Condition, dispersal, and population connectivity of two butterfly species in agricultural landscapes

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The Earth’s biodiversity is currently declining through species extinctions and reductions in population abundances. In recent years, several studies documented massive insect declines, in particular in agricultural landscapes. Such losses will likely feedback on ecosystems and human societies alike, through a reduction in the goods and services biodiversity provides. While the evidence for large-scale insect declines is rapidly increasing, the underlying causes are debated but hitherto not well understood. Land-use intensification has been repeatedly suggested to be a major driver, and recent studies show that insect declines are associated with agriculture at the landscape scale. This implies an important and hitherto probably underestimated role of habitat area and connectivity, and thus dispersal and resource availability. Using two butterfly species with contrasting dispersal ability (Coenonympha pamphilus, Pieris rapae), I here focus on two important aspects potentially underlying insect declines in agricultural landscapes, namely the impact of (1) constraints on dispersal and (2) a lack of adult food (nectar) resources. Both are intimately associated, as nectar largely fuels dispersal in butterflies, while dispersal ability will affect the likelihood of reaching such resources in fragmented landscapes. Patterns will be compared among replicated traditional and (highly fragmented) modern agricultural landscapes, differing in land use intensity and habitat networks. I will use a highly integrated approach combining field collections, morphological and physiological analyses, common garden experiments, GIS analyses, and fine-scale landscape genomics. The latter enables investigating dispersal even at small spatial scales with unprecedented rigour. I will investigate (1) butterfly condition, (2) flight morphology, (3) flight capacity and propensity, (4) population genetic structure, and (5) variation in metabolic pathways. The integration of different approaches will considerably enhance our understanding of butterfly declines in agricultural landscapes.