Competition for Pollinators between Simultaneously Flowering Species

Species with similar floral structures and with similar flowering periods and time of pollen and nectar presentation may compete for the service of the same pollinators. The outcome of interspecific competition was analyzed with a simple two-species model. The reproductive success of a species depends on its relative frequency. The minority species will be at a reproductive handicap because it suffers a larger percentage of heterospecific pollinations. The reproductive handicap of the minority species leads to a smaller standing crop in the next generation, which in turn enhances the minority disadvantage. This should lead to rapid exclusion of the minority species from the immediate flora. An increase in pollinator constancy to a given plant species retards the elimination of the rarer species. Pollinator preference for a given plant species may enhance or retard this progression depending on whether the minority species is preferred, since preference alters the effective frequencies of the two species. The minority disadvantage is reduced if the competing species have different habitat requirements or if they form large patches of regular size.