ABSTRACT1. Man-made barriers such as dams affect the movement of aquatic species, reducing gene flow and genetic variability. Such encroachments may also lead to selective changes in life history and behaviour. Hydropower construction worldwide has fragmented many previously continuous fish habitats, leading to loss of populations and production. It is therefore important to assess potential impacts on habitats before such developments begin.2. Here, the potential ecological and evolutionary consequences of planned hydropower development on two migratory salmonid fishes -brown trout (Salmo trutta) and European grayling (Thymallus thymallus) -were assessed, combining telemetry with population genetics. Almost 200 fish were radio-tagged and tracked weekly between March and November. Using microsatellite markers, the genetic population structure was assessed and the number of migrants among different river sections identified for both species.3. Overall, both species displayed extensive within-and between-river movement, with larger home ranges in grayling than in trout. Regular movements between distinct spawning, feeding and wintering areas were common. These vital habitats were often located within areas of planned hydropower development.4. Both species exhibited significant population genetic structuring within the study area, with waterfalls acting as impassable barriers to upstream gene flow for grayling. The structuring was more developed for trout than for grayling. However, downstream gene flow was common, resulting in a highly admixed trout population below a waterfall.5. The large-scale movement patterns and extensive connectivity of the system indicate that habitat fragmentation and changes in water flow will adversely affect both species, but most strongly the trout. The reduction in water flow over large and productive stretches of the river might select for less migratory genotypes in both species. The loss of particular genotypes may reduce the biocomplexity of the system and overall population resilience.

Impacts of climate change on ocean productivity sustaining world fisheries are predominantly negative but vary greatly among regions. We assessed how 39 fisheries resources-ranging from data-poor to data-rich stocks-in the North East Atlantic are most likely affected under the intermediate climate emission scenario RCP4.5 towards 2050. This region is one of the most productive waters in the world but subjected to pronounced climate change, especially in the northernmost part. In this climate impact assessment, we applied a hybrid solution combining expert opinions (scorings)-supported by an extensive literature review-with mechanistic approaches, considering stocks in three different large marine ecosystems, the North, Norwegian and Barents Seas. This approach enabled calculation of the directional effect as a function of climate exposure and sensitivity attributes (life-history schedules), focusing on local stocks (conspecifics) across latitudes rather than the species in general. The resulting synopsis (50-82°N) contributes substantially to global assessments of major fisheries (FAO, The State of World Fisheries and Aquaculture, 2020), complementing related studies off northeast United States (35-45°N) (Hare et al.,

No abstract

Gene flow has the potential to both constrain and facilitate adaptation to local environmental conditions. The early stages of population divergence can be unstable because of fluctuating levels of gene flow. Investigating temporal variation in gene flow during the initial stages of population divergence can therefore provide insights to the role of gene flow in adaptive evolution. Since the recent colonization of Lake Lesjaskogsvatnet in Norway by European grayling (Thymallus thymallus), local populations have been established in over 20 tributaries. Multiple founder events appear to have resulted in reduced neutral variation. Nevertheless, there is evidence for local adaptation in early life-history traits to different temperature regimes. In this study, microsatellite data from almost a decade of sampling were assessed to infer population structuring and its temporal stability. Several alternative analyses indicated that spatial variation explained 2-3 times more of the divergence in the system than temporal variation. Over all samples and years, there was a significant correlation between genetic and geographic distance. However, decomposed pairwise regression analysis revealed differing patterns of genetic structure among local populations and indicated that migration outweighs genetic drift in the majority of populations. In addition, isolation by distance was observable in only three of the six years, and signals of population bottlenecks were observed in the majority of samples. Combined, the results suggest that habitat-specific adaptation in this system has preceded the development of consistent population substructuring in the face of high levels of gene flow from divergent environments.

BackgroundHuman cases of plague (Yersinia pestis) infection originate, ultimately, in the bacterium's wildlife host populations. The epidemiological dynamics of the wildlife reservoir therefore determine the abundance, distribution and evolution of the pathogen, which in turn shape the frequency, distribution and virulence of human cases. Earlier studies have shown clear evidence of climatic forcing on contemporary plague abundance in rodents and humans.ResultsWe find that high-resolution palaeoclimatic indices correlate with plague prevalence and population density in a major plague host species, the great gerbil (Rhombomys opimus), over 1949-1995. Climate-driven models trained on these data predict independent data on human plague cases in early 20th-century Kazakhstan from 1904-1948, suggesting a consistent impact of climate on large-scale wildlife reservoir dynamics influencing human epidemics. Extending the models further back in time, we also find correspondence between their predictions and qualitative records of plague epidemics over the past 1500 years.ConclusionsCentral Asian climate fluctuations appear to have had significant influences on regional human plague frequency in the first part of the 20th century, and probably over the past 1500 years. This first attempt at ecoepidemiological reconstruction of historical disease activity may shed some light on how long-term plague epidemiology interacts with human activity. As plague activity in Central Asia seems to have followed climate fluctuations over the past centuries, we may expect global warming to have an impact upon future plague epidemiology, probably sustaining or increasing plague activity in the region, at least in the rodent reservoirs, in the coming decades.See commentary: http://www.biomedcentral.com/1741-7007/8/108

25Knowledge of genetic diversity among wild populations is becoming increasingly important as more species are 26 recognized for their bioeconomic value. Industrialization of natural resources, such as kelp in the marine 27 shallow sublittoral zone through cultivation and wild-harvesting, may lead to extensive translocation and local 28 population decimation. Without adequate resilience in the form of genetic diversity within and across 29 populations and given the potential introduction of deleterious alleles from translocations, such 30 anthropogenically pressured populations may not be able to sufficiently respond to future climate and other 31 stressors. Here we provide an assessment of the genetic heterogeneity of two bioeconomically important kelp 32 species, Laminaria hyperborea and Saccharina latissima, across the Norwegian coastal region from South 33 (57°N) to North (78°N), by applying microsatellite genotyping. Isolation by distance was found for both kelp 34 species when comparing genetic distance to geographic distance. L. hyperborea clustered into four distinct 35 genetic groups corresponding to distinct geographical ecoregions, whereas S. latissima did not show equally 36 strong geographical structuring but separated into three geographical clusters along the Norwegian coast. No 37 genetic differentiation was found within the Norwegian Skagerrak region, corroborating previous findings. The 38 identified genetic clustering of both kelp species supports the retention of established management regions along 39the Norwegian coast and argues for the continuation of a regional focused management plan for kelp resources. 40 2 Further, the results demonstrate that care should be taken to prevent translocation of kelp between ecoregions in 41 the ongoing industrialization of kelp cultivation, to maintain a healthy coastal ecosystem and sound natural 42 population genetic diversity. 43 44

Sufficient genetic diversity can aid populations to persist in dynamic and fragmented environments. Understanding which mechanisms regulate genetic diversity of riverine fish can therefore advance current conservation strategies. The aim of this study was to investigate how habitat fragmentation interacted with population genetic diversity and individual behaviour of freshwater fish in large river systems. We studied a population of the long-distance migratory, iteroparous freshwater salmonid European grayling (Thymallus thymallus) in south-eastern Norway. Genotyping (n = 527) and radio-tracking (n = 54) of adult fish throughout a 169-km river section revealed three major migration barriers limiting gene flow and depleting genetic diversity upstream. Individuals from upstream areas that had dispersed downstream of barriers showed different movement behaviour than local genotypes. No natal philopatry was found in a large unfragmented river section, in contrast to strong fidelity to spawning tributaries known for individuals overwintering in lakes. We conclude that (a) upstream sub-populations in fragmented rivers show less genetic variation, making it less likely for them to adapt to environmental changes; (b) fish with distinct genotypes in the same habitat can differ in their behaviour; (c) spawning site selection (natal philopatry) can differ between fish of the same species living in different habitats.Together this implies that habitat loss and fragmentation may differently affect individual fish of the same species if they live in different types or sections of habitat. Studying behaviour and genetic diversity of fish can unravel their complex ecology and help minimize human impact.

Background: Although some mechanisms of habitat adaptation of conspecific populations have been recently elucidated, the evolution of female preference has rarely been addressed as a force driving habitat adaptation in natural settings. Habitat adaptation of fire salamanders (Salamandra salamandra), as found in Middle Europe (Germany), can be framed in an explicit phylogeographic framework that allows for the evolution of habitat adaptation between distinct populations to be traced. Typically, females of S. salamandra only deposit their larvae in small permanent streams. However, some populations of the western post-glacial recolonization lineage use small temporary ponds as larval habitats. Pond larvae display several habitat-specific adaptations that are absent in stream-adapted larvae. We conducted mate preference tests with females from three distinct German populations in order to determine the influence of habitat adaptation versus neutral genetic distance on female mate choice. Two populations that we tested belong to the western post-glacial recolonization group, but are adapted to either stream or pond habitats. The third population is adapted to streams but represents the eastern recolonization lineage.