Format: ORAL

Jennifer N. Boyd1, Jenny Cruse-Sanders2, Jill T. Anderson3, Carol Baskauf4, Jessica Bryzski5, Annie Lindsay4, Jared Odell1, Will Rodgers2

1. Department of Biology, Geology, and Environmental Science, University of Tennessee at Chattanooga, Chattanooga, Tennessee, USA 2. State Botanical Garden of Georgia, University of Georgia, Athens, Georgia, USA 3. Department of Biology, Austin Peay State University, Clarksville, Tennessee, USA 4. Department of Plant Genetics, Odum School of Ecology, University of Georgia, Athens, Georgia, USA 5. Department of Biology, Seton Hill University, Greensburg, Pennsylvania, USA

The enduring question of why some species are rare while others are common has important implications for the conservation of rare species and overall biodiversity. In the context of both current constraints to their ranges and their responses to rapid rates of contemporary environmental change, rare species can be limited in their capacities to adapt or migrate due to low genetic diversity and/or fitness as is suggested by previous research and our recent meta-analytic work. While the ability of rare species to acclimate also could influence their current rarity and responses to environmental change, this capacity has been relatively underexplored in rare species. To compare the capacity of rare versus common species to acclimate, we investigated the phenotypic plasticity of individuals of rareBoechera perstellata(Brauns rockcress) and Pityopsis ruthii (Ruths golden aster) with their widespreadcongeners B. laevigataand P. graminifolia propagated from seed collected from several populations throughout their ranges in controlled-environment growth chamber experiments. In contrast to our predictions that rarity would be associated with acclimatory constraints, both rare species exhibited phenotypic plasticity in response to changes in light and water availability that were comparable or greater than that exhibited by their common congeners. However, rare species were comparably constrained in their ability to acclimate to temperature. Overall, our findings elucidate the narrow ranges and habitat specificities of these rare endemic species of the southeastern USA and their vulnerability to future environmental change. To further explore the potential role of acclimatory constraints in species rarity we offer recommendations for field-based transplant experiments of endemic rare species such as B. perstellata and P. ruthii beyond their natural ranges.