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73 results for “charr”

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dryad36/100

Monitoring genome-wide diversity over contemporary time with new indicators applied to Arctic charr populations

Genetic diversity is fundamental to the adaptive potential and survival of species. Although its importance has long been recognized in science, it has a history of neglect within policy – until now. The new Global Biodiversity Framework recently adopted by the Convention on Biological Diversity, states that genetic diversity must be maintained at levels assuring adaptive potential of populations, and includes metrics for systematic monitoring of genetic diversity in so called indicators. Similarly, indicators for genetic diversity are being developed at national levels. Here, we apply new indicators for Swedish national use to one of the northernmost salmonid fishes, the Arctic charr (Salvelinus alpinus). We sequence whole genomes to monitor genetic diversity over four decades in three landlocked populations inhabiting protected alpine lakes in central Sweden. We find levels of genetic diversity, inbreeding and load to differ among lakes but remain stable over time. Effective population sizes are generally small (<500), suggesting a limited ability to maintain adaptive variability if genetic exchange with nearby populations became eliminated. We identify genomic regions potentially shaped by selection; SNPs exhibiting population divergence exceeding expectations under drift and a putative selective sweep acting within one lake to which the competitive brown trout was introduced during the sampling period. Identified genes appear involved in immunity and salinity tolerance. Present results suggest that genetically vulnerable populations of Arctic charr have maintained neutral and putatively adaptive genetic diversity despite small effective sizes, attesting the importance of continued protection and assurance of gene flow among populations.

opencc-zeroJan 2024View details →

dryad36/100

Genomic basis of deep‐water adaptation in Arctic Charr (Salvelinus alpinus) morphs

Colonization of extreme habitats requires extensive adaptation to novel environmental challenges. Deep-water environments (>50 m) have high hydrostatic pressure, low temperature, and low light, requiring physiological and visual system adaptation, but genomic mechanisms underlying evolution in these environments are rarely known. Post-glacial colonization of Gander Lake in Newfoundland, Canada, by Arctic Charr (Salvelinus alpinus) provides the opportunity to study the genomic basis of adaptation to extreme deep-water environments. Here, we compare genomic and morphometric divergence between a phenotypically divergent deep-water, demersal morph adapted to depths of up to 288m and a larger, piscivorous morph occupying shallower depths. Using a SNP array and resequencing of nuclear and mitochondrial genomes, we find moderate genetic divergence (FST = 0.15 - 0.11) between morphs, consistent with divergence in body shape and size, despite absence of mitochondrial genome divergence. Outlier analyses identified three key genes with very high divergence against a genome-wide distribution of diverged genomic islands containing genes with functions related to deep-water adaptation such as sensory processes, ligand binding and regulation of transcription. Quantification of SNP array signal intensity variation associated with complex polymorphisms (e.g. copy number variants), similarly uncovered genetic separation of morphs and coincided with several islands of genomic divergence, but also revealed additional genomic regions and molecular mechanisms associated with depth adaptation. Together, these results show that adaptation to an extreme deep-water environment has been facilitated by multiple polymorphism types with roles in cellular and physiological processes, providing insight into the genomic basis of adaptation in extreme environments.

opencc-zeroFeb 2022View details →

dryad36/100

Genetic data from: Cryptic persistence and loss of local endemism in Lake Constance charr subject to anthropogenic disturbance

Habitat restoration can help to protect and support endangered species. Following the restoration of Lake Constance to oligotrophic conditions, deep-water charr (originally described as Salvelinus profundus Schillinger, 1901) were rediscovered after more than 40 years of presumed extinction caused by eutrophication. Subsequent targeted surveys lead to the capture of a further 127 deep-water charr and 233 sympatric normal charr, Salvelinus cf. umbla. Given a history of intensive stocking in the lake and the possibility of introgressive hybridization, a discussion arose about the genetic status and future conservation strategies of both forms. The current study gathered life history traits and morphological and population genomic data for both extant forms, for comparison with 60–120 years' worth of historical data and museum specimens. The extant deep-water charr resembled historical specimens in terms of body shape, but significant differences between historical and extant normal charr included a decline in gill raker number over time and distinctly different body shapes and growth patterns. RAD-based population genomic analyses of the contemporary samples support these results, revealing the two extant forms to be highly divergent, albeit with a few putative hybrids. SNPs-based population assignment tests of historical and contemporary samples strongly suggest that deep-water charr persisted unaltered in Lake Constance during the eutrophic phase. Meanwhile, none of the historical genomic samples could be assigned to the extant normal S. cf. umbla population. Functional analyses of gill raker number and stocking intensity pointed to stocking with non-endemic charr as the most likely reason for the disappearance of the endemic normal form. These results show that interplay between different anthropogenic impacts, i.e. eutrophication and stocking can lead to irreversible but hard-to-detect impacts on endemic biodiversity. Understanding these impacts is a prerequisite for effective conservation of endangered populations of cryptic fish.

opencc-zeroOct 2022View details →

dryad36/100

Temporal stability of polymorphic Arctic charr parasite communities reflect sustained divergent trophic niches

Polymorphic Arctic charr Salvelinus alpinus populations frequently display distinct differences in habitat use, diet and parasite communities. Changes to the relative species densities and composition of the wider fish community have the potential to alter the habitat-niche of sympatric Arctic charr populations. This study evaluated the temporal stability of the parasite community, diet and stable isotopes (δ13C, δ15N) of three sympatric Arctic charr morphs (piscivore, benthivore and planktivore) from Loch Rannoch, Scotland, in relation to changes to the fish community. All Arctic charr morphs displayed distinct differences parasite communities, diet and stable isotope signatures over time, despite the establishment of four new trophically transmitted parasite taxa, and increased fish and zooplankton consumption by the piscivorous and planktivore morphs respectively. Native parasite prevalence also increased in all Arctic charr morphs. Overall, Loch Rannoch polymorphic Arctic charr morph populations have maintained their distinct trophic niches and parasite communities through time despite changes in the fish community. This result indicates that restocking of a native fish species has the potential to induce shifts in the parasite community and diet of Arctic charr morphs.

opencc-zeroOct 2022View details →

dryad36/100

Data from: Thermal habitat fragmentation in stratified lakes induces resource waves that brook charr track across seasons

The spatial configuration of thermal habitats constrains the thermoregulatory performance of ectotherms. Thermal landscapes also vary through time, which is particularly relevant in seasonal environments such as temperate lakes. Indeed, elevated temperatures in the epilimnion of dimictic lakes during summer could substantially reduce the use of this habitat by cold-stenothermic fish during the stratified period. The main objective of this study was to evaluate whether thermal habitat fragmentation in stratified lakes modulates accessibility to resources that brook charr, Salvelinus fontinalis, which is a mobile consumer, can track across seasons. More specifically, we hypothesize that reduced access to the littoral habitat during summer enhances foraging opportunities in this habitat during winter. We used an automatic acoustic telemetry system offering full coverage of the lake to continuously record brook charr locations across seasons, and we estimated zoobenthos abundances in the littoral habitat using image processing and semi-automatic classification. While brook charr concentrate in the metalimnion of the pelagic habitat in summer, most individuals in winter shift to a shallow bay that is unexploited in summer due to thermal constraints. In this habitat, zoobenthos abundance is more than twice as high at the end of the summer compared to littoral habitats close to the thermal refuge in the pelagic habitat. Surprisingly, brook charr showed strong within-lake site fidelity between two consecutive summers, which suggests that spatial memory could be a key driver of seasonal habitat use in this lacustrine population. Overall, our results suggest that thermal barriers create fragmentation between littoral and pelagic habitats that in turn produces resource opportunities that brook charr can track across seasons.

opencc-zeroMay 2024View details →

zenodo36/100

Fig. 13 in Histopathological characterisation of retinal lesions associated to Diplostomum species (Platyhelminthes: Trematoda) infection in polymorphic Arctic charr Salvelinus alpinus

Fig. 13. Diplostomum sp. metacercaria in a choroidal vessel. Scale bar = 200 μm.

opencc-by-4.0Apr 2018View details →

zenodo36/100

Supplementary data for: "Emergence of Potential Anadromous Arctic Charr (Salvelinus alpinus) Habitats in the Svalbard Archipelago after the End of the Little Ice Age"

Supplementary data for: “Emergence of Potential Anadromous Arctic Charr (Salvelinus alpinus) Habitats in the Svalbard Archipelago after the End of the Little Ice Age” <a href="https://doi.org/10.1029/2024JG008367">https://doi.org/10.1029/2024JG008367</a>   Abstract: Glaciers in the Svalbard Archipelago are retreating rapidly in response to climate change. The retreat of glaciers leads to alteration of the hydrological and thermal regimes of the freshwater ecosystems. In this delicate context, existing anadromous Arctic charr (Salvelinus alpinus) populations are at severe risk and might disappear from the archipelago. However, the retreat of glaciers also promotes the formation of new lake systems that might be suitable for colonization by anadromous Arctic charr. These systems may provide a substantial opportunity for the establishment of new populations of anadromous charr, potentially buffering the decline in existing systems. To date, there is a lack of information on the number of recently deglaciated lake systems that have emerged since the end of the Little Ice Age (ca. 1920) that might be suitable for charr colonization. Therefore, the goal of this paper is to provide an initial assessment of the number of these lakes. To this end, and in accordance with previously published research, this study assesses whether a recently deglaciated lake system is potentially open to colonization based on gradient, river length, and lake surface area. Depending on the applied threshold (four in total), up to 24 lake systems are classified as potentially open to colonization by anadromous Arctic charr, with Spitsbergen emerging as a colonization hotspot. The findings of this paper might serve as basis for new studies and for implementing proactive management and conservation strategies to protect anadromous charr populations.   Data description:   Recently_Deglaciated_Systems [EPGS: 25833] - Shapefile containing the information of 168 lake systems that emerged between 1936/1938 and 2020 in the Svalbard Archipelago ID: Identification number X: Easting Y: Northing Fall?: Presence of the lake system in fall (with dates when the lake was visible in satellite images) Spring?: Presence of the lake system in spring (with dates when the lake was visible in satellite images) Info: information regarding the type of system (i.e., larger lake surrounded by lakes and ponds or system of multiple lakes and ponds). If blank, lake is considered single.   Analysis [EPGS: 25833] - Shapefile containing the analysis of 125 lake systems with connection to the ocean. ID: Identification number X: Easting Y: Northing Surface (km2): Surface of the connected recently deglaciated lake system (km2) Elevation (m): Elevation of the outlet (m) Length (m): River length (m) Slope (%): Slope of the river (%) SV1: Result of the classification with SV1 SV2: Result of the classification with SV2 HY: Result of the classification with HY NO: Result of the classification with NO

opencc-by-4.0Nov 2024View details →

dryad36/100

Relationships between egg size and maternal size, life-history forms, and habitats of Greenlandic Arctic charr (Salvelinus alpinus)

Arctic charr (Salvelinus alpinus [L.] complex) has been widely used as a model system for studies in evolutionary ecology because of its diversity in feeding ecology, habitat use, life-history forms, and associated morphologies observed in matured individuals. However, we still know relatively little about traits exhibited early in life of the species, although the trait diversity of matured individuals may largely be shaped during development. Egg size is a key determinant ofvarious traits exhibited early in life. Therefore, describing egg size variation within- and between-individuals as well as the link between egg size and adult traits will be a useful step in understanding the early life trait diversity of Arctic charr. Here, using Greenlandic Arctic charr, which includes alternative life-history forms (i.e., anadromous and resident) and spawning habitat use (i.e., lake- and river- spawner), we described egg size variation (i.e., clutch-mean egg diameter and within-clutch variation) and explored the link between egg size variation and female body length, life-history form, and spawning habitats. As in many other fishes, clutch-mean egg diameter increased with female body length. No significant effect of other female traits on clutch mean-egg diameter was detected, suggesting that female body size variation could be a direct cause of early life history trait variation. On the other hand, we found that the degree of within-clutch variation of the anadromous life-history form was higher than that of the resident life-history form. The pattern could be interpreted in an adaptive context. For instance, given that the anadromous life-history form tends to be semelparous, anadromous females could decrease the likelihood of complete reproductive failure by producing variable-sized offspring within a clutch since at least some offspring are expected to be matched to the prevailing environment.

opencc-zeroNov 2022View details →

dryad36/100