those of D. opaca but has elliptic sterile pinnae (vs usually parallel-sided), tends to dry dark green (vs dark brown), and often has a rachises without wings (vs rachises winged in the distal part).

Additional specimens examined — BRAZIL: AMAZONAS: Río Juruá , 1.5 km northwest from village of Xibauá , 05°53'S, 67°52'W, 110 m, 2 Apr 2012, Tuomisto 15796 (SP!, TUR-2!); Río Juruá , 3 km northeast from village of Novo Horizonte, 05°02'S, 67°08'W, 90 m, 27 Mar 2012, Tuomisto 15876 (SP!, TUR-4!); Río Juruá , 3 km northwest from village of Roque, 05°05'S, 67°14'W, 100 m, 28 Mar 2012, Tuomisto 15886 (SP, AAU!, TUR!); Río Juruá , 1.5 km northwest from village of Xibauá, 05°53'S, 67°52'W, 110 m, 2 Apr 2012, Tuomisto 16052 (SP!, MO!, TUR!); Río Juruá, 4 km northeast from village of Deixa Falar, 06°41'S, 70°19'W, 180 m, 5 May 2012, Tuomisto 16590 (SP!, TUR-2!); Río Juruá, 4.5 km southwest from village of Monte Verde, 06°39'S, 69°22'W, 130 m, 29 May 2012, Tuomisto 16759 (SP!, TUR!) .