P L Workman

Bio: P L Workman is an academic researcher. The author has contributed to research in topics: Genotype & Population. The author has an hindex of 1, co-authored 1 publications receiving 1061 citations.

Estimating F-statistics for the analysis of population structure.

Abstract: This journal frequently contains papers that report values of F-statistics estimated from genetic data collected from several populations. These parameters, FST, FIT, and FIS, were introduced by Wright (1951), and offer a convenient means of summarizing population structure. While there is some disagreement about the interpretation of the quantities, there is considerably more disagreement on the method of evaluating them. Different authors make different assumptions about sample sizes or numbers of populations and handle the difficulties of multiple alleles and unequal sample sizes in different ways. Wright himself, for example, did not consider the effects of finite sample size. The purpose of this discussion is to offer some unity to various estimation formulae and to point out that correlations of genes in structured populations, with which F-statistics are concerned, are expressed very conveniently with a set of parameters treated by Cockerham (1 969, 1973). We start with the parameters and construct appropriate estimators for them, rather than beginning the discussion with various data functions. The extension of Cockerham's work to multiple alleles and loci will be made explicit, and the use of jackknife procedures for estimating variances will be advocated. All of this may be regarded as an extension of a recent treatment of estimating the coancestry coefficient to serve as a mea-

Separating the wheat from the chaff: patterns of genetic differentiation in high gene flow species

Abstract: In many marine species, high levels of gene flow ensure that the genetic signal from population differentiation is weak. As a consequence, various errors associated with estimating population genetic parameters that might normally be safely Ignored assume a relatively greater importance. This fact has important implications for the use of genetic data to address two common questions in fishery conservation and management: (1) How many stocks of a given species are there? and (2) How much gene flow occurs among stocks? This article discusses strategies to maximize the signal:nolse ratio in genetic studies of marine species and suggests a quantitative method to correct for bias due to a common sampling problem. For many marine species, however, genetic methods alone cannot fully resolve these key management questions because the amount of migration necessary to eliminate most genetic evidence of stock structure (only a handful of Individuals per generation) will generally be Inconsequential as a force for rebuilding depleted populations on a time scale of interest to humans. These limitations emphasize the importance of understanding the biology and life history of the target speciesfirst, to guide design of the sampling program, and second, so that additional information can be used to supplement Indirect estimates of migration rates based on genetic data.