scholarly journals Cline coupling and uncoupling in a stickleback hybrid zone

2015 ◽  
Author(s):  
Tim Vines ◽  
Anne Dalziel ◽  
Arianne Albert ◽  
Thor Veen ◽  
Patricia Schulte ◽  
...  
Keyword(s):  
Gene Flow ◽  
Hybrid Zone ◽  
Morphological Traits ◽  
Genetic Locus ◽  
Direct Selection ◽  
Divergent Natural Selection ◽  
Ecological Selection ◽  
Linkage Disequilibria ◽  
The Face ◽  
Freshwater Stickleback

Strong ecological selection on a genetic locus can maintain allele frequency differences between populations in different environments, even in the face of hybridization. When alleles at divergent loci come into tight linkage disequilibria, selection acts on them as a unit and can significantly reduce gene flow. For populations interbreeding across a hybrid zone, linkage disequilibria between loci can force clines to share the same slopes and centers. However, strong ecological selection can push clines away from the others, reducing linkage disequilibria and weakening the barrier to gene flow. We looked for this ‘cline uncoupling’ effect in a hybrid zone between stream resident and anadromous sticklebacks at two genes known to be under divergent natural selection (Eda and ATP1a1) and five morphological traits that repeatedly evolve in freshwater stickleback. We used 10 anonymous SNPs to characterize the shape of the zone. We found that the clines at Eda, ATP1a1, and four morphological traits were concordant and coincident, suggesting that direct selection on each is outweighed by the indirect selection generated by linkage disequilibria. Interestingly, the cline for pectoral fin length was much steeper and displaced 200m downstream, and two anonymous SNPs also had steep clines.

scholarly journals Deleterious mutations in a hybrid zone: can mutational load decrease the barrier to gene flow?

2002 ◽  
Vol 80 (3) ◽  
pp. 197-204 ◽  
Author(s):  
NICOLAS BIERNE ◽  
THOMAS LENORMAND ◽  
FRANÇOIS BONHOMME ◽  
PATRICE DAVID
Keyword(s):  
Gene Flow ◽  
Hybrid Zone ◽  
Small Population ◽  
Structured Populations ◽  
Mutational Load ◽  
Deleterious Mutations ◽  
Migration Rates ◽  
Linkage Disequilibria ◽  
Deleterious Alleles ◽  
Population Sizes

The aim of this paper is to investigate the effect of deleterious mutations in a hybrid zone maintained by selection against hybrids. In such zones, linkage disequilibria among hybrid depression loci, resulting from a balance between migration and selection, are crucial in maintaining the barrier because they allow each locus, in addition to its own selection coefficient, to cumulate indirect selective effects from other loci. Deleterious alleles produce heterosis and increase by this means the effective migration rate in structured populations. In a hybrid zone, they therefore contribute to decrease linkage disequilibria as well as the barrier to gene flow imposed by hybrid depression. However, deleterious mutations have no effect: (i) when selection against hybrids is weak, because linkage disequilibria are small even without heterosis in this case, or (ii) when selection against hybrids is so strong that it overwhelms heterosis. On the other hand, with moderate selection against hybrids, the decrease in the strength of the barrier due to heterosis may reach detectable levels, although it requires relatively small population sizes and/or migration rates. The effect is expected to be small and only within small genomes where loci are tightly linked can it become strong. Nevertheless, neglecting mutational load may to some extent obscure the estimations of selective parameters based either on artificial F1 crosses or on cline characteristics.

scholarly journals Population genetics of Aedes albopictus (Diptera: Culicidae) in its native range in Lao People’s Democratic Republic

2019 ◽  
Vol 12 (1) ◽  
Author(s):  
Maysa Tiemi Motoki ◽  
Dina Madera Fonseca ◽  
Elliott Frederic Miot ◽  
Bruna Demari-Silva ◽  
Phoutmany Thammavong ◽  
...  
Keyword(s):  
Population Structure ◽  
Gene Flow ◽  
Aedes Albopictus ◽  
Isolation By Distance ◽  
Genetic Locus ◽  
Lao Pdr ◽  
Phylogenetic Network ◽  
Population Expansion ◽  
Recent Population Expansion ◽  
The Usa

Abstract Background The Asian tiger mosquito, Aedes (Stegomyia) albopictus (Skuse) is an important worldwide invasive species and can be a locally important vector of chikungunya, dengue and, potentially, Zika. This species is native to Southeast Asia where populations thrive in both temperate and tropical climates. A better understanding of the population structure of Ae. albopictus in Lao PDR is very important in order to support the implementation of strategies for diseases prevention and vector control. In the present study, we investigated the genetic variability of Ae. albopictus across a north-south transect in Lao PDR. Methods We used variability in a 1337-bp fragment of the mitochondrial cytochrome c oxidase subunit 1 gene (cox1), to assess the population structure of Ae. albopictus in Lao PDR. For context, we also examined variability at the same genetic locus in samples of Ae. albopictus from Thailand, China, Taiwan, Japan, Singapore, Italy and the USA. Results We observed very high levels of genetic polymorphism with 46 novel haplotypes in Ae. albopictus from 9 localities in Lao PDR and Thailand populations. Significant differences were observed between the Luangnamtha population and other locations in Lao PDR. However, we found no evidence of isolation by distance. There was overall little genetic structure indicating ongoing and frequent gene flow among populations or a recent population expansion. Indeed, the neutrality test supported population expansion in Laotian Ae. albopictus and mismatch distribution analyses showed a lack of low frequency alleles, a pattern often seen in bottlenecked populations. When samples from Lao PDR were analyzed together with samples from Thailand, China, Taiwan, Japan, Singapore, Italy and the USA, phylogenetic network and Bayesian cluster analysis showed that most populations from tropical/subtropical regions are more genetically related to each other, than populations from temperate regions. Similarly, most populations from temperate regions are more genetically related to each other, than those from tropical/subtropical regions. Conclusions Aedes albopictus in Lao PDR are genetically related to populations from tropical/subtropical regions (i.e. Thailand, Singapore, and California and Texas in the USA). The extensive gene flow among locations in Lao PDR indicates that local control is undermined by repeated introductions from untreated sites.

scholarly journals Differences in dietary composition and preference maintained despite gene flow across a woodrat hybrid zone

2021 ◽  
Author(s):  
Danny P. Nielsen ◽  
Marjorie D. Matocq
Keyword(s):  
Gene Flow ◽  
Hybrid Zone ◽  
Dietary Composition

Shallow genetic divergence and distinct phenotypic differences between two Andean hummingbirds: Speciation with gene flow?

The Auk ◽  
2019 ◽  
Vol 136 (4) ◽  
Author(s):  
Catalina Palacios ◽  
Silvana García-R ◽  
Juan Luis Parra ◽  
Andrés M Cuervo ◽  
F Gary Stiles ◽  
...  
Keyword(s):  
Gene Flow ◽  
Genetic Differentiation ◽  
Incomplete Lineage Sorting ◽  
Lineage Sorting ◽  
Phenotypic Differences ◽  
Adaptive Mechanisms ◽  
The Face ◽  
Gloger’S Rule ◽  
Divergence With Gene Flow ◽  
Neutral Markers

Abstract Ecological speciation can proceed despite genetic interchange when selection counteracts the homogenizing effects of migration. We tested predictions of this divergence-with-gene-flow model in Coeligena helianthea and C. bonapartei, 2 parapatric Andean hummingbirds with marked plumage divergence. We sequenced putatively neutral markers (mitochondrial DNA [mtDNA] and nuclear ultraconserved elements [UCEs]) to examine genetic structure and gene flow, and a candidate gene (MC1R) to assess its role underlying divergence in coloration. We also tested the prediction of Gloger’s rule that darker forms occur in more humid environments, and examined morphological variation to assess adaptive mechanisms potentially promoting divergence. Genetic differentiation between species was low in both ND2 and UCEs. Coalescent estimates of migration were consistent with divergence with gene flow, but we cannot reject incomplete lineage sorting reflecting recent speciation as an explanation for patterns of genetic variation. MC1R variation was unrelated to phenotypic differences. Species did not differ in macroclimatic niches but were distinct in morphology. Although we reject adaptation to variation in macroclimatic conditions as a cause of divergence, speciation may have occurred in the face of gene flow driven by other ecological pressures or by sexual selection. Marked phenotypic divergence with no neutral genetic differentiation is remarkable for Neotropical birds, and makes C. helianthea and C. bonapartei an appropriate system in which to search for the genetic basis of species differences employing genomics.

scholarly journals Ecological Divergence and the Origins of Intrinsic Postmating Isolation with Gene Flow

2011 ◽  
Vol 2011 ◽  
pp. 1-15 ◽  
Author(s):  
Aneil F. Agrawal ◽  
Jeffrey L. Feder ◽  
Patrik Nosil
Keyword(s):  
Linkage Disequilibrium ◽  
Gene Flow ◽  
Natural Selection ◽  
Theoretical Models ◽  
Ecological Speciation ◽  
Divergent Selection ◽  
Postmating Isolation ◽  
Divergent Natural Selection ◽  
Mathematical Exploration ◽  
Neutral Gene

The evolution of intrinsic postmating isolation has received much attention, both historically and in recent studies of speciation genes. Intrinsic isolation often stems from between-locus genetic incompatibilities, where alleles that function well within species are incompatible with one another when brought together in the genome of a hybrid. It can be difficult for such incompatibilities to originate when populations diverge with gene flow, because deleterious genotypic combinations will be created and then purged by selection. However, it has been argued that if genes underlying incompatibilities are themselves subject to divergent selection, then they might overcome gene flow to diverge between populations, resulting in the origin of incompatibilities. Nonetheless, there has been little explicit mathematical exploration of such scenarios for the origin of intrinsic incompatibilities during ecological speciation with gene flow. Here we explore theoretical models for the origin of intrinsic isolation where genes subject to divergent natural selection also affect intrinsic isolation, either directly or via linkage disequilibrium with other loci. Such genes indeed overcome gene flow, diverge between populations, and thus result in the evolution of intrinsic isolation. We also examine barriers to neutral gene flow. Surprisingly, we find that intrinsic isolation sometimes weakens this barrier, by impeding differentiation via ecologically based divergent selection.

scholarly journals Genetic mechanisms preventing the fusion of ecotypes even in the face of gene flow

2012 ◽  
Vol 2 (1) ◽  
Author(s):  
Issei Ohshima
Keyword(s):  
Gene Flow ◽  
The Face ◽  
Genetic Mechanisms

scholarly journals Study on dispersion of genetic variation among Indian garlic ecotypes using agro morphological traits

2020 ◽  
Vol 80 (01) ◽  
Author(s):  
Ashwini Prashant Benke ◽  
Anil Khar ◽  
Vijay Mahajan ◽  
Amarjeet Gupta ◽  
Major Singh
Keyword(s):  
Morphological Traits ◽  
Germplasm Collection ◽  
Principal Component ◽  
Pooled Analysis ◽  
Direct Selection ◽  
Marketable Yield ◽  
Plant Weight ◽  
Medicinal Value ◽  
Number Of Leaves ◽  
Clustering Pattern

Garlic (Allium sativum L.) a clonally propagated bulbous crop, is of high medicinal value owing to its sulphur-containing compounds. Although asexually propagated, garlic depicts wide genetic diversity in agro-morphological traits and biochemical composition. A study was conducted to dissect the extent of genetic divergence among 625 Indian garlic genotypes considering 21 agro-morphological traits. Pooled analysis exhibited significant variation among accessions for various morphological traits. Ward’s clustering method clustered germplasm collection into three distinct groups. Clustering pattern did not correspond with geographical origin of accessions. Strong and positive correlation of marketable yield with plant weight with leaves (r = 0.83), plant weight without leaves (r = 0.84), average bulb weight (r = 0.50), plant height (r = 0.58), pseudostem length (r = 0.59), number of leaves (r = 0.54) and weight of fifty cloves (r = 0.49) was recorded. These traits will be useful for direct selection in crops like garlic. Principal Component analysis minimised 21 components up to 12 vectors which measured nearly 90% variation. Conservation of such vital and diverse garlic genotype is prerequisite to assure successful selection breeding programme.

scholarly journals Sex− and species−biased gene flow in a spotted eagle hybrid zone

2011 ◽  
Vol 11 (1) ◽  
Author(s):  
Niclas Backström ◽  
Ülo Väli
Keyword(s):  
Gene Flow ◽  
Hybrid Zone
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