Habitat and conservation of the enigmatic damselfly Ischnura pumilio

Abstract

Ischnura pumilio is threatened in the UK and its habitat requirements are not well understood. This study tests previously held notions of the habitat requirements of I. pumilio, investigates the features of a habitat influencing odonate species composition and provides recommendations for habitat creation and management for I. pumilio persistence. Thirty-one sites across south west England with past I. pumilio records were surveyed in 2006. Environmental variables and odonate abundance were recorded. Odonate species composition and I. pumilio abundance were related to environmental variables using multivariate techniques and GLM. Ischnura pumilio was found at a wide variety of habitat types; key habitat features were a muddy substrate with some open ground, turbid water, and low levels of shade. It was associated with increased structural diversity of vegetation away from water but low maximum height; characteristic of early-successional sites. The variables predicting odonate composition were location, shade, level of disturbance, water depth, and cover of terrestrial dwarf shrubs and Sphagnum species. Vegetation height and structure were also highly influential to at least 20 m from water. This study indicates that odonate habitat management should include adjacent hinterland. Management for I. pumilio may be complicated by the species’ use of two habitat types, each with associated problems. Furthermore, odonate species diversity was negatively associated with I. pumilio abundance, which may cause conflict of interest when managing habitats.