Effects of agriculture on evolution of native species

Background/Question/Methods

Anthropogenic disturbances, such as urbanization, fragmentation, and introduction of invasive species, can homogenize biotic communities by reducing the variation in species composition across locations. For example, global agricultural intensification has ­increased pesticide use has and led to increased similarities in both bee and hemipteran communities relative to non-agricultural areas. Agriculture has the potential to significantly impact diversity of natural communities. Proximity to agriculture may lead to altered evolutionary trajectories for native species via altered natural selection. No studies have experimentally examined the possible evolutionary consequences of landscape-level homogenization of biotic interactions. We explored how proximity of wild plants (Helianthus annuus texanus) to crops (crop sunflowers: Helianthus annuus) altered their mutualist and antagonist interaction partners, and subsequent altered natural selection on traits. 

Results/Conclusions

By experimentally manipulating the proximity of a native sunflower species to crop sunflowers, we found that mutualist pollinators largely increased in abundance on wild sunflowers near sunflower crops, while antagonists decreased abundance on wild sunflowers near sunflower crops.  In turn, natural selection on floral traits was altered across the landscape due to changes in abundance and community structure of mutualists and antagonists. Crops altered natural selection on floral traits of native sunflowers, and reduced spatial variation in selection near relative to far from crops. Furthermore, all floral traits have nonzero heritabilities, suggesting that altered natural selection will have evolutionary consequences for this species.