A two-year life history cycle model for autumn and spring seedling coexistence in an annual plant—An example of intraspecific niche differentiation

Abstract

Intraspecific variation plays an important role in species coexistence and community assembly. In this paper, we propose a model for the coexistence of autumn and spring seedlings within one species of annual plants—intraspecific niche complementarity of a two-year life history cycle. There is an unsynchronized germination behavior in some species exhibiting a two-year life history cycle in which one population produces coexisting autumn and spring seedlings. Our soil seed bank coexistence model predicts that the optimal autumn germination fraction must maximize the harmonic mean of the number of seeds that germinate in two different seasons. Moreover, we extended classic annual soil seed bank dynamic models using evolutionary stability and density dependent theory. Our model can be applied not only to winter or spring annuals but also to autumn- and spring-seedling plants coexisting in one population. Under an evolutionarily stable coexistence of autumn- and spring-seedling plants within one population, our model suggests that the greater the ratio of seeds produced by a plant germinated in spring relative to the seeds germinated in autumn, the greater is the germination fraction in autumn. The germination behaviors of plants with unsynchronized two-year life history cycles are a new example of intraspecific niche differentiation in annuals.