Evolution of large flowers and associated specialized pollination mechanisms may increase the genetic relatedness of seeds within multi-ovulate ovaries by pollination of all ovules by one pollen parent, minimizing effects of competition among developing seeds through kin selection. Using phylogenetically independent trait data, Bawa et al. show strong correlated evolution between flower size and seed number.
Angiosperms seem to fall into two categories: large flowers with specialized pollinators and many seeded fruits, illustrated by the stinking iris, Iris foetidissima (Iridaceae), and small flowers pollinated by generalist insects or wind and single or few seeded fruits, illustrated by the false Solomon’s seal, Maianthemum racemosum (Asparagaceae).
Bawa, K. S., Ingty, T., Revell, L. J., & Shivaprakash, K. N. (2018). Correlated evolution of flower size and seed number in flowering plants (monocotyledons). Annals of Botany, 123(1), 181–190. https://doi.org/10.1093/aob/mcy154