Population dynamics and conservation of a specialized predator:: A case study of Maculinea arion

We employ an empirically motivated case model approach to investigate the theoretical foundations for the conservation of the endangered butterfly Maculinea arion. Maculinea butterflies have highly specialized larvae that sequentially exploit a plant and an ant species. Our study establishes that M. arion's specialized life cycle, including scramble competition for limiting resources, and the spatially discrete nature of its resources, make it more sensitive to environmental variation and more prone to local extinction than other univoltine phytophagous species. We find that the number and spatial distribution of the butterfly's resources are key factors in their population dynamics, especially for M. arion populations in habitats associated with high larval survival and high adult fecundity. Factors that increase juvenile competition have first a positive effect on adult population size, but beyond a threshold this effect becomes negative. In general, oscillatory dynamics emerge for high potential growth rates and spatially homogeneous juvenile competition. We discuss the relevance of our results to population management, investigate the consequences of environmental variation, and consider different scenarios of conservation. Our model, although based on the Maculinea genus, should apply to a broad range of species for which the form of competitive interactions changes predictably at distinct points in the life cycle. Complex life cycles can lead to negative feedbacks involving parameters that are usually thought to optimize population size. We suggest that conservation strategies are neither generalizable for the Maculinea genus nor for disparate populations of each species of Maculinea, and rather that management should be conducted on a case-by-case basis.