The fragmentation of populations is an increasingly important problem in the conservation of endangered species. Under these conditions, rare migration events may have important effects for the rescue of small and inbred populations. However, the relevance of such migration events to genetically depauperate natural populations is not supported by empirical data. We show here that the genetic diversity of the severely bottlenecked and geographically isolated Scandinavian population of grey wolves (Canis lupus), founded by only two individuals, was recovered by the arrival of a single immigrant. Before the arrival of this immigrant, for several generations the population comprised only a single breeding pack, necessarily involving matings between close relatives and resulting in a subsequent decline in individual heterozygosity. With the arrival of just a single immigrant, there is evidence of increased heterozygosity, signi cant outbreeding (inbreeding avoidance), a rapid spread of new alleles and exponential population growth. Our results imply that even rare interpopulation migration can lead to the rescue and recovery of isolated and endangered natural populations.

European hedgehogs, Erinaceus europaeus and E. concolor , are among the many European plant and animal taxa that have been subjected to cyclical restriction to glacial refugia and interglacial expansion. An analysis of 95 mitotypes, comprising partial cytochrome b and control region sequences, shows deep divergence between the two hedgehog species. Three europaeus and two concolor clades are clearly identified and are consistent with previously identified refugia for Europe: the Iberian peninsula, Italy, and the Balkans. The degree of mitochondrial divergence among these clades suggests pre-Pleistocene separation of the refugial populations. In contrast, analysis of two nuclear introns clearly separates the two concolor clades, as in the mitochondrial data, but cannot discriminate the three europaeus clades. This discrepancy between nuclear and mitochondrial data is attributed to historical differences in the refugial population size of europaeus and concolor . The geographical distribution of mitotypes is analysed using nested clade analysis. This method, by including unobserved ('missing') mitotypes, can identify mitotype groupings that remain undetected in conventional analyses. However, the application of nested clade analysis to the study of refugial populations may be hampered by such factors as the loss of haplotypes from the refugial areas by repeated contractions of the population and the recent time scale of colonization relative to mutation rate.

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Single nucleotide polymorphisms (SNPs) have the potential to become the genetic marker of choice in studies of the ecology and conservation of natural populations because of their capacity to access variability across the genome. In this study, we provide one of the first demonstrations of SNP discovery in a wild population in order to address typical issues of importance in ecology and conservation in the recolonized Scandinavian and neighbouring Finnish wolf Canis lupus populations. Using end sequence from BAC (bacterial artificial chromosome) clones specific for dogs, we designed assays for 24 SNP loci, 20 sites of which had previously been shown to be polymorphic in domestic dogs and four sites were newly identified as polymorphic in wolves. Of the 24 assayed loci, 22 SNPs were found to be variable within the Scandinavian population and, importantly, these were able to distinguish individual wolves from one another (unbiased probability of identity of 4.33 x 10(-8)), providing equivalent results to that derived from 12 variable microsatellites genotyped in the same population. An assignment test shows differentiation between the Scandinavian and neighbouring Finnish wolf populations, although not all known immigrants are accurately identified. An exploration of the misclassification rates in the identification of relationships shows that neither 22 SNP nor 20 microsatellite loci are able to discriminate across single order relationships. Despite the remaining obstacle of SNP discovery in nonmodel organisms, the use of SNPs in ecological and conservation studies is encouraged by the advent of large scale screening methods. Furthermore, the ability to amplify extremely small fragments makes SNPs of particular use for population monitoring, where faecal and other noninvasive samples are routinely used.

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Habitat fragmentation can act to cause reproductive isolation between conspecifics and undermine species' persistence, though most studies have reported the genetic condition of populations that have already declined to a very small size. We examined genetic diversity within the vulnerable, declining koala (Phascolarctos cinereus) population in Southeast Queensland, Australia to determine the genetic impact of ongoing threatening processes. Five hundred and twelve koalas from ten Southeast Queensland Local Government Areas on the mainland and one island were genotyped at six polymorphic microsatellite loci. Based on Bayesian cluster analysis incorporating spatial data, the regional koala population was subdivided into six clusters, with location of major roads and rivers appearing to be consistent with being barriers to gene flow. The distribution of mtDNA control region haplotypes identified distinct coastal and inland clades suggesting that historically there was gene flow between koalas along the coast (though little interchange between coastal and inland animals). In contrast, koalas from the Koala Coast (Brisbane City, Logan City and Redland Shire) were shown by microsatellite analysis to be genetically distinct from adjacent areas. It is likely, therefore, that more recent reductions in population size and restricted gene flow through urbanisation have contributed to the genetic differentiation of koalas in the Koala Coast region.

The aim of this component was to establish the range of DLA diversity in as many dog breeds as possible. In particular, we wanted to collect breeds that had not previously been studied. Data were submitted of 937 dogs of over 80 different breeds, and these included 17 'new' breeds. Twenty-eight new alleles were identified including 21 DLA-DRB1, 2 DLA-DQA1 and 5 DLA-DQB1 alleles. These occurred in many new haplotype combinations. One haplotype was identified that appeared to lack DQB1. Two other haplotypes carry two DQB1 genes. It was clear that each dog breed has a restricted range of DLA alleles and haplotypes, and no breed had all 88 haplotypes identified in this study.

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