Plants, being at the base of most all food chains, are responsible for feeding the world.  In other words, plants provide the necessary energy to sustain all animal life either directly (through herbivory) or indirectly (because carnivores eat herbivores).  Over the eons, because of this tremendous pressure on plants, they have evolved a remarkable diversity of strategies to defend against being consumed. Theory, observations, and experiments have all implicated insect herbivores as key agents shaping the evolution of plant traits.  For example, plants possess a variety of heritable physical (e.g., thorns, spines) and chemical (e.g., toxins such as cyanide) traits that ward off herbivores.  Yet, despite some important demonstrations of how insect herbivores impose natural selection on plants, how plant populations respond to this selection in real time is virtually unknown.  Indeed, there have been no multigenerational studies that have followed the evolutionary trajectory of plant defenses. This data has been lacking, in part because of technical difficulties in tracking changes in the frequency of particular genes as plant populations evolve.  This project addressed this major gap in our scientific understanding with newly developed molecular techniques to fingerprint genotypes of a native wildflower, the common evening primrose plant (Oenothera biennis).

Because this project was conducted in field plots, the we gained new insight into both the general evolutionary process, and the specific traits that evolve in response to insect herbivore attack. Despite the importance of evolution in all of biology, few studies have demonstrated evolution in real time.  In particular, complex ecological interactions make it difficult to observe evolution in natural environments.  We definitively showed that insects drive evolutionary change in a native plant in the field, and that this outcome was only partly predictable by short-term studies.  Two stresses, insect pest attack and competition with weeds, were connected in a previously unknown way, and yet plants evolved to cope with both stresses. Because plants directly or indirectly feed all animals, demonstrating plant evolution in response to insects is a milestone in biology. 

In addition, broader impacts of this study included educational efforts directed to K-12 students, undergraduates, graduate students, and the general public.  Because the we examined evolutionary changes over relatively short time scales, engaging teachers and the general public was accomplished through outreach efforts and field trips.  By presenting “evolution in action,” the message of evolution by natural selection and plant-herbivore interactions was taken into the k-12 classroom via an established program at Cornell (Cornell Institute for Biology Teachers).  

Last Modified: 10/02/2012
Modified by: Anurag Agrawal