PLANT SIZE AND SPATIAL PATTERN IN A NATURAL-POPULATION OF MYOSOTIS-MICRANTHA

We examined spatial distributions and plant sizes along a transect thr ough a natural population of a winter annual, Myosotis micrantha. A si ze hierarchy existed, as indicated by high values of Gini coefficients of inequality for plant mass and correlated measures. Plants with no immediate conspecific neighbors were larger than plants with one or mo re near neighbors, suggesting that competition from near neighbors dep ressed plant size. However, there was strong positive spatial autocorr elation in plant size: large plants were associated with large neighbo rs and small ones with small neighbors. Plant size was also positively correlated with the combined biomass of near neighbors. The populatio n formed a two-phase mosaic of patches of relatively large plants alte rnating with patches of smaller plants. The data suggest that individu al plants compete with conspecifics, but the effects of competition ar e symmetrical. The most likely explanations for this spatially structu red size hierarchy are variation in plant density, patchy distribution of resources, or a combination of the two.