Abstract
In this study, we developed a nearly unbiased estimator of contemporary effective mother size in a population, which is based on a known maternal half-sibling relationship found within the same cohort. Our method allows for variance of the average number of offspring per mother (i.e., parental variation, such as age-specific fecundity) and variance of the number of offspring among mothers with identical reproductive potential (i.e., nonparental variation, such as family-correlated survivorship). We also developed estimators of the variance and coefficient of variation of contemporary effective mother size and qualitatively evaluated the performance of the estimators by running an individual-based model. Our results provide guidance for (i) a sample size to ensure the required accuracy and precision when the order of effective mother size is available and (ii) a degree of uncertainty regarding the estimated effective mother size when information about the size is unavailable. To the best of our knowledge, this is the first report to demonstrate the derivation of a nearly unbiased estimator of effective population size; however, its current application is limited to effective mother size and situations, in which the sample size is not particularly small and maternal half-sibling relationships can be detected without error. The results of this study demonstrate the usefulness of a sibship assignment method for estimating effective population size; in addition, they have the potential to greatly widen the scope of genetic monitoring, especially in the situation of small sample size.
Highlights
Contemporary effective population size, which is sensitive to ecological time-scale events, has become recognized as an informative parameter in a focus population, especially in the context of conservation biology and wildlife management (Luikart et al 2010)
This approach is based on the number of maternal HS (MHS) pairs found within the same cohort and on modeling that explicitly incorporates overdispersed reproduction, assuming that kinships are genetically detected without any error
We evaluated the performance of the estimators (N^e;1, ^v, and cbv) for a situation in which the number of mothers, N, and the combined effect of deviation from the Poisson, c, were unknown
Summary
Contemporary effective population size, which is sensitive to ecological time-scale events, has become recognized as an informative parameter in a focus population, especially in the context of conservation biology and wildlife management (Luikart et al 2010). We propose a new method for estimating the contemporary effective mother size in a population This approach is based on the number of maternal HS (MHS) pairs found within the same cohort and on modeling that explicitly incorporates overdispersed reproduction, assuming that kinships are genetically detected without any error. Other parameter values used in f(λ) are provided in Appendix A This definition is similar to the inbreeding effective population size (Nordborg and Krone 2002), as the probability of sharing an MHS relationship (π) is identical to the probability that two individuals share a mother in the previous breeding season. We did not consider the case of overdispersion (e.g., c > 1) because an estimation of an extra parameter is needed (see Kitada et al 2000) and the comparison of the case goes beyond the scope of this work
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