EFFECTS OF ASEXUAL REPRODUCTION ON THE NEIGHBORHOOD AREA OF CYCLICAL PARTHENOGENS

The habitat occupied by a subpopulation and within which there is rand om mating is known as its 'neighborhood area'. Neighborhood area is de pendent on dispersal rates and organisms with low rates of dispersal a re expected to have small neighborhood areas. In the absence of evolut ionary forces, neighborhood areas under sexual reproduction will be co nstant in size as long as dispersal patterns do not change. This scena rio differs when reproduction is by cyclical parthenogenesis since rec ombination and dispersal may occur in different generations. In genera l, dispersal distances increase with the number of parthenogenetic gen erations. We show that cyclical parthenogenesis increases neighborhood area which, concomitantly, decreases the potential for genetic subdiv ision. It is noteworthy, however, that the increase in neighborhood ar ea is a decreasing function of the number of parthenogenetic generatio ns. This mechanism may have important implications for the population structure of planktonic rotifers living in a horizontally undifferenti ated habitat. In such habitats organisms are effectively unrestricted in their lateral movements. Because rotifers typically have low disper sal rates spatial genetic discontinuities may develop that divide the population into genetically distinct subpopulations. Countering this t endency is the increased neighborhood area produced by dispersal durin g the parthenogenetic phase. Thus cyclical parthenogenesis in organism s like rotifers may have important and previously unreported effects o n the population's genetic structure.