Nectar resource limitation in agricultural landscapes : effects on behaviour and life-history traits in the meadow brown butterfly (Maniola jurtina)

Pollinator declines in agricultural landscapes have been attributed to the increasing scarcity of nectar sources, amongst other factors. Butterfly abundance and diversity are often correlated with nectar resource availability, but experimental, causal evidence for nectar-related effects on butterfly performance are still rare. This PhD thesis aims at evaluating the impact of a reduction in nectar quality, quantity and both combined on life-history traits and adult behaviour of a grassland butterfly in intensive, nectar-poor versus extensive, nectar-rich agricultural landscapes. We used the Meadow Brown, Maniola jurtina as a model species. We identified different foraging patterns of M. jurtina populations and individuals living in either nectar-rich grasslands and in flower-poor hay meadows, and found changes in behaviour after mowing. We tested the effects of nectar quality and quantity under semi-controlled conditions on a series of traits linked to survival, fecundity, flight performance and metabolism, and found strong negative effects of nectar limitation on butterfly condition. The differences between individuals from intensive and extensive agricultural landscapes suggested adaptations to altered resource availability relative to agricultural intensification. Consequences of agri-environmental schemes are discussed in terms of the effective use of uncut zones left in mown meadows. This PhD thesis contributes to our understanding of the importance of nectar feeding in adult butterflies, and of the significance of nectar source limitation for the population viability of flower-visiting insects in changing anthropogenic landscapes.