scholarly journals Hybrid asexuality as a primary reproductive barrier: on the interconnection between asexuality and speciation

2016 ◽  
Author(s):  
Karel Janko ◽  
Jan Pačes ◽  
Hilde Wilkinson-Herbots ◽  
Rui J Costa ◽  
Jan Röslein ◽  
...  
Keyword(s):  
Gene Flow ◽  
Reproductive Barrier ◽  
Published Data ◽  
Gene Pools ◽  
Hybrid Zones ◽  
Interspecific Gene Flow ◽  
Species Pairs ◽  
History Of ◽  
Gradual Accumulation ◽  
Fish Hybrids

Speciation usually proceeds in a continuum from intensively hybridizing populations until the formation of irreversibly isolated species. Restriction of interspecific gene flow may often be achieved by gradual accumulation of intrinsic postzygotic incompatibilities with hybrid infertility typically evolving more rapidly than inviability. A reconstructed history of speciation in European loaches (Cobitis) reveals that accumulation of postzygotic reproductive incompatibilities may take an alternative, in the literature largely neglected, pathway through initiation of hybrids' asexuality rather than through a decrease in hybrids' fitness. Combined evidence shows that contemporary Cobitis species readily hybridize in hybrid zones, but their gene pools are isolated as hybridization produces infertile males and fertile but clonally reproducing females that cannot mediate introgressions. Nevertheless, coalescent analyses indicated intensive historical gene flow during earlier stages of Cobitis diversification, suggesting that non-clonal hybrids must have existed in the past. The revealed patterns imply that during the initial stages of speciation, hybridization between little diverged species produced recombinant hybrids mediating gene flow, but growing divergence among species caused disrupted meiosis in hybrids resulting in their clonality, which acts as a barrier to gene flow. Comparative analysis of published data on other fish hybrids corroborated the generality of our findings; the species pairs producing asexual hybrids were more genetically diverged than those pairs producing fertile sexual hybrids but less diverged than species pairs producing infertile hybrids. Hybrid asexuality therefore appears to evolve at lower divergence than other types of postzygotic barriers and might thus represent a primary reproductive barrier in many taxa.

scholarly journals Resolving spatial complexities of hybridization in the context of the gray zone of speciation in North American ratsnakes (Pantherophis obsoletus complex)

2020 ◽  
Author(s):  
Frank T. Burbrink ◽  
Marcelo Gehara ◽  
Edward A. Myers
Keyword(s):  
Gene Flow ◽  
Spatial Information ◽  
Hybrid Zones ◽  
Gray Zone ◽  
Population Genomic ◽  
Species Pairs ◽  
History Of ◽  
Flow Changes ◽  
Network Approaches ◽  
Obsoletus Complex

AbstractInferring the history of divergence between species in a framework that permits the presence of gene flow has been crucial for characterizing the gray zone of speciation, which is the period of time where lineages have diverged but have not yet achieved strict reproductive isolation. However, estimates of both divergence times and rates gene flow often ignore spatial information, for example the formation and shape of hybrid zones. Using population genomic data from the eastern ratsnake complex (Pantherophis obsoletus), we infer phylogeographic groups, gene flow, changes in demography, the timing of divergence, and hybrid zone widths. We examine the spatial context of diversification by linking migration and timing of divergence to the location and widths of hybrid zones. Artificial neural network approaches are applied to understand how landscape features and past climate have influenced population genetic structure among these lineages prior to hybridization. Rates of migration between lineages are associated with the width and shape of hybrid zones. Timing of divergence is not related to migration rate across species pairs and is therefore a poor proxy for inferring position in the gray zone. However, timing of divergence is related to the number of loci weakly introgressing through hybrid zones.

scholarly journals Molecular Signatures of Reticulate Evolution within the Complex of European Pine Taxa

Forests ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 489
Author(s):  
Bartosz Łabiszak ◽  
Witold Wachowiak
Keyword(s):  
Gene Flow ◽  
Reticulate Evolution ◽  
Modeling Framework ◽  
Closely Related Species ◽  
Interspecific Gene Flow ◽  
Nucleotide Sequence Variation ◽  
History Of ◽  
Best Fitting ◽  
Species Integrity

Speciation mechanisms, including the role of interspecific gene flow and introgression in the emergence of new species, are the major focus of evolutionary studies. Inference of taxonomic relationship between closely related species may be challenged by past hybridization events, but at the same time, it may provide new knowledge about mechanisms responsible for the maintenance of species integrity despite interspecific gene flow. Here, using nucleotide sequence variation and utilizing a coalescent modeling framework, we tested the role of hybridization and introgression in the evolutionary history of closely related pine taxa from the Pinus mugo complex and P. sylvestris. We compared the patterns of polymorphism and divergence between taxa and found a great overlap of neutral variation within the P. mugo complex. Our phylogeny reconstruction indicated multiple instances of reticulation events in the past, suggesting an important role of interspecific gene flow in the species divergence. The best-fitting model revealed P. mugo and P. uncinata as sister species with basal P. uliginosa and asymmetric migration between all investigated species after their divergence. The magnitude of interspecies gene flow differed greatly, and it was consistently stronger from representatives of P. mugo complex to P. sylvestris than in the opposite direction. The results indicate the prominent role of reticulation evolution in those forest trees and provide a genetic framework to study species integrity maintained by selection and local adaptation.

scholarly journals Altitudinal gradients, plant hybrid zones and evolutionary novelty

2014 ◽  
Vol 369 (1648) ◽  
pp. 20130346 ◽  
Author(s):  
Richard J. Abbott ◽  
Adrian C. Brennan
Keyword(s):  
Gene Flow ◽  
Mount Etna ◽  
Hybrid Zones ◽  
Evolutionary Novelty ◽  
Altitudinal Gradients ◽  
Interspecific Gene Flow ◽  
Adaptive Introgression ◽  
Local Environments ◽  
The Face ◽  
Plant Hybrid

Altitudinal gradients are characterized by steep changes of the physical and biotic environment that present challenges to plant adaptation throughout large parts of the world. Hybrid zones may form where related species inhabit different neighbouring altitudes and can facilitate interspecific gene flow and potentially the breakdown of species barriers. Studies of such hybrid zones can reveal much about the genetic basis of adaptation to environmental differences stemming from changes in altitude and the maintenance of species divergence in the face of gene flow. Furthermore, owing to recombination and transgressive effects, such hybrid zones can be sources of evolutionary novelty. We document plant hybrid zones associated with altitudinal gradients and emphasize similarities and differences in their structure. We then focus on recent studies of a hybrid zone between two Senecio species that occur at high and low altitude on Mount Etna, Sicily, showing how adaptation to local environments and intrinsic selection against hybrids act to maintain it. Finally, we consider the potential of altitudinal hybrid zones for generating evolutionary novelty through adaptive introgression and hybrid speciation. Examples of homoploid hybrid species of Senecio and Pinus that originated from altitudinal hybrid zones are discussed.

scholarly journals Modeling the Multiple Facets of Speciation-with-Gene-Flow Towards Inferring the Divergence History of Lake Whitefish Species Pairs (Coregonus Clupeaformis)

2016 ◽  
Author(s):  
Clément Rougeux ◽  
Louis Bernatchez ◽  
Pierre-Alexandre Gagnaire
Keyword(s):  
Gene Flow ◽  
Genomic Variation ◽  
Secondary Contact ◽  
Lake Whitefish ◽  
Lineage Sorting ◽  
Effective Population ◽  
Modeling Framework ◽  
Species Pairs ◽  
History Of ◽  
And Migration

AbstractParallel divergence patterns across replicated species pairs occurring in similar environmental contrasts may arise through distinct evolutionary scenarios. Deciphering whether such parallelism actually reflects repeated parallel divergence driven by divergent selection or a single divergence event with subsequent gene flow needs to be ascertained. Reconstructing historical gene flow is therefore of fundamental interest to understand how demography and selection jointly shaped genomic divergence during speciation. Here, we use an extended modeling framework to explore the multiple facets of speciation-with-gene-flow with demo-genetic divergence models that capture both temporal and genomic variation in effective population size and migration rate. We investigate the divergence history of five sympatric Lake Whitefish limnetic (dwarf) and benthic (normal) species pairs characterized by variable degrees of ecological divergence and reproductive isolation. Genome-wide SNPs were used to document the extent of genetic differentiation in each species pair, and 26 divergence models were fitted and compared to the unfolded joint allele frequency spectrum of each pair. We found evidence that a recent (circa 3000-4000 generations) asymmetrical secondary contact between expanding post-glacial populations has accompanied Whitefish diversification. Our results suggest that heterogeneous genomic differentiation patterns have emerged through the combined effects of linked selection generating variable rates of lineage sorting across the genome during geographical isolation, and heterogeneous introgression eroding divergence at different rates across the genome upon secondary contact. This study thus provides a new retrospective insight into the historical demographic and selective processes that shaped a continuum of divergence associated with ecological speciation.

scholarly journals Extensive Interspecific Gene Flow Shaped Complex Evolutionary History and Underestimated Species Diversity in Rapidly Radiated Dolphins

2021 ◽  
Author(s):  
Weijian Guo ◽  
Di Sun ◽  
Yang Cao ◽  
Linlin Xiao ◽  
Xin Huang ◽  
...  
Keyword(s):  
Gene Flow ◽  
Bayesian Methods ◽  
Phylogenetic Relationships ◽  
Evolutionary History ◽  
Phylogenetic Reconstruction ◽  
Genomic Data ◽  
Sliding Window ◽  
Interspecific Gene Flow ◽  
History Of ◽  
Relationship Of

AbstractRecently diverged taxa are often characterized by high rates of hybridization, which can complicate phylogenetic reconstruction. For this reason, the phylogenetic relationships and evolutionary history of dolphins are still not very well resolved; the question of whether the genera Tursiops and Stenella are monophyletic is especially controversial. Here, we performed re-sequencing of six dolphin genomes and combined them with eight previously published dolphin SRA datasets and six whole-genome datasets to investigate the phylogenetic relationships of dolphins and test the monophyly hypothesis of Tursiops and Stenella. Phylogenetic reconstruction with the maximum likelihood and Bayesian methods of concatenated loci, as well as with coalescence analyses of sliding window trees, produced a concordant and well-supported tree. Our studies support the non-monophyletic status of Tursiops and Stenella because the species referred these genera do not form exclusive monophyletic clades. This suggests that the current taxonomy of both genera might not reflect their evolutionary history and may underestimate their diversity. A four-taxon D-statistic (ABBA-BABA) test, five-taxon DFOIL test, and tree-based PhyloNet analyses all showed extensive gene flow across dolphin species, which could explain the instability in resolving phylogenetic relationship of oceanic dolphins with different and limited markers. This study could be a good case to demonstrate how genomic data can reveal complex speciation and phylogeny in rapidly radiating animal groups.

scholarly journals Paracoccidioides genomes reflect high levels of species divergence and little interspecific gene flow

2020 ◽  
Author(s):  
Heidi Mavengere ◽  
Katlheen Mattox ◽  
Marcus M Teixeira ◽  
Victoria E. Sepúlveda ◽  
Oscar M. Gomez ◽  
...  
Keyword(s):  
Gene Flow ◽  
Fungal Pathogens ◽  
Fungal Species ◽  
Species Boundaries ◽  
Whole Genome ◽  
Gene Exchange ◽  
Interspecific Gene Flow ◽  
Systematic Effort ◽  
Species Pairs ◽  
Show Evidence

ABSTRACTThe fungus Paracoccidioides spp. is a prevalent human pathogen endemic to South America. The genus is composed of five species. In this report, we use 37 whole genome sequences to study the allocation of genetic variation in Paracoccidioides. We tested three genome-wide predictions of advanced speciation, namely, that all species should be reciprocally monophyletic, that species pairs should be highly differentiated along the whole genome, and that there should be low rates of interspecific gene exchange. We find support for these three hypotheses. Species pairs with older divergences show no evidence of gene exchange, while more recently diverged species pairs show evidence of modest rates of introgression. Our results indicate that as divergence progresses, species boundaries become less porous among Paracoccidioides species. Our results suggest that species in Paracoccidioides are at different stages along the divergence continuum.IMPORTANCEParacoccidioides is the causal agent of the most frequent systemic mycosis in Latin America. Most of the inference of the evolutionary history of Paracoccidioides has used only a handful of molecular markers. In this report, we evaluate the extent of genome divergence among Paracoccidioides species and study the possibility of interspecific gene exchange. We find that all species are highly differentiated. We also find that the amount of gene flow between species is low and in some cases even completely absent in spite of geographic overlap. Our study constitutes a systematic effort to identify species boundaries in fungal pathogens, and determine the extent of gene exchange among fungal species.

scholarly journals Genomic and geographic footprints of differential introgression between two highly divergent fish species

2017 ◽  
Author(s):  
Ahmed Souissi ◽  
François Bonhomme ◽  
Manuel Manchado ◽  
Lilia Bahri-Sfar ◽  
Pierre-Alexandre Gagnaire
Keyword(s):  
Gene Flow ◽  
Hybrid Zone ◽  
Demographic History ◽  
Genetic Interactions ◽  
Solea Senegalensis ◽  
Integrative Approach ◽  
Gene Pools ◽  
Mediterranean Populations ◽  
Genome Wide ◽  
History Of

AbstractInvestigating variation in gene flow across the genome between closely related species is important to understand how reproductive isolation builds up during the speciation process. An efficient way to characterize differential gene flow is to study how the genetic interactions that take place in hybrid zones selectively filter gene exchange between species, leading to heterogeneous genome divergence. In the present study, genome-wide divergence and introgression patterns were investigated between two sole species, Solea senegalensis and Solea aegyptiaca, using a restriction-associated DNA sequencing (RAD-Seq) approach to analyze samples taken from a transect spanning the hybrid zone. An integrative approach combining geographic and genomic clines methods with an analysis of individual locus introgression taking into account the demographic history of divergence inferred from the joint allele frequency spectrum was conducted. Our results showed that only a minor fraction of the genome can still substantially introgress between the two species due to genome-wide congealing. We found multiple evidence for a preferential direction of introgression in the S. aegyptiaca genetic background, indicating a possible recent or ongoing movement of the hybrid zone. Deviant introgression signals found in the opposite direction supported that the Mediterranean populations of S. senegalensis could have benefited from adaptive introgression. Our study thus illustrates the varied outcomes of genetic interactions between divergent gene pools that recently met after a long history of divergence.

scholarly journals Natural selection maintains species despite widespread hybridization in the desert shrub Encelia

2020 ◽  
Author(s):  
Christopher D DiVittorio ◽  
Sonal Singhal ◽  
Adam B Roddy ◽  
Felipe Zapata ◽  
David D Ackerly ◽  
...  
Keyword(s):  
Gene Flow ◽  
Natural Selection ◽  
Field Experiments ◽  
Population Genomics ◽  
Coastal Dunes ◽  
Species Boundaries ◽  
Hybrid Zones ◽  
Desert Shrubs ◽  
Species Complexes ◽  
Species Pairs

ABSTRACTNatural selection is an important driver of genetic and phenotypic differentiation between species. A powerful way to test the role of natural selection in the formation and maintenance of species is to study species complexes in which potential gene flow is high but realized gene flow is low. For a recent radiation of New World desert shrubs (Encelia: Asteraceae), we use fine-scale geographic sampling and population genomics to determine patterns of gene flow across two hybrid zones formed between two independent pairs of species with parapatric distributions. After finding evidence for extremely strong selection at both hybrid zones, we use a combination of field experiments, high-resolution imaging, and physiological measurements to determine the ecological basis for selection at one of the hybrid zones. Our results identify multiple ecological mechanisms of selection (drought, salinity, herbivory, and burial) that together are sufficient to maintain species boundaries despite high rates of hybridization. Given that multiple pairs of species hybridize at ecologically divergent parapatric boundaries in the adaptive radiation of Encelia, such mechanisms may maintain species boundaries throughout this group.SIGNIFICANCE STATEMENTIn Baja California, the deserts meet the coastal dunes in a narrow transition visible even from satellite images. We study two species pairs of desert shrubs (Encelia) that occur across this transition. Although these species can interbreed, they remain distinct. Using a combination of genetics, field experiments, 3D-imaging, and physiological measurements, we show that natural selection counteracts the homogenizing effects of gene exchange. The different habitats of these species create multiple mechanisms of selection - drought, salinity, herbivory, and burial, which together maintain these species in their native habitats and their hybrids in intermediate habitats. This study illustrates how environmental factors influence traits and fitness and how this in turn maintain species, highlighting the importance of natural selection in speciation.

Sign in / Sign up

Export Citation Format

Share Document