Sperm Competition and the Dynamics of X Chromosome Drive: Stability and Extinction

Genetics ◽  
2002 ◽  
Vol 160 (4) ◽  
pp. 1721-1731 ◽  
Author(s):  
Jesse E Taylor ◽  
John Jaenike
Keyword(s):  
Sex Ratio ◽  
Sperm Competition ◽  
X Chromosome ◽  
Sex Chromosome ◽  
Basin Of Attraction ◽  
Male Mating ◽  
Male And Female ◽  
Mating Rate ◽  
Female Mating ◽  
Balanced Polymorphism

AbstractSeveral empirical studies of sperm competition in populations polymorphic for a driving X chromosome have revealed that Sex-ratio males (those carrying a driving X) are at a disadvantage relative to Standard males. Because the frequency of the driving X chromosome determines the population-level sex ratio and thus alters male and female mating rates, the evolutionary consequences of sperm competition for sex chromosome meiotic drive are subtle. As the SR allele increases in frequency, the ratio of females to males also increases, causing an increase in the male mating rate and a decrease in the female mating rate. While the former change may exacerbate the disadvantage of Sex-ratio males during sperm competition, the latter change decreases the incidence of sperm competition within the population. We analyze a model of the effects of sperm competition on a driving X chromosome and show that these opposing trends in male and female mating rates can result in two coexisting locally stable equilibria, one corresponding to a balanced polymorphism of the SR and ST alleles and the second to fixation of the ST allele. Stochastic fluctuations of either the population sex ratio or the SR frequency can then drive the population away from the balanced polymorphism and into the basin of attraction for the second equilibrium, resulting in fixation of the SR allele and extinction of the population.

II.—Prenatal Death in the Pig and its Effect upon the Sex-Ratio

1927 ◽  
Vol 46 ◽  
pp. 9-14 ◽  
Author(s):  
F. A. E. Crew
Keyword(s):  
Sex Ratio ◽  
Sex Chromosome ◽  
Selective Mortality ◽  
Cytological Evidence ◽  
Male And Female ◽  
Primary Sex Ratio ◽  
The Future ◽  
Secondary Sex Ratio

The cytological evidence concerning the pig is that the sex of the future individual is determined at the time of fertilisation, and that in respect of the elements of the sex-chromosome sex-determining mechanism the male is digametic. If this is so, if the two sorts of sperm are produced in equal numbers, if each kind is equally viable and functional, and if fertilisation is at random, then a primary sex-ratio (that which obtains at the time of conception) of equality must follow. If male and female zygotes are equally viable, then the secondary sex-ratio (that which obtains at the time of gestation) will also be equality. A secondary sex-ratio other than equality must be the reflection of an unequal primary sex-ratio, the result of a differential production of the two sorts of gametes elaborated by the digametic sex, of a selective fertilisation by these, or of a sexually selective mortality among the embryos or/and fœtuses. A secondary sex-ratio of equality can follow a pronounced inequality in the primary sex-ratio if a sexually selective mortality operates prenatally.

scholarly journals The potential for a released autosomal X-shredder becoming a driving-Y chromosome and invasively suppressing wild populations of malaria mosquitoes

2019 ◽  
Author(s):  
Yehonatan Alcalay ◽  
Silke Fuchs ◽  
Roberto Galizi ◽  
Federica Bernardini ◽  
Roya Elaine Haghighat-Khah ◽  
...  
Keyword(s):  
Sex Ratio ◽  
Y Chromosome ◽  
X Chromosome ◽  
Sex Chromosome ◽  
Unexpected Event ◽  
Meiotic Sex Chromosome Inactivation ◽  
Ratio Distortion ◽  
High Fraction ◽  
Malaria Mosquitoes ◽  
Population Suppression

AbstractSynthetic sex-ratio distorters based on X-chromosome shredding are predicted to be more efficient than sterile males for population suppression of malaria mosquitoes using genetic control. X-chromosome shredding operates through the targeted elimination of X-chromosome-bearing gametes during male spermatogenesis, resulting in males that have a high fraction of male offspring. Strains harboring autosomal constructs containing a modified endonuclease I-PpoI have now been developed in the malaria mosquito Anopheles gambiae, resulting in strong sex-ratio distortion towards males. Data are being gathered for these strains for submission of regulatory dossiers for contained use and subsequent field release in West Africa. Since autosomal X-shredders are transmitted in a Mendelian fashion and can be selected against their frequency in the population is expected to decline once releases are halted. However, any unintended transfer of the X-shredder to the Y-chromosome could theoretically change these dynamics: This could lead to 100% transmission of the newly Y-linked X-shredder to the predominant male-biased offspring and its insulation from negative selection in females, resulting in its potential spread in the population and ultimately to suppression. Here, we analyze plausible mechanisms whereby an autosomal X-shredder could become linked to the Y-chromosome after release and provide data regarding its potential for activity should it become linked to the Y-chromosome. Our results strongly suggest that Y-chromosome linkage through remobilization of the transposon used for the initial genetic transformation is unlikely, and that, in the unexpected event that the X-shredder becomes linked to the Y-chromosome, expression and activity of the X-shredder would likely be inhibited by meiotic sex chromosome inactivation. We conclude that a functioning X-shredding-based Y-drive resulting from a naturally induced transposition or translocation of the transgene onto the Y-chromosome is unlikely.

scholarly journals redkmer: an assembly-free pipeline for the identification of abundant and specific X-chromosome target sequences for X-shredding by CRISPR endonucleases

2017 ◽  
Author(s):  
Philippos Aris Papathanos ◽  
Nikolai Windbichler
Keyword(s):  
Sex Ratio ◽  
X Chromosome ◽  
Single Molecule ◽  
Sex Chromosome ◽  
Insect Pest ◽  
Gene Array ◽  
Ribosomal Gene ◽  
Long Reads ◽  
Target Sequences ◽  
Harmful Insect

AbstractCRISPR-based synthetic sex ratio distorters, that operate by shredding the X-chromosome during male meiosis, are promising tools for the area-wide control of harmful insect pest or disease vector species. However, the selection of gRNA targets, in the form of high-copy sequence repeats on the X chromosome of a given species, is difficult since such repeats are not accurately resolved in genome assemblies and can’t be assigned to chromosomes with confidence. We have therefore developed the redkmer computational pipeline, designed to identify short and highly-abundant sequence elements occurring uniquely on the X-chromosome. Redkmer was designed to use as input exclusively raw WGS data from males and females. We tested redkmer with suitable short and long read WGS data ofAn. gambiae, the major vector of human malaria, in which the X-shredding paradigm was originally developed. Redkmer establishes long reads as chromosomal proxies with excellent correlation to the genome assembly and uses them to rank X-candidate kmers for their level of X-specificity and abundance. Redkmer identified a high-confidence set of 25-mers, many of which belong to previously known X-chromosome specific repeats ofAn. gambiae, including the ribosomal gene array and the selfish genetics elements harbored within it. WGS data from a control strain in which these repeats are also present on the Y chromosome confirmed the elimination of these kmers in the filtering steps. Finally, we show that redkmer output can be linked directly to gRNA selection and can also inform gRNA off-target prediction. The redkmer pipeline is designed to enable the generation of synthetic sex ratio distorters for the control of harmful insect species of medical or agricultural importance. It proceeds from WGS input data to deliver candidate X-specific CRISPR gRNA candidate target sequences. In addition the output of redkmer, including the prediction of chromosomal origin of single-molecule long reads and chromosome specific kmers, could also be used for the characterization of other biologically relevant sex chromosome sequences, a task that is frequently hampered by the repetitiveness of sex chromosome sequence content.

The Evolution of Large Testes: Sperm Competition or Male Mating Rate?

Ethology ◽  
2011 ◽  
Vol 118 (2) ◽  
pp. 107-117 ◽  
Author(s):  
Karim Vahed ◽  
Darren J. Parker
Keyword(s):  
Sperm Competition ◽  
Male Mating ◽  
Mating Rate

scholarly journals The evolution of optimal female mating rate changes the coevolutionary dynamics of female resistance and male persistence

2012 ◽  
Vol 367 (1600) ◽  
pp. 2339-2347 ◽  
Author(s):  
Erem Kazancıoğlu ◽  
Suzanne H. Alonzo
Keyword(s):  
Sexual Conflict ◽  
Mating Success ◽  
Male Mating ◽  
Theoretical Studies ◽  
Male Mating Success ◽  
Female Resistance ◽  
Previous Theory ◽  
Mating Rate ◽  
Mating Patterns ◽  
Female Mating

Mating decisions usually involve conflict of interests between sexes. Accordingly, males benefit from increased number of matings, whereas costs of mating favour a lower mating rate for females. The resulting sexual conflict underlies the coevolution of male traits that affect male mating success (‘persistence’) and female traits that affect female mating patterns (‘resistance’). Theoretical studies on the coevolutionary dynamics of male persistence and female resistance assumed that costs of mating and, consequently, the optimal female mating rate are evolutionarily constant. Costs of mating, however, are often caused by male ‘persistence’ traits that determine mating success. Here, we present a model where the magnitude of costs of mating depend on, and evolve with, male persistence. We find that allowing costs of mating to depend on male persistence results in qualitatively different coevolutionary dynamics. Specifically, we find that male traits such as penis spikes that harm females are not predicted to exhibit runaway selection with female resistance, in contrast to previous theory that predicts indefinite escalation. We argue that it is essential to determine when and to what extent costs of mating are caused by male persistence in order to understand and accurately predict coevolutionary dynamics of traits involved in mating decisions.

scholarly journals Modifier Genes of the Sex Ratio Trait in Drosophila pseudoobscura

Genetics ◽  
1987 ◽  
Vol 116 (2) ◽  
pp. 275-283
Author(s):  
Gary Cobbs
Keyword(s):  
Sex Ratio ◽  
Y Chromosome ◽  
X Chromosome ◽  
High Frequency ◽  
Sex Chromosome ◽  
Drosophila Pseudoobscura ◽  
Sterile Male ◽  
Very High Frequency ◽  
Very High ◽  
Chromosome Nondisjunction

ABSTRACT The msr trait of Drosophila pseudoobscura occurs when "sex-ratio" males produce a very high frequency of null-X sperm which give rise to sterile male (X/O) progeny. The trait involves dramatically lowered fecundity due to spermiogenic failure. The msr trait is multigenic and the genes are located on autosomes II, III and IV of the L116 laboratory stock. This stock also carries genes on the Y chromosome that lower the level of msr. When the genes on the L116 autosomes are present together or with those on the Y chromosome of other stocks, they interact cooperatively to produce very high levels of msr. The msr genes require the presence of a sex-ratio X chromosome to have any effect and thus may be regarded as modifiers of the "sex-ratio" phenotype. Crosses show that the genes causing msr are primarily recessive but have some expression when heterozygous. Sex chromosome nondisjunction is proposed as the mechanism underlying the msr trait.

scholarly journals Sexual conflict and intrasexual polymorphism promote assortative mating and halt population differentiation

2019 ◽  
Vol 286 (1899) ◽  
pp. 20190251 ◽  
Author(s):  
Lars Lønsmann Iversen ◽  
Erik I. Svensson ◽  
Søren Thromsholdt Christensen ◽  
Johannes Bergsten ◽  
Kaj Sand-Jensen
Keyword(s):  
Empirical Evidence ◽  
Assortative Mating ◽  
Sexual Conflict ◽  
Evolutionary Dynamics ◽  
Population Divergence ◽  
Male Mating ◽  
Common View ◽  
Male And Female ◽  
Female Mating ◽  
Female Polymorphism

Sexual conflict is thought to be an important evolutionary force in driving phenotypic diversification, population divergence, and speciation. However, empirical evidence is inconsistent with the generality that sexual conflict enhances population divergence. Here, we demonstrate an alternative evolutionary outcome in which sexual conflict plays a conservative role in maintaining male and female polymorphisms locally, rather than promoting population divergence. In diving beetles, female polymorphisms have evolved in response to male mating harassment and sexual conflict. We present the first empirical evidence that this female polymorphism is associated with (i) two distinct and sympatric male morphological mating clusters (morphs) and (ii) assortative mating between male and female morphs. Changes in mating traits in one sex led to a predictable change in the other sex which leads to predictable within-population evolutionary dynamics in male and female morph frequencies. Our results reveal that sexual conflict can lead to assortative mating between male offence and female defence traits, if a stable male and female mating polymorphisms are maintained. Stable male and female mating polymorphisms are an alternative outcome to an accelerating coevolutionary arms race driven by sexual conflict. Such stable polymorphisms challenge the common view of sexual conflict as an engine of rapid speciation via exaggerated coevolution between sexes.

scholarly journals 344ICSI-MEDIATED GENE TRANSFER SKEWS SEX RATIO AGAINST FEMALE BIRTHS IN MICE

2004 ◽  
Vol 16 (2) ◽  
pp. 292
Author(s):  
P.N. Moreira ◽  
B. Pintado ◽  
L. Montoliu ◽  
A. Gutiérrez-Adán
Keyword(s):  
Gene Transfer ◽  
Sex Ratio ◽  
X Chromosome ◽  
Sex Chromosome ◽  
Single Gene ◽  
Transgenic Animals ◽  
Sperm Nucleus ◽  
Dna Molecules ◽  
Female Embryo ◽  
Foreign Dna

ICSI-mediated gene transfer has been used as an alternative method to pronuclear microinjection for the genomic modification of many species. With this method, transgenic embryos are produced by the microinjection of metaphase II oocytes with spermatozoa previously incubated with foreign DNA. Recently, it was shown in mice that the low percentage of transgenic animals produced from injected oocytes, results from the fact that the expression of foreign DNA is associated with paternal chromosome degradation (Szczygiel M.A. et al., 2003 Biol. Reprod. 68, 1903–1910). It is also known that sex chromosomes localize preferentially, at least in humans, on the periphery of the sperm nucleus on sub-acrosomal regions (Sbracia M. et al., 2002 Hum. Reprod. 17, 320–324), suggesting a high level of interaction with foreign DNA molecules with possible impact on the sex ratio of the offspring. In order to test this hypothesis we have compared ICSI (no DNA), and with ICSI-mediated EGFP (5Kb plasmid DNA from Clonetech, Spain) transfer, with ICSI-mediated YRT3 (a mouse tyrosinase gene derivative YAC-DNA with 100Kb; Montoliu L. et al., 1996 EMBO) transfer. Gametes were from 6–8 weeks old CD1 mice. ICSI-mediated gene transfer with post-thawed immotile spermatozoa, extended in M2 medium in the absence of ion chelators (EDTA and EGTA), was done as previously described (Szczygiel M.A. et al., 2003 Biol. Reprod. 68, 1903–1910). Table 1 below summarizes the data collected. Relative to our control, sex ratio deviation was a consequence of the coinjection of DNA. Forty-three percent of males were obtained with regular ICSI, whereas 64% and 65% were the respective percentages when EGFP or YRT3 DNA was coinjected with spermatozoa. This statistically significant (P<0.05, z-test, Sigma Stat, Jandel Scientific, USA) sex ratio deviation, favoring male ICSI offspring when foreign DNA is coinjected, may result from a higher female embryo susceptibility to parental sex chromosome fragmentation induced by the interaction with foreign DNA molecules. Possible impairment of X chromosome inactivation and dosage compensation resulting from the fragmentation of the sex chromosome on X-carrying spermatozoa could explain this female embryo degeneration. Supporting this view, it was recently shown in mice that sex ratio can be skewed against female births by a mutation in a single gene of the X chromosome (Tsix) involved in such mechanisms (Lee J.T., 2002 Nat. Genet.). In conclusion, mouse ICSI-mediated gene transfer induces sex ratio deviation favoring male offspring. Table 1 Sex ratio of the offspring obtained with ICSI, ICSI-mediated EGFP transfer, and ICSI-mediated YRT3 transfer

The DEVELOPMENT OF Elaeidobius kamerunicus FAUST POPULATION AFTER INTRODUCTION AND THE IMPROVEMENT OF OIL PALM FRUIT SET IN SERAM ISLAND, MOLLUCAS, INDONESIA

2016 ◽  
Vol 24 (1) ◽  
pp. 47-55
Author(s):  
Agus Eko Prasetyo ◽  
Agus Susanto
Keyword(s):  
Sex Ratio ◽  
Oil Palm ◽  
Fruit Set ◽  
Average Risk ◽  
Palm Fruit ◽  
Male And Female ◽  
Risk Of Death ◽  
North Sumatra ◽  
Female Flowers ◽  
Elaeidobius Kamerunicus

Elaeidobius kamerunicus is the main pollinating agent in oil palm plantations in Indonesia today. The development of oil palm plantations in new areas requires introduction of these insects, moreover the new areas are located on different islands. First introduction of Elaeidobius kamerunicus Faust had been done from North Sumatra to Seram Island on 23 September 2013. The introduction was performed on larva and pupa stadium in 4-5 days post anthesising of male inflorescences. The introduction of E. kamerunicus using plywood boxes has an average risk of death by 7.89% at 6 days delivery period. Observation before releasing of the weevils showed that this insect was not detected in both of oil palm male and female flowers and the oil palm fruit set was very low approximately 11.27%. For about 500 weevils/ha were released in Marnuhu estate and could be developed into 362,401 weevils/ha in 5 months with 97.86% of oil palm sex ratio. The oil palm fruit sets were increased after 1 and 2 months introduction, 53.70% and 75.56 %, respectively. The lower sex ratio of oil palm or the more availability of male inflorescences make growth of E. kamerunicus population became faster and the greater number of weevils that visiting anthesising of female flowers make the higher value of oil palm fruit set.

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