Taxonomy

Najas flexilis | Slender Naiad

Distribution

Status

Conservation status


HABITATS DIRECTIVE ARTICLE 17 REPORTING
Range
Favourable
Population
Inadequate
Habitat
Inadequate
Future Prospects
Inadequate
Overal Assessment of Conservation Status
Inadequate
Overal trend in Conservation Status
Stable

Source: NPWS 2013.


IUCN Conservation Status
Ireland (1)*
Endangered
Europe (2)
Vulnerable [B2ab(iv)]
Global (3)
Not evaluated

Source(1): Curtis, T.G.F and McGough H.N. 1988; (2) Lansdown, R.V. 2013; (3) The IUCN Red List of Threatened Species. Version 2014.2

* This Red List is acknowledged as needing to be updated.The Red List category shown is updated from that appearing in the original 1988 document, due to changes in the Red List categories.

Legal status

Protected by the following legal instruments:

  • Habitats Directive [92/42/EEC] Annex II, Annex IV
  • Convention on the Conservation of European Wildlife and Natural Habitats (Bern Convention) Appendix I
  • Wildlife Act (1976)
  • Flora Protection Order 1999
  • Wildlife (Amendment) Act (2000).

Native status

Native.

Species Biology

Identification

An aquatic species, usually permanently submerged in freshwater deeper than 1 meter but shallower than 5 meters. It is a delicate, much branched, hairless annual to 30cms. Leaves are unstalked, opposite or whorled with a sheathing base, to 25mm long, narrow, linear. Leaves are sparsely toothed or not at all. Male and female flowers are separate on the same plant. No sepals or petals. Flowers are in leaf axils, the male protected by a bract or spathe until pollination. Male flowers have one unstalked anther. Female flowers have one carpel. The fruit is an unstalked drupe.

No vegetative reproduction. 

Flowers in August.

Sources: Parnell J., Curtis, T., 2012; Stace C., 1997; Wingfield et al, 2004.

Habitat

Lit areas of clear, lowland, freshwater lakes of circum-neutral pH. Usually in water deeper than 1 meter, shallower than 5 meters on substrate from mud to fine sand. Najas flexilis appears to have quite specific requirements with regard to pH, alkalinity, calcium and phosphate, as well as turbidity and depth.

It occurs in clear freshwater lakes, most often in mesotrophic lakes, but will occur in some oligotrophic lakes.

  • Acid oligotrophic lakes (FL2)
  • Mesotrophic lakes (FL4).

Sources: Wingfield et al 2004; NPWS 2013; Fossitt, J.A. 2001.


Threats faced

THREAT
ARTICLE 17  CODE
RANKING
Water abstractions from groundwater
J02.07
HIGH
Diffuse pollution to surface waters due to agricultural and forestry activities
H01.05HIGH
Diffuse pollution to surface waters due to household sewage and waste waters
H01.08HIGH
Diffuse pollution to surface waters due to other sources not listed
H01.09HIGH
Pollution to surface waters by industrial plants
H01.01MEDIUM
Changes in abiotic conditions
M01MEDIUM
Invasive non-native species
I01
LOW
Other point source pollution to surface water
H01.03LOW
Human induced changes to hydraulic conditions
J02LOW
Silting up
K01.02LOW
Drying out
K01.03LOW
Species composition change (succession)
K02.01LOW
Accumulation of organic material
K02.02LOW

Source: NPWS 2013.

The Threats identified in the Article 17 reporting document accord well with those threats identified at a European Level for the species in the IUCN Red List account 2013. The IUCN threat list, at a European level, also includes reports from Latvia that professional fishing is a threat in that country.

Source: Lansdown, R.V. 2013

Conservation actions

In the Article 17 Habitats Directive reporting for the period 2007-2012 Conservation Measures implemented or being implemented during the period were;

  • Continued legal protection of the species and its habitats inside and outside of Natura 2000 sites.
  • Restoring / improving water quality' inside and outside of Natura 2000 sites.
Sources: NPWS 2013.




Distribution

World distribution(GBIF)

North America, Europe, Asia. Most frequent in North America. Within Europe, most frequent in Britain and Ireland. (Wingfield et al 2004).

Accuracy of world distribution shown in the Global Biodiversity Information Facility (GBIF) map below will be constrained by, amongst other factors, data held but not shared by countries and organizations not participating in the GBIF.




Irish distribution

Western, mainly Donegal, Mayo, Galway, Kerry.



Temporal change

Records submitted to Data Centre in 2021

The following map is interactive. If you would prefer to view it full screen then click here.

How can you help

The National Biodiversity Data Centre is trying to improve our knowledge on the distribution of the Slender Naiad (Najas flexilis) in Ireland. Should you observe the species, please submit sighting to add to the database. Detailed observations will assist us gaining a better insight into where the species is most abundant in Ireland and we might also be able to detect regional variations. Please submit any sightings and photographs at:

http://records.biodiversityireland.ie/


All records submitted on line can be viewed on Google Maps – once checked and validated these will be added to the database and made available for conservation and research.

Further information

For further information contact Dr. Liam Lysaght llysaght@biodiversityireland.ie

References

Publications

Curtis, T.G.F and McGough H.N., 1988. The Irish Red Date List 1 Vascular Plants. Wildlife Service, Dublin.Published by The Stationery Office.

Fossitt, J.A., 2001. A Guide to Habitats in Ireland. The Heritage Council.

Lansdown, R.V. 2013. Najas flexilis. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 26 September 2014.

NPWS, 2007. The Status of EU Protected Habiats and Species Vol 2.

NPWS, 2013. The Status of EU Protected Habitats and Species in Ireland.  Species Assessments Volume 3. Version 1.0. Unpublished Report, National Parks & Wildlife Services. Department of Arts, Heritage and the Gaeltacht, Dublin, Ireland.

Parnell J., Curtis T., 2012. Webb's An Irish Flora. Cork University Press.

Stace, C., 1997.New Flora of the British Isles, Second Edition. Cambridge University Press.

Wingfield, R.A., Murphy, K.J., Hollingsworth, P. and Gaywood, M.J., 2004.The Ecology of Najas flexilis. Scottish Natural Heritage Commissioned Report No. 017 (ROAME No.F98PA02)







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