Deviation from idealized population | Predicted effect onN_{e}/N (with respect toidealized population) | Observation or statistical test | Hypothesized effect on observed N_{e}/N? |
---|---|---|---|

Fluctuating population size | Decrease | N (1987) ≈ N (1998); temporal method N_{e} ≈ coalescent method N_{e} | Small |

Biased sex ratio | Decrease | Sex ratio does not deviate from 1:1 (P = 0.52; t-test) | Small |

Nondiscrete (i.e., overlapping) generations | Increase | Correction increases N_{e} by factor of 4.81 | Small |

Population structure (migration-drift equilibrium with local inbreeding) | Decrease | N_{e}/N = 0.96 when F-statistics were substituted into equilibrium models | Small |

Metapopulation structure (with variance in productivity among demes) | Decrease | See text | Large |

Variance in reproductive success among individuals | Decrease | P = 0.00007 required to solve for observed N_{e}/N; unrealistically small | Small |

Variance in productivity among demes | Decrease | P = 0.058 required to solve for observed N_{e}/N, provided that variance in productivity is equal to variance in individual reproductive success | Large |