Altruism or selfishness: floral behaviour based on genetic relatedness with neighbouring plants.

Kin recognition in plants may lead to plastic changes in their behaviour, such as altering their floral display size. In this study, we conducted evolutionary simulations of the 2 floral tactics utilized by plants depending on the genetic relatedness of their neighbouring plants. We found that the evolutionary consequences of the floral display size in plants can be classified into 4 types, based on whether the floral display size increased or decreased in comparison with the case of plants disabled of kin recognition. As a typical result, the plants that grew with kin behaved altruistically by increasing their floral display size, whereas those that coexisted with strangers behaved selfishly by reducing their floral display size, as is observed in the field. The kin recognition and resultant evolution of the floral display size had a spillover effect on the population scale. Kin recognition generally increased the intraspecific variation in the floral display size and seed production and decreased the genetic diversity of plant populations.