The relationship between plant and butterfly biodiversity is altered by compound effects of human activities at landscape and regional scales

Understanding how human activities influence biodiversity is a pressing challenge. Here, we ask whether obligate biotic interactions between plants and butterflies respond to patterns in anthropogenic disturbance at landscape and regional scales. We used hierarchical models to understand how the relationships between alpha and beta taxonomic diversities of butterflies and plants change across landscapes and regions exposed to a gradient of anthropogenic influence. Analyzing 1,682 sampling sites in which butterfly and plant species were both inventoried, from 45 studies identified through a literature review, we found that ecological communities sampled in highly disturbed areas displayed a lower number of butterfly species per plant species, and more homogenized butterfly communities. These responses were exacerbated when human activities affected both the landscape and the region hosting the plant and butterfly communities assessed. Our results suggest that human activities can differentially affect butterflies and plants, two co-evolved groups, thus altering long-term eco-evolutionary dynamics. They also hint at how the negative effects of human activities on biodiversity compound between landscape and regional scales, illustrating the importance of multi-scale analyses and approaches for understanding and protecting biodiversity globally.