PS 22-49 - Demography modelling of Echinacea laevigata, a rare endemic, leads to management and monitory best practices

Abstract: Conservation of rare endemic plants is especially important for maintaining regional diversity and in reducing the impacts of homogenization. Research on rare endemic plants often focuses on mechanisms related to reproductive biology such as genetic variability and pollen limitation. Less well studied is how other life history traits impact reproduction. We examined the effect of plant size on reproduction and other demographic factors in a federally-listed, threatened species, smooth coneflower (Echinacea laevigata), which is a narrow endemic in forest glade habitats from Georgia to Virginia, USA. Our goal was to use demographic attributes to determine impacts on rarity and best monitoring and management practices for conservation. We tagged plants and recorded the size and reproductive status of all individuals in five plots that represented five subpopulations at a site in Montgomery County, Virginia, USA from 2014 to 2017. We used Integral Projection Modelling to assess key aspects of the life cycle, estimated how year to year changes in size and reproductive status impacted population growth, survival, and future reproduction. We found that a few plants reproduced each year (range: 1.2-18.2%). Plant size in one year was a strong predictor of probability of survival, reproduction, and growth, the next year. We identified a population level cost of reproduction that reduced lambda by 2%. Reproductive plants experienced additional costs in survival, growth, and future reproduction. Smooth coneflower life history attributes were more indicative of herbaceous perennials adapted to forests than those adapted to grasslands. This work demonstrates that plant size has a strong impact on reproductive dynamics and reproduction can incur a cost to future population dynamics. We also determined that the number of flowering plants was relatively adequate for monitoring populations even when few plants flowered. Lastly, management of this species should focus on preserving environmental conditions that promote plant growth such as preventing woody encroachment.