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Open Access Highly Accessed Research article

Drift by drift: effective population size is limited by advection

John P Wares1* and James M Pringle2

  • * Corresponding author: John P Wares

  • † Equal contributors

Author Affiliations

1 Department of Genetics, University of Georgia, Life Science Building, Athens, Georgia 30602, USA

2 Department of Earth Sciences, University of New Hampshire, Durham, New Hampshire 03824, USA

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BMC Evolutionary Biology 2008, 8:235  doi:10.1186/1471-2148-8-235

Published: 18 August 2008



Genetic estimates of effective population size often generate surprising results, including dramatically low ratios of effective population size to census size. This is particularly true for many marine species, and this effect has been associated with hypotheses of "sweepstakes" reproduction and selective hitchhiking.


Here we show that in advective environments such as oceans and rivers, the mean asymmetric transport of passively dispersed reproductive propagules will act to limit the effective population size in species with a drifting developmental stage. As advection increases, effective population size becomes decoupled from census size as the persistence of novel genetic lineages is restricted to those that arise in a small upstream portion of the species domain.


This result leads to predictions about the maintenance of diversity in advective systems, and complements the "sweepstakes" hypothesis and other hypotheses proposed to explain cases of low allelic diversity in species with high fecundity. We describe the spatial extent of the species domain in which novel allelic diversity will be retained, thus determining how large an appropriately placed marine reserve must be to allow the persistence of endemic allelic diversity.