Hymenophyllum caudatum Bosch is one of 24 species of filmy ferns described for the temperate forests of South America. In insular Chile, the species is found in the Juan Fernández Archipelago (e.g. Furniel 2018) and on Mocha Island (e.g. Reiche 1903), more than 600 km and 32 km from the mainland, respectively. The known range of this species on the continent places the northern distribution limit on the Alejandro Selkirk (33°44'39.17''S) and Robinson Crusoe (33°38'34.33''S) Islands in the Archipelago above (Valparaiso Region), while on the mainland, the northernmost record is located on the coastal strip of Concepción city (Parque Hualpén, Biobío Region, 36°47'07.86''S). The southern limit is found at Puerto Edén, on Wellington Island, Magallanes Region (49°09'S -74°26'20"W) (pers. comm. Alicia Marticorena, curator of the CONC Herbarium, see also Diem and Lichtenstein 1959, Rodríguez 1995, Rodríguez et al. 2009, Larsen et al. 2013). In Argentina, the species occurs in the Province of Chubut, in Lago Puelo National Park (e.g. Cassá De Pazos et al. 2010) and Los Alerces National Park (see Larsen et al. 2013). The wide range of the species determines its occurrence in a Mediterranean-temperate transition zone to the north and anti-boreal climate to the south (Luebert and Pliscoff 2006).

A similar species with comparable morphology is found in the Atlantic Forest of Brazil, around 2000 km distant. Although precedents were arguing for morphological differences between the species found in Chile and Brazil (e.g. Diem and Lichtenstein 1959, Rodríguez 1995, Ebihara et al. 2006), evidence was insufficient to classify these populations as two separate species. However, based on genetic and morphological traits, Larsen et al. (2020) propose the name H. caudatum for the species found in the temperate forests of Chile and Argentina, while the species growing in the tropical and subtropical forests of Brazil would retain the original name given to the species: Hymenophyllum caudiculatum.

H. caudatum inhabits very humid and shady mature forests. In general, it has an epiphytic habit on trunks. However, it is also possible to observe it on the ground or on rocks (Larsen et al. 2013, Furniel 2018), even on decaying logs (e.g. Pincheira-Ulbrich et al. 2021).

In a botanical exploration conducted on 14 September 2021 in the Los Ruiles sector of Los Ruiles National Reserve (Maule Region, Chile; Fig. 1), ten fronds of H. caudatum were observed in a small ravine (35°49'55.58"S; 72°30'42.55"W). The species was found on the southeast face and at the base of a partially moss-covered rock at 228 m above sea level (Fig. 2, Fig. 3). The finding in this wilderness area extends the distribution by 120 km northwards on the mainland, which until now was limited to the coastal area of Concepción city (36°47'07.86") (e.g. Rodríguez 1995, Rodríguez et al. 2009). The sample was deposited in Universidad de Concepción's Herbarium under code CONC 192213.

Figure 1.  

Location map of Los Ruiles National Reserve.

a

b

Figure 2.

Photographs of the site where the species was found. The dotted white line represents the rock's visual boundary and yellow dotted line represents the stream. The orange circles delimit some fronds of H. caudatum.

a: Accompanying species: Hymenophyllum tunbrigense, Chusquea culeou and also a single leaf of Nothofagus glauca.  
b: Accompanying species: Fascicularia bicolor, Jovellana punctata and Lapageria rosea.  

a

b

c

d

e

f

Figure 3.

Specimen of H. caudatum.

a: Frond  
b: Petiole and rachis  
c: Rhizome  
d: Petiole and rhizome (human finger scale)  
e: Sorus (human finger scale)  
f: Sorus  

The site is located about 240 m on a straight line from the main access to the Reserve, surrounded by a forest of Nothofagus glauca Krasser. To reach the site, a footpath, not open to the public, is followed before turning off along a ravine (Fig. 2).

On the same rock, we counted 57 fronds of Hymenophyllum tunbrigense (L.) Sm., two rosettes of Fascicularia bicolor (Ruiz & Pav.) Mez and one individual of Lapageria rosea Ruiz & Pav, with a climbing habit, fallen on the rock from a culm of Chusquea culeou E. Desv. In a radius of three metres from the centre of the rock, Persea lingue (Ruiz & Pav.) Nees (DBH = 10 cm) and Aextoxicon punctatum Ruiz & Pav. (DBH = 32 cm) were present in the tree layer and Cryptocarya alba (Molina) Looser was present on the forest floor at the regeneration stage. In the shrub stratum, Azara petiolaris (D.Don) I.M.Johnst., Jovellana punctata Ruiz & Pav., Rhamnus diffusus Clos., Baccharis racemosa DC. and Ugni candollei (Barnéoud) O. Berg were observed. On the herbaceous layer, Adiantum chilense Kaulf., Chusquea coleu, Dioscorea bridgesii Griseb. ex Kunth, Nassella spp. and Greigia sphacelata (Ruiz & Pav.) Regel were present. The climber Lardizabala biternata Ruiz & Pav. was also recorded at a diameter of more than 1 cm on an individual of A. punctatum (Table 1).

Importance for conservation

To Pedro Jara, manager of Reserva Nacional Los Ruiles, for his guidance in the field. To Alicia Marticorena, for generously providing the geographic distribution data of H. caudatum from the CONC Herbarium. To Natalia Gallardo for her support in the field. To Claudia Carrasco, for her dedicated cartographic work. To Fulgent Coritico and an anonymous reviewer for their feedback. To Anatoliy Khapugin for handling the manuscript. This research was supported by the Chilean agency ANID FONDECYT, under post-doctoral project number 3200698.