Sustainability of dioecious and hermaphrodite populations on a lattice.

Sexual reproduction may be divided into two main categories: hermaphroditism and dioecy (Botany)/gonochorism (Zoology). Simultaneous hermaphrodites can function in both male and female roles whereas a dioecious/gonochorist population consists of distinct male and female individuals. Mean-field calculations, which ignore spatial aspects, suggest that self-incompatible hermaphrodites should have a twofold advantage over dioecious population when reproduction is limited by mating encounters. By use of stochastic spatial simulations we demonstrate that hermaphroditism has an even greater advantage when local interactions are considered. This result provides further support for the observation that hermaphroditism is associated with sedentary species, such as plants and animals with poor mate search efficiency. We also investigate the finite size effects associated with the well-known quadratic contact process.