Effects of asexual reproduction on the neighborhood area of cyclical parthenogens

Abstract

The habitat occupied by a subpopulation and within which there is random mating is known as its ‘neighborhood area’. Neighborhood area is dependent on dispersal rates and organisms with low rates of dispersal are expected to have small neighborhood areas. In the absence of evolutionary forces, neighborhood areas under sexual reproduction will be constant in size as long as dispersal patterns do not change. This scenario differs when reproduction is by cyclical parthenogenesis since recombination and dispersal may occur in different generations. In general, dispersal distances increase with the number of parthenogenetic generations. We show that cyclical parthenogenesis increases neighborhood area which, concomitantly, decreases the potential for genetic subdivision. It is noteworthy, however, that the increase in neighborhood area is a decreasing function of the number of parthenogenetic generations.

This mechanism may have important implications for the population structure of planktonic rotifers living in a horizontally undifferentiated habitat. In such habitats organisms are effectively unrestricted in their lateral movements. Because rotifers typically have low dispersal rates spatial genetic discontinuities may develop that divide the population into genetically distinct subpopulations. Countering this tendency is the increased neighborhood area produced by dispersal during the parthenogenetic phase. Thus cyclical parthenogenesis in organisms like rotifers may have important and previously unreported effects on the population’s genetic structure.