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Numerous empirical studies have reported lack of migration-drift equilibrium in wild populations. Determining the causes of nonequilibrium population structure is challenging because different evolutionary processes acting at a variety of spatiotemporal scales can produce similar patterns. Studies of contemporary populations in northern latitudes suggest that nonequilibrium population structure is probably caused by recent colonization of the region after the last Pleistocene ice age ended ~13 000 years ago. The chum salmon's ( Oncorhynchus keta) range was fragmented by dramatic environmental changes during the Pleistocene. We investigated the population structure of chum salmon on the North Alaska Peninsula ( NAP) and, using both empirical data and simulations, evaluated the effects of colonization timing and founder population heterogeneity on patterns of genetic differentiation. We screened 161 single nucleotide polymorphisms and found evidence of nonequilibrium population structure when the slope of the isolation-by-distance relationship was examined at incremental spatial scales. In addition, simulations suggested that this pattern closely matched models of recent colonization of the NAP by secondary contact. Our results agree with geological and archaeological data indicating that the NAP was a dynamic landscape that may have been more recently colonized than during the last deglaciation because of dramatic changes in coastal hydrology over the last several thousand years. [ABSTRACT FROM AUTHOR]

An introduction to articles published within the issue is presented, including an approach to discover single-nucleotide polymorphisms (SNP) for population genetics study of the ringed seal Pusa hispida hispida, the growth and reproduction in genes of Atlantic cod Gadus morhua, and the use of Illumina GAII technology to map black cottonwood Populas trichocarpa transcriptome data to the completed genome.

Genetic diversity and population structure of snapper (Pagrus auratus, Bloch and Schneider), a coastal demersal sparid fish, were determined using six nuclear microsatellite loci and SSCP (single strand conformational polymorphism) analysis of themitochondrial (mt) DNA D-loop in samples collected across the range of the species in New Zealand. Microsatellite data showed similar results to allozyme data collected in the late 1970s that found differentiation between the north-east and southern populations. In addition, an isolated population of snapper in Tasman Bay was identified. The two data sets provide evidence for the temporal stability of the genetic population structure of snapper over 22 years, with differentiation over relatively small spatial scales separated by oceanographic boundaries rather than isolation by distance. In contrast to nuclear markers, mtDNA did not reveal any significant genetic heterogeneity among samples. [ABSTRACT FROM AUTHOR]