The use of genetic markers to study ecosystem health and function is a burgeoning line of scientific research. Studying the distribution and change in allele and gene frequencies helps us understand the how populations are impacted by environmental changes. What factors drive evolutionary change or stasis in a population? How much genetic variation exists within a population? What is the amount or pattern of genetic variation within and among populations? By asking these questions within the context of ecology and ecological significance, SERC scientists study how adaptation, speciation and population subdivision and structure are affected by excess nutrient inputs, invasive species, mercury methylation and factors related to climate change.