scholarly journals Fitness consequences of a non-recombining sex-ratio drive chromosome can explain its prevalence in the wild

2019 ◽  
Vol 286 (1917) ◽  
pp. 20192529 ◽  
Author(s):  
Kelly A. Dyer ◽  
David W. Hall
Keyword(s):  
Sex Ratio ◽  
Sperm Competition ◽  
Natural Populations ◽  
Theoretical Models ◽  
Host Population ◽  
Gene Drive ◽  
Fitness Consequences ◽  
In The Wild ◽  
And Performance ◽  
Drive Systems

Understanding the pleiotropic consequences of gene drive systems on host fitness is essential to predict their spread through a host population. Here, we study sex-ratio (SR) X-chromosome drive in the fly Drosophila recens , where SR causes the death of Y-bearing sperm in male carriers. SR males only sire daughters, which all carry SR, thus giving the chromosome a transmission advantage. The prevalence of the SR chromosome appears stable, suggesting pleiotropic costs. It was previously shown that females homozygous for SR are sterile, and here, we test for additional fitness costs of SR. We found that females heterozygous for SR have reduced fecundity and that male SR carriers have reduced fertility in conditions of sperm competition. We then use our fitness estimates to parametrize theoretical models of SR drive and show that the decrease in fecundity and sperm competition performance can account for the observed prevalence of SR in natural populations. In addition, we found that the expected equilibrium frequency of the SR chromosome is particularly sensitive to the degree of multiple mating and performance in sperm competition. Together, our data suggest that the mating system of the organism should be carefully considered during the development of gene drive systems.

scholarly journals Natural selection acts on Atlantic salmon major histocompatibility (MH) variability in the wild

2007 ◽  
Vol 274 (1611) ◽  
pp. 861-869 ◽  
Author(s):  
Elvira de Eyto ◽  
Philip McGinnity ◽  
Sofia Consuegra ◽  
Jamie Coughlan ◽  
Jarle Tufto ◽  
...  
Keyword(s):  
Natural Selection ◽  
Atlantic Salmon ◽  
Balancing Selection ◽  
Natural Populations ◽  
Class Ii ◽  
Major Histocompatibility ◽  
Genotype Frequencies ◽  
Fitness Consequences ◽  
In The Wild ◽  
Class Ii Alpha

Pathogen-driven balancing selection is thought to maintain polymorphism in major histocompatibility (MH) genes. However, there have been few empirical demonstrations of selection acting on MH loci in natural populations. To determine whether natural selection on MH genes has fitness consequences for wild Atlantic salmon in natural conditions, we compared observed genotype frequencies of Atlantic salmon ( Salmo salar ) surviving in a river six months after their introduction as eggs with frequencies expected from parental crosses. We found significant differences between expected and observed genotype frequencies at the MH class II alpha locus, but not at a MH class I-linked microsatellite or at seven non-MH-linked microsatellite loci. We therefore conclude that selection at the MH class II alpha locus was a result of disease-mediated natural selection, rather than any demographic event. We also show that survival was associated with additive allelic effects at the MH class II alpha locus. Our results have implications for both the conservation of wild salmon stocks and the management of disease in hatchery fish. We conclude that natural or hatchery populations have the best chance of dealing with episodic and variable disease challenges if MH genetic variation is preserved both within and among populations.

scholarly journals Experiments confirm a dispersive phenotype associated with a natural gene drive system

2021 ◽  
Vol 8 (5) ◽  
Author(s):  
Jan-Niklas Runge ◽  
Anna K. Lindholm
Keyword(s):  
Sperm Competition ◽  
Local Density ◽  
House Mice ◽  
Gene Drive ◽  
Wild Type ◽  
Fitness Costs ◽  
Oestrus Cycle ◽  
Drive Systems ◽  
Average Body ◽  
Average Body Weight

Meiotic drivers are genetic entities that increase their own probability of being transmitted to offspring, usually to the detriment of the rest of the organism, thus ‘selfishly’ increasing their fitness. In many meiotic drive systems, driver-carrying males are less successful in sperm competition, which occurs when females mate with multiple males in one oestrus cycle (polyandry). How do drivers respond to this selection? An observational study found that house mice carrying the t haplotype, a meiotic driver, are more likely to disperse from dense populations. This could help the t avoid detrimental sperm competition, because density is associated with the frequency of polyandry. However, no controlled experiments have been conducted to test these findings. Here, we confirm that carriers of the t haplotype are more dispersive, but we do not find this to depend on the local density. t -carriers with above-average body weight were particularly more likely to disperse than wild-type mice. t -carrying mice were also more explorative but not more active than wild-type mice. These results add experimental support to the previous observational finding that the t haplotype affects the dispersal phenotype in house mice, which supports the hypothesis that dispersal reduces the fitness costs of the t .

scholarly journals Can CRISPR-based gene drive be confined in the wild? A question for molecular and population biology

2017 ◽  
Author(s):  
John M. Marshall ◽  
Omar S. Akbari
Keyword(s):  
Population Biology ◽  
Gene Editing ◽  
Gene Drive ◽  
In The Wild ◽  
Drive Systems ◽  
Chain Drives

AbstractThe recent discovery of CRISPR and its application as a gene editing tool has enabled a range of gene drive systems to be engineered with much greater ease. In order for the benefits of this technology to be realized, drive systems must be developed that are capable of both spreading into populations to achieve their desired impact, and being recalled in the event of unwanted consequences or public disfavor. We review the performance of three broad categories of drive systems at achieving these goals - threshold-dependent drives, homing-based drive and remediation systems, and temporally self-limiting systems such as daisy-chain drives.

scholarly journals Eco-Evolutionary Dynamics of Episomes among Ecologically Cohesive Bacterial Populations

mBio ◽  
2015 ◽  
Vol 6 (3) ◽  
Author(s):  
Hong Xue ◽  
Otto X. Cordero ◽  
Francisco M. Camas ◽  
William Trimble ◽  
Folker Meyer ◽  
...  
Keyword(s):  
Gene Transfer ◽  
Evolutionary Dynamics ◽  
Natural Populations ◽  
Antibiotic Resistance Genes ◽  
Host Population ◽  
Bacterial Populations ◽  
In The Wild ◽  
Host Phylogeny ◽  
High Fraction ◽  
Extensive Exchange

ABSTRACTAlthough plasmids and other episomes are recognized as key players in horizontal gene transfer among microbes, their diversity and dynamics among ecologically structured host populations in the wild remain poorly understood. Here, we show that natural populations of marineVibrionaceaebacteria host large numbers of families of episomes, consisting of plasmids and a surprisingly high fraction of plasmid-like temperate phages. Episomes are unevenly distributed among host populations, and contrary to the notion that high-density communities in biofilms act as hot spots of gene transfer, we identified a strong bias for episomes to occur in free-living as opposed to particle-attached cells. Mapping of episomal families onto host phylogeny shows that, with the exception of all phage and a few plasmid families, most are of recent evolutionary origin and appear to have spread rapidly by horizontal transfer. Such high eco-evolutionary turnover is particularly surprising for plasmids that are, based on previously suggested categorization, putatively nontransmissible, indicating that this type of plasmid is indeed frequently transferred by currently unknown mechanisms. Finally, analysis of recent gene transfer among plasmids reveals a network of extensive exchange connecting nearly all episomes. Genes functioning in plasmid transfer and maintenance are frequently exchanged, suggesting that plasmids can be rapidly transformed from one category to another. The broad distribution of episomes among distantly related hosts and the observed promiscuous recombination patterns show how episomes can offer their hosts rapid assembly and dissemination of novel functions.IMPORTANCEPlasmids and other episomes are an integral part of bacterial biology in all environments, yet their study is heavily biased toward their role as vectors for antibiotic resistance genes. This study presents a comprehensive analysis of all episomes within several coexisting bacterial populations ofVibrionaceaefrom the coastal ocean and represents the largest-yet genomic survey of episomes from a single bacterial family. The host population framework allows analysis of the eco-evolutionary dynamics at unprecedented resolution, yielding several unexpected results. These include (i) discovery of novel, nonintegrative temperate phages, (ii) revision of a class of episomes, previously termed “nontransmissible,” as highly transmissible, and (iii) surprisingly high evolutionary turnover of episomes, manifest as frequent birth, spread, and loss.

scholarly journals Prevalence, transmission and intensity of infection by a microsporidian sex ratio distorter in natural Gammarus duebeni populations

Parasitology ◽  
1997 ◽  
Vol 114 (3) ◽  
pp. 231-236 ◽  
Author(s):  
A. M. DUNN ◽  
M. J. HATCHER
Keyword(s):  
Sex Ratio ◽  
Natural Populations ◽  
Infection Intensity ◽  
Host Population ◽  
Parasite Infection ◽  
Parasite Transmission ◽  
Target Tissue ◽  
Intensity Of Infection ◽  
Gonadal Tissue ◽  
Crustacean Host

This is a report of the prevalence, transmission and intensity of infection of a microsporidian sex ratio distorter in natural populations of its crustacean host Gammarus duebeni. Prevalence in the adult host population reflects differences in the intensity of infection in transovarially infected embryos and in adult gonadal tissue. The efficiency of transovarial parasite transmission to young also differs between populations, but this alone is insufficient to explain observed patterns of prevalence. Infection intensity may be important in determining future infection of target tissue in the adult and subsequent transmission to future host generations. We consider patterns of parasite infection in terms of selection on transmission and virulence.

scholarly journals Association of polyandry and sex-ratio drive prevalence in natural populations of Drosophila neotestacea

2013 ◽  
Vol 280 (1769) ◽  
pp. 20131397 ◽  
Author(s):  
Cheryl A. Pinzone ◽  
Kelly A. Dyer
Keyword(s):  
Sex Ratio ◽  
Natural Populations ◽  
Wild Type ◽  
Mating Rate ◽  
Selfish Genetic Elements ◽  
Intragenomic Conflict ◽  
Genetic Suppressors ◽  
Population Crash ◽  
In The Wild ◽  
Average Fertility

Selfish genetic elements bias their own transmission to the next generation, even at the expense of the fitness of their carrier. Sex-ratio (SR) meiotic drive occurs when an X-chromosome causes Y-bearing sperm to die during male spermatogenesis, so that it is passed on to all of the male's offspring, which are all daughters. How SR is maintained as a stable polymorphism in the absence of genetic suppressors of drive is unknown. Here, we investigate the potential for the female remating rate to affect SR dynamics in natural populations, using the fly Drosophila neotestacea . In controlled laboratory conditions, females from populations where SR is rare mate more often than females from populations where SR is common. Furthermore, only when males mate multiply does the average fertility of SR males relative to wild-type males decrease to a level that can prevent SR from spreading. Our results suggest that differences in the female mating rate among populations may contribute to SR dynamics in the wild, and thus also affect the outcome of this intragenomic conflict. In line with this, we also present evidence of a localized population crash due to SR that may have resulted from habitat fragmentation along with a reduced mating rate.

scholarly journals Suppression gene drive in continuous space can result in unstable persistence of both drive and wild-type alleles

2019 ◽  
Author(s):  
Jackson Champer ◽  
Isabel Kim ◽  
Samuel E. Champer ◽  
Andrew G. Clark ◽  
Philipp W. Messer
Keyword(s):  
Natural Populations ◽  
Spatial Models ◽  
Ecological Factors ◽  
Natural Environments ◽  
Gene Drive ◽  
Wild Type ◽  
Lower Efficiency ◽  
Continuous Space ◽  
Selfish Genetic Elements ◽  
Drive Systems

ABSTRACTRapid evolutionary processes can produce drastically different outcomes when studied in panmictic population models versus spatial models where the rate of evolution is limited by dispersal. One such process is gene drive, which allows “selfish” genetic elements to quickly spread through a population. Engineered gene drive systems are being considered as a means for suppressing disease vector populations or invasive species. While laboratory experiments and modeling in panmictic populations have shown that such drives can rapidly eliminate a population, it is not yet clear how well these results translate to natural environments where individuals inhabit a continuous landscape. Using spatially explicit simulations, we show that instead of population elimination, release of a suppression drive can result in what we term “chasing” dynamics. This describes a condition in which wild-type individuals quickly recolonize areas where the drive has locally eliminated the population. Despite the drive subsequently chasing the wild-type allele into these newly re-colonized areas, complete population suppression often fails or is substantially delayed. This delay increases the likelihood that the drive becomes lost or that resistance evolves. We systematically analyze how chasing dynamics are influenced by the type of drive, its efficiency, fitness costs, as well as ecological and demographic factors such as the maximal growth rate of the population, the migration rate, and the level of inbreeding. We find that chasing is generally more common for lower efficiency drives and in populations with low dispersal. However, we further find that some drive mechanisms are substantially more prone to chasing behavior than others. Our results demonstrate that the population dynamics of suppression gene drives are determined by a complex interplay of genetic and ecological factors, highlighting the need for realistic spatial modeling to predict the outcome of drive releases in natural populations.

scholarly journals Artificial Triple Wolbachia Infection in Aedes albopictus Yields a New Pattern of Unidirectional Cytoplasmic Incompatibility

2010 ◽  
Vol 76 (17) ◽  
pp. 5887-5891 ◽  
Author(s):  
Yuqing Fu ◽  
Laurent Gavotte ◽  
David R. Mercer ◽  
Stephen L. Dobson
Keyword(s):  
Aedes Albopictus ◽  
Cytoplasmic Incompatibility ◽  
Natural Populations ◽  
Wolbachia Infection ◽  
Host Population ◽  
Invasive Pest ◽  
Gene Drive ◽  
Population Replacement ◽  
Asian Tiger ◽  
Spread Of Infection

ABSTRACT Obligately intracellular Wolbachia bacteria infect numerous invertebrates and often manipulate host reproduction to facilitate the spread of infection. An example of reproductive manipulation is Wolbachia-induced cytoplasmic incompatibility (CI), which occurs commonly in insects. This CI has been the focus both of basic scientific studies of naturally occurring invasion events and of applied investigations on the use of Wolbachia as a vehicle to drive desired genotypes into insect populations (“gene drive” or “population replacement” strategies). The latter application requires an ability to generate artificial infections that cause a pattern of unidirectional incompatibility with the targeted host population. A suggested target of population replacement strategies is the mosquito Aedes albopictus (Asian tiger mosquito), an important invasive pest and disease vector. Aedes albopictus individuals are naturally “superinfected” with two Wolbachia types: wAlbA and wAlbB. Thus, generating a strain that is unidirectionally incompatible with field populations requires the introduction of an additional infection into the preexisting superinfection. Although prior reports demonstrate an ability to transfer Wolbachia infections to A. albopictus artificially, including both intra- and interspecific Wolbachia transfers, previous efforts have not generated a strain capable of invading natural populations. Here we describe the generation of a stable triple infection by introducing Wolbachia wRi from Drosophila simulans into a naturally superinfected A. albopictus strain. The triple-infected strain displays a pattern of unidirectional incompatibility with the naturally infected strain. This unidirectional CI, combined with a high fidelity of maternal inheritance and low fecundity effects, suggests that the artificial cytotype could serve as an appropriate vehicle for gene drive.

scholarly journals Ant collective behavior is heritable and shaped by selection

2019 ◽  
Author(s):  
Justin T. Walsh ◽  
Simon Garnier ◽  
Timothy A. Linksvayer
Keyword(s):  
Body Size ◽  
Natural Selection ◽  
Sex Ratio ◽  
Collective Behavior ◽  
Genetic Correlations ◽  
Natural Populations ◽  
The Body ◽  
Collective Behaviors ◽  
Fitness Consequences ◽  
Caste Ratio

AbstractCollective behaviors are widespread in nature and usually assumed to be strongly shaped by natural selection. However, the degree to which variation in collective behavior is heritable and has fitness consequences -- the two prerequisites for evolution by natural selection -- is largely unknown. We used a new pharaoh ant (Monomorium pharaonis) mapping population to estimate the heritability, genetic correlations, and fitness consequences of three collective behaviors (foraging, aggression, and exploration) as well as body size, sex ratio, and caste ratio. Heritability estimates for the collective behaviors were moderate, ranging from 0.17 to 0.32, but lower than our estimates for the heritability of caste ratio, sex ratio, and the body size of new workers, queens, and males. Moreover, variation among colonies in collective behaviors was phenotypically correlated, suggesting that selection may shape multiple colony collective behaviors simultaneously. Finally, we found evidence for directional selection that was similar in strength to estimates of selection in natural populations. Altogether, our study begins to elucidate the genetic architecture of collective behavior and is one of the first studies to demonstrate that it is shaped by selection.

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