The species was originally described in the genus Scorzonera (S. fistulosa Brot.; Brotero 1804), but several morphological and cytogenetic characters supported its later exclusion not only from Scorzonera but also from the subtribe Scorzonerinae (Blanca and Díaz de la Guardia, 1985). These characters suggested a relationship with the Hypochaeridinae.

Recent molecular studies have remarked the relatively ancient origin (Miocene) and evolutionary isolation of the Avellara lineage and have revealed an unexpected affinity with the more widespread genera Prenanthes and Urospermum (Fernández-Mazuecos et al. 2016). Avellara fistulosa is the only species in its genus and is very distinctive from both morphological and ecological perspectives.

This is a highly restricted endemic species that is currently known only from one location in the Doñana National Park in southwestern Spain. Its extent of occurrence (EOO) and area of occupancy (AOO) are only 32 km². Other recorded populations in southwestern Spain (La Paja lagoon, Cádiz) and in Portugal have become extinct, probably as a result of habitat loss due to urbanization and agricultural activity, and it is considered possibly extinct in Portugal. Its main current threat is the high density of large herbivores in its habitat, which produce trampling and overgrazing probably affecting its genetic diversity by precluding sexual reproduction and favouring clonal reproduction. It is also threatened by the abstraction of groundwater that may modify its habitat. The species is listed as Critically Endangered [CR B1ab(iii,v)].

This is an endemic Iberian species restricted to coastal areas of the west and southwest Iberian Peninsula. It is currently known to persist in a single population (with several subpopulations) in southwestern Spain (Doñana National Park, Huelva Province). A second locality in southwestern Spain (La Paja lagoon, Cádiz Province) was extinct by the end of the 20th century (Font Quer 1927, Sánchez García 2000); the species has been the focus of recent conservation reintroduction at this locality, however, the success of this reintroduction is awaiting confirmation.

In Portugal, the species was historically reported from two areas in the centre-north (the surroundings of the Aveiro lagoon and the Sado estuary; Blanca and Díaz de la Guardia 1985). In the 1990s, it was observed in the southwest (west of São Teotónio; A. Carapeto pers. comm. 2016), however, the wetland areas at this locality were destroyed recently as a result of agricultural development. Recent field surveys have failed to find historical localities, which suggests that the species might be extinct in Portugal; Carapeto et al. (2020) considered the species to be possibly extinct in Portugal, with no records since the early 1990s.

Therefore, the species is now considered to occur in a single location in the Doñana National Park. This locality constitutes a geographically and ecologically distinct area and the location is defined by the main threats to the persistence of the species (habitat loss, herbivory, abstraction of groundwater) which may affect all extant individuals. The extent of occurrence (EOO) and area of occupancy (AOO) of this single known location is estimated at only 32 km². The EOO based on the minimum convex polygon which contains all the sites of occurrence was smaller than the AOO (grid size 2 km), therefore the EOO was made equal to the AOO, as indicated by IUCN guidelines.

In Spain, the species was reported as abundant in the 1920s in the currently extinct location at La Paja lagoon (Font Quer 1927, Sánchez García 2000). The most recent census data in the Doñana National Park estimated between 1,450 and 3,000 individuals (Ortiz Herrera et al. 2004, Hiraldo 2007). However, due to the vegetative reproduction of the species, these figures refer to flowering stems (ramets), not to genetically different individuals (genets). The actual number of genets is probably much lower, as indicated by the high clonality levels found in a population genetic survey (Fernández-Mazuecos et al. 2016). In Portugal, extensive and recurrent field surveys have failed to locate the four localities where the species was historically recorded (Blanca and Díaz de la Guardia 1985). The last known collection from Portugal (Aveiro) dates back to 1989, and the southwestern population observed in the 90s (west of São Teotónio) seems to have been destroyed. Based on the existing information, the species’ range and population number have considerably decreased in the last century.

The species displays a narrow ecological range. It requires meso-oligotrophic soils in temporary water bodies subject to periodic flooding. It is located in coastal plains (usually sandy peatlands with low-mineralised waters). At the only known extant native location (Doñana National Park) the primary vegetation is mainly formed of meadows and rush beds, dominated by Juncaceae (Juncus spp.: J. effusus, J. heterophyllus) and Cyperaceae (Eleocharis palustris, Bolboschoenus maritimus, Cyperus rotundus), among other plants (Oenanthe fistulosa, Baldellia ranunculoides, etc.) (Ortiz Herrera et al. 2004, Martín-Bravo et al. 2015). Due to the strong herbivory in its habitat, plants of Avellara may frequently be found sheltered in larger rush clumps.

Habitat loss as a result of extensive urbanization and agricultural activity, including the draining and silting of wetlands, is likely the main cause of its hypothesized historical range contraction (Ortiz Herrera et al. 2004, Cabezudo et al. 2005). Currently, the most serious threat to the species’ persistence appears to be the heavy grazing by wild (deer, including Fallow Deer, Wild Boar) and semi-wild (cows, horses) herbivores, which are present in high densities in Doñana National Park (Soriguer Escofet et al. 2001, De Vita et al. 2012) and have a large appetite for its fleshy stems and leaves (Ortiz Herrera et al. 2004, Martín-Bravo et al. 2015). This strong herbivory may also preclude sexual reproduction by trampling and eating of capitula, thus favouring vegetative reproduction via rhizomes and therefore affecting genetic diversity. This could be one of the factors underlying the alarmingly low levels of detected genetic diversity and the prevalence of clonal reproduction in Avellara (Fernández-Mazuecos et al. 2016).

Abstraction of groundwater for agricultural use and domestic water supply is also a serious threat as all the known sites of occurrence of the species in the Doñana National Park are located in the catchment of a single aquifer (Instituto Tecnológico Geominero de España 1998, López Albacete 2009). This aquifer is currently undergoing over-exploitation (Trick and Custodio 2004, Manzano et al. 2009, WWF 2009, Ruiz et al. 2013, Díaz Paniagua and Aragonés 2015) and a lowering of groundwater level could seriously impact the species’ habitat. The same could result from the eutrophication of surface and aquifer waters as a result of agriculture, especially intensive crops on sand (located in the Doñana periphery); nutrients from fertilisers are lixiviated to the ground and contaminate the subterranean water (P. Garcia Murillo pers. comm. 2016).

In addition, climate change is also predicted to produce a reduction in groundwater supplies in the Doñana National Park (Guardiola-Albert and Jackson 2011). Finally, the threat of heavy metals pollution by mine tailing spills should be considered, as shown by the Aznalcóllar disaster in the surroundings of the Doñana National Park in 1998 (Grimalt et al. 1998).

The plant is not directly utilised. It is considered an indicator of high water quality (García Murillo et al. 2009).

The species is not legally protected at the national level in Spain or Portugal, although it is listed as Critically Endangered (CR) in the Spanish Red Book of vascular plants because of its extremely reduced range, demographic regression and habitat loss (Ortiz et al. 2004, Cabezudo et al. 2005, Moreno 2008, Martín-Bravo et al. 2015). At the regional level within Spain, it is legally protected in Andalusia (Spain). The single extant population is included in a Spanish National Park.

A conservation introduction of Avellara plants (germinated from seeds collected in Doñana National Park) is being undertaken at a historical location of the species (La Paja lagoon, Cádiz, Spain) by the Botany area, Universidad Pablo de Olavide (Seville). The plants are monitored and the results of this conservation action are being evaluated (Martín-Bravo et al. 2015). La Paja wetland has been subjected to restoration projects and is currently a natural reserve, where fencing prevents herbivory pressure, therefore excluding some of the main threats for the species (habitat loss and overgrazing).

Additional conservation measures include the fencing of one of its subpopulations in the Doñana National Park to exclude herbivores. The density of large herbivores in the Doñana National Park should be controlled to prevent overgrazing (Valdés et al. 2010). Adult plants and seeds of the species have been included in Spanish ex situ conservation collections (Andalusian Germplasm Bank, Córdoba) and botanical gardens and universities in Spain (Royal Botanical Garden, Madrid; Botanical Garden of the Santander Financial City, Boadilla del Monte, Madrid; Botanical Garden of San Fernando, Cádiz; Universidad Pablo de Olavide, Seville) and Portugal (Jardim Botânico da Universidade de Coimbra). More information about the reproductive biology of the species would be important to understand its current conservation status and would help to design effective conservation actions. The introduction of improved water resource management within the Doñana National Park is also required.

This species is an ancient, evolutionarily isolated lineage, which displays high phylogenetic singularity. It has been proposed as a flagship, priority species for plant conservation in Spain and Portugal (Fernández-Mazuecos et al. 2016). An integrated conservation strategy that comprises both in situ and ex situ programs are considered essential to succeed in the conservation of this endangered species.

Further field survey is required to confirm the current restricted distribution of the plant; it is considered possible that the species may persist in Portugal in suitable habitat (A. Carapeto pers. comm. 2016) but it is certain that if they exist, such sites will be in need of conservation actions.