scholarly journals Gene Flow and Genetic Variation Explain Signatures of Selection across a Climate Gradient in Two Riparian Species

Genes ◽  
2019 ◽  
Vol 10 (8) ◽  
pp. 579 ◽  
Author(s):  
Hopley ◽  
Byrne
Keyword(s):  
Genetic Variation ◽  
Gene Flow ◽  
Environmental Gradients ◽  
Genetic Connectivity ◽  
Heterogeneous Environments ◽  
Climate Gradients ◽  
Climate Gradient ◽  
Riparian Species ◽  
High Gene ◽  
Signatures Of Selection

Many species occur across environmental gradients and it is expected that these species will exhibit some signals of adaptation as heterogeneous environments and localized gene flow may facilitate local adaptation. While riparian zones can cross climate gradients, many of which are being impacted by climate change, they also create microclimates for the vegetation, reducing environmental heterogeneity. Species with differing distributions in these environments provide an opportunity to investigate the importance of genetic connectivity in influencing signals of adaptation over relatively short geographical distance. Association analysis with genomic data was used to compare signals of selection to climate variables in two species that have differing distributions along a river traversing a climate gradient. Results demonstrate links between connectivity, standing genetic variation, and the development of signals of selection. In the restricted species, the combination of high gene flow in the middle and lower catchment and occurrence in a microclimate created along riverbanks likely mitigated the development of selection to most climatic variables. In contrast the more widely distributed species with low gene flow showed a stronger signal of selection. Together these results strengthen our knowledge of the drivers and scale of adaptation and reinforce the importance of connectivity across a landscape to maintain adaptive potential of plant species.

scholarly journals Going with the flow: analysis of population structure reveals high gene flow shaping invasion pattern and inducing range expansion of Mikania micrantha in Asia

2020 ◽  
Vol 125 (7) ◽  
pp. 1113-1126
Author(s):  
Achyut Kumar Banerjee ◽  
Zhuangwei Hou ◽  
Yuting Lin ◽  
Wentao Lan ◽  
Fengxiao Tan ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Population Structure ◽  
Genetic Variation ◽  
Gene Flow ◽  
Genetic Distance ◽  
Range Expansion ◽  
Mikania Micrantha ◽  
High Gene Flow ◽  
Genetic Pattern ◽  
High Gene

Abstract Background and Aims Mikania micrantha, a climbing perennial weed of the family Asteraceae, is native to Latin America and is highly invasive in the tropical belt of Asia, Oceania and Australia. This study was framed to investigate the population structure of M. micrantha at a large spatial scale in Asia and to identify how introduction history, evolutionary forces and landscape features influenced the genetic pattern of the species in this region. Methods We assessed the genetic diversity and structure of 1052 individuals from 46 populations for 12 microsatellite loci. The spatial pattern of genetic variation was investigated by estimating the relationship between genetic distance and geographical, climatic and landscape resistances hypothesized to influence gene flow between populations. Key Results We found high genetic diversity of M. micrantha in this region, as compared with the genetic diversity parameters of other invasive species. Spatial and non-spatial clustering algorithms identified the presence of multiple genetic clusters and admixture between populations. Most of the populations showed heterozygote deficiency, primarily due to inbreeding, and the founder populations showed evidence of a genetic bottleneck. Persistent gene flow throughout the invasive range caused low genetic differentiation among populations and provided beneficial genetic variation to the marginal populations in a heterogeneous environment. Environmental suitability was found to buffer the detrimental effects of inbreeding at the leading edge of range expansion. Both linear and non-linear regression models demonstrated a weak relationship between genetic distance and geographical distance, as well as bioclimatic variables and environmental resistance surfaces. Conclusions These findings provide evidence that extensive gene flow and admixture between populations have influenced the current genetic pattern of M. micrantha in this region. High gene flow across the invaded landscape may facilitate adaptation, establishment and long-term persistence of the population, thereby indicating the range expansion ability of the species.

Molecular genetic variation in a widespread forest tree species Eucalyptus obliqua (Myrtaceae) on the island of Tasmania

2011 ◽  
Vol 59 (3) ◽  
pp. 226 ◽  
Author(s):  
Justin A. Bloomfield ◽  
Paul Nevill ◽  
Brad M. Potts ◽  
René E. Vaillancourt ◽  
Dorothy A. Steane
Keyword(s):  
Genetic Variation ◽  
Gene Flow ◽  
Environmental Gradients ◽  
Molecular Genetic ◽  
Continuous Distribution ◽  
Main Mode ◽  
Chloroplast Microsatellite ◽  
Eastern Australia ◽  
Nuclear Microsatellite ◽  
Microsatellite Diversity

Eucalyptus obliqua L’Hér. is widespread across south-eastern Australia. On the island of Tasmania it has a more-or-less continuous distribution across its range and it dominates much of the wet sclerophyll forest managed for forestry purposes. To understand better the distribution of genetic variation in these native forests we examined nuclear microsatellite diversity in 432 mature individuals from 20 populations of E. obliqua across Tasmania, including populations from each end of three locally steep environmental gradients. In addition, chloroplast microsatellite loci were assessed in 297 individuals across 31 populations. Nuclear microsatellite diversity values in E. obliqua were high (average HE = 0.80) and inbreeding coefficients low (average F = 0.02) within these populations. The degree of differentiation between populations was very low (FST = 0.015). No significant microsatellite differentiation could be found across three locally steep environmental gradients, even though there is significant genetic differentiation in quantitative traits. This suggests that the observed quantitative variation is maintained by natural selection. Population differentiation based on chloroplast haplotypes was high (GST = 0.69) compared with that based on nuclear microsatellites, suggesting that pollen-mediated gene flow is >150 times the level of seed-mediated gene flow in this animal-pollinated species; hence, pollen is likely to be the main mode of gene flow countering selection along local environmental gradients. Implications of these results for silvicultural practices are discussed.

scholarly journals Recent large-scale landscape changes, genetic drift and reintroductions characterize the genetic structure of Norwegian wild reindeer

2019 ◽  
Vol 20 (6) ◽  
pp. 1405-1419 ◽  
Author(s):  
Kjersti S. Kvie ◽  
Jan Heggenes ◽  
Bård-Jørgen Bårdsen ◽  
Knut H. Røed
Keyword(s):  
Genetic Variation ◽  
Gene Flow ◽  
Genetic Structure ◽  
Population Size ◽  
Genetic Drift ◽  
Genetic Connectivity ◽  
Conservation Strategies ◽  
Landscape Changes ◽  
Anthropogenic Habitat ◽  
Wild Reindeer

Abstract Landscape changes, such as habitat loss and fragmentation, subdivide wild populations, reduce their size, and limit gene flow. These changes may further lead to depletion of genetic variation within populations as well as accelerating differentiation among populations. As a migratory species requiring large living areas, wild reindeer (Rangifer tarandus) is highly vulnerable to human activity. The number and continued presence of wild reindeer have been significantly reduced due to accelerating anthropogenic habitat modifications, as well as displacement in benefit of domesticated herds of the species. As a basis for future management strategies we assess genetic structure and levels of genetic variation in Norwegian wild reindeer by analysing 12 microsatellite loci and the mitochondrial control region in 21 management units with varying population sizes. Overall, both markers showed highly varying levels of genetic variation, with reduced variation in the smaller and more isolated populations. The microsatellite data indicated a relationship between population size and genetic variation. This relationship was positive and linear until a threshold for population size was reached at approximately 1500 reindeer. We found high levels of differentiation among most populations, indicating low levels of gene flow, but only a weak correlation between geographic and genetic distances. Our results imply that the genetic structure of Norwegian wild reindeer is mainly driven by recent colonization history, population size, as well as human-induced landscape fragmentation, restricting gene flow and leading to high levels of genetic drift. To sustain viable populations, conservation strategies should focus on genetic connectivity between populations.

scholarly journals Eco-evolutionary community turnover following environmental change

2018 ◽  
Author(s):  
Jesse R. Lasky
Keyword(s):  
Genetic Diversity ◽  
Gene Flow ◽  
Environmental Change ◽  
Community Dynamics ◽  
Environmental Gradients ◽  
Interspecific Variation ◽  
Community Response ◽  
High Gene Flow ◽  
High Gene ◽  
Response To Environmental Change

AbstractCo-occurring species often differ in intraspecific genetic diversity, which in turn can affect adaptation in response to environmental change. Specifically, the simultaneous evolutionary responses of co-occurring species to temporal environmental change may influence community dynamics. Local adaptation along environmental gradients combined with gene flow can promote genetic diversity of traits under selection within populations. Here I build off existing quantitative genetic theory to study community dynamics of locally adapted species in response to temporal environmental change. I show that species with greater gene flow have lower equilibrium population size due to maladaptive immigrant genotypes (migration load). However, following abrupt environmental change that leaves all species initially maladapted, high gene flow species adapt faster due to greater standing genetic diversity. As a result, communities may undergo a transient reversal in relative abundance, sometimes only after substantial lag periods. If constant temporal environmental change is applied, the community exhibits a shift toward stable dominance by species with intermediate gene flow. High gene flow species can sometimes increase abundance under environmental change if environmental change supresses superior competitor but lower gene flow species. The community dynamics observed here parallel the purely ecological successional dynamics following disturbances and are analogous to the transient benefit of hypermutator alleles under changing environments. My results demonstrate how interspecific variation in life history can have far-reaching impacts on eco-evolutionary community response to environmental change.

scholarly journals Microsatellite markers from Peronospora tabacina, the cause of blue mold of tobacco, reveal species origin, population structure, and high gene flow

2021 ◽  
Author(s):  
Marcin Nowicki ◽  
Denita Hadziabdic Guerry ◽  
Robert N Trigiano ◽  
Fabian Runge ◽  
Marco Thines ◽  
...  
Keyword(s):  
Population Structure ◽  
Genetic Variation ◽  
Gene Flow ◽  
Blue Mold ◽  
Long Distance ◽  
Peronospora Tabacina ◽  
Species Origin ◽  
High Gene Flow ◽  
High Gene ◽  
Wind Currents

Peronospora tabacina is an obligate parasite that causes blue mold of tobacco. The pathogen reproduces primarily asexually by sporangia, and sexual oospores are a rarely observed form of propagation. A collection of 122 isolates of P. tabacina was genotyped using nine microsatellites to assess the population structure of individuals from subpopulations collected from Central, Southern, and Eastern Europe, the Middle East, Central and North America, and Australia. Genetic variation among the six subpopulations accounted for about 8% of total variation with moderate levels of genetic differentiation, high gene flow among these subpopulations, and a positive correlation between geographic and genetic distance (r = 0.225; P<0.001). Evidence of linkage disequilibrium (P<0.001) showed that populations contained partially clonal subpopulations, except subpopulations from Australia and Mediterranean Europe. High genetic variation and population structure among samples could be explained by continuous gene flow across continents via infected transplant exchange and/or long-distance dispersal of sporangia via wind currents. This study analyzed the most numerous P. tabacina collection to date and allowed conclusions on the migration, mutation, and evolutionary history of this obligate biotrophic oomycete. The evidence pointed to the species origin in Australia and identified intra- and inter-continental migration patterns of this important pathogen.

scholarly journals Standing genetic variation and chromosomal rearrangements facilitate local adaptation in a marine fish

2019 ◽  
Author(s):  
Hugo Cayuela ◽  
Quentin Rougemont ◽  
Martin Laporte ◽  
Claire Mérot ◽  
Eric Normandeau ◽  
...  
Keyword(s):  
Genetic Variation ◽  
Gene Flow ◽  
Local Adaptation ◽  
Marine Fish ◽  
Environmental Conditions ◽  
Chromosomal Rearrangements ◽  
Northwest Atlantic ◽  
High Gene Flow ◽  
High Gene ◽  
Spawning Sites

AbstractPopulation genetic theory states that adaptation most frequently occurs from standing genetic variation, which results from the interplay between different evolutionary processes including mutation, chromosomal rearrangements, drift, gene flow and selection. To date, empirical work focusing on the contribution of standing genetic variation to local adaptation in the presence of high gene flow has been limited to a restricted number of study systems. Marine organisms are excellent biological models to address this issue since many species have to cope with variable environmental conditions acting as selective agents despite high dispersal abilities. In this study, we examined how, demographic history, standing genetic variation linked to chromosomal rearrangements and shared polymorphism among glacial lineages contribute to local adaptation to environmental conditions in the marine fish, the capelin (Mallotus villosus). We used a comprehensive dataset of genome-wide single nucleotide polymorphisms (25,904 filtered SNPs) genotyped in 1,359 individuals collected from 31 spawning sites in the northwest Atlantic (North America and Greenland waters). First, we reconstructed the history of divergence among three glacial lineages and showed that they diverged from 3.8 to 1.8 MyA. Depending on the pair of lineages considered, historical demographic modelling provided evidence for divergence with gene flow and secondary contacts, shaped by barriers to gene flow and linked selection. We next identified candidate loci associated with reproductive isolation of these lineages. Given the absence of physical or geographic barriers, we thus propose that these lineages may represent three cryptic species of capelin. Within each of these, our analyses provided evidence for large Ne and high gene flow at both historical and contemporary time scales among spawning sites. Furthermore, we detected a polymorphic chromosomal rearrangement leading to the coexistence of three haplogroups within the Northwest Atlantic lineage, but absent in the other two clades. Genotype-environment associations revealed molecular signatures of local adaptation to environmental conditions prevailing at spawning sites. Altogether, our study shows that standing genetic variation associated with both chromosomal rearrangements and ancestral polymorphism contribute to local adaptation in the presence of high gene flow.

scholarly journals High gene flow maintains genetic diversity following selection for high EPSPS copy number in the weed kochia (Amaranthaceae)

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Sara L. Martin ◽  
Leshawn Benedict ◽  
Wei Wei ◽  
Connie A. Sauder ◽  
Hugh J. Beckie ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Genetic Variation ◽  
Gene Flow ◽  
Herbicide Resistance ◽  
Random Mating ◽  
Weed Species ◽  
Canadian Prairie ◽  
High Gene Flow ◽  
High Gene ◽  
Selection For

Abstract Kochia, a major weed species, has evolved resistance to four herbicide modes of action. Herbicide resistance appears to spread quickly, which could result in diminished standing genetic variation, reducing the ability of populations to adapt further. Here we used double digest restriction enzyme associated sequencing to determine the level of gene flow among kochia populations and whether selection for glyphosate resistance reduces genetic variation. Canadian Prairie populations show little to no genetic differentiation (FST = 0.01) and no correlation between genetic and geographic distance (r2 = − 0.02 p = 0.56), indicating high gene flow and no population structure. There is some evidence that kochia populations are genetically depauperate compared to other weed species, but genetic diversity did not differ between glyphosate susceptible and resistant populations or individuals. The inbreeding coefficients suggest there are 23% fewer heterozygotes in these populations than expected with random mating, and no variation was found within the chloroplast. These results indicate that any alleles for herbicide resistance can be expected to spread quickly through kochia populations, but there is little evidence this spread will reduce the species’ genetic variation or limit the species’ ability to respond to further selection pressure.

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