Exploring the interplay between ecology and evolution of plant-herbivore interactions

Marc Johnson (April 4, 2011)

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(Co)evolutionary ecologists have long appreciated that ecology drives evolution, and that evolution ultimately shapes the ecological processes and patterns of populations and communities over long periods of time. However, it remains unclear how these two processes interact to affects the ecology, evolution and coevolution of communities over short timescales (e.g. one to several generations). We address this problem by studying interactions between a native plant (common evening primrose, Oenothera biennis) and the diverse assemblage of arthropods that interact with this plant. Using a combination of field experiments and theory we address two related hypotheses: First, we examine if herbivory drives rapid evolution of life-history and plant defensive traits within plant populations. Second, we test whether standing genetic variation and rapid evolution within plant populations shape the structure and dynamics of arthropod communities over one to several generations. In support of the first hypothesis, we find that herbivores impose natural selection on many heritable plant traits. Using an experimental evolution approach in the field, we show that this selection causes rapid evolution within plant populations over just three generations. In support of the second hypothesis, we find that standing genetic variation in evening primrose is an important ecological factor affecting the abundance of many herbivore populations, as well as the composition and diversity of over 100 arthropod species in the community. Using quantitative genetics theory and simulations, we show that the observed natural selection and evolution within evening primrose is expected to drive rapid ecological changes in arthropod abundance and diversity. Therefore in this plant-herbivore system, ecological and evolutionary dynamics interact over very short time scales and using an eco-evolutionary approach provides greater insight into the factors that affect both the ecology and evolution of ecosystems.