How do sessile dioecious species cope with their males?

Area of Science:

• Ecology
• Evolutionary Biology
• Plant Reproduction

Background:

• Dioecious plants, with separate male and female individuals, may experience a 'seed-shadow handicap' limiting seed dispersal compared to hermaphrodites.
• This handicap potentially reduces the number of local patches colonized by seeds in dioecious populations.

Purpose of the Study:

• To assess the spatially mediated cost of the seed-shadow handicap using an analytical model.
• To evaluate invasion criteria between dioecious and hermaphrodite species with identical demographic parameters but differing fecundity.

Main Methods:

• Development of an analytical model incorporating lottery-based recruitment and dispersal stochasticity.
• Analysis of reciprocal invasion scenarios between dioecious and hermaphrodite species.

Main Results:

• The seed-shadow handicap can be overcome by sufficiently high dispersal or survival rates, facilitated by dispersal stochasticity creating empty patches.
• Reciprocal invasion between species differing only in fecundity was not possible.
• Low fecundity and aggregated seed distribution amplify dispersal stochasticity and the benefits of low mortality for dioecy.

Conclusions:

• Dispersal stochasticity and high dispersal/survival rates are key factors mitigating the seed-shadow handicap in dioecious plants.
• The relative success of dioecy versus hermaphroditism is influenced by fecundity, mortality, dispersal rates, and seed distribution patterns.