Land-use change is one of the primary drivers of species loss (1), yet little is known about its effect on other components of biodiversity that may be at risk (2). Here, we ask whether, and to what extent, landscape simplification, measured as the percentage of arable land in the landscape, disrupts the functional and phylogenetic association between primary producers and consumers. Across seven European regions, we inferred the potential associations (functional and phylogenetic) between host plants and butterflies in 561 seminatural grasslands. Local plant diversity showed a strong bottom-up effect on butterfly diversity in the most complex landscapes, but this effect disappeared in simple landscapes. The functional associations between plant and butterflies are, therefore, the results of processes that act not only locally but are also dependent on the surrounding landscape context. Similarly, landscape simplification reduced the phylogenetic congruence among host plants and butterflies indicating that closely related butterflies become more generalist in the resources used. These processes occurred without any detectable change in species richness of plants or butterflies along the gradient of arable land. The structural properties of ecosystems are experiencing substantial erosion, with potentially pervasive effects on ecosystem functions and future evolutionary trajectories. Loss of interacting species might trigger cascading extinction events and reduce the stability of trophic interactions, as well as influence the longer term resilience of ecosystem functions. From an applied perspective, conservation efforts might fail if we do not consider how landscape simplification affects the cross-trophic-level diversity associations in a local community (3). Conservation interventions aimed at restoring consumer diversity by enhancing local plant resources is likely to be more effective in regions where landscape simplification has been less marked. Therefore, we suggest that monitoring of the relationships between the diversities of these taxa can serve as an early warning signal of ecosystem health and conservation status (2). In conclusion, our novel approach reveals that other components of biodiversity are lost well before the species richness variation. Our measures of functional and phylogenetic associations across trophic levels, and how they change in response to landscape simplification, contribute to a growing understanding of the properties that determine ecosystem resilience.
(1) Newbold, T. et al. Global effects of land use on local terrestrial biodiversity. Nature 520, 45-50 (2015).
(2) Valiente-Banuet, A. et al. Beyond species loss: the extinction of ecological interactions in a changing world. Funct. Ecol. 29, 299-307 (2015).
(3) Harvey, E. et al. Bridging ecology and conservation: from ecological networks to ecosystem function. J. Appl. Ecol. 54, 371-379 (2017).