Limited genetic parallelism underlies recent, repeated incipient speciation in geographically proximate populations of an Arctic fish ( Salvelinus alpinus ) (original) (raw)
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Extensive genetic differentiation between recently evolved sympatric Arctic charr morphs
2018
The availability of diverse ecological niches can promote adaptation of trophic specializations and related traits, as has been repeatedly observed in evolutionary radiations of freshwater fish. The role of genetics, environment and history in ecologically driven divergence and adaptation, can be studied on adaptive radiations or populations showing ecological polymorphism. Salmonids, especially theSalvelinusgenus, are renowned for both phenotypic diversity and polymorphism. Arctic charr (Salvelinus alpinus) invaded Icelandic streams during the glacial retreat (about 10,000 years ago) and exhibits many instances of sympatric polymorphism. Particularly well studied are the four morphs in Lake Þingvallavatn in Iceland. The small benthic (SB), large benthic (LB), planktivorous (PL) and piscivorous (PI) charr differ in many regards, including size, form and life history traits. To investigate relatedness and genomic differentiation between morphs we identified variable sites from RNA-se...
2008
A suite of 10 microsatellite loci was used to examine genetic divergence between two sympatric morphs of Arctic charr Salvelinus alpinus ('dark' and 'pale') inhabiting Gander Lake, Newfoundland. Results can be summarized as follows: (1) the morphs are strongly reproductively isolated -gene flow-migration estimates were consistently low in long and short-term evolutionary timescales of analysis; (2) intermorph divergence based on allele size (R ST ) was significantly larger than those based on allele state (y) implying a cumulative effect of stepwiselike mutations; (3) historical (coalescent) and current (linkage disequilibrium) point estimates of effective population size (N e ) were consistently higher for dark than for pale S. alpinus. The first and second findings lend support to the hypothesis that divergence between forms may have preceded the last glacial period (ending c. 12 000 years BP). The third finding argues for significant differences in habitat quantity and quality between morphs, which were emphasized in a previous study. Overall, these analyses underscore the importance of genetic assessment and monitoring in the conservation of fish diversity, with emphasis on 'rare' or under-represented forms among temperate species pairs.
Genetic differences between two sympatric morphs of Arctic charr confirmed by microsatellite DNA
Journal of Fish Biology, 2004
Significant genetic differences (F ST ¼ 0Á032) were found between littoral and profundal morphs of Arctic charr Salvelinus alpinus from Fjellfrøsvatn, northern Norway, using microsatellite DNA analysis. The morphs had strong reproductive isolation in time and space; the segregation of a separate profundal morph is rare in postglacial lakes. # 2004 The Fisheries Society of the British Isles
The Genomic Consistency of the Loss of Anadromy in an Arctic Fish (Salvelinus alpinus)
The American Naturalist, 2022
The potentially significant genetic consequences associated with the loss of migratory capacity of diadromous fishes which have become "landlocked" in freshwater are poorly understood. Consistent selective pressures associated with freshwater residency may drive repeated differentiation both between allopatric landlocked and anadromous populations and within landlocked populations (resulting in sympatric morphs). Alternatively, the strong genetic drift anticipated in isolated landlocked populations could hinder consistent adaptation, limiting genetic parallelism. Understanding the degree of genetic parallelism underlying differentiation
Rapid and coupled phenotypic and genetic divergence in Icelandic Arctic char ( Salvelinus alpinus
Canadian Journal of Fisheries and Aquatic Sciences, 1999
Resource polymorphism has been proposed as an important phase of diversification and speciation in vertebrates. Studies of fish in young lakes of the Northern Hemisphere indicate variably advanced cases of adaptive trophic diversification. We have previously proposed a scheme describing this variation in terms of a gradient of resource-based polymorphic traits, emphasizing flexible behaviour in early phases and morphological divergence in more advanced phases. Here, we present data on Arctic char (Salvelinus alpinus) in Icelandic lakes exhibiting a variable degree of phenotypic and genotypic segregation. We show that (i) the morphs are at different levels of phenotypic segregation and reproductive isolation and in one case completely reproductively isolated, (ii) morphs within lakes appear to be of intralacustrine origin, and (iii) the morphological and genetic divergence of morphs is correlated, suggesting a role for trophic adaptation as a driving force in morph segregation.
The Genomic Consistency of the Loss of Anadromy in an Arctic Fish (Salvelinus alpinus)
The American Naturalist, 2022
The potentially significant genetic consequences associated with the loss of migratory capacity of diadromous fishes which have become "landlocked" in freshwater are poorly understood. Consistent selective pressures associated with freshwater residency may drive repeated differentiation both between allopatric landlocked and anadromous populations and within landlocked populations (resulting in sympatric morphs). Alternatively, the strong genetic drift anticipated in isolated landlocked populations could hinder consistent adaptation, limiting genetic parallelism. Understanding the degree of genetic parallelism underlying differentiation
Biological Journal of the Linnean Society, 2012
The expression of two or more discrete phenotypes amongst individuals within a species (morphs) provides multiple modes upon which selection can act semi-independently, and thus may be an important stage in speciation. In the present study, we compared two sympatric morph systems aiming to address hypotheses related to their evolutionary origin. Arctic charr in sympatry in Loch Tay, Scotland, exhibit one of two discrete, alternative body size phenotypes at maturity (large or small body size). Arctic charr in Loch Awe segregate into two temporally segregated spawning groups (breeding in either spring or autumn). Mitochondrial DNA restriction fragment length polymorphism analysis showed that the morph pairs in both lakes comprise separate gene pools, although segregation of the Loch Awe morphs is more subtle than that of Loch Tay. We conclude that the Loch Awe morphs diverged in situ (within the lake), whereas Loch Tay morphs most likely arose through multiple invasions by different ancestral groups that segregated before post-glacial invasion (i.e. in allopatry). Both morph pairs showed clear trophic segregation between planktonic and benthic resources (measured by stable isotope analysis) but this was significantly less distinct in Loch Tay than in Loch Awe. By contrast, both inter-morph morphological and life-history differences were more subtle in Loch Awe than in Loch Tay. The strong ecological but relatively weak morphological and life-history divergence of the in situ derived morphs compared to morphs with allopatric origins indicates a strong link between early ecological and subsequent genetic divergence of sympatric origin emerging species pairs. The emergence of parallel specialisms despite distinct genetic origins of these morph pairs suggests that the effect of available foraging opportunities may be at least as important as genetic origin in structuring sympatric divergence in post-glacial fishes with high levels of phenotypic plasticity.
The consequences of genomic architecture on ecological speciation in postglacial fishes
Current Zoology, 2013
The quest for the origin of species has entered the genomics era. Despite decades of evidence confirming the role of the environment in ecological speciation, an understanding of the genomics of ecological speciation is still in its infancy. In this review, we explore the role of genomic architecture in ecological speciation in postglacial fishes. Growing evidence for the number, location, effect size, and interactions among the genes underlying population persistence, adaptive trait divergence, and reproductive isolation in these fishes reinforces the importance of considering genomic architecture in studies of ecological speci-ation. Additionally, these populations likely adapt to new freshwater environments by selection on standing genetic variation, as de novo mutations are unlikely under such recent divergence times. We hypothesize that modular genomic architectures in postglacial fish taxa may be associated with the probability of population persistence. Empirical studies have...