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Proximity to crop relatives determines patterns of natural selection in a wild sunflower

Citation

Mitchell, Nora; Chamberlain, Scott; Whitney, Kenneth (2021), Proximity to crop relatives determines patterns of natural selection in a wild sunflower, Dryad, Dataset, https://doi.org/10.5061/dryad.bg79cnp9g

Abstract

Abiotic and biotic heterogeneity result in divergent patterns of natural selection in nature, with important consequences for fundamental evolutionary processes including local adaptation, speciation and diversification. However, increasing amounts of the global terrestrial surface are homogenized by agriculture (which covers nearly 50% of terrestrial vegetated land surface) and other anthropogenic activities. Agricultural intensification leads to highly simplified biotic communities for many taxa, which may alter natural selection through biotic selective agents. In particular, the presence of crops may alter selection on traits of closely related wild relatives via shared mutualists and antagonists such as pollinators and herbivores. We asked how the presence of crop sunflowers (Helianthus annuus) alters natural selection on reproductive traits of wild sunflowers (H. a. texanus). Across two years and multiple sites, we planted replicated paired populations of wild H. a. texanus bordering sunflower crop fields vs. approximately 2.5 km away. We measured fitness, floral traits, and interactions of the plants with insect pollinators and seed predators. We found limited evidence that proximity to crop sunflowers altered selection on individual traits, as total or direct selection differed by proximity for only three of eleven traits: ray length (a marginally significant effect), Isophrictis (Gelechiidae, moth) attack, and Neolasioptera (Cecidomyiidae, midge) attack. Direct (but not total) selection was significantly more heterogenous far from crop sunflowers relative to near crop sunflowers. Both mutualist pollinators and antagonist seed predators mediated differences in selection in some population-pairs near versus far from crop sunflowers. Here we demonstrate that agriculture can influence the evolution of wild species via altered selection arising from shared biotic interactions, complementing previously demonstrated evolutionary effects via hybridization.

Methods

Data were collected between 2010 and 2011 from five experimental sites of planted Helianthus annuus ssp. texanus across Texas. Raw trait data on floral, inflorescence, and whole-plant traits were compiled.

Usage Notes

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Funding

National Science Foundation, Award: DEB 0716868

Prairie Biotic Research