Sweeney, B.W., and R.L. Vannote. 1982. Evolution 36:810–821.
Adult emergence of the mayfly Dolania americana is highly synchronous, occurring during a two week period in late May or early June. Larvae transform at the water surface into the winged adult just before sunrise during each day of this period. Adults mate, oviposit, and die in less than one hour. Adults are preyed on by both aerial (birds, bats, dragonflies) and aquatic (whirligig beetles) predators. The number of D. americana adults that emerge each day can vary by several orders of magnitude due to certain unknown factors. The percentage of adults that succumb to predators, aerial and/or aquatic, on a given day is inversely related to the total number of adults available as prey each day. This inverse relationship supports a predator satiation hypothesis concerning the adaptive significance of reproductive synchrony in this species. Thus, an individual adult D. americana maximizes its chance for successful reproduction by emerging synchronously with other members of its own cohort. Adult emergence data on several other mayfly species are presented to show that reproductive synchrony similar to D. americana is widespread among mayflies. An alternative hypothesis concerning reproductive synchrony among mayflies is that the adaptive significance lies mainly with increasing the probability of each sex finding a mate during the brief adult stage. This hypothesis is tested indirectly by comparing the degree of adult reproductive synchrony of three parthenogenetic species with the synchrony of bisexual species. Past workers have predicted that parthenogenetic species should exhibit a decay or loss in reproductive synchrony because selective processes concerning mating success are not applicable. It is shown that reproductive synchrony among parthenogenetic mayflies is equal to or greater than synchrony of bisexual species. Predator satiation is proposed as an alternative factor for future studies on the adaptive significance of reproductive synchrony in mayflies.