Isoetes azorica 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Plantae Tracheophyta Lycopodiopsida IsoËtales IsoËtaceae

Scientific Name: Isoetes azorica Durieu ex Milde
Common Name(s):
English Azorean Quillwort
Isoëtes azorica Durieu ex Milde
Taxonomic Source(s): Christenhusz, M. and Raab-Straube, E. von. 2013. Polypodiopsida. Euro+Med Plantbase - the information resource for Euro-Mediterranean plant diversity. (Accessed: 2015).
Taxonomic Notes:

There are no significant taxonomic issues associated with this name.

Assessment Information [top]

Red List Category & Criteria: Vulnerable A4ce; C2a(i) ver 3.1
Year Published: 2017
Date Assessed: 2016-06-02
Assessor(s): Christenhusz, M., Lansdown, R.V., Bento Elias, R., Dyer, R., Ivanenko, Y., Rouhan, G., Rumsey, F. & Väre, H.
Reviewer(s): García, M. & Schaefer, H.
Isoetes azorica is an aquatic quillwort restricted to the Azores and is suspected to have declined more than 30% for a three generation period (around 30 years), considering 20 years in the past and 10 in the future. It is threatened by invasive species, pollution and eutrophication from cattle, and general degradation of its habitat. In addition, there are fewer than 10,000 mature individuals in total, and less than 1,000 in each subpopulation. It is therefore listed here as Vulnerable.
Previously published Red List assessments:

Geographic Range [top]

Range Description:Isoetes azorica is restricted to the Azores (Schäfer 2005, Euro+Med Plantbase 2006-2010) where it is found in crater lakes on the islands of Corvo, Flores, Faial, Pico, Sao Jorge and Terceira. The total geographic range estimated is between 13 and 16 km² (Commission of the European Communities 2009; GBIF data). Its area of occupancy (AOO) is 16 km².
Countries occurrence:
Portugal (Azores)
Additional data:
Estimated area of occupancy (AOO) - km2:16
Lower elevation limit (metres):400
Upper elevation limit (metres):1000
Range Map:Click here to open the map viewer and explore range.

Population [top]


The total population size of this species is estimated to be 2,000 to 3,000 individuals by Schäfer (2005). This estimate might be slightly low, but the total number of mature individuals is surely below the threshold of 10,000 mature individuals, with less than 1,000 individuals in each subpopulation. In total, there are around 11 subpopulations (F. Rumsey pers. comm. 2016). The generation length is around 10 years and the decline is at least 25% (Martin et al. 2008). This decline has occurred over the last 30 years in the Azores, which corresponds to the period with highest degradation of the habitats in the islands (R. Elias pers. comm. 2016). If current threats of eutrophication and invasive species continue, the species will face continuing declining by more than 30% over a three generation period. Additionally, there has been a decline in the extent and quality of its habitat (F. Rumsey pers. comm. 2016).

Current Population Trend:Decreasing
Additional data:
Number of mature individuals:2500-3000Continuing decline of mature individuals:Yes
Population severely fragmented:No

Habitat and Ecology [top]

Habitat and Ecology:This species grows exclusively in permanent or temporary crater lakes, pools and ponds between 400 to 1,000 m elevation. It is adapted to oligotrophic waters with low botanical diversity. It can also be found in ponds and lakes with higher nutrient availability and diversity. It is found in the Habitats Directive's habitat 3130 Oligotrophic to mesotrophic standing waters with vegetation of the Littorelletea uniflorae and/or of the Isoëto-Nanojuncetea (Tutin et al. 1964, Commission of the European Communities 2009).
Generation Length (years):10

Use and Trade [top]

Use and Trade: The species is not utilised.

Threats [top]

Major Threat(s): The main and increasing threats to this plant species come from the spread of invasive macrophytes, pollution and eutrophication by cattle farming (Pietsch 1994). The subpopulation at Lagoa do Negro on Terceira has been dramatically reduced (<70%) in less than ten years, by the arrival and spread of Sagittaria subulata (F. Rumsey, pers. obs. 2010). One of the three subpopulations on Flores has recently (2010) suffered considerable mortality as a consequence of pollution leaching from a nearby rubbish tip (F. Rumsey pers. comm. 2010). The subpopulation in the Caldeirao Lake at Corvo (a nature reserve) has almost disappeared as a consequence of eutrophication and cattle grazing in the crater (all year ca 200 cattle individuals are allowed to roam freely in the reserve and rely on the lake as their only water source). The common practice to pump water out of the lakes in the summer to fill water tanks for cattle is a threat especially on Pico and Flores, where this practice leads to dramatic reduction of the water levels (e.g., in 2015). Further threats to the species are grazing, leisure fishing, the construction of paths, canalisation, modifying structures of inland water courses and other human induced changes in hydraulic conditions (Commission of the European Communities 2009).

Conservation Actions [top]

Conservation Actions: This species is listed on Annex II of the Habitats Directive and under Appendix I of the Convention on the Conservation of European Wildlife and Natural Habitats (Bern Convention) under the Top 100 as Priority for Conservation (Martin et al. 2008) and under regional legislation (Decree 12/2015). There is no other information available on conservation actions, but it is found in protected areas throughout its range. As a minimum, the following conservation measures should be undertaken:
  • Remove cattle from areas with Isoetes subpopulations.
  • Assess the size of subpopulations and establish a basis for monitoring to measure trends.
  • Compile information on the life history of I. azorica, with emphasis on dispersal and subpopulation or metapopulation dynamics.
  • Assess the risk from various threats listed and potential for these threats to be controlled or eliminated.
  • Given the small size of the known subpopulations, the sites should come under better legal environmental protection and these sites (already in natural areas) should be better managed to preserve this species.

Citation: Christenhusz, M., Lansdown, R.V., Bento Elias, R., Dyer, R., Ivanenko, Y., Rouhan, G., Rumsey, F. & Väre, H. 2017. Isoetes azorica. The IUCN Red List of Threatened Species 2017: e.T162270A85430204. . Downloaded on 20 June 2018.
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