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Title: Assessment of the distribution of Bembidion testaceum and reasons for its decline
Author: J.P. Sadler
Author: D Bell
Author: P.M. Hammond
Author: Agency : Bristol Environment
Document Type: Monograph
Annotation: Environment Agency Project ID:EAPRJOUT_1198, Representation ID: 377, Object ID: 2417
Abstract:
Bembidion testaceum Duftschmid is one the most enigmatic and poorly researched beetle species associated with exposed riverine sediments (ERS). A detailed review of the distribution and ecology of species was carried out in the summer of 2004. The research involved a combination of literature search on the existing knowledge of the species, confirmation of records using museum specimens, field survey of sites where B. testaceum has been recorded previously (excluding Scotland) and limited autecological work. The work has shown that the species has a northerly and westerly distribution in the United Kingdom and although it is listed as Nb (Nationally Scarce) in the conservation literature its present distribution indicates that it is very rare in the UK. The desk study suggested records of the species from 15 UK 10km squares of which 4 were post-1980 records. The fieldwork and the museum work helped both to confirm the species presence on some of its former sites and to uncovered new, previously undocumented specimens and records. Thirty-four new records were uncovered as a result of the museum visits and an additional 17 new records derive from the fieldwork. An analysis of the consolidated list of 74 secure records for the species suggested long term persistence of populations on the Rivers Usk and Monnow in Wales, and the Rivers Teme, South Tyne, Devil’s Water and Tyne in England. Although old records exist B. testaceum has not been found on a number of rivers in SW Scotland (e.g. Nith and Clyde), Cumbria (e.g. Eden, Irthing), Wales (Wye and Taff), the Yorkshire Derwent and rivers in Devon (e.g. the Dart, Teign and Exe), despite a reasonable amount of recent fieldwork. One might, therefore, cautiously accept that some of the absences highlighted in this study are real or, if not, indicate very low population levels. At the very least this work illustrates that the species conservation status warrants redesignation from Nb to RDB2. The records examined during this work when coupled with fieldwork observations illustrate that the species can be found in a range of sedimentary or morphology units on UK rivers, and even anthropogenic habitats such as gravel pits and newly created rivers. However, the species shows strong microhabitat and sedimentary affinities to unconsolidated, unvegetated sediment of varying sizes ranging from pebbles to cobbles overlying coarse and clean sands. It is clear also from fieldwork in areas of former records that the species does not enjoy siltation. The species appears to be deleteriously affected by habitat loss at both the local and catchment scales. The report concludes with recommendations for further work.
Publisher: Environment Agency
Subject Keywords: RiversSedimentsPopulationSpecies distributionGeographical distributionAquatic insectsNature conservation
Geographic Keywords: United Kingdom
Taxonomic Keywords: Bembidion testaceum
Extent: 91
Permalink: http://www.environmentdata.org/archive/ealit:4641
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