Lost and found: the rediscovery of the lost fern species Asplenium achalense (Aspleniaceae) and assessment of its conservation status MAR CE L O ARANA* 1 , 2 , 3 , 4 ,EVA N G E L I N A NATA L E 3 , 4 and ANTO N I A OGGERO 3 , 4


Abstract The fern of Achala Asplenium achalense Hieron. (Aspleniaceae), endemic to north-west and central Argentina, was formerly considered a lost species. We de- scribe its rediscovery in August 2022 in the Yungas biogeo- graphical province, compile a map of all historical and current records of the species, and propose an IUCN Red List status. We estimated the fern of Achala’s range using the area of occupancy of the rediscovered popula- tion, calculated as 4 km2 because it is located in a single 2 × 2 km grid square. The extent of occurrence cannot be calculated because only a single living population is known. These data suggest a provisional categorization of the fern of Achala as Critically Endangered based on criteria B2ab(i,ii,iii,iv,v). The species should be considered Regionally Extinct in its locus classicus in Comechingones biogeographical province. We recommend securing the conservation of the single known population (which does not lie within a conservation unit), further surveys for the species in the five protected areas where it was recorded historically, and restoration of the species in the wild. To support the latter, we are cultivating spores and gameto- phytes of the fern of Achala, in collaboration with collea- gues from the National University of La Plata.


Keywords Argentina, Aspleniaceae, Asplenium achalense, biogeographical province, conservation status, fern of Achala, IUCN Red List, rediscovery


C


urrent estimates of species extinction rates are three to four orders of magnitude greater than background


extinction rates (Barnosky et al., 2011), and of the c. 160,000 species so far assessed for the IUCN Red List, 28% are considered threatened with extinction (IUCN, 2024). Additionally, there is a subset of described species that


*Corresponding author, marana@exa.unrc.edu.ar 1Instituto Criptogámico, Fundación Miguel Lillo, Miguel Lillo 251, T4000JFE,


San Miguel de Tucumán, Tucumán, Argentina 2IUCN Species Survival Commission Temperate South American Plants


Specialist Group 3Grupo GIVE, Departamento Ciencias Naturales, Facultad de Ciencias Exactas, Físico-Químicas y Naturales, Instituto de Ciencias de la Tierra, Biodiversidad y


Ambiente, Universidad Nacional de Río Cuarto, Córdoba, Argentina 4Instituto deCiencias de laTierra,Biodiversidad yAmbiente (ICBIA),Universidad Nacional de Río Cuarto-CONICET, Río Cuarto, Cordoba, Argentina


Received 3 May 2023. Revision requested 20 July 2023. Accepted 4 March 2024. First published online 9 September 2024.


have not been seen in the wild for a long time and it is there- fore unclear whether they are extinct or simply lost. Long & Rodriguez (2022,p. 481) defined a lost species as ‘one not confirmed alive by photographic, audio or genetic informa- tion for over 10 years in the wild, and has no ex situ popu- lation under human care’. The Search for Lost Species, launched in 2017, is looking for plants, animals and fungi (Re:wild, 2023), with 12 of the most wanted species so far found. Although there are no ferns on the list of most wanted species, some have been rediscovered: Jamesonia maxonii (Lellinger) Pabón-Mora & F. González (Pteridaceae) was rediscovered in the Paramos of Colombia after being considered extinct for 5 decades (González et al., 2015), and Anogramma ascensionis (Hook.) Diels (Pteridaceae), endemic to Ascension Island, was rediscovered in 2009 after a similar period (Baker et al., 2014). In Argentina, Asplenium L. is the most species-rich fern


genus, with 38 native taxa, occurring mainly in the Neotropical area of the country, with a few species in the Andean region (Arana et al., 2020). The fern of Achala Asplenium achalense Hieron. was described by the German botanist Hieronymus (1896) from Pampa de Achala, Córdoba province, central Argentina. This fern is characterized by pendant pinnate fronds up to 80 cm long (Plate 1a,b). The label data of the type specimen indicates it was growing in rock crevices in grasslands at 1,200– 2,000 m in the Comechingones biogeographical province, in mountainous regions of central Argentina (Arana et al., 2021a; Plate 1d). In the 20th century the species was found as an epiphyte in forests of the Yungas biogeographical province, a biodiverse area rich in species of Lauraceae and Myrtaceae (Arana et al., 2021a; Plate 1c). The Yungas is one of the centres of fern diversity in the Southern Cone of South America (Ponce & Arana, 2019; Arana & Ponce, 2021), and is an area of conservation pri- ority because of its high species richness and endemism and its importance for biogeographical connectivity (Arana et al., 2021a). The fern of Achala belongs to a complex of species, but


Arana et al. (2022) characterized it as a well-defined taxon endemic to north-west and central Argentina. The 18 known herbarium specimens unequivocally referred to A. achalense were collected during the 19th and 20th centur- ies, the most recent in 1993 in the province of Salta (Arana et al., 2022). In c. 50 3–5 day field trips from 1999 onwards


This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution and reproduction, provided the original article is properly cited. Oryx, 2024, 58(5), 607–610 © The Author(s), 2024. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605324000486


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