Effects of sib-competition on female reproductive success in Salvia lutescens Koidz. var. crenata

Question: Does female reproductive success of a plant become saturated with an increase in seed production due to sib-competition? Organism: A perennial herb Salvia lutescens Koidz. var. crenata. Site of experiments: An experimental garden of Tohoku University, Sendai, northern Honshu, Japan. Methods: We transplanted 19 parents to the experimental garden after natural pollination. We monitored the survival and flower production of seedlings from those parents for 2 years. Results: The mean local sib-seedling density increased with an increase in the number of seedlings produced by their parent. The density of sib-seedlings at a distance of 0-1 cm from a focal seedling had negative effects on the survival of the focal seedling. As a result, there was no difference in the number of surviving seedlings between large and small parents in the 2 year period. However, the total number of flowers of the progeny produced by a parent increased linearly with an increase in the number of seeds produced by their parent. Furthermore, the number of flowers of a progeny increased with an increase in the number of seeds produced by its parent, which means that there is a positive relation between the quality of surviving progeny and the number of seeds of its parents. Conclusion: The female fitness gain curve becomes saturated with an increase in the size of its parent in terms of seedling establishment, but it increases without saturation in terms of flower production by progeny.