Theory and practice for managing a disturbance-dependent butterfly.
Hodgson, Jenny*,1, Moilanen, Atte2, Thomas, Chris1, 1 University of York, York, UK2 Department of Biological and Environmental Sciences, Helsinki, Finland
ABSTRACT- Many species of conservation concern are found in early-successional habitats. Through the processes of disturbance and succession, the spatial distribution of suitable habitat for these species is continually changing. In the literature of metapopulation biology it has often been acknowledged that habitat patches may sometimes become unsuitable, and that new suitable habitat may be created, but these possibilities have rarely been made explicit in metapopulation models. We have adapted a widely-used Stochastic Patch Occupancy Model to include disturbance and succession. The model is flexible enough to include different disturbance types and to allow these to happen at different rates in different parts of the landscape. We have used our model to explore the dynamics of a well-studied species: the silver studded blue butterfly (Plebejus argus, Lycaenidae) in a landscape of heathland habitat in North Wales, UK, where detailed fire records have been kept. We have found that the rate of burning seen between 1991 and 2002 would probably not be sufficient by itself to sustain the silver studded blue populations in the long term. However, fire is not the only type of disturbance that can create silver studded blue habitat. Based on colony surveys conducted in 1983 and 2004, it seems that sea spray and mechanical disturbance by humans and livestock are at least as important as fire. We show that including disturbance types where succession proceeds more slowly can greatly increase the average persistence time of the metapopulation. We also show how the model can be used for conservation planning: finding the pattern of planned burns that most improves the persistence time of the metapopulation.
Key words: plebejus argus, metapopulation, disturbance, succession
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