Closing the Evolutionary Gap: measuring genetic diversity and habitat resilience in support of plant conservation and preservation E. Esselman Rare plant conservation plays a vital and important role in the evolutionary development of ecological habitats. The extinction of plant species creates an evolutionary gap or empty space in the evolutionary process. Species extinction removes not only the disappearing species but also the possible evolutionary impact of that species on others. The three studies included in this session used a variety of methods to ascertain the health and resiliency of disturbed habitats or endangered species. These studies examined genetic diversity among selected plant populations, studied various plant species for evidence of hybridization, and examined the floristic quality of a previously disturbed field in Illinois. Hybridization can contribute to the extinction of rare species by inhibiting its ability to reproduce. Genetic diversity is a measure of how well a species can adapt and evolve to changes in the environment. The studies separately used ISSR molecular markers and the Floristic Quality Index to determine these effects.