The ecology and conservation of the Southern Damselfly (Coenagrion mercuriale – Charpentier) in Britain

Abstract

This R&D Technical Report presents the results of a PhD study on the ecology and conservation of the Southern Damselfly commissioned by the UK Steering Group in 1998. The life cycle and development of this species were investigated as well as reproduction, mortality and dispersal of the mature adult stage. Large-scale habitat use (across sites) and small-scale habitat use (within a site by adults and larvae) were examined. In light of these results, this report recommends management (and monitoring) regimes for the Southern Damselfly in Britain. The findings of this report on aspects of the species’ basic ecology can be summarised as follows: 1. The Southern Damselfly requires two years for larval development in Britain 2. The flight period of the adults is shorter in Britain than in Europe and daily emergence depends on climatic variables. 3. Mortality was consistently low in the mature adult stage and at emergence but high in the egg and immature adult stages. 4. Climatic variables influenced mature adult survival, whether individuals were present at the breeding site and whether they engaged in reproductive activity given that they were present 5. The Southern Damselfly was found to be relatively sedentary but the field observed dispersal rate was probably sufficient for colonisation events and exchange of individuals to occur frequently between populations in large clusters of sites in Britain. 6. Soft-stemmed, submerged and semi-emergent herbs were favoured for oviposition whilst tall emergents with rigid upright stems were favoured for emergence. 7. Dispersal seemed highly dependent on aspects of landscape structure. The Southern Damselfly was found to be restricted in its national and global distribution probably by climatic variables including temperature and by the availability of its biotopes. It is further restricted within these biotopes because it is stenotopic i.e. highly sensitive to a number of habitat factors such as sunlight, shade, water flow and aquatic and bankside vegetation structure.

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ORCID for Tim Sykes: orcid.org/0000-0002-0665-0368

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