Habitat preferences and conservation of the marbled jewel beetle Poecilonota variolosa (Buprestidae)

Detailed knowledge on habitat requirements is a key to successful conservation actions. The marbled jewel beetle Poecilonota variolosa (Buprestidae) has a wide global distribution but populations are often scarce and typically fragmented. In Sweden it is monophagous on aspen Populus tremula and is classified as near threatened on the Swedish Red List due to its rapid population decline. This study aimed to investigate habitat preferences and regional-scale distribution patterns of P. variolosa in southern Sweden in order to suggest conservation measures. Aspen trees in four study areas in the province of Småland were surveyed for exit holes during late summer 2011. The occurrence and number of exit holes (both new and old ones) per tree were compared between study areas and habitat types, and were related to the sun exposure and bark thickness of individual trees. Further, the occurrence of new and older exit holes was related to tree sun exposure and bark thickness. The most preferred habitat types were aspens on clear-cuts, followed by roadside aspens, aspens in pastures, and aspens in closed forest. Thick bark and high sun exposure were consistently significant as predictors for both occurrence and number of new exit holes per tree. The majority of exit holes were located towards south. Our results indicate several useful management measures: to retain aspen on clear-cuts, to cut alongside roads and around some selected coarse aspens in closed forests and in pastures.