Anna Palmé

Power for detecting genetic divergence: differences between statistical methods and marker loci

Information on statistical power is critical when planning investigations and evaluating empirical data, but actual power estimates are rarely presented in population genetic studies. We used computer simulations to assess and evaluate power when testing for genetic differentiation at multiple loci through combining test statistics or P values obtained by four different statistical approaches, viz. Pearsons chi‐square, the log‐likelihood ratio G‐test, Fishers exact test, and an FST‐based permutation test. Factors considered in the comparisons include the number of samples, their size, and the number and type of genetic marker loci. It is shown that power for detecting divergence may be substantial for frequently used sample sizes and sets of markers, also at quite low levels of differentiation. The choice of statistical method may be critical, though. For multi‐allelic loci such as microsatellites, combining exact P values using Fishers method is robust and generally provides a high resolving power. In contrast, for few‐allele loci (e.g. allozymes and single nucleotide polymorphisms) and when making pairwise sample comparisons, this approach may yield a remarkably low power. In such situations chi‐square typically represents a better alternative. The G‐test without Williamss correction frequently tends to provide an unduly high proportion of false significances, and results from this test should be interpreted with great care. Our results are not confined to population genetic analyses but applicable to contingency testing in general.

Spatial genetic structure of northern pike (Esox lucius) in the Baltic Sea.

The genetic relationships among 337 northern pike (Esox lucius) collected from the coastal zone of the central Baltic region and the Finnish islands of Åland were analysed using five microsatellite loci. Spatial structure was delineated using both traditional F‐statistics and individually based approaches including spatial autocorrelation analysis. Our results indicate that the observed genotypic distribution is incompatible with that of a single, panmictic population. Isolation by distance appears important for shaping the genetic structure of pike in this region resulting in a largely continuous genetic change over the study area. Spatial autocorrelation analysis (Morans I) of individual pairwise genotypic data show significant positive genetic correlation among pike collected within geographical distances of less than c. 100–150 km (genetic patch size). We suggest that the genetic patch size may be used as a preliminary basis for identifying management units for pike in the Baltic Sea.

Potentials for monitoring gene level biodiversity : using Sweden as an example

Programs for monitoring biological diversity over time are needed to detect changes that can constitute threats to biological resources. The convention on biological diversity regards effective monitoring as necessary to halt the ongoing erosion of biological variation, and such programs at the ecosystem and species levels are enforced in several countries. However, at the level of genetic biodiversity, little has been accomplished, and monitoring programs need to be developed. We define “conservation genetic monitoring” to imply the systematic, temporal study of genetic variation within particular species/populations with the aim to detect changes that indicate compromise or loss of such diversity. We also (i) identify basic starting points for conservation genetic monitoring, (ii) review the availability of such information using Sweden as an example, (iii) suggest categories of species for pilot monitoring programs, and (iv) identify some scientific and logistic issues that need to be addressed in the context of conservation genetic monitoring. We suggest that such programs are particularly warranted for species subject to large scale enhancement and harvest—operations that are known to potentially alter the genetic composition and reduce the variability of populations.

Release of alien populations in Sweden

Abstract Introduction of alien species is a major threat to biological diversity. Although public attention typically focuses on the species level, guidelines from the Convention of Biological Diversity define alien species to include entities below species level. This inclusion recognizes that release of nonlocal populations of native species may also result in negative effects on biodiversity. In practice, little is known about the extent, degree of establishment, or the effects on natural gene pools of such releases. Existing information on the releases in Sweden shows that alien populations are spread to a great extent. The most commonly released species include brown trout, Atlantic salmon, Arctic char, common whitefish, Scots pine, Norway spruce, mallard duck, gray partridge, and pheasant. Although millions of forest trees, fish, and birds are released annually, poor documentation makes the geographic and genetic origin of these populations, as well as the sites where they have been released, largely unclear. We provide recommendations for urgently needed first steps relating to the risks and problems associated with release of alien populations.

Census (NC) and genetically effective (Ne) population size in a lake-resident population of brown trout Salmo trutta

Census (N(C)) and effective population size (N(e)) were estimated for a lake-resident population of brown trout Salmo trutta as 576 and 63, respectively. The point estimate of the ratio of effective to census population size (N(e):N(C)) for this population is 0.11 with a range of 0.06-0.26, suggesting that N(e):N(C) ratio for lake-resident populations agree more with estimates for fishes with anadromous life histories than the small ratios observed in many marine fishes.

Conservation genetics without knowing what to conserve: the case of the Baltic harbour porpoise Phocoena phocoena

Effective conservation requires that arguments for identifying units for preservation and management are based on scientifically sound information. There is a strong conservation concern for the ha ...

The genetic structure of harbour porpoises in the Baltic Sea relative to adjacent waters remains to be clarified: a reply to Berggren & Wang

The genetic structure of harbour porpoise in the Baltic Sea relative to adjacent waters remains to be clarified: a reply to Berggren & Wang