Demographics and spatial ecology in a population of cryptic wood white butterfly Leptidea juvernica in Northern Ireland

Abstract

The cryptic wood white Leptidea juvernica is one of a newly-discovered species complex comprising three morphologically similar species in Europe. In the British Isles, L. juvernica is absent from Great Britain, but is widespread in Ireland, where it has experienced recent declines; it is classed as a priority species in Northern Ireland. Using a mark–recapture approach, this study aims to elucidate the population and spatial ecology of L. juvernica based on a population resident on a small, suburban site and to propose conservation measures. The results demonstrated that populations of L. juvernica, even on small sites, can reach high numbers during the peak flight season. Unusually for European Pieridae, there was only weak evidence of protandry in this population, possibly reflecting weather conditions prior to the flight season. The spatial distribution and abundance of L. juvernica was associated with the distribution of its larval host-plants, as well as maintaining close proximity to south-facing habitat edges for shelter. Males had a closer association to sheltered habitat edges, whilst females were found more commonly on open ground with a shorter sward which was the preferred egg-laying habitat. Long vegetation in sheltered areas was important for roosting during periods of non-activity. These results inform conservation measures which will benefit L. juvernica; appropriate measures focus on habitat management providing a mosaic of open, semi-natural grassland interspersed with tall vegetation, scrub, and trees.