Format: ORAL

Jennifer M. Cruse-Sanders1, Jennifer N. Boyd2, Jill T. Anderson1, Carol Baskauf3, Jessica Bryzski4, Annie Lindsay3, Jared Odell2, Will Rogers1

1. University of Georgia, Athens, Georgia, USA 2. University of Tennessee at Chattanooga, Chattanooga, Tennessee, USA 3. Austin Peay State University, Clarksville, Tennessee, USA 4. Seton Hill University, Greensburg, Pennsylvania, USA

Environmental change, accelerated by anthropogenic activities, threatens many species and can be particularly challenging for rare plants with potentially limited capacity for migration and adaptation relative to more common species. Plant species differ dramatically in their prevalence in natural landscapes with some species characterized as rare due to restricted geographic distribution, low local abundance or habitat specialization. Several questions arise from these observed patterns, including ecoevolutionary causes and consequences of rarity. Our metaanalyses of population genetic diversity, fitness and functional traits in rare and common congeneric plant species compared 252 rare species and 267 common congeners. Patterns identified for rare species included reduced population genetic diversity and fertilization efficiency, inbreeding depression and depressed fitness among other traits. Our recent comparisons of phenotypic plasticity and genetic diversity between rare and common congeners collected from natural populations elucidate rarity and vulnerability of an endangered riparian plant, Pityopsis ruthii, compared to more common congener, P. graminifolia. Pityopsis ruthii (Asteraceae) is a narrowly endemic perennial herb that grows in rocky crevices within a short distance along the banks of two rivers in Tennessee, USA. Pityopsis graminifolia is widespread within wooded savannahs, open grasslands and roadsides across the southeastern USA. Genetic diversity across the range of both species was estimated at nine putatively neutral microsatellite loci. Results indicated that P. ruthii exhibited reduced genetic diversity relative to its more common congener. These results were compared with other population genetic studies of field collected congeneric pairs of rare and common perennial herbaceous species in the southeastern USA and evaluated along with other measures of fitness. Overall, rare species exhibited lower levels of genetic diversity and limited capacity to adapt or migrate in response to environmental change, highlighting potentially significant vulnerability to future change.