COSTS OF PRODUCING CLONAL OFFSPRING AND THE EFFECTS OF PLANT SIZE ON POPULATION-DYNAMICS OF THE WOODLAND HERB UVULARIA-PERFOLIATA (LILIACEAE)

1 Clonal propagation is an important means of population increase in m any temperate woodland herbs. The production of vegetative propagules is often limited by the patchy availability of light in the understore y. A field study and a greenhouse experiment investigated the patterns of clonal growth under different light conditions in the shade-tolera nt herb species Uvularia perfoliata. 2 In the field study, vegetative propagation in four populations, two growing under closed canopy and t wo in gaps, was compared. A significantly higher proportion of plants in gap populations produced clonal offspring than plants from closed-c anopy populations, possibly because of higher light availability. The cost to plants of producing clonal offspring was seen as a significant ly lower probability of survival and reduced capacity of the survivors for future clonal propagation. 3 In the greenhouse experiment, offspr ing ramets of three size classes (small, medium and large) from both c losed-canopy and gap sites were grown under low and high light conditi ons. Plants grown from larger ramets from both sites produced more clo nal offspring and invested more biomass in reserves and clonal propaga tion than plants grown from small ramets. Counter to our expectations, plants did not produce more clonal offspring in high light than in lo w light. However, plants invested more biomass in clonal propagation i n high light, especially if they were grown from larger ramets. The on ly evidence for adaptation to conditions at the site of origin was tha t increased reserve allocation in high light was more marked in plants from gaps. The effect of ramet size on performance was stronger than the effect of light level or site of origin of plants, although plants grown from larger ramets also benefited more from high light. 4 Unles s plants have sufficient biomass and morphological capacity their posi tive response to high light is delayed. Although clonal propagation is always costly, costs are less severe in gaps where plants have the po tential to produce clonal offspring repeatedly in consecutive seasons. Our results also show that plant size has a potential long-term effec t on population dynamics of this species, with the advantages of large size expressed over several generations.