PLANT OUTLIERS - AN ECOGENETIC PERSPECTIVE

Members of colonial plant species often occur as scattered individuals well beyond the borders of local populations. The ecological and gene tical importance of these outliers to local populations and to the spe cies as a whole have not been considered. A review of the reproductive biology of outliers and of sparse plants in general indicates that th ey produce fewer seeds per flower than plants within populations. Neve rtheless, they successfully interbreed over large distances. I propose that outliers form large, diffuse assemblages of interbreeding plants that may fill the gaps between some local populations. These outlier assemblages may be prime sources of extraneous pollen and seeds, retar d the divergence of local populations between which they reside, and f orm the nuclei for new populations. Outliers may receive more or less pest pressure than plants within populations. They serve as interpopul ation bridges for pathogens and herbivores.