The consequences of demand-driven seed provisioning for sexual differences in reproductive investment in Thalictrum occidentale (Ranunculaceae)

Many iteroparous angiosperms may benefit from flexible annual resource allocation in response to variable reproductive opportunities induced by external conditions. If maximal reproductive investment is fixed, lack of reproductive sinks would cause resource redistribution to other sinks. Alternatively, reproductive investment may vary depending on the demand of reproductive sinks, changing source-sink relations. In particular, differential responses by males and females to the demands of flower and seed production may cause sexual dimorphism. We assess the occurrence of demand-driven seed allocation by females and its implications for sexual differences in reproductive investment, including the dynamics of mass and carbon allocation and the physiological cost of reproduction, for a dioecious, perennial herb, Thalictrum occidentale. We specifically quantified allocation responses to partial defoliation, which reduced current resource supply, and partial flower/fruit removal, which reduce...