Fitness costs of herbicide resistance across natural populations of the common morning glory, Ipomoea purpurea

Although fitness costs associated with plant defensive traits are widely expected, they are not universally detected, calling into question their generality. Here we examine the potential for life history trade-offs associated with herbicide resistance by examining seed germination, root growth, and above-ground growth across 43 naturally occurring populations of Ipomoea purpurea that vary in their resistance to RoundUp(R), the most commonly used herbicide worldwide. We find evidence for life history trade-offs associated with all three traits; highly resistant populations had lower germination rates, shorter roots and smaller above-ground size. A visual exploration of the data indicated that the type of trade-off may differ among populations. Our results demonstrate that costs of adaptation may be present at stages other than simply the production of progeny in this agricultural weed. Additionally, the cumulative effect of costs at multiple life cycle stages can result in severe consequences to fitness when adapting to novel environments.