A resurrection experiment reveals reduced adaptive potential in a common agricultural weed

Abstract

Teaser TextAdaptive evolution is essential for populations facing rapid anthropogenic change, yet realized evolutionary responses often fall short of expectations. Using a resurrection experiment with Ipomoea purpurea, we reveal that the genetic covariance structure underlying pollination and mating-system traits has become more constraining over time. Traits involved in pollinator attraction evolved within a decade, but flowering phenology--critical for coping with climate-driven shifts--was hindered by increasingly restrictive genetic covariances. Our findings suggest that temporal changes in genetic constraints can substantially dampen adaptive potential, even when selection pressures are strong. Adaptive evolution is critical to population responses under accelerating anthropogenic global change. Although theory and some empirical work suggest that contemporary rates of environmental change can be met by equally rapid evolutionary shifts, mismatches between expected and realized evolution remain common in natural systems. Using a resurrection approach, we demonstrate that the structure of genetic covariances among pollination and mating-system traits in the common morning glory (Ipomoea purpurea) is increasingly constraining evolutionary trajectories. Pollinator-attracting traits evolved or became more favored on a rapid time scale of less than ten years, but genetic covariances between traits limited the adaptive rate and evolutionary trajectory of flowering phenology, a trait with widely recognized importance in adapting to climatic shifts. Our results show that changing patterns of genetic constraint can substantially reduce adaptive potential even when selection favors rapid trait evolution.