Exclusion of the Role of Secondary Contact in an Allele Frequency Cline in the Mussel Mutilus edulis

Evolution ◽  
1985 ◽  
Vol 39 (2) ◽  
pp. 432 ◽  
Author(s):  
Thomas J. Hilbish ◽  
Richard K. Koehn
Keyword(s):  
Allele Frequency ◽  
Secondary Contact

Extensive hybridization between two Andean warbler species with shallow divergence in mtDNA

The Auk ◽  
2021 ◽  
Vol 138 (1) ◽  
Author(s):  
Laura N Céspedes-Arias ◽  
Andrés M Cuervo ◽  
Elisa Bonaccorso ◽  
Marialejandra Castro-Farias ◽  
Alejandro Mendoza-Santacruz ◽  
...  
Keyword(s):  
Genetic Structure ◽  
Contact Zone ◽  
Hybrid Zone ◽  
Secondary Contact ◽  
Tropical Andes ◽  
Phenotypic Data ◽  
Geographic Ranges ◽  
Intermediate Phenotypes ◽  
Ecological Barriers

Abstract Studying processes acting on differentiated populations upon secondary contact, such as hybridization, is important to comprehensively understand how species are formed and maintained over time. However, avian speciation studies in the tropical Andes have largely focused on the role of topographic and ecological barriers promoting divergence in allopatry, seldom examining hybridization and introgression. We describe a hybrid zone involving 2 closely related Andean warblers (Parulidae), the Golden-fronted Redstart (Myioborus ornatus), and the Spectacled Redstart (Myioborus melanocephalus). Geographic ranges of these species abut near the Colombia-Ecuador border and many specimens from the region exhibit intermediate phenotypes, but a formal description of phenotypic variation in the contact zone was heretofore lacking. We collected specimens across a transect encompassing the area where ranges abut and areas where only “pure” parental phenotypes of M. ornatus chrysops and M. melanocephalus ruficoronatus occur. We described variation in plumage traits including patterns of head and ventral coloration and tail markings based on 321 specimens. To describe genetic variation in the contact zone and over a broader phylogeographic context, we used sequences of the mitochondrial ND2 gene for 219 individuals across the transect and the entire range of both species, including all subspecies, from Venezuela to Bolivia. We documented a hybrid zone ~200 km wide based on head coloration, where intermediate plumage phenotypes are most common and “pure” forms do not overlap geographically, consistent with extensive hybridization. Across the range of the M. ornatus–M. melanocephalus complex, mitochondrial genetic structure was shallow, with genetic breaks only coinciding clearly with one topographic feature. Such a low genetic structure is striking given the high diversity in plumage phenotypes and the current taxonomy of the group. Our phenotypic data suggest that barriers to hybridization are not strong, and allow us to postulate hypotheses to be tested using forthcoming genomic data.

Cryptic Diversity and Sexual Selection

2020 ◽  
pp. 447-471
Author(s):  
Matthias Galipaud ◽  
Loïc Bollache ◽  
Clément Lagrue
Keyword(s):  
Sexual Selection ◽  
Morphological Traits ◽  
Character Displacement ◽  
Secondary Contact ◽  
Cryptic Diversity ◽  
Reproductive Character Displacement ◽  
Behavioral Traits ◽  
Genetic Techniques ◽  
Existing Data

Recent advances in molecular and genetic techniques have revealed tremendous hidden genetic diversity in plants and animals. Crustaceans are no exception and, in fact, present one of the highest levels of cryptic diversity among the metazoans. Beyond the importance of such discovery and its multiple implications for taxonomy and ecology, it is now timely to investigate the potential causes of cryptic diversity. This chapter reviews the theoretical and experimental literature, seeking evidences for a relationship between sexual selection and cryptic diversity in crustaceans. It proposes three scenarios for the role of sexual selection on the origin and maintenance of pre-mating isolation and genetic divergence among crustacean populations, and suggests ways to discriminate among them experimentally or using existing data. Assuming that taxonomic identification is largely based on differences in sexually selected morphological traits, it also reviews evidence for a cryptic action of sexual selection on crustacean phenotypes. Specifically, if sexual selection acts primarily on chemical, visual, or behavioral traits, it is likely that allopatric crustacean populations remain morphologically similar even when they are reproductively isolated. This review shows that the strength of sexual selection likely differs among allopatric populations but does not seem to consistently induce pre-mating isolation (e.g. as in copepods and amphipods). Research is now needed to try to identify general patterns and determine the role of sexual selection on pre-mating isolation after secondary contact between populations, through reinforcement and reproductive character displacement.

scholarly journals Mitochondrial Ecophysiology: Assessing the Evolutionary Forces That Shape Mitochondrial Variation

2019 ◽  
Vol 59 (4) ◽  
pp. 925-937 ◽  
Author(s):  
Jessica L McKenzie ◽  
Dillon J Chung ◽  
Timothy M Healy ◽  
Reid S Brennan ◽  
Heather J Bryant ◽  
...  
Keyword(s):  
Adaptive Evolution ◽  
Mitochondrial Function ◽  
Fundulus Heteroclitus ◽  
Secondary Contact ◽  
Mitochondrial Genomes ◽  
Evolutionary Forces ◽  
Population Genomic ◽  
Genomic Studies

Abstract The mitonuclear species concept hypothesizes that incompatibilities between interacting gene products of the nuclear and mitochondrial genomes are a major factor establishing and maintaining species boundaries. However, most of the data available to test this concept come from studies of genetic variation in mitochondrial DNA, and clines in the mitochondrial genome across contact zones can be produced by a variety of forces. Here, we show that using a combination of population genomic analyses of the nuclear and mitochondrial genomes and studies of mitochondrial function can provide insight into the relative roles of neutral processes, adaptive evolution, and mitonuclear incompatibility in establishing and maintaining mitochondrial clines, using Atlantic killifish (Fundulus heteroclitus) as a case study. There is strong evidence for a role of secondary contact following the last glaciation in shaping a steep mitochondrial cline across a contact zone between northern and southern subspecies of killifish, but there is also evidence for a role of adaptive evolution in driving differentiation between the subspecies in a variety of traits from the level of the whole organism to the level of mitochondrial function. In addition, studies are beginning to address the potential for mitonuclear incompatibilities in admixed populations. However, population genomic studies have failed to detect evidence for a strong and pervasive influence of mitonuclear incompatibilities, and we suggest that polygenic selection may be responsible for the complex patterns observed. This case study demonstrates that multiple forces can act together in shaping mitochondrial clines, and illustrates the challenge of disentangling their relative roles.

scholarly journals Phosphodiesterase 4 D Gene Polymorphism in Relation to Intracranial and Extracranial Atherosclerosis in Ischemic Stroke

2011 ◽  
Vol 31 (4) ◽  
pp. 191-197 ◽  
Author(s):  
Jayantee Kalita ◽  
Bindu I. Somarajan ◽  
Bishwanath Kumar ◽  
Sunil Kumar ◽  
Balraj Mittal ◽  
...  
Keyword(s):  
Ischemic Stroke ◽  
Gene Polymorphism ◽  
Allele Frequency ◽  
Mr Angiography ◽  
Genetic Basis ◽  
Total Occlusion ◽  
Phosphodiesterase 4 ◽  
Atherosclerotic Stenosis

In ischemic stroke, extracranial MR angiography (ECMRA) is more frequently abnormal in Caucasians and intracranial (ICMRA) in Asians which may have a genetic basis. We report phosphodiesterase (PDE4D) gene polymorphism and its correlation with MRA findings in patients with ischemic stroke.Consecutive patients with MRI proven ischemic stroke undergoing MRA were included in this study. The severity of atherosclerotic stenosis on MRA was categorized into moderate 50%–80%, severe 80%–99%, and total occlusion 100% using NASCET criteria. The polymorphism in SNP 32, SNP 83 and SNP 87 of PDE4D gene was analyzed by PCR both in the patients and in 188 controls.Among the 148 patients, MRA was abnormal in 77% patients; ECMRA in 53.8%, ICMRA in 66% and both were abnormal in 42% patients. The frequency of CC genotype of PDE4D83 was significantly higher in the patients with ischemic stroke compared to controls (OR 3.38, 95% CI 1.61–7.11,P= 0.001). The frequency of TT genotype of PDE4D87 was significantly higher ICMRA abnormalities (20%) compared to normal ICMRA (2%). The genotype and allele frequency of PDE4D83 and PDE4D32 were not significantly related to MRA abnormalities. The role of PDE4D87 in atherosclerosis needs confirmation in larger studies.

ACE Insertion/Deletion, But Not −240A>T Polymorphism, Modulates the Severity in Heart Failure

2008 ◽  
Vol 56 (8) ◽  
pp. 1004-1010 ◽  
Author(s):  
Cinzia Fatini ◽  
Elena Sticchi ◽  
Rossella Marcucci ◽  
Abdihakim Abdullahi Said ◽  
Stefano Del Pace ◽  
...  
Keyword(s):  
Heart Failure ◽  
Allele Frequency ◽  
Nyha Class ◽  
Severe Heart Failure ◽  
Genotype Distribution ◽  
Multinomial Regression ◽  
Predisposing Factor ◽  
Significant Difference ◽  
Patients With Heart Failure

ObjectiveACE gene is reported to be a candidate gene in heart failure. The insertion/deletion (I/D) polymorphism has been observed to be a predictor of mortality in this disease, but no data are available concerning the role of ACE −240A>T polymorphism. In this study, we investigated the role of ACE I/D and −240A>T polymorphisms in influencing both severity and clinical outcomes in patients with heart failure, according to New York Heart Association (NYHA) class.PatientsWe studied 323 patients with heart failure (258 men/65 women; age, 70.8 ± 11.5 years) followed-up for 11.9 ± 6.6 months.ResultsThe ACE D and −240T allele frequency significantly increased according to the NYHA functional class (P = 0.0002 and P < 0.0001, respectively).No significant difference in ACE polymorphism genotype distribution and allele frequency according to N-terminal pro-brain natriuretic peptide tertiles was observed. At multinomial regression analysis, ACE D but not −240T allele has been evidenced to be a significant and independent predictor of severity for both NYHA III and IV classes (P = 0.01 and P = 0.004, respectively). The ACE D allele prevalence was higher, even if not significantly in both death and rehospitalization groups in comparison with survivors and nonrehospitalized (P = 0.6 and P = 0.9, respectively). No difference in −240T allele frequency has been observed for the ACE −240A>T polymorphism, in relation to both death and rehospitalization (P = 0.1 and P = 0.6, respectively).ConclusionsThis study suggests that ACE I/D polymorphism might represent a predisposing factor to severe heart failure, independently of well-known prognostic markers.

scholarly journals A genetic switch for male UV-iridescence in an incipient species pair of sulphur butterflies

2021 ◽  
Author(s):  
Vincent Ficarrotta ◽  
Joseph J Hanly ◽  
Ling S Loh ◽  
Caroline M Francescutti ◽  
Anna Ren ◽  
...  
Keyword(s):  
Genetic Basis ◽  
Secondary Contact ◽  
Sexual Signals ◽  
Genetic Switch ◽  
Knock Out ◽  
Incipient Species ◽  
Courtship Signal ◽  
Species Formation ◽  
Genomic Landscape

Mating cues evolve rapidly and can contribute to species formation and maintenance. However, little is known about how sexual signals diverge and how this variation integrates with other barrier loci to shape the genomic landscape of reproductive isolation. Here, we elucidate the genetic basis of UV iridescence, a courtship signal that differentiates the males of Colias eurytheme butterflies from a sister species, allowing females to avoid costly heterospecific matings. Anthropogenic range expansion of the two incipient species established a large zone of secondary contact across the eastern US with strong signatures of genomic admixtures spanning all autosomes. In contrast, Z chromosomes are highly differentiated between the two species, supporting a disproportionate role of sex chromosomes in speciation known as the large-X effect. Within this chromosome-wide reproductive barrier, cis-regulatory variation of bric a brac (bab) drives the male UV-iridescence polymorphism between the two species. Bab is expressed in all non-UV scales, and butterflies of either species or sex acquire widespread ectopic iridescence following its CRISPR knock-out, demonstrating that Bab functions as a suppressor of UV-scale differentiation that potentiates mating cue divergence. These results provide new insights into the diversification of sexual signals and the species concept.

Functional polymorphism of the myeloperoxidase gene (G-463A) in depressive patients

2010 ◽  
Vol 22 (5) ◽  
pp. 218-222 ◽  
Author(s):  
Piotr Gałecki ◽  
Antoni Florkowski ◽  
Kinga Bobińska ◽  
Janusz Śmigielski ◽  
Małgorzata Bieńkiewicz ◽  
...  
Keyword(s):  
Allele Frequency ◽  
Depressive Disorders ◽  
Genotype Distribution ◽  
Functional Polymorphism ◽  
Single Nucleotide ◽  
Significant Difference ◽  
Inflammatory Processes ◽  
Healthy Control ◽  
Depressive Patients

Gałecki P, Florkowski A, Bobińska K, Śmigielski J, Bieńkiewicz M, Szemraj J. Functional polymorphism of the myeloperoxidase gene (G-463A) in depressive patients.Objective:Myeloperoxidase (MPO) is an enzyme involved in the production of hypochloric acid as well as other reactive oxygen species. This enzyme plays a significant role in inflammatory processes. In view of the observed associations between depression and such inflammatory processes, as well as of the reports that confirm the presence of oxidative stress in depression, this study was designed to assess the correlation, if any, between the single nucleotide polymorphism G-463A of the MPO gene and the risk of recurrent depressive disorders (DD).Methods:The study was carried out in a group of 149 patients with recurrent DD and 149 healthy control subjects. Genotyping was performed by PCR/restriction fragment length polymorphism.Results:A comparison between healthy controls and depressive patients showed a statistically significant difference in genotype distribution and allele frequency in the studied groups. Genotype distribution and allele frequency did not correlate with clinical variables of the patients.Conclusion:The obtained results of the study allow us to draw a cautious conclusion about the role of the analysed G-463A MPO polymorphism in recurrent DD development, which, however, requires eventual confirmation in further studies.

scholarly journals Quaternary climate changes as speciation drivers in the Amazon floodplains

2020 ◽  
Vol 6 (11) ◽  
pp. eaax4718 ◽  
Author(s):  
Gregory Thom ◽  
Alexander T. Xue ◽  
André O. Sawakuchi ◽  
Camila C. Ribas ◽  
Michael J. Hickerson ◽  
...  
Keyword(s):  
Environmental Changes ◽  
Demographic History ◽  
Secondary Contact ◽  
Phylogenomic Analysis ◽  
Population Isolation ◽  
Quaternary Climate ◽  
Species Complexes ◽  
Historical Processes ◽  
Quaternary Climate Changes

The role of climate as a speciation driver in the Amazon has long been discussed. Phylogeographic studies have failed to recover synchronous demographic responses across taxa, although recent evidence supports the interaction between rivers and climate in promoting speciation. Most studies, however, are biased toward upland forest organisms, while other habitats are poorly explored and could hold valuable information about major historical processes. We conducted a comparative phylogenomic analysis of floodplain forest birds to explore the effects of historical environmental changes and current connectivity on population differentiation. Our findings support a similar demographic history among species complexes, indicating that the central portion of the Amazon River basin is a suture zone for taxa isolated across the main Amazonian sub-basins. Our results also suggest that changes in the fluvial landscape induced by climate variation during the Mid- and Late Pleistocene drove population isolation, leading to diversification with subsequent secondary contact.

scholarly journals How Facilitation May Interfere with Ecological Speciation

2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
P. Liancourt ◽  
P. Choler ◽  
N. Gross ◽  
X. Thibert-Plante ◽  
K. Tielbörger
Keyword(s):  
Ecological Speciation ◽  
Theoretical Research ◽  
Secondary Contact ◽  
Positive Interactions ◽  
Evolutionary Diversification ◽  
Incipient Species ◽  
Modelling Framework ◽  
Vast Literature ◽  
Marginal Habitats

Compared to the vast literature linking competitive interactions and speciation, attempts to understand the role of facilitation for evolutionary diversification remain scarce. Yet, community ecologists now recognize the importance of positive interactions within plant communities. Here, we examine how facilitation may interfere with the mechanisms of ecological speciation. We argue that facilitation is likely to (1) maintain gene flow among incipient species by enabling cooccurrence of adapted and maladapted forms in marginal habitats and (2) increase fitness of introgressed forms and limit reinforcement in secondary contact zones. Alternatively, we present how facilitation may favour colonization of marginal habitats and thus enhance local adaptation and ecological speciation. Therefore, facilitation may impede or pave the way for ecological speciation. Using a simple spatially and genetically explicit modelling framework, we illustrate and propose some first testable ideas about how, when, and where facilitation may act as a cohesive force for ecological speciation. These hypotheses and the modelling framework proposed should stimulate further empirical and theoretical research examining the role of both competitive and positive interactions in the formation of incipient species.

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