scholarly journals Genomic signatures of spatially divergent selection at clownfish range margins

2021 ◽  
Vol 288 (1952) ◽  
pp. 20210407
Author(s):  
René D. Clark ◽  
Matthew L. Aardema ◽  
Peter Andolfatto ◽  
Paul H. Barber ◽  
Akihisa Hattori ◽  
...  
Keyword(s):  
Gene Flow ◽  
Candidate Genes ◽  
Local Adaptation ◽  
Genetic Drift ◽  
Divergent Selection ◽  
Species Range ◽  
Evolutionary Forces ◽  
The Core ◽  
Range Edge ◽  
Genomic Signatures

Understanding how evolutionary forces interact to drive patterns of selection and distribute genetic variation across a species' range is of great interest in ecology and evolution, especially in an era of global change. While theory predicts how and when populations at range margins are likely to undergo local adaptation, empirical evidence testing these models remains sparse. Here, we address this knowledge gap by investigating the relationship between selection, gene flow and genetic drift in the yellowtail clownfish, Amphiprion clarkii, from the core to the northern periphery of the species range. Analyses reveal low genetic diversity at the range edge, gene flow from the core to the edge and genomic signatures of local adaptation at 56 single nucleotide polymorphisms in 25 candidate genes, most of which are significantly correlated with minimum annual sea surface temperature. Several of these candidate genes play a role in functions that are upregulated during cold stress, including protein turnover, metabolism and translation. Our results illustrate how spatially divergent selection spanning the range core to the periphery can occur despite the potential for strong genetic drift at the range edge and moderate gene flow from the core populations.

Evolutionary ecology at the extremes of species’ ranges

2010 ◽  
Vol 18 (NA) ◽  
pp. 1-20 ◽  
Author(s):  
David C. Hardie ◽  
Jeffrey A. Hutchings
Keyword(s):  
Evolutionary Ecology ◽  
Extinction Risk ◽  
Species Range ◽  
Local Extinction ◽  
Peripheral Populations ◽  
Species Ranges ◽  
Evolutionary Forces ◽  
Range Edge ◽  
Evolutionary Innovation ◽  
Abiotic Stressors

The nature of species at the extremes of their ranges impinges fundamentally on diverse biological issues, including species’ range dynamics, population variability, speciation and conservation biology. We review the literature concerning genetic and ecological variation at species’ range edges, and discuss historical and contemporary forces that may generate observed trends, as well as their current and future implications. We discuss literature which shows how environmental, ecological and evolutionary factors act to limit species’ ranges, and how these factors impose selection for adaptation or dispersal in peripheral populations exposed to extreme and stochastic biotic and abiotic stressors. When conditions are sufficiently harsh such that local extinction is certain, peripheral populations may represent temporary offshoots from stable core populations. However, in cases where peripheral populations persist at the range edge under divergent or extreme conditions, biologically significant differences can arise from historical and contemporary ecological and evolutionary forces. In many such cases reviewed herein, peripheral populations tended to diverge from the species’ core, and to display lower genetic diversity or greater stress-adaptation. We conclude that while such populations may be of particular conservation value as significant components of intraspecific biodiversity or sources of evolutionary innovation and persistence during environmental change, small and greatly variable population size, especially combined with low genetic variability, can result in elevated extinction risk in harsh and stochastic peripheral environments. As a result, while peripheral populations should not be dismissed as evolutionary dead-ends destined for local extinction, neither should they be uncritically granted inherently superior significance based only on their peripheral position alone.

scholarly journals Genomic assessment of local adaptation in dwarf birch to inform assisted gene flow

2019 ◽  
Author(s):  
James S. Borrell ◽  
Jasmin Zohren ◽  
Richard A. Nichols ◽  
Richard J. A. Buggs
Keyword(s):  
Climate Change ◽  
Gene Flow ◽  
Local Adaptation ◽  
Environmental Variables ◽  
Allele Frequencies ◽  
Species Range ◽  
Conservation Action ◽  
Mean Temperature ◽  
Diurnal Range ◽  
Dwarf Birch

AbstractWhen populations of a rare species are small, isolated and declining under climate change, some populations may become locally maladapted. Detecting this maladaptation may allow effective rapid conservation interventions, even if based on incomplete knowledge. Population maladaptation may be estimated by finding genome-environment associations (GEA) between allele frequencies and environmental variables across a local species range, and identifying populations whose allele frequencies do not fit with these trends. We can then design assisted gene flow strategies for maladapted populations, to adjust their allele frequencies, entailing lower levels of intervention than with undirected conservation action. Here, we investigate this strategy in Scottish populations of the montane plant dwarf birch (Betula nana). In genome-wide single nucleotide polymorphism (SNP) data we found 267 significant associations between SNP loci and environmental variables. We ranked populations by maladaptation estimated using allele frequency deviation from the general trends at these loci; this gave a different prioritization for conservation action than the Shapely Index, which seeks to preserve rare neutral variation. Populations estimated to be maladapted in their allele frequencies at loci associated with annual mean temperature were found to have reduced catkin production. Using an environmental niche modelling (ENM) approach, we found annual mean temperature (35%), and mean diurnal range (15%), to be important predictors of the dwarf birch distribution. Intriguingly, there was a significant correlation between the number of loci associated with each environmental variable in the GEA, and the importance of that variable in the ENM. Together, these results suggest that the same environmental variables determine both adaptive genetic variation and species range in Scottish dwarf birch. We suggest an assisted gene flow strategy that aims to maximize the local adaptation of dwarf birch populations under climate change by matching allele frequencies to current and future environments.

scholarly journals Gene swamping alters evolution during range expansions in the protist Tetrahymena thermophila

2020 ◽  
Vol 16 (6) ◽  
pp. 20200244
Author(s):  
Felix Moerman ◽  
Emanuel A. Fronhofer ◽  
Andreas Wagner ◽  
Florian Altermatt
Keyword(s):  
Genetic Variation ◽  
Gene Flow ◽  
Tetrahymena Thermophila ◽  
Species Range ◽  
Ph Gradient ◽  
Life History Strategies ◽  
Range Edge ◽  
Asymmetric Dispersal ◽  
Accelerated Evolution ◽  
Range Core

At species’ range edges, individuals often face novel environmental conditions that may limit range expansion until populations adapt. The potential to adapt depends on genetic variation upon which selection can act. However, populations at species’ range edges are often genetically depauperate. One mechanism increasing genetic variation is reshuffling existing variation through sex. Sex, however, can potentially limit adaptation by breaking up existing beneficial allele combinations (recombination load). The gene swamping hypothesis predicts this is specifically the case when populations expand along an abiotic gradient and asymmetric dispersal leads to numerous maladapted dispersers from the range core swamping the range edge. We used the ciliate Tetrahymena thermophila as a model for testing the gene swamping hypothesis. We performed replicated range expansions in landscapes with or without a pH-gradient, while simultaneously manipulating the occurrence of gene flow and sexual versus asexual reproduction. We show that sex accelerated evolution of local adaptation in the absence of gene flow, but hindered it in the presence of gene flow. However, sex affected adaptation independently of the pH-gradient, indicating that both abiotic gradients and the biotic gradient in population density lead to gene swamping. Overall, our results show that gene swamping alters adaptation in life-history strategies.

scholarly journals Pervasive Genomic Signatures of Local Adaptation to Altitude Across Highland Specialist Andean Hummingbird Populations

2021 ◽  
Author(s):  
Marisa C W Lim ◽  
Ke Bi ◽  
Christopher C Witt ◽  
Catherine H Graham ◽  
Liliana M Dávalos
Keyword(s):  
Gene Flow ◽  
Local Adaptation ◽  
Genetic Drift ◽  
Population Genetic ◽  
Environmental Gradients ◽  
Functional Differentiation ◽  
High Elevation ◽  
Nucleotide Polymorphisms ◽  
Peruvian Andes ◽  
Tropical Mountains

Abstract Populations along steep environmental gradients are subject to differentiating selection that can result in local adaptation, despite countervailing gene flow, and genetic drift. In montane systems, where species are often restricted to narrow ranges of elevation, it is unclear whether the selection is strong enough to influence functional differentiation of subpopulations differing by a few hundred meters in elevation. We used targeted capture of 12 501 exons from across the genome, including 271 genes previously implicated in altitude adaptation, to test for adaptation to local elevations for 2 highland hummingbird species, Coeligena violifer (n = 62) and Colibri coruscans (n = 101). For each species, we described population genetic structure across the complex geography of the Peruvian Andes and, while accounting for this structure, we tested whether elevational allele frequency clines in single nucleotide polymorphisms (SNPs) showed evidence for local adaptation to elevation. Although the 2 species exhibited contrasting population genetic structures, we found signatures of clinal genetic variation with shifts in elevation in both. The genes with SNP-elevation associations included candidate genes previously discovered for high-elevation adaptation as well as others not previously identified, with cellular functions related to hypoxia response, energy metabolism, and immune function, among others. Despite the homogenizing effects of gene flow and genetic drift, natural selection on parts of the genome evidently optimizes elevation-specific cellular function even within elevation range-restricted montane populations. Consequently, our results suggest local adaptation occurring in narrow elevation bands in tropical mountains, such as the Andes, may effectively make them “taller” biogeographic barriers.

Demography and Evolution in an Immigrant Ethnic Community: Hungarian Settlement, Louisiana, USA

1983 ◽  
Vol 15 (2) ◽  
pp. 223-236 ◽  
Author(s):  
Tibor Koertvelyessy
Keyword(s):  
Gene Flow ◽  
Natural Selection ◽  
Genetic Drift ◽  
Demographic Characteristics ◽  
Ethnic Population ◽  
Marriage Patterns ◽  
Evolutionary Forces ◽  
Evolutionary Force ◽  
Demographic Processes ◽  
Over Time

SummaryThis paper describes the fertility, mortality, and marriage patterns of the Hungarian Settlement, Louisiana, USA, immigrant ethnic population and relates these demographic processes to the evolutionary forces of natural selection, genetic drift, and gene flow. The results indicate that the maximum opportunity for natural selection decreased over time, and natural selection could have operated in the case of this population at only a very moderate level. The demographic characteristics of this population suggest that genetic drift may be important as an agent of microdifferentiation. Gene flow, however, appears to be the most important evolutionary force in this population. The process, based on the increasing incorporation of non-Hungarians into the gene pool, is causing the breakdown of this ethnic/genetic isolate.

scholarly journals Genomic signatures of local adaptation reveal source-sink dynamics in a high gene flow fish species

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
Katherine Cure ◽  
Luke Thomas ◽  
Jean-Paul A. Hobbs ◽  
David V. Fairclough ◽  
W. Jason Kennington
Keyword(s):  
Gene Flow ◽  
Local Adaptation ◽  
Fish Species ◽  
Genomic Signatures ◽  
High Gene Flow ◽  
High Gene ◽  
Source Sink

scholarly journals The impact of global selection on local adaptation and reproductive isolation

2019 ◽  
Author(s):  
Gertjan Bisschop ◽  
Derek Setter ◽  
Marina Rafajlović ◽  
Stuart J.E. Baird ◽  
Konrad Lohse
Keyword(s):  
Gene Flow ◽  
Reproductive Isolation ◽  
Local Adaptation ◽  
Genetic Load ◽  
Divergent Selection ◽  
Mutation Process ◽  
Genome Wide ◽  
The Impact ◽  
Two Populations ◽  
Global Selection

AbstractDespite the homogenising effect of strong gene flow between two populations, adaptation under symmetric divergent selection pressures results in partial reproductive isolation: adaptive substitutions act as local barriers to gene flow, and if divergent selection continues unimpeded, this will result in complete reproductive isolation of the two populations, i.e. speciation. However, a key issue in framing the process of speciation as a tension between local adaptation and the homogenising force of gene flow is that the mutation process is blind to changes in the environment and therefore tends to limit adaptation. Here we investigate how globally beneficial mutations (GBMs) affect divergent local adaptation and reproductive isolation. When phenotypic divergence is finite, we show that the presence of GBMs limits local adaptation, generating a persistent genetic load at the loci which contribute to the trait under divergent selection and reducing genome-wide divergence. Furthermore, we show that while GBMs cannot prohibit the process of continuous differentiation, they induce a substantial delay in the genome-wide shutdown of gene flow.

Population structure in a wide-ranging coastal teleost (Argyrosomus japonicus, Sciaenidae) reflects marine biogeography across southern Australia

2016 ◽  
Vol 67 (8) ◽  
pp. 1103 ◽  
Author(s):  
Thomas C. Barnes ◽  
Claudia Junge ◽  
Steven A. Myers ◽  
Mathew D. Taylor ◽  
Paul J. Rogers ◽  
...  
Keyword(s):  
South Africa ◽  
Population Structure ◽  
Gene Flow ◽  
Genetic Drift ◽  
Isolation By Distance ◽  
Marine Species ◽  
Global Scale ◽  
Genetic Population Structure ◽  
Genetic Population ◽  
Evolutionary Forces

Population structure in marine teleosts is often investigated to aid conservation and fisheries management (e.g. to assess population structure to inform restocking programs). We assessed genetic population structure of the important estuary-associated marine fish, mulloway (Argyrosomus japonicus), within Australian waters and between Australia and South Africa. Genetic variation was investigated at 13 polymorphic microsatellite markers. FST values and Bayesian estimates in STRUCTURE suggested population differentiation of mulloway within Australia and confirm strong differentiation between South Africa and Australia. The 12 Australian sample sets fell into one of four spatially separated genetic clusters. Initially, a significant signal of isolation-by-distance (IBD) was evident among Australian populations. However, further investigation by decomposed-pairwise-regression (DPR) suggested five sample sets were influenced more by genetic-drift, rather than gene-flow and drift equilibrium, as expected in strong IBD cases. Cryptic oceanographic and topographical influences may isolate mulloway populations from south-western Australia. The results demonstrate that DPR is suitable to assess population structure of coastal marine species where barriers to gene flow may be less obvious than in freshwater systems. Information on the relative strengths of gene flow and genetic drift facilitates a more comprehensive understanding of the evolutionary forces that lead to population structure, which in turn informs fisheries and assists conservation management. Large-bodied predatory scale-fish may be under increasing pressure on a global scale, owing to a variety of anthropogenic reasons. In southern Australia, the iconic sciaenid A. japonicus (mulloway, jewfish or kob) is no exception. Despite the species supporting important fisheries, much of its ecology is poorly understood. It is possible that a greater understanding of their genetic population structure can help ensure a sustainable future for the only southern Australian sciaenid.

scholarly journals The impact of global selection on local adaptation and reproductive isolation

2020 ◽  
Vol 375 (1806) ◽  
pp. 20190531 ◽  
Author(s):  
Gertjan Bisschop ◽  
Derek Setter ◽  
Marina Rafajlović ◽  
Stuart J. E. Baird ◽  
Konrad Lohse
Keyword(s):  
Gene Flow ◽  
Reproductive Isolation ◽  
Local Adaptation ◽  
Genetic Load ◽  
Divergent Selection ◽  
Mutation Process ◽  
Genome Wide ◽  
The Impact ◽  
Two Populations ◽  
Global Selection

Despite the homogenizing effect of strong gene flow between two populations, adaptation under symmetric divergent selection pressures results in partial reproductive isolation: adaptive substitutions act as local barriers to gene flow, and if divergent selection continues unimpeded, this will result in complete reproductive isolation of the two populations, i.e. speciation. However, a key issue in framing the process of speciation as a tension between local adaptation and the homogenizing force of gene flow is that the mutation process is blind to changes in the environment and therefore tends to limit adaptation. Here we investigate how globally beneficial mutations (GBMs) affect divergent local adaptation and reproductive isolation. When phenotypic divergence is finite, we show that the presence of GBMs limits local adaptation, generating a persistent genetic load at the loci that contribute to the trait under divergent selection and reducing genome-wide divergence. Furthermore, we show that while GBMs cannot prohibit the process of continuous differentiation, they induce a substantial delay in the genome-wide shutdown of gene flow. This article is part of the theme issue ‘Towards the completion of speciation: the evolution of reproductive isolation beyond the first barriers’.

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