Valerianella Rimosa (Bastard)
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Valerianella rimosa (Bastard) Broad-fruited Cornsalad VALERIANACEAE SYN.: Valerianella auricula DC. Status: Nationally Rare Endangered 14 10-km squares post 1987 UK BAP Priority Species since 1998 Lead partner: Plantlife UK Biodiversity Action Plan: The following are the current targets following the 2005 Targets Review: T1. Maintain viable populations at extant ‘natural’ sites where the species is deemed to be long established. T2. Achieve a 2-fold increase in the area of habitat suitable for the natural colonization of the species by 2010 in priority areas. Progress on targets as reported in the UKBAP 2005 reporting round can be viewed by selecting this species and logging in as a guest on the following web site: http://www.ukbap- reporting.org.uk/ The full Action Plan for Valerianella rimosa can be viewed on the following web site: http://www.ukbap.org.uk/UKPlans.aspx?ID=625 Work on Valerianella rimosa is supported by: 1 Contents Status: ...................................................................................................................1 UK Biodiversity Action Plan: .......................................................................................1 1. Morphology, Identification, Taxonomy & Genetics................................................2 1.1. Morphology & Identification ..........................................................................2 1.2. Taxonomic Considerations ............................................................................3 1.3. Genetic implications.....................................................................................3 2. Distribution & Current Status ...........................................................................3 2.1. Europe.......................................................................................................3 2.2. United Kingdom ..........................................................................................3 2.2.1 England ..................................................................................................4 2.2.2 Northern Ireland ......................................................................................6 2.2.3 Scotland .................................................................................................7 2.2.4 Wales.....................................................................................................7 2.3 Ireland ......................................................................................................7 2.4 Channel Islands ..........................................................................................7 3. Ecology & Life Cycle........................................................................................7 4. Habitat Requirements......................................................................................8 4.1. The Landscape Perspective ...........................................................................8 4.2. Communities & Vegetation............................................................................9 4.3. Summary of Habitat Requirements ................................................................9 5. Management Implications .............................................................................. 10 6. Threats/ Factors leading to loss or decline or limiting recovery ............................ 10 7. Current Conservation Measures ...................................................................... 11 7.1. In-Situ Measures....................................................................................... 11 7.2. Ex-Situ Measures ...................................................................................... 12 7.3. Research Data .......................................................................................... 12 7.4. Monitoring Valerianella rimosa and the Common Monitoring Standard ............... 12 8. References .................................................................................................. 12 9. Contacts...................................................................................................... 13 10. Acknowledgments......................................................................................... 13 11. Links .......................................................................................................... 13 1. Morphology, Identification, Taxonomy & Genetics 1.1. MORPHOLOGY & IDENTIFICATION A slender, often much-branched plant, rarely more than 30cm tall. The leaves are narrow and lanceolate, sometimes with a few teeth near the base. The leaves are initially formed in a basal rosette, with stem leaves in pairs alternating up the stem as it elongates. The flowers are borne in moderately dense, bifurcating clusters, frequently with a single flower in the axil of the lowest fork. The flowers are approximately 2mm in diameter, with five equal, white (sometimes pink-tinged) petals. The seeds are nearly spherical, approximately 1.5mm in diameter with a single terminal tooth, the clusters at the ends of the stems being quite eye- catching when large numbers of well-grown plants are present. 2 This species can be confused with other species of cornsalad, especially Valerianella dentata (Clapham et al., 1987; Stace, 1997). The species can be easily distinguished by seed morphology as follows: Seed without persistent tooth-like calyx: V. locusta, V. carinata Seed with tubular, six-toothed calyx: V. eriocarpa Smooth-surfaced, inflated seed with a single, small calyx-tooth: V. rimosa Ribbed-surfaced, narrow seed with a single large calyx-tooth: V. dentata 1.2. TAXONOMIC CONSIDERATIONS None. e ENETIC IMPLICATIONS g 1.3. G No studies on genetic diversity within this species have been carried out. Such a study would be desirable to elucidate relationships between populations. © Bob Gibbons / Natural Ima Fig 1. Valerianella rimosa 2. Distribution & Current Status 2.1. EUROPE The species occurs in Southern-central Europe, and is threatened in Germany, the Netherlands and Switzerland (Wigginton, 1999). 2.2. UNITED KINGDOM Overview Valerianella rimosa is found almost exclusively in arable habitats in Britain, and it also occurs in disturbed sites adjacent to arable land and on former arable land until the associated perennial vegetation becomes too closed. Although in the past it was mainly associated with light calcareous soils, it now occurs on a wide variety of soil types. In a recent survey of all known localities (Wilson, 2004), at six sites it was present on acidic shales, possibly with the influence of more base-rich intrusions and deposits of wind-blown sand. Four sites were on Jurassic limestone, three on chalk, one on chalky boulder clay and one on acidic Tertiary sand. 3 This species was known in Britain in the Iron Age, and it is thought to be an archaeophyte (a plant naturalized in Britain before 1500AD). Although records are widespread throughout southern Britain with isolated sites as far north as central Scotland, it has never been abundant. The majority of sites have been to the south of a line from the Humber to the Severn Estuaries. In the New Atlas of the British Flora, Valerianella rimosa has a change index of –2.55, the 22nd greatest of any species in the British flora (Preston et al., 2002). This species was not included in the BSBI/Nature Conservancy Council arable plant survey (Smith 1986). The total number of 10km squares from which it was recorded before 1970 is 149, but it was only known from 38 between 1950 and 1970. Numbers of records fell to 14 10km squares between 1970 and 1986, and it has been recorded from 14 10km squares between 1987 and 2006. There appears therefore to have been a serious decline of this species, although as with many annuals, caution must be observed in the interpretation of these figures, as this is a species with a history of erratic appearance at many of its arable localities. A review of its status in 1999 concluded that there were only four extant sites (Wigginton, 1999), but recent survey work has shown this to be unduly pessimistic. There may be some potential for recovery from the seed-bank, but the longevity of seed is unknown. Some of the rarity of this species in the past may have been due to the close morphological similarity to the congeneric Valerianella dentata, from which it is only reliably distinguishable by the shape of the seed. Valerianella is now a better understood genus, but even so, small populations can be difficult to find when growing with V. dentata. It is an Endangered species (Cheffings & Farrell, 2005) and is included on the priority list of the UK Biodiversity Action Plan. There are no obviously casual or ruderal sites, and this species is not included in seed-mixes of annual species used for landscaping projects. 2.2.1 ENGLAND The historic distribution of Valerianella rimosa is largely restricted to the south of a line from the Humber to the Severn estuaries (Perring & Walters, 1982). There is a scattering of records north of this to Cumbria. This distribution has become increasingly accentuated in recent years as it has become rarer (Preston et al., 2004). Of the 16 currently known English sites, all but two (in Buckinghamshire and Bedfordshire) are in the south-western corner. Five of these are in Cornwall and Devon. Only three current English sites have reliably large populations. Near Burford in Oxfordshire, it occurs in large quantities in at least three fields on heavy soils over Cotswold limestone. Associate species include Scandix pecten-veneris,