scholarly journals Expected patterns of local ancestry in a hybrid zone

2018 ◽  
Author(s):  
Joel Smith ◽  
Bret Payseur ◽  
John Novembre
Keyword(s):  
Reproductive Isolation ◽  
Purifying Selection ◽  
Hybrid Zones ◽  
Qualitative Properties ◽  
Hybrid Fitness ◽  
Local Ancestry ◽  
Migration History ◽  
Local Patterns ◽  
Candidate Loci ◽  
Genomic Patterns

1AbstractThe initial drivers of reproductive isolation between species are poorly characterized. In cases where partial reproductive isolation exists, genomic patterns of variation in hybrid zones may provide clues about the barriers to gene flow which arose first during the early stages of speciation. Purifying selection against incompatible substitutions that reduce hybrid fitness has the potential to distort local patterns of ancestry relative to background patterns across the genome. The magnitude and qualitative properties of this pattern are dependent on several factors including migration history and the relative fitnesses for different combinations of incompatible alleles. We present a model which may account for these factors and highlight the potential for its use in verifying the action of natural selection on candidate loci implicated in reducing hybrid fitness.

scholarly journals Ecological divergence in sympatry causes gene misregulation in hybrids

2019 ◽  
Author(s):  
Joseph A. McGirr ◽  
Christopher H. Martin
Keyword(s):  
Gene Expression ◽  
Reproductive Isolation ◽  
Differentially Expressed ◽  
F1 Hybrids ◽  
Adaptive Divergence ◽  
Lower Hybrid ◽  
Hybrid Fitness ◽  
Hybrid Gene ◽  
San Salvador ◽  
Ecological Selection

AbstractEcological speciation occurs when reproductive isolation evolves as a byproduct of adaptive divergence between populations. However, it is unknown whether divergent ecological selection on gene regulation can directly cause reproductive isolation. Selection favoring regulatory divergence between species could result in gene misregulation in F1 hybrids and ultimately lower hybrid fitness. We combined 58 resequenced genomes with 124 transcriptomes to test this hypothesis in a young, sympatric radiation of Cyprinodon pupfishes endemic to San Salvador Island, Bahamas, which consists of a dietary generalist and two novel trophic specialists – a molluscivore and a scale-eater. We found more differential gene expression between closely related sympatric specialists than between allopatric generalist populations separated by 1000 km. Intriguingly, 9.6% of genes that were differentially expressed between sympatric species were also misregulated in their F1 hybrids. Consistent with divergent ecological selection causing misregulation, a subset of these genes were in highly differentiated genomic regions and enriched for functions important for trophic specialization, including head, muscle, and brain development. These regions also included genes that showed evidence of hard selective sweeps and were significantly associated with oral jaw length – the most rapidly diversifying skeletal trait in this radiation. Our results indicate that divergent ecological selection in sympatry can cause hybrid gene misregulation which may act as a primary reproductive barrier between nascent species.SignificanceIt is unknown whether the same genes that regulate ecological traits can simultaneously contribute to reproductive barriers between species. We measured gene expression in two trophic specialist species of Cyprinodon pupfishes that rapidly diverged from a generalist ancestor. We found genes differentially expressed between species that also showed extreme expression levels in their hybrid offspring. Many of these genes showed signs of selection and have putative effects on the development of traits that are important for ecological specialization. This suggests that genetic variants contributing to adaptive trait divergence between parental species negatively interact to cause hybrid gene misregulation, potentially producing unfit hybrids. Such loci may be important barriers to gene flow during the early stages of speciation, even in sympatry.

scholarly journals Morphologically cryptic Amazonian bird species pairs exhibit strong postzygotic reproductive isolation

2018 ◽  
Vol 285 (1874) ◽  
pp. 20172081 ◽  
Author(s):  
Paola Pulido-Santacruz ◽  
Alexandre Aleixo ◽  
Jason T. Weir
Keyword(s):  
Reproductive Isolation ◽  
Amazon Basin ◽  
Species Recognition ◽  
Bird Species ◽  
Hybrid Zones ◽  
Hybrid Index ◽  
Postzygotic Isolation ◽  
Genome Wide ◽  
Species Pairs ◽  
Hybrid Classes

We possess limited understanding of how speciation unfolds in the most species-rich region of the planet—the Amazon basin. Hybrid zones provide valuable information on the evolution of reproductive isolation, but few studies of Amazonian vertebrate hybrid zones have rigorously examined the genome-wide underpinnings of reproductive isolation. We used genome-wide genetic datasets to show that two deeply diverged, but morphologically cryptic sister species of forest understorey birds show little evidence for prezygotic reproductive isolation, but substantial postzygotic isolation. Patterns of heterozygosity and hybrid index revealed that hybrid classes with heavily recombined genomes are rare and closely match simulations with high levels of selection against hybrids. Genomic and geographical clines exhibit a remarkable similarity across loci in cline centres, and have exceptionally narrow cline widths, suggesting that postzygotic isolation is driven by genetic incompatibilities at many loci, rather than a few loci of strong effect. We propose Amazonian understorey forest birds speciate slowly via gradual accumulation of postzygotic genetic incompatibilities, with prezygotic barriers playing a less important role. Our results suggest old, cryptic Amazonian taxa classified as subspecies could have substantial postzygotic isolation deserving species recognition and that species richness is likely to be substantially underestimated in Amazonia.

scholarly journals Multi-locus interactions and the build-up of reproductive isolation

2020 ◽  
Vol 375 (1806) ◽  
pp. 20190543 ◽  
Author(s):  
I. Satokangas ◽  
S. H. Martin ◽  
H. Helanterä ◽  
J. Saramäki ◽  
J. Kulmuni
Keyword(s):  
Reproductive Isolation ◽  
Empirical Work ◽  
Hybrid Fitness ◽  
Epistatic Interactions ◽  
Genome Scans ◽  
Theoretical Approaches ◽  
Genome Wide ◽  
Experimental Approaches ◽  
Polymorphism Data

All genes interact with other genes, and their additive effects and epistatic interactions affect an organism's phenotype and fitness. Recent theoretical and empirical work has advanced our understanding of the role of multi-locus interactions in speciation. However, relating different models to one another and to empirical observations is challenging. This review focuses on multi-locus interactions that lead to reproductive isolation (RI) through reduced hybrid fitness. We first review theoretical approaches and show how recent work incorporating a mechanistic understanding of multi-locus interactions recapitulates earlier models, but also makes novel predictions concerning the build-up of RI. These include high variance in the build-up rate of RI among taxa, the emergence of strong incompatibilities producing localized barriers to introgression, and an effect of population size on the build-up of RI. We then review recent experimental approaches to detect multi-locus interactions underlying RI using genomic data. We argue that future studies would benefit from overlapping methods like ancestry disequilibrium scans, genome scans of differentiation and analyses of hybrid gene expression. Finally, we highlight a need for further overlap between theoretical and empirical work, and approaches that predict what kind of patterns multi-locus interactions resulting in incompatibilities will leave in genome-wide polymorphism data. This article is part of the theme issue ‘Towards the completion of speciation: the evolution of reproductive isolation beyond the first barriers’.

scholarly journals Genomics of isolation in hybrids

2012 ◽  
Vol 367 (1587) ◽  
pp. 439-450 ◽  
Author(s):  
Zachariah Gompert ◽  
Thomas L. Parchman ◽  
C. Alex Buerkle
Keyword(s):  
Reproductive Isolation ◽  
Genetic Architecture ◽  
Large Scale ◽  
Empirical Studies ◽  
Hybrid Zones ◽  
Direct Measure ◽  
Fitness Effects ◽  
Outlier Loci ◽  
Admixed Population ◽  
Genome Level

Hybrid zones are common in nature and can offer critical insights into the dynamics and components of reproductive isolation. Hybrids between diverged lineages are particularly informative about the genetic architecture of reproductive isolation, because introgression in an admixed population is a direct measure of isolation. In this paper, we combine simulations and a new statistical model to determine the extent to which different genetic architectures of isolation leave different signatures on genome-level patterns of introgression. We found that reproductive isolation caused by one or several loci of large effect caused greater heterogeneity in patterns of introgression than architectures involving many loci with small fitness effects, particularly when isolating factors were closely linked. The same conditions that led to heterogeneous introgression often resulted in a reasonable correspondence between outlier loci and the genetic loci that contributed to isolation. However, demographic conditions affected both of these results, highlighting potential limitations to the study of the speciation genomics. Further progress in understanding the genomics of speciation will require large-scale empirical studies of introgression in hybrid zones and model-based analyses, as well as more comprehensive modelling of the expected levels of isolation with different demographies and genetic architectures of isolation.

scholarly journals Cytonuclear Genetic Incompatibilities in Plant Speciation

Plants ◽  
2020 ◽  
Vol 9 (4) ◽  
pp. 487 ◽  
Author(s):  
Zoé Postel ◽  
Pascal Touzet
Keyword(s):  
Reproductive Isolation ◽  
Plant Species ◽  
Mating Systems ◽  
Cell Function ◽  
Evolutionary Processes ◽  
Hybrid Fitness ◽  
Plant Mating Systems ◽  
The Impact ◽  
Cytonuclear Interaction ◽  
Endosymbiotic Origin

Due to the endosymbiotic origin of organelles, a pattern of coevolution and coadaptation between organellar and nuclear genomes is required for proper cell function. In this review, we focus on the impact of cytonuclear interaction on the reproductive isolation of plant species. We give examples of cases where species exhibit barriers to reproduction which involve plastid-nuclear or mito-nuclear genetic incompatibilities, and describe the evolutionary processes at play. We also discuss potential mechanisms of hybrid fitness recovery such as paternal leakage. Finally, we point out the possible interplay between plant mating systems and cytonuclear coevolution, and its consequence on plant speciation.

scholarly journals Limited intrinsic postzygotic reproductive isolation despite chromosomal rearrangements between closely related sympatric species of small ermine moths (Lepidoptera: Yponomeutidae)

2019 ◽  
Vol 128 (1) ◽  
pp. 44-58 ◽  
Author(s):  
Katerina H Hora ◽  
František Marec ◽  
Peter Roessingh ◽  
Steph B J Menken
Keyword(s):  
Reproductive Isolation ◽  
Parental Species ◽  
Meiotic Chromosome ◽  
Chromosomal Rearrangements ◽  
Sympatric Species ◽  
Hybrid Fitness ◽  
New Host ◽  
Closely Related Species ◽  
Postzygotic Reproductive Isolation

Abstract In evolutionarily young species and sympatric host races of phytophagous insects, postzygotic incompatibility is often not yet fully developed, but reduced fitness of hybrids is thought to facilitate further divergence. However, empirical evidence supporting this hypothesis is limited. To assess the role of reduced hybrid fitness, we studied meiosis and fertility in hybrids of two closely related small ermine moths, Yponomeuta padella and Yponomeuta cagnagella, and determined the extent of intrinsic postzygotic reproductive isolation. We found extensive rearrangements between the karyotypes of the two species and irregularities in meiotic chromosome pairing in their hybrids. The fertility of reciprocal F1 and, surprisingly, also of backcrosses with both parental species was not significantly decreased compared with intraspecific offspring. The results indicate that intrinsic postzygotic reproductive isolation between these closely related species is limited. We conclude that the observed chromosomal rearrangements are probably not the result of an accumulation of postzygotic incompatibilities preventing hybridization. Alternative explanations, such as adaptation to new host plants, are discussed.

THE GENETIC ARCHITECTURE OF REPRODUCTIVE ISOLATION IN LOUISIANA IRISES: HYBRID FITNESS IN NATURE

Evolution ◽  
2009 ◽  
Vol 63 (10) ◽  
pp. 2581-2594 ◽  
Author(s):  
Sunni J. Taylor ◽  
Michael Arnold ◽  
Noland H. Martin
Keyword(s):  
Reproductive Isolation ◽  
Genetic Architecture ◽  
Hybrid Fitness

scholarly journals Erratum: Admixture in European Populus hybrid zones makes feasible the mapping of loci that contribute to reproductive isolation and trait differences

Heredity ◽  
2006 ◽  
Vol 98 (3) ◽  
pp. 183-183 ◽  
Author(s):  
C Lexer ◽  
C A Buerkle ◽  
J A Joseph ◽  
B Heinze ◽  
M F Fay
Keyword(s):  
Reproductive Isolation ◽  
Hybrid Zones

scholarly journals HYBRID ZONES AND REPRODUCTIVE ISOLATION

Evolution ◽  
1965 ◽  
Vol 19 (4) ◽  
pp. 449-458 ◽  
Author(s):  
R. S. Bigelow
Keyword(s):  
Reproductive Isolation ◽  
Hybrid Zones

scholarly journals Real-time geographic settling of a hybrid zone between the invasive winter moth (Operophtera brumata L.) and the native Bruce spanworm (O. bruceata Hulst)

2021 ◽  
Author(s):  
Jeremy Andersen ◽  
Nathan Havill ◽  
George Boettner ◽  
Jennifer Chandler ◽  
Adalgisa Caccone ◽  
...  
Keyword(s):  
Real Time ◽  
Hybrid Zone ◽  
Native Species ◽  
Hybrid Zones ◽  
Operophtera Brumata ◽  
Hybrid Fitness ◽  
Cold Temperatures ◽  
Winter Moth ◽  
The Stability ◽  
Bruce Spanworm

Hybridization plays an important and underappreciated role in shaping the evolutionary trajectories of species. Following the introduction of a non-native organism to a novel habitat, hybridization with a native congener may affect the probability of establishment of the introduced species. In most documented cases of hybridization between a native and a non-native species, a mosaic hybrid zone is formed, with hybridization occurring heterogeneously across the landscape. In contrast, most naturally occurring hybrid zones are clinal in structure. Here we report on a long-term microsatellite dataset that monitored hybridization between the invasive winter moth, Operophtera brumata (Lepidoptera: Geometridae), and the native Bruce spanworm, O. bruceata, over a 12-year period. Our results document one of the first examples of the real-time formation and geographic settling of a clinal hybrid zone. In addition, by comparing one transect in Massachusetts where extreme winter cold temperatures have been hypothesized to restrict the distribution of winter moth, and one in coastal Connecticut, where winter temperatures are moderated by Long Island Sound, we find that the location of the hybrid zone appears to be independent of environmental variables and maintained under a tension model wherein the stability of the hybrid zone is constrained by population density, reduced hybrid fitness, and low dispersal rates. Documenting the formation of a contemporary clinal hybrid zone may provide important insights into the factors that shaped other well-established hybrid zones.

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