Morphology, reproductive strategy, and genetic diversity of the rare Atlantic coastal plain flower, Sabatia Kennedyana (Fern): Variation across the species range and in anthropogenically disturbed habitat

Morphology and genetics of the threatened plant, Sabatia kennedyana , were examined in Nova Scotia, Massachusetts and North Carolina. From north to south, sexual characters increased in size and number, but relative investment in asexual traits was least in Massachusetts. For all locations, nuclear-DNA polymorphism was high for rare plants. Much higher chloroplast diversity in Nova Scotia than the U.S. demonstrates that northern populations harbor ancestral diversity. Nova Scotian chloroplast data also revealed isolation-by-distance, evidence of long-term stability and indication that these populations did not result from northward post-glacier range expansion. Instead, plants existed within glacial refugia near Nova Scotia and Massachusetts, while Carolinian populations resulted from expansion. Within Nova Scotia, comparisons of undisturbed versus anthropogenically-disturbed sites suggested that variation in morphological and genetic polymorphism estimates were not influenced by disturbance. However, regression slopes of relatedness against distance revealed that intra-population spatial genetic structuring was deteriorating in disturbed shoreline habitats.