|Scientific Name:||Lactuca watsoniana|
|Taxonomic Notes:||Lactuca watsoniana Trel. is a tertiary wild relative of lettuce, L. sativa L. (USDA, ARS, National Genetic Resources Program 2010). However, according to H. Schaefer (pers. comm. 2010), its position in the genus Lactuca is not confirmed and it might turn out to belong to another Asteraceae genus as its morphology is quite different from all other Lactuca species.|
|Red List Category & Criteria:||Endangered B2ab(i,ii,iii); C2a(i) ver 3.1|
|Reviewer(s):||Kell, S.P. & Nieto, A.|
|Contributor(s):||Duarte, M.C., Magos Brehm, J., Tavares, M., Carvalho, M., Draper Munt, D., Santos Guerra, A., Kell, S.P. & Hargreaves , S.|
Lactuca watsoniana is assessed as Endangered because its area of occupancy (AOO) is less than 500 km², the population is severely fragmented and there is a continuing decline in the extent of occurrence (EOO), AOO and area, extent and quality of its habitat. The population comprises less than 2,500 mature individuals, there are less than 250 mature individuals in each subpopulation and there is a continuing decline in the population size.
L. watsoniana is endemic to the Azores where it has been collected from Faial, Pico, São Miguel, Terceira and São Jorge (Schaefer 2002, 2003). Its area of occupancy (AOO) is less than 500 km2.
|Range Map:||Click here to open the map viewer and explore range.|
It has been recorded at eight localities (Universidade dos Açores 2008) and has been described as scattered, very rare and in danger of extinction (Schaefer 2002, 2003). Sjögren (2001) noted that in the few localities in which it is found, there is a small number of plants and Schaefer (2005) recorded a total of 500–1,000 plants. There are very few young plants in the population; the reason is unknown, but it might be related to herbivore pressure (introduced rabbits) or a decrease in pollinators (H. Schaefer pers. comm. 2010).
The Commission of the European Communities (2009) reported that this species has "poor propects" and is "likely to struggle unless conditions change", but also that its range trend was stable during the period 1992–2006 and that the population trend was increasing during the period 1992–2005. However, this information is erroneous; according to H. Schaefer (pers. comm. 2010) this reported increase was due to some new populations that were recorded after monitoring began recently that had previously been overlooked and does not represent an increase in the population. The population has been decreasing during the past two centuries (Schaefer 2003).
|Habitat and Ecology:||
It grows in volcanic craters and deep narrow ravines, in juniper forests between 500 and 870 m (Feráková 1977, Schaefer 2002, 2003), and in scrublands. It favours habitats rich in water and nutrients and has a preference for altitude—55 % of the populations studied were between 800 and 900 m (Commission of the European Communities 2009). Habitats Directive habitats where this species can occur are: Macaronesian mesophile grasslands and endemic forests with Juniperus brevifolia (a priority habitat) (Commission of the European Communities 2009).
|Use and Trade:||L. watsoniana is a tertiary wild relative of and potential gene donor to lettuce, L. sativa.|
The main threats are livestock grazing and invasive species leading to a reduction in suitable habitat. Threats reported by the Commission of the European Communities (2009) include:
It is listed as priority species on Annex II of the EU Habitats Directive and has been listed as Endangered (EN) B2ab(i,ii,iii); C2a(i) (Corvelo 2010).
No germplasm accessions of L. watsoniana are reported by EURISCO to be stored in European genebanks (EURISCO Catalogue 2010). However, it is in cultivation in the botanical garden of Faial, Azores, where seeds are also stored.
It occurs in protected areas but this does not stop invasion by exotic species such as Hydrangea macrophylla and Hedychium gardnerianum, which greatly reduce its habitat, and invasive rabbits that feed on it and might be especially problematic for seedlings and young plants (H. Schaefer pers. comm. 2010). It is currently monitored by the local conservation department and the Azorean biodiversity group of the Universidade dos Açores.
|Citation:||Schaefer, H. 2013. Lactuca watsoniana. The IUCN Red List of Threatened Species. Version 2015.2. <www.iucnredlist.org>. Downloaded on 03 August 2015.|
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