Clonal growth of Lithospermum caroliniense (Boraginaceae) in contrasting sand dune habitats

The occurrence of clonal growth of distylous Lithospermum caroliniense was investigated in a population in the Nebraska Sandhills, an area where sand dunes have been relatively stable for at least 1500-3000 yr, and compared t o a population occurring at the Indiana Dunes, an area of active sand dune formation. Spatial autocorrelation analysis indicated the occurrence of sig nificant clonal propagation of genetically based floral morphs at Arapaho P rairie, but not for the Indiana Dunes. Apparent clonal growth in the Sandhi lls population had no overall negative effect on pollen deposition or fecun dity relative to the Indiana population, although in some large clones the proportion of compatible pollen grains on stigmas was lower. Clonal growth may have occurred in the Sandhills population because of the greater age an d stability of the Nebraska Sandhills; infrequent establishment of seedling s permits detection of clonal growth using the spatial pattern of floral mo rphs. At the Indiana dunes, repeated cycles of dune formation provide condi tions favoring establishment of seedlings, and sand dune succession results in disappearance of L. caroliniense before the development of clones.