Biodiversity continues to decline at both the species and genetic levels due to the impacts of humans on the environment. However, scientists currently have little knowledge of how declines in genetic diversity within species may affect the functioning of complex ecological communities. Plants posses many traits involved in defenses against herbivores, and these traits are often highly variable within populations. We will use two such traits in black mustard (Brassica nigra) to investigate how genetic variation in traits may affect the interactions between different plant species. In our experiments, we will manipulate the presence or absence of several groups of herbivores in order to determine how they affect the competitive outcome between plant species. We will also explore how this competitive outcome is altered by the genetic variation in defensive traits in B. nigra. Additionally, genetic variation is the fuel for natural selection. Therefore, we will investigate how this genetic variation is itself influenced by the ecological community, such as the diversity of plant or herbivore species, through altered patterns of natural selection. These findings on the interplay between genetic variation within a species and interactions between species in complex ecological communities will have important insights into the management of genetic diversity in both natural and agricultural systems. Understanding what role genetic variation may play in the interactions within complex communities is vital if we are to make accurate predictions about how communities will change as genetic diversity continues to decline.
