Population Dynamics of Leedy's Roseroot Using Molecular Marker Data

The dynamics of small, natural plant populations are not well understood, and long-term studies of them are rare. Leedy’s roseroot (Rhodiola integrifolia ssp. leedyi) is a rare plant species that is restricted to cool, moist, cliff habitats. It has six known populations, two in New York, and four in Minnesota. We are investigating Leedy’s roseroot’s population characteristics using both microsatellite markers and field-based demographic data from ten of the last 14 years. With these data we have estimated effective to actual population size ratios (N_e/N) for five of the populations. In 2010 we collected census data for the Minnesota populations, leaf samples from 24 to 50 individuals from three of the Minnesota populations, and leaf samples from three and 48 individuals from the New York populations. We have successfully extracted DNA, generated microsatellite markers at eight loci for 142 individuals, and used the program OneSamp to estimate N_e from our microsatellite data. Preliminary results show that five of the eight primers are polymorphic. The multi year field-based estimates of N_e/N have fluctuated dramatically, ranging from approximately zero to 0.72, and the molecular N_e/N estimates range from 0.12 to 0.57. The microsatellite marker data will also be useful for revealing genetic divergence and gene flow among populations. Our results help the managers of Leedy’s roseroot populations set their conservation priorities, they establish a baseline for comparison with future Leedy’s roseroot population dynamics, and they provide a case study of the dynamics of small populations of a rare plant.