Drift by drift: effective population size is limited by advection.

John P Wares,James M Pringle

doi:10.1186/1471-2148-8-235

John P Wares, James M Pringle

Open Access

https://doi.org/10.1186/1471-2148-8-235

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Journal: BMC ecology	Publication Date: Jan 1, 2008
Citations: 77	License type: cc-by

Affiliation: University of Georgia, University of New Hampshire

Abstract

BackgroundGenetic 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.ResultsHere 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.ConclusionThis 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.

Highlights

Genetic estimates of effective population size often generate surprising results, including dramatically low ratios of effective population size to census size
We find that physical drift in the ocean or in a stream supplements genetic drift as a mechanism for losing genetic diversity, and asymmetric dispersal – where larvae
While a species' fecundity may be associated with dispersal potential in marine organisms [42], fecundity alone is not predictive of Ne/N [43] – suggesting that other factors, including advection, may be involved in the relationship between Ne and actual census size

Summary

Introduction

Genetic estimates of effective population size often generate surprising results, including dramatically low ratios of effective population size to census size. This is true for many marine species, and this effect has been associated with hypotheses of "sweepstakes" reproduction and selective hitchhiking. Research has shown many cases in which Ne as estimated from genetic markers is several orders of magnitude lower than would be predicted based on census size (N) and a species' reproductive traits [9], and it has been suggested that extremely high variance in reproductive success (the "sweepstakes" models of [1,6]) or genomewide selective sweeps [10,11] may be causal mechanisms. We find that physical drift in the ocean or in a stream supplements genetic drift as a mechanism for losing genetic diversity, and asymmetric dispersal – where larvae (page number not for citation purposes)

Methods

Discussion

Conclusion