Background: Brown troutSalmo truttahave been described in terms of five major mtDNA lineages, four of which correspond to major ocean basins, and one, according to some authors, to a distinct taxon, marbled troutSalmo marmoratus. The Atlantic and Danubian lineages of brown trout meet in a poorly documented contact zone in Central Europe. The natural versus human mediated origin of the Atlantic lineage in the upper Danube is a question of both theoretical and practical importance with respect to conservation management. We provide a comprehensive population genetic analysis of brown trout in the region with the aim of evaluating the geographic distribution and genetic integrity of these two lineages in and around their contact zone.Results: Genetic screening of 114 populations of brown trout across the Danube/Rhine/Elbe catchments revealed a counter-intuitive phylogeographic structure with near fixation of the Atlantic lineage in the sampled portions of the Bavarian Danube. Along the Austrian Danube, phylogeographic informative markers revealed increasing percentages of Danube-specific alleles with downstream distance. Pure Danube lineage populations were restricted to peri-alpine isolates within previously glaciated regions. Both empirical data and simulated hybrid comparisons support that trout in non-glaciated regions north and northeast of the Alps have an admixed origin largely based on natural colonization. In contrast, the presence of Atlantic basin alleles south and southeast of the Alps stems from hatchery introductions and subsequent introgression. Despite extensive stocking of the Atlantic lineage, little evidence of first generation stocked fish or F₁hybrids were found implying that admixture has been established over time.Conclusions: A purely phylogeographic paradigm fails to describe the distribution of genetic lineages ofSalmoin Central Europe. The distribution pattern of the Atlantic and Danube lineages is extremely difficult to explain without invoking very strong biological mechanisms.The peri-alpine distribution of relict populations of pure Danubian lineage brown trout implies that they colonized headwater river courses post-glacially ahead of the expansion of the Atlantic lineage. The recognition of natural as opposed to anthropogenic introgression of the Atlantic lineage into Danubian gene pools is of fundamental importance to management strategies.

Perennial cereal crops could limit the negative impacts of agriculture on the environment and climate change. In cold temperate climates, perennial plants must be adapted to seasonal changes and abiotic stresses, such as frost, to be able to regrow for several years. Wild crop relatives that are perennials and already adapted to cold temperate climates may provide genetic resources for breeding new perennial cereal grain crops. Barley (Hordeum vulgare) is one of the most important cereals in northern agricultural areas, and its related perennial species may be good candidates for the development of perennial cereals. We evaluated a diverse set of 17 wild perennial Hordeum species represented by 67 accessions in field conditions with a cold winter climate and long days during summer in Central Sweden (latitude 60° N). Six species (H. brevisubulatum, H. bulbosum, H. fuegianum, H. jubatum, H. lechleri and H. secalinum) showed regrowth and formation of spikes for four seasons. The most distant perennial relative of barley, H. stenostachys, showed weak regrowth. H. bulbosum, the closest perennial barley relative, had a large number of accessions with wide geographic origins that showed good regrowth. Together with its storage bulbs and its cross-compatibility with barley, this makes H. bulbosum an important genetic resource for the development of perennial Hordeum grains using either the domestication or the wide-hybridization strategy.