Abstract
The Large Copper butterfly, Lycaena dispar batavus, is extinct in Britain and rapidly declining in Europe, due predomi- nantly to loss of its wetland habitats. Northern populations have more specialised foodplant and habitat requirements than their more southerly counterparts and rely solely on Rumex hydrolapathum, the Great Water Dock, as their hostplants. Southern colonies use a greater range of Rumex. Previous work has shown that specialisation is not due to foodplant chemistry and in this paper we investi- gate the ability of different Rumex species to support the larval stages of L. d. batavus in a natural environment. Comparisons were also made between a captive colony at Woodwalton Fen, Cambridgeshire, UK and native larvae at De Weerribben, Netherlands. Field experiments using a captive colony revealed that other Rumex hosts can successfully support larvae throughout each of their larval stages in wet grassland and fenland habitats with no significant differences in survival rates compared with their natural host- plant R. hydrolapathum. An overwintering experiment using a native wild population of both butterfly and Rumex species in De Weerribben found 25% of larvae survived on the natural hostplant R. hydrolapathum and no survivors on alternative Rumex hosts. It is suggested that R. crispus and R. obtusifolius growing in their natural habitat may harbour significant competitors to L. d. batavus leading to its specialisation on R. hydrolapathum in fenland habitats.
Highlights
The subspecies of the large copper butterfly Lycaena dispar batavus is confined to the Netherlands and regarded as endangered (Oostermeijer, 1996)
It is suggested that R. crispus and R. obtusifolius growing in their natural habitat may harbour significant competitors to L. d. batavus leading to its specialisation on R. hydrolapathum in fenland habitats
We investigate the ability of L. d. batavus larvae to survive on potential Rumex host plants R. crispus and R. obtusifolius compared to their natural host R. hydrolapathum during each stage of their life cycle, pre-diapause, diapause and post-diapause, as determined by the numbers starting and finishing each stage
Summary
The subspecies of the large copper butterfly Lycaena dispar batavus is confined to the Netherlands and regarded as endangered (Oostermeijer, 1996). This subspecies, and related univoltine populations, that utilise a single larval foodplant Rumex hydrolapathum, have suffered the more severe decline due to wetland drainage and are currently of more conservation concern than the more geographically widespread bivoltine subspecies L. d. Since this does not appear to be a nutritional specialisation, an alternative explanation is that each plant species may differ in its ability to provide suitable protection for larvae against the hostilities of their environment at one or more of their life stages. The ability of these alternative host plants to successfully support all three life stages to allow progression into the subsequent stages of development is crucial
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