Size dependency of sexual reproduction and of clonal growth in two perennial plants

Abstract

We compared the size dependency of sexual reproduction and clonal growth in two clonal perennials that inhabit old fields, Aster lanceolatus and Solidago canadensis. In both species there was a threshold size required for sexual reproduction to occur, and above that threshold reproductive output increased linearly with vegetative mass. Biomass allocated to clonal growth was also highly correlated with vegetative mass in both species, but there was no evidence of a threshold size for clonal growth. The absence of a clear size threshold for clonal growth emphasizes the similarity between clonal growth (vegetative reproduction) by rhizomes and growth of other vegetative parts, as opposed to sexual reproductive allocation. In both species there were differences in the allocation patterns of plants derived from seeds and those derived from rhizomes. Although seed- and rhizome-derived plants did not differ in phenology and size, the latter allocated more biomass to sexual reproduction and clonal growth in both species. Key words: clonal growth, size dependency, reproduction, Aster lanceolatus, Solidago canadensis, size threshold.