scholarly journals Assortative Mating in Hybrid Zones Is Remarkably Ineffective in Promoting Speciation

2020 ◽  
Vol 195 (6) ◽  
pp. E150-E167 ◽  
Author(s):  
Darren E. Irwin
Keyword(s):  
Assortative Mating ◽  
Hybrid Zones

scholarly journals Assortative mating in hybrid zones is remarkably ineffective in promoting speciation

2019 ◽  
Author(s):  
Darren E. Irwin
Keyword(s):  
Assortative Mating ◽  
F1 Hybrids ◽  
Secondary Contact ◽  
Hybrid Zones ◽  
Mating Types ◽  
Postzygotic Isolation ◽  
Small Reduction ◽  
Hybrid Fitness ◽  
Prezygotic Isolation ◽  
Two Populations

AbstractAssortative mating and other forms of partial prezygotic isolation are often viewed as being more important than partial postzygotic isolation (low fitness of hybrids) early in the process of speciation. Here I simulate secondary contact between two populations (‘species’) to examine effects of pre- and postzygotic isolation in preventing blending. A small reduction in hybrid fitness (e.g., 10%) produces a narrower hybrid zone than a strong but imperfect mating preference (e.g., 10x stronger preference for conspecific over heterospecific mates). This is because, in the latter case, rare F1 hybrids find each other attractive (due to assortative mating), leading to the gradual buildup of a full continuum of intermediates between the two species. The cline is narrower than would result from purely neutral diffusion over the same number of generations, largely due to the frequency-dependent mating disadvantage of individuals of rare mating types. Hybrids tend to pay this cost of rarity more than pure individuals, meaning there is an induced postzygotic isolation effect of assortative mating. These results prompt a questioning of the concept of partial prezygotic isolation, since it is not very isolating unless there is also postzygotic isolation.

scholarly journals Mate choice enhances post-zygotic barriers to gene flow via ancestry bundling

2021 ◽  
Author(s):  
Pavitra Muralidhar ◽  
Graham Coop ◽  
Carl Veller
Keyword(s):  
Gene Flow ◽  
Mate Choice ◽  
Assortative Mating ◽  
Hybrid Zones ◽  
Genetic Introgression ◽  
Genetic Isolation ◽  
Common Features ◽  
Genome Wide ◽  
Zygotic Selection

Hybridization and subsequent genetic introgression are now known to be common features of the histories of many species, including our own. Following hybridization, post-zygotic selection tends to purge introgressed DNA genome-wide. While mate choice can prevent hybridization in the first place, it is also known to play an important role in post-zygotic selection against hybrids, and thus the purging of introgressed DNA. However, this role is usually thought of as a direct one: a mating preference for conspecifics reduces the sexual fitness of hybrids, reducing the transmission of introgressed ancestry. Here, we explore a second, indirect role of mate choice as a barrier to gene flow. Under assortative mating, parents covary in their ancestry, causing ancestry to be "bundled" in their offspring and later generations. This bundling effect increases ancestry variance in the population, enhancing the efficiency with which post-zygotic selection purges introgressed DNA. Using whole-genome simulations, we show that the bundling effect can comprise a substantial portion of mate choice's overall effect as a postzygotic barrier to gene flow, and that it is driven by ancestry covariances both between and within maternally and paternally inherited genomes. Using estimates of the strength of assortative mating in avian hybrid zones, we calculate that the bundling effect of mate choice may increase the amount of purging of introgressed DNA by 40-80%, contributing substantially to the genetic isolation of species.

scholarly journals Definition and Properties of Disequilibrium Statistics for Associations Between Nuclear and Cytoplasmic Genotypes

Genetics ◽  
1987 ◽  
Vol 115 (4) ◽  
pp. 755-768
Author(s):  
Marjorie A Asmussen ◽  
Jonathan Arnold ◽  
John C Avise
Keyword(s):  
Assortative Mating ◽  
Initial Conditions ◽  
Random Mating ◽  
Nuclear Gene ◽  
Data Sets ◽  
Mixed Mating ◽  
Hybrid Zones ◽  
Genotype Frequencies ◽  
Conventional Models ◽  
Mixed Mating Model

ABSTRACT We define and establish the interrelationships of four components of statistical association between a diploid nuclear gene and a uniparentally transmitted, haploid cytoplasmic gene: an allelic (gametic) disequilibrium (D), which measures associations between alleles at the two loci; and three genotypic disequilibria (D  1, D  2, D  3), which measure associations between two cytotypes and the three respective nuclear backgrounds. We also consider an alternative set of measures, including D and the residual disequilibrium (d). The dynamics of these disequilibria are then examined under three conventional models of the mating system: (1) random mating; (2a) assortative mating without dominance (the "mixed-mating model"); and (2b) assortative mating with dominance ("O'Donald's model"). The trajectories of gametic disequilibria are similar to those for pairs of unlinked nuclear loci. The dynamics of genotypic disequilibria exhibit a variety of behaviors depending on the model and the initial conditions. Procedures for statistical estimation of cytonuclear disequilibria are developed and applied to several real and hypothetical data sets. Special attention is paid to the biological interpretations of various categories of allelic and genotypic disequilibria in hybrid zones. Genetic systems for which these statistics might be appropriate include nuclear genotype frequencies in conjunction with those for mitochondrial DNA, chloroplast DNA, or cytoplasmically inherited microorganisms.

Assortative Mating in Hybrid Zones between Chromosomal Races of the Common Shrew Sorex araneus L. (Soricidae, Soricomorpha)

2020 ◽  
Vol 10 (2) ◽  
pp. 81-90
Author(s):  
V. N. Orlov ◽  
D. M. Krivonogov ◽  
E. V. Cherepanova ◽  
A. V. Shchegol’kov ◽  
O. O. Grigorieva
Keyword(s):  
Assortative Mating ◽  
Common Shrew ◽  
Sorex Araneus ◽  
Hybrid Zones ◽  
Chromosomal Races ◽  
The Common ◽  
Common Shrew Sorex Araneus

scholarly journals ASSORTATIVE MATING AND SPATIAL STRUCTURE IN HYBRID ZONES

Evolution ◽  
2010 ◽  
Vol 64 (2) ◽  
pp. 444-455 ◽  
Author(s):  
Leithen K. M'Gonigle ◽  
Richard G. FitzJohn
Keyword(s):  
Spatial Structure ◽  
Assortative Mating ◽  
Hybrid Zones

Assortative mating in the hybrid zones of the common shrew (Sorex araneus mammalia) chromosome race West Dvina

2013 ◽  
Vol 451 (1) ◽  
pp. 217-220 ◽  
Author(s):  
V. N. Orlov ◽  
Yu. M. Borisov ◽  
E. V. Cherepanova ◽  
A. N. Milishnikov
Keyword(s):  
Assortative Mating ◽  
Common Shrew ◽  
Sorex Araneus ◽  
Chromosome Race ◽  
Hybrid Zones ◽  
The Common ◽  
Common Shrew Sorex Araneus

scholarly journals The effects of assortative mating and migration on cytonuclear associations in hybrid zones.

Genetics ◽  
1989 ◽  
Vol 122 (4) ◽  
pp. 923-934 ◽  
Author(s):  
M A Asmussen ◽  
J Arnold ◽  
J C Avise
Keyword(s):  
Assortative Mating ◽  
Hybrid Zone ◽  
Evolutionary Dynamics ◽  
Initial Conditions ◽  
Likelihood Method ◽  
Hybrid Population ◽  
Hybrid Zones ◽  
Gene Frequencies ◽  
Nonrandom Mating ◽  
And Migration

Abstract We examine the influence of nonrandom mating and immigration on the evolutionary dynamics of cytonuclear associations in hybrid zones. Recursion equations for allelic and genotypic cytonuclear disequilibria were generated under models of (1) migration alone, assuming hybrid zone matings are random with respect to cytonuclear genotype; and (2) migration in conjunction with refined epistatic mating, in which females of the pure parental species preferentially mate with conspecific males. Major results are as follows: (a) even the slightest migration removes the dependency of the final outcome on initial conditions, producing a unique equilibrium in which both pure parental genotypes are maintained in the hybrid zone; (b) in contrast to nuclear genes, the dynamics of cytoplasmic allele frequencies appear robust to changes in the assumed mating system, yet are particularly sensitive to gene flow; (c) continued immigration can generate permanent cytonuclear disequilibria, whether mating is random or assortative; and (d) the order of population censusing (before versus after reproduction by immigrants) can have a dramatic effect on the magnitude but not the pattern of cytonuclear disequilibria. Using the maximum likelihood method, the parameter space of migration rates and assortative mating rates was examined for best fit to observed cytonuclear disequilibria data in a hybrid population of Hyla tree frogs. An epistatic mating model with a total immigration rate of about 32% per generation produces equilibrium gene frequencies and cytonuclear disequilibria consistent with the empirical observations.

scholarly journals The effects of frequency-dependent sexual selection, mating-trait architecture and matching rule on hybrid zone dynamics in crows

2020 ◽  
Author(s):  
Dirk Metzler ◽  
Ulrich Knief ◽  
Joshua V. Peñalba ◽  
Jochen B. W. Wolf
Keyword(s):  
Sexual Selection ◽  
Assortative Mating ◽  
Hybrid Zone ◽  
Secondary Contact ◽  
Hybrid Zones ◽  
Moderate Degree ◽  
Matching Rule ◽  
Trait Loci ◽  
Spatio Temporal ◽  
Hooded Crows

AbstractHybrid zones provide a window into the evolutionary processes governing species divergence. While the role of postzygotic isolation has been extensively characterized in the context of hybrid zones, the contribution of prezygotic isolation is less well explored. In particular, the effect of assortative mate choice, the underlying preference function, the architecture of the mating trait and the strength of sexual selection are worthy of investigation. Here, we explore this question by means of a mathematical model parameterized with empirical data from the hybrid zone between all-black carrion and grey-coated hooded crows. The best-fit model resulted in narrow clines for two mating-trait loci coding for colour phenotype maintained by a moderate degree of assortative mating. Epistasis between the two loci induced hybrid-zone movement in favor of alleles conveying dark plumage followed by a shift in the opposite direction favouring grey-coated phenotypes ∼1,200 generations after secondary contact. Unlinked neutral loci diffused near-unimpeded across the zone. This study demonstrates that sexual selection created by assortative mating can explain steep transitions in mating-trait loci without generalizing to genome-wide reproductive isolation. It further emphasizes the importance of mating-trait architecture for spatio–temporal hybrid-zone dynamics.

scholarly journals Cytonuclear Theory for Haplodiploid Species and X-Linked Genes. I. Hardy-Weinberg Dynamics and Continent-Island, Hybrid Zone Models

Genetics ◽  
1997 ◽  
Vol 147 (1) ◽  
pp. 321-338
Author(s):  
Michael A D Goodisman ◽  
Marjorie A Asmussen
Keyword(s):  
Assortative Mating ◽  
Hybrid Zone ◽  
Random Mating ◽  
Diploid Species ◽  
Specific Gene ◽  
Hybrid Zones ◽  
Pure Type ◽  
Special Cases ◽  
Source Populations ◽  
And Migration

Abstract We develop models that describe the cytonuclear structure for either a cytoplasmic and nuclear marker in a haplodiploid species or a cytoplasmic and X-linked marker in a diploid species. Sex-specific disequilibrium statistics that summarize nonrandom cytonuclear associations in such systems are defined, and their basic Hardy-Weinberg dynamics and admixture formulae are delimited. We focus on the context of hybrid zones and develop continent-island models whereby individuals from two genetically differentiated source populations migrate into and mate within a single zone of admixture. We examine the effects of differential migration of the sexes, assortative mating by pure type females, and census time (relative to mating and migration), as well as special cases of random mating and migration subsumed under the general models. We show that pure type individuals and nonzero cytonuclear disequilibria can be maintained within a hybrid zone if there is continued migration from both source populations, and that females generally have a greater influence over these cytonuclear variables than males. The resulting theoretical framework can be used to estimate the rates of assortative mating and sex-specific gene flow in hybrid zones and other zones of admixture involving haplodiploid or sex-linked cytonuclear data.

Sign in / Sign up

Export Citation Format

Share Document