Danaea dilatata Keskiniva & Tuomisto, 2024

Keskiniva, Venni & Tuomisto, Hanna, 2024, Danaea (Marattiaceae) keeps diversifying, part 1: eighteen new species, Willdenowia 53 (3), pp. 173-228 : 192-194

6. Danaea dilatata Keskiniva & Tuomisto , sp. nov. (D. subg. Arthrodanaea C. Presl ) – Fig. 14 .

Holotype: French Guiana, in sylvis montosis, comitatus de Genes, ad margines torrentium et rivulorum, 1847, Leprieur s.n. ( GH!).

Diagnosis — Similar to Danaea bipinnata Tuomisto but differing in larger size (sterile leaves 60–75 cm vs 38– 62 cm long); more nodes on petioles (2–4 vs 0–2); and oblanceolate fertile pinnae (vs elliptic).

Description — Rhizomes erect, radial, 1.5–2.5 cm in diam., to at least 7 cm long. Sterile leaves 60–75 cm long; petioles 31–43 cm long, with 2–4 nodes, not winged; laminae 29–32 × 21–27 cm, (long-)obovate to elliptic, imparipinnate, distal pinnae smallest, 6–7 pinna-pairs, medial pinnae 3–3.5 cm apart, almost concolorous, light to dark brown, texture thin, rachises not winged; terminal pinnae 12–13 × 3.0– 3.9 cm, elliptic to lanceolate, bases acute to cuneate, apices 1.8–2.2 cm long, acuminate, margins of apices entire to slightly sinuate; largest lateral pinnae 13–17 × 3.0– 3.9 cm, 4.8–5.5 times as long as wide without apex, widest at or above middle, bases symmetrical (acute) or asymmetrical (acute to obtuse proximally, acute distally), apices 2.0– 3.8 cm long, (long-) acuminate, margins of apices entire to sinuate; veins 12– 18 per cm, mostly forked at costae (sometimes mostly forked above costa or many simple). Fertile leaves 66–90 cm long; petioles 40–62 cm long, 3–4 nodes; laminae 26–28 × 14–18 cm, long-obovate, imparipinnate, distal pinnae smallest, 6–8 pinna-pairs; terminal pinnae 5.3– 8.0 × 1.2–1.6 cm, lanceolate, bases acute, cuneate or acuminate, apices (long-)acuminate; largest lateral pinnae 7.8–11 × 1.3–1.7 cm, oblanceolate (to narrow-elliptic), bases acute, apices 1.4–2.0 cm long, (long-)acuminate, margins of apices serrulate at shoulder of pinna, sinuate at tip, synangia ascending. Juveniles not known.

Distribution and habitat — Known from Guyana and French Guiana. Fig. 15 .

Conservation status — We place Danaea dilatata in the Near Threatened (NT) category ( IUCN 2012). All known collections of this species are from the second half of the 19 th century or the beginning of the 20 th. Consequently, it is difficult to know the exact localities and their status. Based on the estimated localities, D. dilatata has an Extent of occurrence of 10 km 2 and it is known from only nine collections from 5 locations, which corresponds to the VU category. The locations are not inside protected areas, but there appears to be no imminent threat to all its subpopulations.

Etymology — The species epithet refers to the symmetrically outward-bending synangia that form a dilating pattern especially in the proximal part of the fertile pinnae.

Remarks — F. M. R. Leprieur was about to describe this species as Danaea polyphylla , which is written on several of the specimens, but we could not find a formal description of that name. We do not have genetic data for this species, but with a Guianan distribution it is geographically distant from the western Amazonian D. bipinnata , which it most closely resembles. Danaea dilatata has generally more nodes on petioles than D. bipinnata (2–4 vs 0–2) and has generally larger sterile leaves (60–75 cm vs 38–62 cm long).

Danaea dilatata shares the acute to cuneate bases and (long-)acuminate apices typical of the fertile pinnae of D. bipinnata and D. arbuscula Christenh. & Tuomisto. However, the fertile pinnae of D. dilatata are usually oblanceolate and rather uniform in shape (vs elliptic and more variable with sometimes very long-acuminate bases and apices in D. bipinnata and D. arbuscula ). Secondary veins in the fertile pinnae of D. dilatata resemble a fountain, curving up and then to the sides (vs usually more straight in D. bipinnata and especially D. arbuscula ).

Danaea dilatata has generally more nodes per petioles than D. arbuscula (0–2 vs 2–4), generally more fertile pinnae (6–8 vs usually less than 6) that are generally narrower (1.3–1.7 cm vs 1.6–4.0 cm wide), and the sterile pinnae of D. dilatata are thinner than the often leathery, thick pinnae of D. arbuscula . The terminal pinna is the same size as the distal pair of lateral pinnae and smaller than other lateral pinnae (vs terminal pinnae usually as large as or larger than the largest lateral pinnae in D. arbuscula ).

Danaea dilatata differs from D. geniculata Raddi , especially the northern specimens of the latter, in that its fertile pinnae are acute to cuneate (vs truncate) at bases and (long-)acuminate (vs acute to obtuse) at apices, and the sterile pinnae are usually broader (minimum 3.0 cm vs 2.1 cm wide) and have longer apices (2.0– 3.8 cm vs 0.8–1.8 cm).

Danaea leprieurii Kunze is a smaller plant than D. dilatata (sterile leaves 15–45 cm vs 60–75 cm long) with fewer sterile pinnae (2–6 vs 6–8 pairs) that also differ in being shorter (5.2–13 vs 13–17 cm), more parallel-sided and with generally more asymmetrical bases.

Danaea trinitatensis Christenh. & Tuomisto is generally a smaller plant (23–64 cm vs 60–75 cm) with usually shorter pinnae (min. 6.2 cm vs min. 12.8 cm long), fewer pinna-pairs (1–7 vs 6–7), pinna apices that are often clearly sinuate (vs entire or only slightly sinuate), and often sterile margins on fertile pinnae (vs synangia always reaching the margins in D. dilatata ). The leaves of D. trinitatensis dry to a light yellowish green colour (vs darker brown in D. dilatata ).

The sterile leaves of Danaea dilatata have more pinna-pairs (6–8) than those of D. danaëpinna Christenh. (1–5) or D. polymorpha Lepr. (2–4) and they dry to a darker brown colour (vs light grey or green in D. danaëpinna and D. polymorpha ).

Additional specimens examined — FRENCH GUIANA: In montosis Diaboli, 1850, Leprieur 254 (E! (E00157002), US! ( US 1505176)); Comitatus de Genes, ad margines torrentium et rivulorum, 1847, Leprieur 274 (GH!, US! (00650785)); Jenman’s Demerara label (with year 1897) and hand-written text: “Collected by Leprieur , French Guiana”, Leprieur s.n. (NY!); Leprieur s.n. (NY 00029576!)). — GUYANA: Essequibo River, Moraballi Creek, near Bartica, 1929, Richards 751 (BM, K!); Demerara, 1897, Jenman 55 ( US! (1120091)); Jul 1847, Leprieur s.n. (P! (P01420459)).

Figures

Fig. 14. Danaea dilatata: A: medial sterile pinna apex; B: medial fertile pinna; C: fertile leaf; D: sterile lamina; E: fragment of erect rhizome. – A, B, D, E: Leprieur s.n. (GH); C: Leprieur 274 (GH). – Drawn by Venni Keskiniva.

Fig. 15. Distribution of types and paratypes of Danaea dilatata and D. opaca.