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 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.

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.

Phenotypic evidence for an extensive mosaic hybrid zone between two species of columbine, Aquilegia flavescens and A. formosa

Botany ◽  
2020 ◽  
Vol 98 (8) ◽  
pp. 459-467
Author(s):  
Jeffrey S. Groh ◽  
Quentin C.B. Cronk
Keyword(s):  
Hybrid Zone ◽  
Elevational Gradient ◽  
Hybrid Population ◽  
Clinal Variation ◽  
Hybrid Zones ◽  
Contact Zones ◽  
Structure And Dynamics ◽  
Ecological Selection ◽  
Herbarium Collections ◽  
Lineage Diversification

Describing the structure and dynamics of hybrid zones has important consequences for our understanding of lineage diversification. Herbarium collections constitute an extensive, though often underutilized, morphological resource that can potentially be leveraged to identify and describe hybrid zones. We demonstrate the use of herbarium collections to describe the structure of a hybrid zone between two North American columbines, Aquilegia flavescens S. Watson and A. formosa Fisch. ex DC. Hybrid indices were calculated from floral morphology measurements and mapped using geolocation data, revealing an extensive and consistent pattern of floral intermediacy in several contact zones. Population phenotype samples from contact zones corroborate these findings and strongly suggest introgression. At one locality with a confirmed hybrid population, floral phenotypes show clinal variation in parental-type morphology along an elevational gradient, in the direction predicted by the divergent elevational distributions of these taxa. We argue that these patterns together reflect a habitat-associated mosaic hybrid zone, consistent with divergent ecological selection maintaining the structure of the hybrid zone.

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 Landscape resistance constrains hybridization across contact zones in a reproductively and morphologically polymorphic salamander

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Guillermo Velo-Antón ◽  
André Lourenço ◽  
Pedro Galán ◽  
Alfredo Nicieza ◽  
Pedro Tarroso
Keyword(s):  
Contact Zone ◽  
Environmental Heterogeneity ◽  
Evolutionary Dynamics ◽  
Morphological Differentiation ◽  
Phenotypic Traits ◽  
Hybrid Zones ◽  
Landscape Resistance ◽  
Phenotypic Differentiation ◽  
Contact Zones

AbstractExplicitly accounting for phenotypic differentiation together with environmental heterogeneity is crucial to understand the evolutionary dynamics in hybrid zones. Species showing intra-specific variation in phenotypic traits that meet across environmentally heterogeneous regions constitute excellent natural settings to study the role of phenotypic differentiation and environmental factors in shaping the spatial extent and patterns of admixture in hybrid zones. We studied three environmentally distinct contact zones where morphologically and reproductively divergent subspecies of Salamandra salamandra co-occur: the pueriparous S. s. bernardezi that is mostly parapatric to its three larviparous subspecies neighbours. We used a landscape genetics framework to: (i) characterise the spatial location and extent of each contact zone; (ii) assess patterns of introgression and hybridization between subspecies pairs; and (iii) examine the role of environmental heterogeneity in the evolutionary dynamics of hybrid zones. We found high levels of introgression between parity modes, and between distinct phenotypes, thus demonstrating the evolution to pueriparity alone or morphological differentiation do not lead to reproductive isolation between these highly divergent S. salamandra morphotypes. However, we detected substantial variation in patterns of hybridization across contact zones, being lower in the contact zone located on a topographically complex area. We highlight the importance of accounting for spatial environmental heterogeneity when studying evolutionary dynamics of hybrid zones.

scholarly journals Spatial and space-time correlations in systems of subpopulations with genetic drift and migration.

Genetics ◽  
1993 ◽  
Vol 133 (3) ◽  
pp. 711-727
Author(s):  
B K Epperson
Keyword(s):  
Population Genetics ◽  
Time Correlation ◽  
Space Time ◽  
Spatial Correlations ◽  
Gene Frequencies ◽  
Migration Patterns ◽  
Migration Rates ◽  
Space And Time ◽  
Time Correlations ◽  
And Migration

Abstract The geographic distribution of genetic variation is an important theoretical and experimental component of population genetics. Previous characterizations of genetic structure of populations have used measures of spatial variance and spatial correlations. Yet a full understanding of the causes and consequences of spatial structure requires complete characterization of the underlying space-time system. This paper examines important interactions between processes and spatial structure in systems of subpopulations with migration and drift, by analyzing correlations of gene frequencies over space and time. We develop methods for studying important features of the complete set of space-time correlations of gene frequencies for the first time in population genetics. These methods also provide a new alternative for studying the purely spatial correlations and the variance, for models with general spatial dimensionalities and migration patterns. These results are obtained by employing theorems, previously unused in population genetics, for space-time autoregressive (STAR) stochastic spatial time series. We include results on systems with subpopulation interactions that have time delay lags (temporal orders) greater than one. We use the space-time correlation structure to develop novel estimators for migration rates that are based on space-time data (samples collected over space and time) rather than on purely spatial data, for real systems. We examine the space-time and spatial correlations for some specific stepping stone migration models. One focus is on the effects of anisotropic migration rates. Partial space-time correlation coefficients can be used for identifying migration patterns. Using STAR models, the spatial, space-time, and partial space-time correlations together provide a framework with an unprecedented level of detail for characterizing, predicting and contrasting space-time theoretical distributions of gene frequencies, and for identifying features such as the pattern of migration and estimating migration rates in experimental studies of genetic variation over space and time.

scholarly journals Nitrate-Nitrogen Leaching and Modeling in Intensive Agriculture Farmland in China

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
Ligang Xu ◽  
Hailin Niu ◽  
Jin Xu ◽  
Xiaolong Wang
Keyword(s):  
Nitrate Leaching ◽  
Soil Profile ◽  
Nitrate Nitrogen ◽  
Initial Conditions ◽  
Simulated Data ◽  
Intensive Agriculture ◽  
Health Concern ◽  
N Leaching ◽  
And Migration ◽  
Leachm Model

Protecting water resources from nitrate-nitrogen (NO3-N) contamination is an important public health concern and a major national environmental issue in China. Loss of NO3-N in soils due to leaching is not only one of the most important problems in agriculture farming, but is also the main factor causing nitrogen pollution in aquatic environments. Three typical intensive agriculture farmlands in Jiangyin City in China are selected as a case study for NO3-N leaching and modeling in the soil profile. In this study, the transport and fate of NO3-N within the soil profile and nitrate leaching to drains were analyzed by comparing field data with the simulation results of the LEACHM model. Comparisons between measured and simulated data indicated that the NO3-N concentrations in the soil and nitrate leaching to drains are controlled by the fertilizer practice, the initial conditions and the rainfall depth and distribution. Moreover, the study reveals that the LEACHM model gives a fair description of the NO3-N dynamics in the soil and subsurface drainage at the field scale. It can also be concluded that the model after calibration is a useful tool to optimize as a function of the combination “climate-crop-soil-bottom boundary condition” the nitrogen application strategy resulting for the environment in an acceptable level of nitrate leaching. The findings in this paper help to demonstrate the distribution and migration of nitrogen in intensive agriculture farmlands, as well as to explore the mechanism of groundwater contamination resulting from agricultural activities.

scholarly journals Modelling of dust generation, transport and remobilization in full-metal fusion reactors

2022 ◽  
Author(s):  
Svetlana Ratynskaia ◽  
Ladislas Vignitchouk ◽  
Panagiotis Tolias
Keyword(s):  
Initial Conditions ◽  
External Input ◽  
Dust Particles ◽  
Fusion Reactors ◽  
Dust Production ◽  
Dust Transport ◽  
Dust Generation ◽  
Wall Interaction ◽  
And Migration ◽  
Generation Mechanisms

Abstract The design, licensing and operation of magnetic confinement fusion reactors impose various limitations on the amount of metallic dust particles residing inside the plasma chamber. In this context, predictive studies of dust production and migration constitute one of the main sources of relevant data. These are mainly conducted using dust transport codes, which rely on coupled dust-plasma and dust-wall interaction models, and require external input on the dust and droplet initial conditions. Some particularities of dust modelling in reactor-relevant conditions are analyzed with an emphasis on dust generation mechanisms relevant for disruption scenarios and on dust remobilization mechanisms relevant for ramp-up scenarios. Emerging topics such as dust production by runaway electron impact and pre-plasma remobilization of magnetic dust are also discussed.

Sign in / Sign up

Export Citation Format

Share Document