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1.
Patterns of phenotypic and genetic variability show hidden diversity in Scottish Arctic charr 总被引：1，自引：1，他引：1
C. E. Adams D. Fraser A. J. Wilson G. Alexander M. M. Ferguson S. Skulason 《Ecology of Freshwater Fish》2007,16(1):78-86
Abstract – This study examined the degree and pattern of variability in trophic morphology in Arctic charr ( Salvelinus alpinus L. ) at three spatial scales: across 22 populations from Scotland and between and within two adjacent catchments (Laxford and Shin) in northern Scotland. In addition, the variability at six microsatellite loci between and within the Laxford and Shin systems was determined. Habitat use by charr differed significantly between populations. The pattern of variability in trophic morphology, known to influence foraging ability in charr, showed a very high degree of between-population variation with at least 52% of population pairs showing significant differences in head shape. Trophic morphology and genetic variation was also high over small geographical scales; variation being as high between charr from lakes within the same catchment, as between adjacent catchments. The pattern of both phenotypic and genotypic variation suggests a mosaic of variation across populations with geographically close populations often as distinct from each other as populations with much greater separation. Very low levels of effective migrants between populations, even within the same catchment, suggest that this variation is being maintained by very low straying rates between phenotypically and genetically distinct populations, even when there is no apparent barrier to movement. We conclude that the genetic and phenotypic integrity of charr populations across Scotland is high and that this adaptive radiation constitutes a 'hidden' element of diversity in northern freshwater systems. Two consequences of this are that the population (rather than the species) makes a more rational unit for the consideration of conservation strategies and that the habitat requirements and therefore management needs may differ significantly between populations. 相似文献
2.
A. Klemetsen P.-A. Amundsen J. B. Dempson B. Jonsson N. Jonsson M. F. O'Connell E. Mortensen 《Ecology of Freshwater Fish》2003,12(1):1-59
Abstract – Among the species in the family Salmonidae, those represented by the genera Salmo, Salvelinus, and Oncorhynchus (subfamily Salmoninae) are the most studied. Here, various aspects of phenotypic and life‐history variation of Atlantic salmon Salmo salar L., brown trout Salmo trutta L., and Arctic charr Salvelinus alpinus (L.) are reviewed. While many strategies and tactics are commonly used by these species, there are also differences in their ecology and population dynamics that result in a variety of interesting and diverse topics that are challenging for future research. Atlantic salmon display considerable phenotypic plasticity and variability in life‐history characters ranging from fully freshwater resident forms, where females can mature at approximately 10 cm in length, to anadromous populations characterised by 3–5 sea‐winter (5SW) salmon. Even within simple 1SW populations, 20 or more spawning life‐history types can be identified. Juveniles in freshwater can use both fluvial and lacustrine habitats for rearing, and while most smolts migrate to sea during the spring, fall migrations occur in some populations. At sea, some salmon undertake extensive oceanic migrations while other populations stay within the geographical confines of areas such as the Baltic Sea. At the other extreme are those that reside in estuaries and return to freshwater to spawn after spending only a few months at sea. The review of information on the diversity of life‐history forms is related to conservation aspects associated with Atlantic salmon populations and current trends in abundance and survival. Brown trout is indigenous to Europe, North Africa and western Asia, but was introduced into at least 24 countries outside Europe and now has a world‐wide distribution. It exploits both fresh and salt waters for feeding and spawning (brackish), and populations are often partially migratory. One part of the population leaves and feeds elsewhere, while another part stays as residents. In large, complex systems, the species is polymorphic with different size morphs in the various parts of the habitat. Brown trout feed close to the surface and near shore, but large individuals may move far offshore. The species exhibits ontogenetic niche shifts partly related to size and partly to developmental rate. They switch when the amount of surplus energy available for growth becomes small with fast growers being younger and smaller fish than slow growers. Brown trout is an opportunistic carnivore, but individuals specialise at least temporarily on particular food items; insect larvae are important for the young in streams, while littoral epibenthos in lakes and fish are most important for large trout. The sexes differ in resource use and size. Females are more inclined than males to become migratory and feed in pelagic waters. Males exploit running water, near‐shore and surface waters more than females. Therefore, females feed more on zooplankton and exhibit a more uniform phenotype than males. The Arctic charr is the northernmost freshwater fish on earth, with a circumpolar distribution in the Holarctic that matches the last glaciation. Recent mtDNA studies indicate that there are five phylogeographic lineages (Atlantic, Arctic, Bering, Siberian and Acadian) that may be of Pleistocene origin. Phenotypic expression and ecology are more variable in charr than in most fish. Weights at maturation range from 3 g to 12 kg. Population differences in morphology and coloration are large and can have some genetic basis. Charr live in streams, at sea and in all habitats of oligotrophic lakes, including very deep areas. Ontogenetic habitat shifts between lacustrine habitats are common. The charr feed on all major prey types of streams, lakes and near‐shore marine habitats, but has high niche flexibility in competition. Cannibalism is expressed in several cases, and can be important for developing and maintaining bimodal size distributions. Anadromy is found in the northern part of its range and involves about 40, but sometimes more days in the sea. All charr overwinter in freshwater. Partial migration is common, but the degree of anadromy varies greatly among populations. The food at sea includes zooplankton and pelagic fish, but also epibenthos. Polymorphism and sympatric morphs are much studied. As a prominent fish of glaciated lakes, charr is an important species for studying ecological speciation by the combination of field studies and experiments, particularly in the fields of morphometric heterochrony and comparative behaviour. 相似文献
3.
Phenotypic plasticity in the morphology of small benthic Icelandic Arctic charr (Salvelinus alpinus) 
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下载免费PDF全文 Bjarni K. Kristjánsson Camille A.‐L. Leblanc Skúli Skúlason Sigurður S. Snorrason David L.G. Noakes 《Ecology of Freshwater Fish》2018,27(3):636-645
Intraspecific phenotypic diversity is the raw material for evolution, so understanding its origin and maintenance is critically important for conservation of biodiversity. Intraspecific diversity in a trait or a suite of traits can result from genetic diversity and/or phenotypic plasticity. The two are, however, not independent as plasticity has been shown to evolve. In this study, we evaluated the importance of phenotypic plasticity in generating morphological diversity in populations of small benthic Arctic charr in Iceland, using a rearing experiment with contrasting modes of feeding. We also examined the association between phenotypic plasticity in offspring groups generated by the contrasting feeding modes and important ecological variables characterising the natural habitats of the respective populations. Although the level of plasticity could not be related to any of the ecological measurements, clear differences in morphological reaction norms among populations suggest that plasticity is an important aspect of morphological diversity of the charr. It is not clear whether that plasticity is adaptive, but it is notable that reaction norms in all populations have similar reaction to the treatments. 相似文献
4.
Abstract – The morphology of three lake-resident Arctic charr, Salvelinus alpinus , populations was studied at two life-history stages in a common-garden experiment. The fish of the same year class were reared under standard hatchery conditions, and 27 morphometric variables (a truss network) were measured from the sampled individuals. Most of the total variation was explained by the overall body robustness, dimensions of the head and caudal peduncle length. After controlling for a body size, significant heterogeneity in body shape was found among populations at both ages. Independent of age, the populations were morphologically highly distinct, although some integration of characters could be found as the fish reached sexual maturity. Sexual divergence accounted for a large part of the within-population shape variation, the mature males having more robust bodies, larger head dimensions and longer pectoral fins compared with the mature females/immature fish. Although the cultured fish may not be totally representative of their wild counterparts, it is reasonable to expect that the observed morphological differences have a genetic basis, presumably reflecting adaptation to local environmental conditions experienced by the charr in their original habitat. 相似文献
5.
Trout and charr, members of the salmonid family, have high conservation value but are also susceptible to anthropogenic threats in part due to the specificity of their habitat requirements. Understanding historical and future threats facing these species is necessary to promote their recovery. Of freshwater trout and charr in the Canadian Rocky Mountain region, westslope cutthroat trout (Oncorhynchus clarkii lewisi), bull trout (Salvelinus confluentus; a charr species) and Athabasca rainbow trout (Oncorhynchus mykiss) are of conservation concern. And indeed, range contractions and declining populations are evident throughout much of their ranges. Range contraction was most evident in the southern Alberta designatable unit (DU) of westslope cutthroat trout. Diminished populations were also evident in the downstream watersheds of the Alberta bull trout range, and throughout the Athabasca rainbow trout range. We assessed historical and future threats to evaluate the relative importance of individual threats to each DU and compare their impact among species. Individual threats fall into the broad categories of angling, non-native species and genes, habitat loss and alteration, and climate change. Severity of each threat varies by DU and reflects the interaction between species’ biology and the location of the DU. Severity of threats facing each DU has changed over time, reflecting extirpation of native populations, changes in management and industry best practices, expansion of non-native species and progressing climate change. The overall threat impact for each DU indicates a high probability of substantial and continuing declines and calls for immediate action. 相似文献
6.
A. F. Walker 《Ecology of Freshwater Fish》2007,16(1):47-53
Abstract – Scotland is a stronghold for Arctic charr, with about 200 freshwater, wholly loch-resident populations, most of which have yet to be studied. To date, no anadromous populations or individual sea-run charr, have been reported. In Scotland, most Arctic charr spawn in stillwater, during autumn and early winter (September to January), with only one population spawning in spring. Spawning in running water does occur, but has been regarded as rare. This paper examines the status of stream spawning of charr in Scotland, describing instances from 10 populations, although two of these are now extinct. Most stream-spawning charr migrate relatively short distances to running water and construct redds in gently flowing water. The longest recorded migration occurs in Loch Insh, Speyside, with fish travelling 15 km within the River Spey. Information on the extent of stream spawning is essential to help conserve the rich phenotypic and genetic diversity of our remaining charr populations. 相似文献
7.
1. This paper highlights the recent extinctions of two native Arctic charr populations in the West of Ireland, one population from the Lough Conn catchment, and a second from the Lough Corrib catchment, respectively. 2. The distribution of charr populations in the two catchments is reviewed. The current distribution information is drawn from recent fish stock surveys (Lough Corrib in 1996, and Lough Conn in 1997 and 1998). Previous records of charr in the literature and unpublished data are described to place the current distribution of charr within these catchments into a historical perspective. 3. The importance of the charr population in Lough Mask (Lough Corrib catchment) is emphasized, as it is one of the last extant examples of charr from a large Irish alkaline lake. 4. Impacts on charr populations in both catchments are discussed and conservation measures proposed. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
8.
Kiira J. Siitari William W. Taylor Stacy A. C. Nelson Kerryann E. Weaver 《Ecology of Freshwater Fish》2011,20(3):431-437
Abstract – Brook charr (Salvelinus fontinalis) is a sentinel fish species that requires clean, cold water habitats generally resulting from landscapes that allow for surface water flows devoid of sediment and contaminants and high groundwater discharge of cold water. As such, brook charr are impacted by land cover changes that alter stream temperature regimes. We evaluated brook charr populations across their eastern and midwestern range in the United States with reference to thermal habitat availability in relationship to land cover and per cent baseflow. We found that while forest cover does protect brook charr thermal habitat, high levels of groundwater discharge can allow for increased levels of agriculture within a watershed by keeping the water cold in spite of warm ambient summer temperatures. Our study concludes that with enhanced communication among land, water and fisheries managers, society can provide for sustainable stream salmonid populations despite increased threats on cold water resources. 相似文献
9.
Latitudinal variation in growth and otolith‐inferred field metabolic rates of Canadian young‐of‐the‐year Arctic charr 下载免费PDF全文
下载免费PDF全文 R. Niloshini Sinnatamby J. Brian Dempson James D. Reist Michael Power 《Ecology of Freshwater Fish》2015,24(3):478-488
Countergradient variation (CGV) is defined as genetic variation that counteracts the negative influences of the physical environment, minimising phenotypic variability along an environmental gradient. CGV is thought to have relevance in predicting the response of organisms to climate variability and change. To test the hypothesis that growth rate increased with latitude, consistent with CGV, young‐of‐the‐year (YOY) Arctic charr, Salvelinus alpinus, were examined along a ~27° latitudinal gradient in central and eastern Canada. Growth rates were estimated from fork lengths standardised by the thermal opportunity for growth based on experienced water temperatures derived using otolith oxygen stable isotopes. Results demonstrated patterns consistent with CGV, where northern populations demonstrated faster growth rates. A secondary aim was to test for similar geographical patterns in otolith‐inferred metabolic rates, which reflect the energetic costs of standard metabolic rate (SMR) and other processes such as feeding, locomotion, thermoregulation, reproduction and growth. Results demonstrated a significant, positive relationship between otolith‐inferred metabolic rate and latitude, which may reflect an increase in one, or a combination, of the above‐noted physiological processes. The similar latitudinal pattern in growth and otolith‐inferred metabolic rates suggests greater intake of food per unit of time by northern fish. The phenotypic variation in physiological traits observed here demonstrates the significant adaptability of Arctic charr to different thermal regimes with different growing season lengths. Determining the relative contributions of phenotypic plasticity and genetic variation to the observed latitudinal variation will be critical to predicting the responses of Arctic charr to climate change more accurately. 相似文献
10.
Body shape variation in two species of darters (Etheostoma,Percidae) and its relation to the environment 下载免费PDF全文
下载免费PDF全文 Environmental variation can shape phenotypic variation in organisms, but most evidence for trait differentiation comes from analyses of dichotomous habitat types that differ in only one or few key environmental factors. In reality, environmental variation is often more subtle, gradual and multifarious. Here, we investigated geographic variation in body shape of two darter species (Etheostoma spectabile and Etheostoma flabellare; Percidae) that occur along river gradients. This study addressed three specific questions: Is there intraspecific geographic variation in the two species across different sites in the Ozark Highlands of Oklahoma (USA)? Is phenotypic variation across sites correlated with abiotic environmental conditions? Do the two species share site‐specific (i.e. convergent) phenotypic variation in areas where they occur together? Our results indicated significant body shape variation in both species. Population differences in body shape were particularly correlated with variation in substrate composition. The combined analysis of both species indicated a small but significant effect of convergence on body shape wherever they are sympatric; shared variation, however, was not related to any environmental variables included in the analysis. While it remains unclear whether phenotypic variation in these species is due to heritable differentiation or environmentally induced plasticity, our results indicate that even subtle and gradual environmental variation can induce substantial variation in phenotypes on a relatively small spatial scale. 相似文献
11.
Jeffrey T. Silverstein 《Fish physiology and biochemistry》2002,27(3-4):173-178
The overall goal of our research is to develop fish with superior growth, and feed efficiency attributes. Feed intake is integral to these characters. Over the last several years we have been working with channel catfish, Ictalurus punctatus, in two directions tied to feed intake regulation. One direction has been to identify genes functioning as physiological regulators of feed intake, and the other has been to measure and characterize the genetic variation in feed intake within and among distinct catfish populations which reveal a wide range in feeding response. The goals are to uncover the genetic basis of physiological variation, to understand the genes and interactions that produce the phenotypic differences observed and to exploit these differences in a selective breeding program. To investigate the links between genetic variation and physiological variation, differences in voluntary feed consumption were documented in two strains of channel catfish. Treatment with orexigenic compounds affected both strains similarly, though anorexigenic compounds inhibited feeding in one strain more than the other and low temperature treatment affected the strains differently with respect to feed efficiency. Phenotypic variation in feed intake among families within one strain suggested that approximately 40% of the variation in feed intake is due to genetic sources. Future work aimed at utilizing strains and families with divergent phenotypes for identifying the specific genes responsible for this variation is discussed. 相似文献
12.
A rapid phenotype deviation is a common population response to atypical environmental conditions in aquatic animals. However, the implications for adaptive specialisation, stochastic segregation and ancestral traits fixation in the stress‐induced phenotype transformation are not clear. Here, we cross‐analyse the populations of commonly fluvial Dolly Varden charr Salvelinus malma multiply locked in small lakes (<1 km2) throughout Kamchatkan volcanic range to assess the ratio of (non)parallel outcomes of phenotype specialisation under stress conditions. The growth rate and definitive size parameters show a twofold difference in six populations inhabiting the same resource‐poor lakes. An inter‐population comparison revealed a weakly pronounced morphological similarity—no directional vector towards lacustrine lifestyle is detected in body and skull shape. Local morphotypes experiencing random segregation and ancestral fixation processes inherit the unique morphometric, meristic and cranial characteristics. The most ancient populations are characterised by the most paedomorphic exterior and archaic anatomical peculiarities. Parallelism in population structure manifests itself in growth acceleration of some mature or maturing individuals resulting in two distinct size groups with different allometric body proportions. Small fish (50–260 g, average age 6–7 years) feed on invertebrates throughout their life, while the biggest ones (290–780 g, average age 8 years) switch to cannibalism. This transformation does not lead to any inherited sympatric polymorphism. Thus, we did not reveal any common vector of the stress‐induced specialisation; adaptive phenotypes are strongly influenced by the resource dynamics. 相似文献
13.
Abstract – In this study, we synthesised the views of 34 participants in a workshop to consider the status and future conservation and management of the Arctic charr ( Salvelinus alpinus L.). These are expressed as a series of resolutions deriving from a conference on Arctic charr conservation held in Perth, Scotland in June 2004. Agreed resolutions from the conference were as follows. (i) The unique diversity of Arctic charr should be recognised for the contribution it makes to biodiversity of northern aquatic communities. (ii) The recognition by the public, nongovernmental organisations and national governments of the importance of Arctic charr in northern ecosystems is an important step to the management and protection that should be pursued. (iii) The taxonomic status of highly variable charr populations requires to be reviewed. (iv) There should be a separate system, complementary to the taxonomic one, which systematically catalogues the biological diversity of S. alpinus . (v) The Arctic charr provides a unique natural resource to study the process of evolution and this requires the highest level of protection from anthropogenic effects. (vi) The status of conservation policy for Arctic charr needs to be urgently reviewed to take account of its unique position in the fauna. 相似文献
14.
15.
贵州境内3个野生大眼鳜群体的形态差异 总被引：3，自引：3，他引：0
为探讨长江和珠江流域野生大眼鳜(Siniperca kneri)的外形差异,本研究基于形态学和框架测量数据,运用多元分析法比较了长江流域乌江沿河、锦江铜仁大眼鳜群体和珠江流域北盘江关岭大眼鳜群体的形态特征。结果表明,铜仁段大眼鳜群体的眼最小,沿河段大眼鳜群体的体型最薄,而关岭段大眼鳜群体的体型最厚,吻最短但尾柄最长。经数据标准化和参数选择后,12个性状参数的数据被用来进行主成分分析(principal component analysis,PCA)。主成分分析提取了2个主成分,其累计贡献率为64.255%,其中第1主成分主要受体宽、尾柄形态、眼间距等性状参数的影响,而第2主成分主要受吻长和眼径大小的影响。应用逐步判别方法(discriminant function analysis,DFA)建立了这3个群体的特征判别函数,其交互验证判别准确率为91.85%。在3个群体之间具有显著差异的12项性状的差异系数(coefficient of difference,CD)均未达到1.28这一亚种分化临界值。长江流域乌江沿河和锦江铜仁大眼鳜群体的外形较为相似,而它们与珠江流域北盘江关岭大眼鳜群体的形态差异较大,但本研究3个群体的形态变异仍为同一物种下的不同地理种群的形态变异,该变异还没有达到亚种变异水平。 相似文献
16.
Trophic polymorphism among Arctic charr Salvelinus alpinus L., from Loch Ericht, Scotland 总被引：2，自引：2，他引：0
Abstract— This article examines the morphology and ecology of Arctic charr Salvelinus alpinus in Loch Ericht, Scotland, Gill netting revealed that two forms of charr existed within the loch, a pale form and a colored form. Multivariate analysis of nine size-corrected morphometric measurements of the head region revealed that pale and colored charr differed significantly in the size and shape of the head characteristics and that both groups were easily discriminated on the basis of these characteristics. Stomach contents showed that the colored form fed predominantly on zooplankton and the pale form mainly consumed benthic macro-invertebrates, with larger pale individuals consuming other fish. On the basis of diet and morphology, the terms planktivorous and piscivorous were adopted for the two forms respectively. Length at age also distinguished the two groups, with piscivorous charr being smaller than colored charr up to age 8+ then surpassing the maximum length attained by planktivorous charr at ages of 9+ and above. The results are discussed in relation to other instances of sympatric morphs of Arctic charr. 相似文献
17.
M Y Norfatimah M N Siti Azizah A S Othman I Patimah & A F J Jamsari 《Aquaculture Research》2009,40(15):1742-1749
A 312 bp segment of the mitochondrial cytochrome b gene was sequenced from 132 sea bass Lates calcarifer individuals from nine populations across Peninsular Malaysia. Phylogenetic analysis and analysis of molecular variance within and among populations showed no significant geographical structuring. Several populations formed discrete units while others were of mixed populations. The former group suggests a low gene flow among some populations while the latter suggests that widespread translocations have impacted the other wild and cultured local populations. The data from this study have important implications for fishery management, conservation of sea bass stocks and translocation policy for aquaculture and stock enhancement in Peninsular Malaysia. 相似文献
18.
Long-term variation in piscivory in a brown trout population: effect of changes in available prey organisms 总被引：5，自引：0，他引：5
Abstract – The piscivorous behaviour in a brown trout ( Salmo trutta L.) population was studied in four discrete periods over seven decades (1917–94) in the hydroelectric reservoir Tunhovdfjord in Norway established in 1919. Piscivorous brown trout were extremely scarce prior to the introduction of two fish species Arctic charr ( Salvelinus alpinus L.) and European minnow ( Phoxinus phoxinus L.) in the 1920s. Brown trout started eating minnow at 17 cm and Arctic charr at 22 cm of length. In the 1950s, the brown trout predated extensively (60% of analysed trout) on Arctic charr and minnow. During the next four decades, the incidence of piscivorous brown trout declined to 15%, whereas the frequency of brown trout eating Arctic charr remained constant at 10%. The growth pattern, expressed as back-calculated length, demonstrated similarity in three periods (1920s, 1960s and 1990s) and improved growth in the 1950s. The improvement was addressed the impoundment of a reservoir upstream. We did not find any marked change in growth rate due to piscivority, but coefficient of variance of back-calculated lengths indicated significant variation in individual growth in age group ≥6 years from 1950 onwards. We accredit this variation to the rise of piscivorous brown trout. 相似文献
19.
Anadromous Arctic charr, Salvelinus alpinus (L.), was introduced to a sub‐Arctic river–lake system near the village of Kujjuuaq, Nunavik, and the stable isotope values and diets of key resident fish species were used to assess changes in feeding patterns. Stable isotope values for most species did not differ significantly between the pre‐ and post‐introduction periods, with observed shifts being within the bounds of expected natural variation. Lake chub, Couesius plumbeus (Agassiz), were the single species to show a difference between study periods, with a small but significant increase in δ15N. No significant post‐introduction changes were seen in lake trout, Salvelinus namaycush (Walbaum), omnivory or in any of the assessed quantitative food web metrics. Gut contents of major fish species similarly showed significant temporal overlap between the pre‐ and post‐introduction periods, and there was no significant change in species' weight–length relationships. The minor ecological impact was interpreted in relation to the availability of open niches exploitable by ecological generalists such as Arctic charr. The explanation accords with the known habitat and feeding flexibility of Arctic charr and the ecological immaturity of sub‐Arctic lakes known to have driven adaptive variation among Arctic charr. Findings suggest that anadromous Arctic charr may be introduced at moderate densities to other sub‐Arctic watersheds without major negative food web consequences for other resident fish species. 相似文献
20.
Abstract – From both a modern and a historical perspective there is little doubt that the Arctic charr, Salvelinus alpinus , in Britain and Ireland (as well as elsewhere) is a 'difficult' species. Historically 15 separate species have been recognised from populations in Britain and Ireland and there have been recent attempts to reassert these specific names. Here we review the evidence for the status of these 'species'. We conclude that the evidence for these 15 being afforded full species status is poor. However, both historical and contemporary data show that Salvelinus alpinus (Linnaeus 1758) in Britain and Ireland exhibits levels of variability in form that is much greater than in other species. We argue that a comprehensive genotypic and phenotypic survey of charr populations in Britain and Ireland is required to determine the full extent of variability and the status of populations with a view of providing suitable protection. 相似文献