Danaea erosa Keskiniva & Tuomisto, 2024

Keskiniva, Venni & Tuomisto, Hanna, 2024, Danaea (Marattiaceae) keeps diversifying, part 1: eighteen new species, Willdenowia 53 (3), pp. 173-228 : 197-199

8. Danaea erosa Keskiniva & Tuomisto , sp. nov. (D. subg. Holodanaea) – Fig. 18 A, B, E, F.

Holotype: Costa Rica, Alajuela, about 30 km above San Ramon on road to Los Angeles Norte, 10°05'N, 84°28'W, 610 m, 10 Jul 1972, McAlpin 1288 ( US! (2682123); isotypes: DUKE, F! (C0613254F)).

Diagnosis — Similar in general appearance to Danaea wendlandii Rchb. f. , D. crispa Endrés & Rchb. f. and D. gracilis Tuomisto & Keskiniva. Differs from D. wendlandii in laminae translucent (vs opaque), concolorous and dark green (vs bicolorous with abaxial side whitish); pinnae somewhat erose (vs not erose); pinna apices usually serrate (vs crenate to serrulate); larger size (sterile leaves 24–39 vs 13–25 cm long, 9–14 vs 4–8 cm wide); and generally more pinna-pairs (10–20 vs 10–15). Differs from D. crispa in pinna margins crenulate (vs crispate); generally larger size (sterile leaves 24–39 cm vs 13–26 cm long, 9–14 cm vs 6–11 cm wide); and generally fewer pinna-pairs (10–20 vs 13–25). Differs from D. gracilis in pinnae somewhat erose (vs not erose); pinna margins crenulate (vs entire); pinna apices usually acute-acuminate (vs obtuse to acute); margins of apices of pinnae serrate (vs crenulate to serrulate); generally larger size (sterile leaves 24–39 vs 11–32 cm long, 9–14 cm vs 5–11 cm wide); and generally fewer pinna-pairs (10–20 vs 15–25).

Description — Rhizomes decumbent to erect, with leaves and roots arranged radially, 1.0– 1.5 cm in diam., to 9 cm long. Sterile leaves 24–39 cm long; petioles 11–14 cm long, with 0–5 nodes, not winged or winged only in distal part; laminae 13–23 × 9–14 cm, (long-)obovate (or lanceolate), paripinnate, 10–20 pinna-pairs, medial pinnae 1.0– 1.1 cm apart, concolorous dark green, texture thin, translucent, rachises winged, wings to 1.0– 1.5 mm wide; largest lateral pinnae 4.5–7.5 × 1.0– 1.4 cm, 4.0– 7.5 times as long as wide without apex, parallel-sided, perpendicular to rachises or slightly ascending, margins undulate when fresh, crenulate and partly erose when dry, bases asymmetrical (obtuse or obtuse proximally, acute distally), apices 0–0.5 cm long, acute, acuminate or cuspidate (or obtuse), margins of apices serrate (to serrulate); veins 11–14 per cm, variable. Fertile leaves 43–44 cm long; petioles 23–27 cm long, 0–1 nodes; laminae 16–21 × c. 6 cm, parallel-sided, paripinnate, 16 pinna-pairs; largest lateral pinnae 3.0–3.3 × 0.4–0.5 cm, linear, slightly ascending, bases symmetrical, obtuse, apices obtuse (mucronate) to acute. Juveniles not known.

Distribution and habitat — Known only from Costa Rica but there it has been observed from sea level to 1150 m. Locally common in primary forests and growing on the banks of small streams. One site is described as wet cloud forest. Fig. 8.

Conservation status — We place Danaea erosa in the Near Threatened (NT) category ( IUCN 2012). It has an Area of occupancy of 20 km 2, which corresponds to the EN category, and an Extent of occurrence of 7606 km 2, which corresponds to the VU category. Despite large collection efforts in Costa Rica, D. erosa is known from only five collections, which indicates that it is rare. However, four of the collections are from protected areas in Costa Rica (Refugio Nacional de Vida Silvestre Barra del Colorado, Braulio Carillo National Park, Parque Nacional Guanacaste). In addition, the species was noted as locally common on the herbarium labels. There appears to be no imminent threat to all its subpopulations if conservation efforts are maintained.

Etymology — Named after the somewhat erose dried pinnae that separate this species from Danaea wendlandii and D. gracilis .

Remarks — Danaea erosa is a rather small, translucent species with undulate margins. In herbarium specimens, the pinnae split along the undulations, creating an incision that runs from the pinna margin toward the costa, making the pinnae appear partly erose in herbarium specimens. Danaea erosa is most similar to D. crispa but has crenulate rather than crispate pinna margins and (according to label information) less undulate margins when fresh ( Fig. 18). In addition, D. erosa is usually larger than D. crispa (sterile leaves 24–34 cm vs 13–26 cm long, 9–14 cm vs 6–11 cm wide) and can have fewer pinna-pairs (10–20 vs 13–25).

In comparison to Danaea wendlandii , D. erosa has pinnae that are translucent (vs opaque), concolorous (vs bicolorous), dark green (vs lighter green), and somewhat erose when dry (vs not erose). In addition, D. erosa usually has sharper pinna apices (acute-acuminate vs obtuse) that are usually more sharply serrate (vs crenate or serrulate). It is also larger (sterile leaves 24–34 vs 13–25 cm long, 9–14 vs 4–8 cm wide) and can have more pinna-pairs (10–20 vs 10–15).

It is possible that Danaea erosa is a hybrid between D. crispa and D. wendlandii , as it has been found growing in locations with both of these present, and it is somewhat intermediate in morphology between them. However, we do not have genetic or cytological data to test this hypothesis.

Danaea gracilis is another translucent and similar looking species. It occurs in the Chocó region in Ecuador, Colombia, and southern Panama. Danaea erosa occurs in northern Costa Rica and differs from D. gracilis by having pinnae that are somewhat erose when dry (vs not erose) and have crenate margins (vs entire) and generally sharper pinna apices (acute to acuminate vs obtuse to acute) with serrate margins of apices (vs slightly crenulate or serrulate) ( Fig. 18). In addition, D. erosa is generally larger than D. gracilis (sterile leaves 24–34 vs 11–32 cm long, 9–14 cm vs 5–11 cm wide), and usually has fewer pinna-pairs (10–20 vs 15–25).

Danaea tenera C. V. Morton is another translucent species from the Chocó region, from which D. erosa differs in being a smaller plant (sterile leaves 24–34 cm vs 35–46 cm long) with shorter pinna apices (0–0.5 vs 0.6–2.4 cm long) that are not as sharply serrate, and by having partly erose pinnae (vs rarely erose).

Additional specimens examined — COSTA RICA: ALAJUELA: Dos Ríos, Finca Montecele, slopes of Volcán Cacao, ridge on left bank of Río Colón , 10°57'N, 85°26'W, 800 m, 15 Apr 2008, Rojas 8446 (MO!) ; HEREDIA: between Río Peje and upper Río Guácimo, Atlantic slope of Volcán Barva, 10°17'N, 84°05'W, 950–1150 m, 11 Nov 1986, Grayum 7797 (MO!) ; LIMÓN: R. N. F. S. Barra del Colorado Llanura de Tortuguero, Sardinas, 10°39'N, 83°44'W, 20 m, 6 Jun 1996, Araya 879 (MO!); Refugio Barra de Colorado , between Río Chirripocito and Río Sardina, 10°38'N, 83°45'W, 10 m, 12 Nov 1988, Grayum 9009 (MO-2!) .