Fig. 2: Life cycle model of annual plants.
Illustration of the life cycle modelled for a dioecious annual plant population. a, Plants to seeds: an ‘effective ovule’ is defined as an ovule capable of fertilization and subsequent seed development and an ‘effective pollen grain’ as a pollen grain that can successfully reach a fertile female plant via wind and germinate. Each fertile female plant produces a Poisson-distributed number of effective ovules with baseline mean nbo. Each fertile male plant produces a Poisson-distributed number of effective pollen grains with baseline mean np(t), which is proportional to the current number of fertile females. Effective pollen grains are randomly distributed among fertile female plants, and fertilized ovules develop into seeds. After reproduction, all plants are removed from the population. b,c, Into and out of the seed bank: age-dependent seed mortality and germination. A seed survives its first year at rate d, after which survival declines with seed age, such that a seed of age a survives at rate d/aq, where q modulates age-dependent mortality. Similarly, germination occurs initially at rate b and declines with seed age, such that a seed of age a germinates at rate b/am, where m modulates age-dependent germination. d, Seed to plants: seedling competition. Germinated seeds become seedlings, which experience density-dependent competition before becoming adult plants. Each seedling at year t survives to adulthood with probability \(c(t)=\,\min (\frac{K}{{N}_{{\rm{sdl}}}(t)},1)\), where Nsdl(t) is the current number of seedlings, and K is the carrying capacity.
