EVOLUTION OF SEED DISPERSAL AND RECRUITMENT IN CLONAL PLANTS

Previous studies have shown that seedling recruitment occurs sporadically in the population dynamics of many clonal plant species, and that a low rate of seed recruitment is associated with high seed dispersal ability. The aim of the present study was to examine these features of clonal plant life histories from an evolutionary point of view. No significant relationships were detected between recruitment pattern, seed size, seed dispersal, and possession of seed bank. However, a tendency was found that species characterized by a persistent seed bank, lack of seed dispersal traits, or repeated seedling recruitment, possess smaller seeds than do other clonal species. Distributions of fruit and life form characters in 35 genera of clonal plants indicated that traits affecting seed dispersal generally are evolutionarily ancestral in relation to the clonal growth form possessed by extant species. This sequence was found in 32 genera whereas the opposite sequence was found in 3 genera. Thus, seed dispersal features have not evolved as a result of recruitment difficulties in the vicinity of adult plants possessing the extant clonal life form. It is suggested that clonal propagation may have been augmented in lineages where long distance seed dispersal predominates, in order to make genet fitness less dependent on local dispersal by seed. A low rate of seedling recruitment within patches of adult plants is the expected outcome of this scenario. Finally. some aspects of how long term environmental changes may affect seedling recruitment in clonal plants are briefly discussed.