scholarly journals Sex Ratios in a Warming World: Thermal Effects on Sex-Biased Survival, Sex Determination, and Sex Reversal

2021 ◽  
Vol 112 (2) ◽  
pp. 155-164
Author(s):  
Suzanne Edmands
Keyword(s):  
High Temperature ◽  
Sex Ratio ◽  
Sex Determination ◽  
Heat Tolerance ◽  
Sex Ratios ◽  
Sex Reversal ◽  
Survival Sex ◽  
Ratio Distortion ◽  
Warming World ◽  
Sex Ratio Distortion

Abstract Rising global temperatures threaten to disrupt population sex ratios, which can in turn cause mate shortages, reduce population growth and adaptive potential, and increase extinction risk, particularly when ratios are male biased. Sex ratio distortion can then have cascading effects across other species and even ecosystems. Our understanding of the problem is limited by how often studies measure temperature effects in both sexes. To address this, the current review surveyed 194 published studies of heat tolerance, finding that the majority did not even mention the sex of the individuals used, with <10% reporting results for males and females separately. Although the data are incomplete, this review assessed phylogenetic patterns of thermally induced sex ratio bias for 3 different mechanisms: sex-biased heat tolerance, temperature-dependent sex determination (TSD), and temperature-induced sex reversal. For sex-biased heat tolerance, documented examples span a large taxonomic range including arthropods, chordates, protists, and plants. Here, superior heat tolerance is more common in females than males, but the direction of tolerance appears to be phylogenetically fluid, perhaps due to the large number of contributing factors. For TSD, well-documented examples are limited to reptiles, where high temperature usually favors females, and fishes, where high temperature consistently favors males. For temperature-induced sex reversal, unambiguous cases are again limited to vertebrates, and high temperature usually favors males in fishes and amphibians, with mixed effects in reptiles. There is urgent need for further work on the full taxonomic extent of temperature-induced sex ratio distortion, including joint effects of the multiple contributing mechanisms.

scholarly journals Sex Chromosome Meiotic Drive in Stalk-Eyed Flies

Genetics ◽  
1997 ◽  
Vol 147 (3) ◽  
pp. 1169-1180 ◽  
Author(s):  
Daven C Presgraves ◽  
Emily Severance ◽  
Gerald S Willrinson
Keyword(s):  
Sex Ratio ◽  
Sex Chromosome ◽  
Sex Ratios ◽  
Natural Populations ◽  
Meiotic Drive ◽  
Operational Sex Ratio ◽  
Genetic Modifiers ◽  
Ratio Distortion ◽  
The Impact ◽  
Sex Ratio Distortion

Meiotically driven sex chromosomes can quickly spread to fixation and cause population extinction unless balanced by selection or suppressed by genetic modifiers. We report results of genetic analyses that demonstrate that extreme female-biased sex ratios in two sister species of stalk-eyed flies, Cyrtodiopsis dalmanni and C. whitei, are due to a meiotic drive element on the X chromosome (Xd). Relatively high frequencies of Xd in C. dalmanni and C. whitei (13–17% and 29%, respectively) cause female-biased sex ratios in natural populations of both species. Sex ratio distortion is associated with spermatid degeneration in male carriers of Xd. Variation in sex ratios is caused by Y-linked and autosomal factors that decrease the intensity of meiotic drive. Y-linked polymorphism for resistance to drive exists in C. dalmanni in which a resistant Y chromosome reduces the intensity and reverses the direction of meiotic drive. When paired with Xd, modifying Y chromosomes (Ym) cause the transmission of predominantly Y-bearing sperm, and on average, production of 63% male progeny. The absence of sex ratio distortion in closely related monomorphic outgroup species suggests that this meiotic drive system may predate the origin of C. whitei and C. dalmanni. We discuss factors likely to be involved in the persistence of these sex-linked polymorphisms and consider the impact of Xd on the operational sex ratio and the intensity of sexual selection in these extremely sexually dimorphic flies.

scholarly journals Horizontal transfer of parasitic sex ratio distorters between crustacean hosts

Parasitology ◽  
1998 ◽  
Vol 117 (1) ◽  
pp. 15-19 ◽  
Author(s):  
A. M. DUNN ◽  
T. RIGAUD
Keyword(s):  
Sex Ratio ◽  
Sex Determination ◽  
Host Specificity ◽  
Host Species ◽  
Horizontal Transfer ◽  
Parasite Infection ◽  
Parasite Transmission ◽  
Ratio Distortion ◽  
Sex Ratio Distortion ◽  
Crustacean Host

Parasitic sex ratio distorters were artificially transferred within and between crustacean host species in order to study the effects of parasitism on host fitness and sex determination and to investigate parasite–host specificity. Implantation of Nosema sp. to uninfected strains of its Gammarus duebeni host resulted in an active parasite infection in the gonad of recipient females and subsequent transovarial parasite transmission. The young of artificially infected females were feminized by the parasite, demonstrating that Nosema sp. is a cause of sex ratio distortion in its host. In contrast, we were unable to cross-infect Armadillidium vulgare with the feminizing microsporidian from G. duebeni or to cross-infect G. duebeni with the feminizing bacterium Wolbachia sp. from A. vulgare.

scholarly journals Environmental Influences on Crustacean Sex Determination and Reproduction: Environmental Sex Determination, Parasitism, and Pollution

2020 ◽  
pp. 394-428
Author(s):  
Alison M. Dunn ◽  
Thierry Rigaud ◽  
Alex T. Ford
Keyword(s):  
Environmental Factors ◽  
Sex Ratio ◽  
Sex Determination ◽  
Environmental Influences ◽  
Host Population ◽  
Adaptive Mechanism ◽  
Environmental Sex Determination ◽  
Individual Fitness ◽  
Ratio Distortion ◽  
Sex Ratio Distortion

This chapter reviews the influences of environmental factors on sex determination, sex ratios, and reproductive behavior in the Crustacea, focusing in particular on amphipod and isopod examples. A range of abiotic and biotic environmental factors influence reproduction in Crustacea, including temperature, day length, pollutants, and parasites. Individual crustaceans may benefit from these environmental influences, but in other cases, reproductive biology responses to biotic and abiotic environments may be detrimental to individual fitness. Environmental Sex Determination (ESD) falls into the former category. ESD is an adaptive mechanism of sex determination that is rare, but has evolved in diverse taxa. Evidence from gammarid amphipods is used to explore the evolution of ESD in response to a patchy environment. While ESD is an adaptive mechanism of sex determination, the impact of other environmental factors can be very costly. Parasitic castrators can lead to a reduction or total cessation of reproduction in crustacean hosts, driving population declines. In contrast, parasitic feminizers convert male hosts into females, enhancing maternal parasite transmission but also leading to sex ratio distortion in the host population. The chapter discusses parasite-host coevolutionary conflict and reviews evidence that selection on the host in response to parasitic sex ratio distortion has led to altered mate choice in amphipods, and to the evolution of a novel system of sex determination in isopods. Human-induced environmental influences can also be seen in Crustacea, and the chapter discusses how parasites, ESD, and endocrine-disrupting chemicals can each affect sex determination and lead to abnormal intersex phenotypes. It ends by highlighting areas for future research on the diverse world of crustacean reproduction.

scholarly journals Patterns and Mechanisms of Sex Ratio Distortion in the Collaborative Cross Mouse Mapping Population

2021 ◽  
Author(s):  
Brett A Haines ◽  
Francesca Barradale ◽  
Beth L Dumont
Keyword(s):  
Sex Ratio ◽  
Sex Determination ◽  
Sex Chromosome ◽  
Collaborative Cross ◽  
Mouse Population ◽  
Genetic Conflict ◽  
Mendelian Expectation ◽  
Ratio Distortion ◽  
Sex Ratio Distortion ◽  
Sex Biases

In species with single-locus chromosome-based mechanisms of sex determination, the laws of segregation predict an equal ratio of females to males at birth. Here, we show that departures from this Mendelian expectation are commonplace in the 8-way recombinant inbred Collaborative Cross (CC) mouse population. More than one-third of CC strains exhibit significant sex ratio distortion (SRD) at wean, with twice as many male-biased than female-biased strains. We show that these pervasive sex biases persist across multiple breeding environments, are stable over time, are not fully mediated by maternal effects, and are not explained by sex-biased neonatal mortality. SRD exhibits a heritable component, but QTL mapping analyses and targeted investigations of sex determination genes fail to nominate any large effect loci. These findings, combined with the reported absence of sex ratio biases in the CC founder strains, suggest that SRD manifests from multilocus combinations of alleles only uncovered in recombined CC genomes. We speculate that the genetic shuffling of eight diverse parental genomes during the early CC breeding generations led to the decoupling of sex-linked drivers from their co-evolved suppressors, unleashing complex, multiallelic systems of sex chromosome drive. Consistent with this interpretation, we show that several CC strains exhibit copy number imbalances at co-evolved X- and Y-linked ampliconic genes that have been previously implicated in germline genetic conflict and SRD in house mice. Overall, our findings reveal the pervasiveness of SRD in the CC population and nominate the CC as a powerful resource for investigating sex chromosome genetic conflict in action.

scholarly journals Resistance to meiotic drive at the MD locus in an Indian wild population of Aedes aegypti

1977 ◽  
Vol 29 (2) ◽  
pp. 123-132 ◽  
Author(s):  
S. G. Suguna ◽  
R. J. Wood ◽  
C. F. Curtis ◽  
A. Whitelaw ◽  
S. J. Kazmi
Keyword(s):  
Sex Ratio ◽  
Aedes Aegypti ◽  
Genetic Control ◽  
Wild Population ◽  
Sex Ratios ◽  
Meiotic Drive ◽  
In The Wild ◽  
Ratio Distortion ◽  
Sex Ratio Distortion ◽  
Different Parts

SUMMARYFemales from an Indian wild population of Aedes aegypti were crossed to males carrying the sex ratio distorter factor MD which shows meiotic drive. Progenies from F1 males were tested for sex ratio distortion, i.e. the chromosomes from the wild females were screened for their resistance to the action of MD. The distribution of sex ratio in the progenies of different F1 males indicated a polymorphism in the wild population for resistant and sensitive variants of the X chromosome. Seven discrete categories of X appear to exist, associated with sex ratios ranging from 50% ♀ to less than 1·25% ♀. The overall level of resistance varied slightly but significantly in different parts of a town. The results are discussed in relation to the use of sex ratio distortion for genetic control of mosquitoes.

Nutritional stress causes male-biased sex ratios in eastern spruce budworm (Lepidoptera: Tortricidae)

2014 ◽  
Vol 146 (2) ◽  
pp. 219-223 ◽  
Author(s):  
Roberto Quezada-García ◽  
Deepa Pureswaran ◽  
Éric Bauce
Keyword(s):  
Sex Ratio ◽  
Sex Ratios ◽  
Spruce Budworm ◽  
Nutritional Stress ◽  
Larval Survival ◽  
Normal Diet ◽  
Lower Percentage ◽  
Differential Mortality ◽  
Ratio Distortion ◽  
Sex Ratio Distortion

AbstractNutritional variability in resources may cause differential mortality between sexes resulting in biased sex ratios. If males and females differ in fitness, then mortality of the more sensitive sex can cause a bias in sex ratios, and can stimulate dispersion of males. We reared three generations of spruce budworm (Choristoneura fumiferana (Clemens); Lepidoptera: Tortricidae) on two artificial diets: a “normal” diet that provided all nutritional requirements for development and a “stress” diet (deficient in sugars and slightly higher in nitrogen), that simulated deterioration of food quality during outbreak conditions and had a detrimental impact on larval survival, development and growth. We tested the effects of continued nutritional stress on the sex ratio of pupae and adults. We found biased sex ratios in favour of males related to diet. Low quality food resulted in fewer females. This distortion was observed from the second generation onward, with a lower percentage of females reaching the pupal and adult stage. These results provide evidence that nutritional variation causes differential mortality between sexes, suggesting that females are more sensitive to nutritional stress. This is the first study that demonstrates sex ratio distortion due to nutritional selection pressure in spruce budworm. Our results indicate the importance of studying sex ratio distortion of spruce budworm in outbreak conditions.

scholarly journals Genetics and Genomics of an Unusual Selfish Sex Ratio Distortion in an Insect

2018 ◽  
Vol 28 (23) ◽  
pp. 3864-3870.e4 ◽  
Author(s):  
Phineas T. Hamilton ◽  
Christina N. Hodson ◽  
Caitlin I. Curtis ◽  
Steve J. Perlman
Keyword(s):  
Sex Ratio ◽  
Ratio Distortion ◽  
Genetics And Genomics ◽  
Sex Ratio Distortion

scholarly journals Analysis of the sex ratio in Bradysia matogrossensis (Diptera, Sciaridae)

2000 ◽  
Vol 23 (1) ◽  
pp. 97-103 ◽  
Author(s):  
Lincoln S. Rocha ◽  
André Luiz P. Perondini
Keyword(s):  
Sex Ratio ◽  
Sex Determination ◽  
X Chromosome ◽  
Control Mechanism ◽  
Sex Ratios ◽  
Laboratory Strain ◽  
Chromosome Elimination ◽  
Common Control ◽  
Males And Females ◽  
Successive Generations

In sciarid flies, the control of sex determination and of the progeny sex ratio is exercised by the parental females, and is based on differential X-chromosome elimination in the initial stages of embryogenesis. In some species, the females produce unisexual progenies (monogenic females) while in others, the progenies consist of males and females (digenic females). The sex ratio of bisexual progenies is variable, and departs considerably from 1:1. Bradysia matogrossensis shows both monogenic and digenic reproduction. In a recently established laboratory strain of this species, 15% of the females were digenic, 10% produced only females, 13% produced only males, and 62% produced progenies with one predominant sex (33% predominantly of female and 29% predominantly male progenies). These progeny sex ratios were maintained in successive generations. Females from female-skewed progenies yielded female- and male-producing daughters in a 1:1 ratio. In contrast, daughters of females from male-skewed progenies produce bisexual or male-skewed progenies. The X-chromosome of B. matogrossensis shows no inversion or other gross aberration. These results suggest that the control of the progeny sex ratio (or differential X-chromosome elimination) involves more than one locus or, at least, more than one pair of alleles. The data also suggest that, in sciarid flies, monogeny and digeny may share a common control mechanism.

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