Mitonuclear speciation

2019 ◽  
pp. 143-178
Author(s):  
Geoffrey E. Hill
Keyword(s):  
Gene Flow ◽  
Mitochondrial Genes ◽  
Nuclear Genes ◽  
Adaptive Divergence ◽  
Isolated Populations ◽  
Rapid Fixation ◽  
Gene Complexes ◽  
Selection For

Current models of speciation assume that species arise when nuclear genotypes diverge following the disruption of gene flow between populations. This chapter explores the idea that speciation is specifically the result of divergence in coadapted mitonuclear gene complexes with divergence of most nuclear genes playing little or no role in speciation. To maintain mitonuclear coadaptation, nuclear genes must coevolve with rapidly changing mitochondrial genes. According to the mitonuclear compatibility concept of species, mitonuclear coevolution in isolated populations leads to speciation because population-specific mitonuclear coadaptations create between-population mitonuclear incompatibilities and hence barriers to gene flow between populations. In addition, selection for adaptive divergence of products of mitochondrial genes can lead to rapid fixation of novel mitochondrial genotypes between populations and consequently to disruption in gene flow between populations as the initiating step in animal speciation. The chapter considers the evidence for the involvement of mitonuclear compatibility in the process of speciation and the implications for this new concept of speciation and species.

scholarly journals Does selection occur at the intermediate zone of two insufficiently isolated populations? A whole-genome analysis along an altitudinal gradient

2021 ◽  
Author(s):  
Naofumi Yoshida ◽  
Shin-Ichi Morinaga ◽  
Takeshi Wakamiya ◽  
Yuu Ishii ◽  
Shosei Kubota ◽  
...  
Keyword(s):  
Gene Flow ◽  
Genetic Structure ◽  
Altitudinal Gradient ◽  
Intermediate Zone ◽  
Adaptive Divergence ◽  
Population Divergence ◽  
Whole Genome ◽  
Isolated Populations ◽  
Whole Genome Analysis ◽  
Single Nucleotide

Abstract Adaptive divergence would occur even between the insufficiently isolated populations when there is a great difference in the environments of their habitats. The individuals present in the intermediate zone of the two divergent populations are expected to have an admixed genetic structure due to gene flow. A selective pressure that acts on the genetically admixed individuals may limit the gene flow and promote the adaptive divergence. Here, we addressed a question whether the selection occurs in the genetically admixed individuals between the divergent populations and assessed its effects on the population divergence. We obtained the whole-genome sequences of a perennial montane plant, Arabidopsis halleri, which has clear phenotypic dimorphisms between altitudes, along an altitudinal gradient of 359–1,317 m with a high spatial resolution (mean altitudinal interval of 20 m). We found the zone where the highland and lowland genes were mixing. Using the FST approach, we found that 35 and 13 genes in the admixed zone had a high frequency of alleles that are accumulated in highland and lowland subpopulations, respectively, suggesting that these genes have been selected in the admixed zone. This selection might limit the gene flow and contribute to the adaptive divergence along the altitudes. In the single-nucleotide polymorphism (SNP)-based analysis, 3,000 out of 27,792 Altitude-Dependent SNPs had extremely high homozygosity in the admixed zone. In 84.7% of these SNPs, the frequency of homozygotes of highland alleles was comparable to that of lowland alleles, suggesting that these alleles are neutral but the heterozygotes were selectively eliminated. The distribution of highland and lowland alleles of these SNPs was not clearly separated between altitudes, implying that such selection did not impede the gene flow. We conclude that the selection occurring at the intermediate altitude affects the genetic structure in the admixed zone and adaptive divergence along the altitudes.

Are there populations suffering genetic erosion that would benefit from augmented gene flow?

2017 ◽  
Author(s):  
Richard Frankham ◽  
Jonathan D. Ballou ◽  
Katherine Ralls ◽  
Mark D. B. Eldridge ◽  
Michele R. Dudash ◽  
...  
Keyword(s):  
Gene Flow ◽  
Genetic Erosion ◽  
Genetic Rescue ◽  
Isolated Populations

Having identified small geographically and genetically isolated populations, we need to determine whether they are suffering genetic erosion, and if so, whether there are any other populations to which they could be crossed. We should next ask whether crossing is expected to be harmful or beneficial, and if beneficial, whether the benefits would be large enough to justify a genetic rescue attempt. Here, we address these questions based on the principles established in the preceding chapters.

scholarly journals Adaptive Divergence under Gene Flow along an Environmental Gradient in Two Coexisting Stickleback Species

Genes ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 435
Author(s):  
Thijs M. P. Bal ◽  
Alejandro Llanos-Garrido ◽  
Anurag Chaturvedi ◽  
Io Verdonck ◽  
Bart Hellemans ◽  
...  
Keyword(s):  
Gene Flow ◽  
Brackish Water ◽  
Environmental Gradient ◽  
Spatial Scales ◽  
Morphological Differentiation ◽  
Genotyping By Sequencing ◽  
Adaptive Divergence ◽  
Linkage Groups ◽  
Closely Related Species ◽  
Genomic Patterns

There is a general and solid theoretical framework to explain how the interplay between natural selection and gene flow affects local adaptation. Yet, to what extent coexisting closely related species evolve collectively or show distinctive evolutionary responses remains a fundamental question. To address this, we studied the population genetic structure and morphological differentiation of sympatric three-spined and nine-spined stickleback. We conducted genotyping-by-sequencing and morphological trait characterisation using 24 individuals of each species from four lowland brackish water (LBW), four lowland freshwater (LFW) and three upland freshwater (UFW) sites in Belgium and the Netherlands. This combination of sites allowed us to contrast populations from isolated but environmentally similar locations (LFW vs. UFW), isolated but environmentally heterogeneous locations (LBW vs. UFW), and well-connected but environmentally heterogenous locations (LBW vs. LFW). Overall, both species showed comparable levels of genetic diversity and neutral genetic differentiation. However, for all three spatial scales, signatures of morphological and genomic adaptive divergence were substantially stronger among populations of the three-spined stickleback than among populations of the nine-spined stickleback. Furthermore, most outlier SNPs in the two species were associated with local freshwater sites. The few outlier SNPs that were associated with the split between brackish water and freshwater populations were located on one linkage group in three-spined stickleback and two linkage groups in nine-spined stickleback. We conclude that while both species show congruent evolutionary and genomic patterns of divergent selection, both species differ in the magnitude of their response to selection regardless of the geographical and environmental context.

Genetic Differentiation in Isolated Populations of Hakea carinata (Proteaceae)

1998 ◽  
Vol 46 (6) ◽  
pp. 671 ◽  
Author(s):  
G. J. Starr ◽  
S. M. Carthew
Keyword(s):  
Gene Flow ◽  
Habitat Fragmentation ◽  
Gene Diversity ◽  
South Australia ◽  
Similar Species ◽  
Isolated Populations ◽  
Plant Populations ◽  
Evolutionary Condition ◽  
Private Alleles

Fragmentation of the landscape by human activity has created small, isolated plant populations. Hakea carinata F. Muell. ex Meissner, a sclerophyllous shrub, is common in isolated fragments of vegetation in South Australia. This study investigated whether habitat fragmentation has caused restrictions to gene flow between populations. Gene diversity (HT = 0.317) is average for similar species but little is held within populations (HS = 0.168) and 46.9% of gene diversity is accounted for between populations. Estimates of gene flow are NM = 0.270 (based on FST) and NM = 0.129 (based on private alleles). Populations are substantially selfing (t = 0.111). Small isolated populations appears to be a long-term evolutionary condition in this species rather than a consequence of habitat fragmentation; however, population extinctions are occurring. Conservation will require the reservation of many populations to represent the genetic variation present in the species.

scholarly journals Rapid, ultra-local adaptation facilitated by phenotypic plasticity

2019 ◽  
Author(s):  
Syuan-Jyun Sun ◽  
Andrew M. Catherall ◽  
Sonia Pascoal ◽  
Benjamin J. M. Jarrett ◽  
Sara E. Miller ◽  
...  
Keyword(s):  
Gene Flow ◽  
Rapid Evolution ◽  
Reaction Norm ◽  
Ancestral Population ◽  
Adaptive Divergence ◽  
Wild Populations ◽  
Rapid Adaptation ◽  
Burying Beetles ◽  
Genetic Accommodation ◽  
Nicrophorus Vespilloides

AbstractModels of ‘plasticity-first’ evolution are attractive because they explain the rapid evolution of new complex adaptations. Nevertheless, it is unclear whether plasticity can still facilitate rapid evolution when diverging populations are connected by gene flow. Here we show how plasticity has generated adaptive divergence in fecundity in wild populations of burying beetlesNicrophorus vespilloides, which are still connected by gene flow, which occupy distinct Cambridgeshire woodlands that are just 2.5km apart and which diverged from a common ancestral population c. 1000-4000 years ago. We show that adaptive divergence is duetothe coupling of an evolved increase in the elevation of the reaction norm linking clutch size to carrion size (i.e. genetic accommodation) with plastic secondary elimination of surplus offspring. Working in combination, these two processes have facilitated rapid adaptation to fine-scale environmental differences, despite ongoing gene flow.

scholarly journals Natural selection for enzyme variants among parthenogenetic Daphnia magna

1972 ◽  
Vol 19 (2) ◽  
pp. 173-176 ◽  
Author(s):  
P. D. N. Hebert ◽  
R. D. Ward ◽  
J. B. Gibson
Keyword(s):  
Natural Selection ◽  
Daphnia Magna ◽  
Genetic Drift ◽  
Isolated Populations ◽  
Electrophoretic Variants ◽  
Enzyme Systems ◽  
Selection For ◽  
Genetically Determined

SUMMARYThe frequencies of genetically determined electrophoretic variants of two enzyme systems in the parthenogenetic crustacean D. magna have been followed in two isolated populations. In both populations a marked excess of hetero-zygotes was found in the later samples. It is concluded that the observed changes in gene and genotypic frequencies are due to natural selection as both migration and genetic drift can be excluded.

Demographic, dispersal, predation and genetic data reveal the potential vulnerability of an endangered rainforest shrub, Triunia robusta (Proteaceae)

2017 ◽  
Vol 65 (3) ◽  
pp. 270 ◽  
Author(s):  
Yoko Shimizu-Kimura ◽  
Scott Burnett ◽  
Alison Shapcott
Keyword(s):  
Gene Flow ◽  
Life Span ◽  
Demographic Data ◽  
Genetic Data ◽  
Seedling Mortality ◽  
Isolated Populations ◽  
Predation Mortality ◽  
Dispersal Vectors ◽  
Limited Gene Flow ◽  
Reproductive Rates

We investigated the population ecology of Triunia robusta (C.T. White) Foreman, an endemic rainforest shrub of south-east Queensland, Australia. Two-time demographic data from 1999 and 2010 were used to estimate the species life span and changes in demographic factors over the 11 year period. The potential dispersal vectors and their activities were monitored, and the effects of predation on seed and seedling mortality were quantified. Published genetic data was used to assess the gene flow distance in years. On average, T. robusta has a life span of 103 years, with a generation time of 44 years. Larger populations (>200) increased in size since 1999, whereas smaller populations retained the same or slightly reduced numbers. Small, isolated populations in the northern distribution range showed substantially lower reproductive rates. Local rodents and marsupials were considered responsible for the majority of observed secondary seed dispersal (<10.3 m) and predation activities. Post-predation mortality was high (82%), with only 12% surviving to become seedlings. The empirical evidence of short-distance dispersal, limited gene flow, high post-predation mortality rates and relatively low reproductive rates, combined with potential absence of primary dispersers suggests that critically small and isolated populations may be highly vulnerable.

scholarly journals Sporadic Genetic Connectivity among Small Insular Populations of the Rare Geoendemic Plant Caulanthus amplexicaulis var. barbarae (Santa Barbara Jewelflower)

2019 ◽  
Vol 110 (5) ◽  
pp. 587-600
Author(s):  
A Millie Burrell ◽  
Jeffrey H R Goddard ◽  
Paul J Greer ◽  
Ryan J Williams ◽  
Alan E Pepper
Keyword(s):  
Gene Flow ◽  
Genetic Connectivity ◽  
Effective Population ◽  
Evolutionary Potential ◽  
Isolated Populations ◽  
Long Distance ◽  
Population Sizes ◽  
History Of ◽  
Small Set ◽  
Nuclear Microsatellite

Abstract Globally, a small number of plants have adapted to terrestrial outcroppings of serpentine geology, which are characterized by soils with low levels of essential mineral nutrients (N, P, K, Ca, Mo) and toxic levels of heavy metals (Ni, Cr, Co). Paradoxically, many of these plants are restricted to this harsh environment. Caulanthus ampexlicaulis var. barbarae (Brassicaceae) is a rare annual plant that is strictly endemic to a small set of isolated serpentine outcrops in the coastal mountains of central California. The goals of the work presented here were to 1) determine the patterns of genetic connectivity among all known populations of C. ampexlicaulis var. barbarae, and 2) estimate contemporary effective population sizes (Ne), to inform ongoing genomic analyses of the evolutionary history of this taxon, and to provide a foundation upon which to model its future evolutionary potential and long-term viability in a changing environment. Eleven populations of this taxon were sampled, and population-genetic parameters were estimated using 11 nuclear microsatellite markers. Contemporary effective population sizes were estimated using multiple methods and found to be strikingly small (typically Ne &lt; 10). Further, our data showed that a substantial component of genetic connectivity of this taxon is not at equilibrium, and instead showed sporadic gene flow. Several lines of evidence indicate that gene flow between isolated populations is maintained through long-distance seed dispersal (e.g., &gt;1 km), possibly via zoochory.

scholarly journals Analysis of genetic population structure and diversity in Mallotus oblongifolius using ISSR and SRAP markers

PeerJ ◽  
2019 ◽  
Vol 7 ◽  
pp. e7173 ◽  
Author(s):  
Wuping Yan ◽  
Juanling Li ◽  
Daojun Zheng ◽  
Cynthia Friedman ◽  
Huafeng Wang
Keyword(s):  
Genetic Diversity ◽  
Gene Flow ◽  
Hainan Island ◽  
Issr Markers ◽  
Adaptive Divergence ◽  
Group Method ◽  
Market Demand ◽  
Srap Markers ◽  
Clustering Model ◽  
Geographical Regions

Background Mallotus oblongifolius, an evergreen shrub endemic to Hainan Island, China, is important both medicinally and economically. Due to its special medicinal significance and the continuing rise of market demand, its populations in the wild have been subject to long-term illegal and unrestrained collection. Hence, an evaluation of genetic variability is essential for the conservation and genetic reserve development of this species. Methods Sequence-related amplified polymorphism (SRAP) and inter-simple sequence repeat (ISSR) markers were employed to assess the genetic diversity and genetic structure of 20 natural populations of M. oblongifolius growing in different eco-geographical regions of Hainan Island, China. Results We revealed a considerable genetic diversity (h = 0.336, I = 0.5057, SRAP markers; h = 0.3068, I = 0.4657, ISSR markers) and weak genetic differentiation (Gst = 0.2764 for SRAP, Gst = 0.2709 for ISSR) with the same gene flow (Nm = 1.3092 for SRAP, Nm = 1.346 for ISSR) among the M. oblongifolius populations. The Mantel Test showed that the distribution of genetic variation among populations could not be explained by the pronounced geographical distances (r = 0.01255, p = 0.5538). All results of the Unweighted Pair Group Method with Arithmetic Mean (UPGMA), Neighbor-joining (NJ), Principal Coordinate Analysis (PCoA) and Bayesian analyses supported a habitat-specific genetic clustering model for M. oblongifolius, indicating a local adaptive divergence for the studied populations. Discussion We suggested that the habitat fragmentation and specificity for M. oblongifolius populations weakened the natural gene flow and promoted an adaptation to special habitats, which was the main reason for local adaptive divergence among M. oblongifolius.

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