scholarly journals GENETIC VARIATION FOR THE SEX RATIO IN NASONIA VITRIPENNIS

Genetics ◽  
1985 ◽  
Vol 110 (1) ◽  
pp. 93-105
Author(s):  
E Davis Parker ◽  
Steven Hecht Orzack
Keyword(s):  
Genetic Variation ◽  
Sex Ratio ◽  
Artificial Selection ◽  
Sex Ratios ◽  
Female Parent ◽  
Parasitoid Wasp ◽  
Selection Response ◽  
Inbred Lines ◽  
Selection Experiment ◽  
Nasonia Vitripennis

ABSTRACT We detected genetic variation for the sex ratio in the parasitoid wasp Nasonia vitripennis by analysis of inbred lines and with an artificial selection experiment. Sex ratios differed significantly among five independently isolated lines. Furthermore, sex ratio in broods produced by single females in single hosts shifted from 80-90% female to 50-55% female in 13 to 15 generations in each of two replicate selection lines. The final sex ratios of both selection lines were significantly lower than any of the inbred line sex ratios. Backcrosses revealed that the selection response was due to nuclear genes acting through the female parent. In light of known facultative sex ratio behavior and major genes affecting sex ratio in Nasonia, our results suggest that population and individual sex ratios in this species are molded by processes at both genetic and behavioral levels.

scholarly journals Genomics of sex allocation in the parasitoid wasp Nasonia vitripennis

2020 ◽  
Author(s):  
Bart A. Pannebakker ◽  
Nicola Cook ◽  
Joost van den Heuvel ◽  
Louis van de Zande ◽  
David M. Shuker
Keyword(s):  
Genetic Variation ◽  
Sex Ratio ◽  
Sex Allocation ◽  
Genetic Basis ◽  
Genome Wide Association Study ◽  
Parasitoid Wasp ◽  
Nasonia Vitripennis ◽  
Ratio Variation ◽  
Genome Wide ◽  
A Genome

AbstractBackgroundWhilst adaptive facultative sex allocation has been widely studied at the phenotypic level across a broad range of organisms, we still know remarkably little about its genetic architecture. Here, we explore the genome-wide basis of sex ratio variation in the parasitoid wasp Nasonia vitripennis, perhaps the best studied organism in terms of sex allocation, and well known for its response to local mate competition (LMC).ResultsWe performed a genome-wide association study (GWAS) for single foundress sex ratios using iso-female lines derived from the recently developed outbred N. vitripennis laboratory strain HVRx. The iso-female lines capture a sample of the genetic variation in HVRx and we present them as the first iteration of the Nasonia vitripennis Genome Reference Panel (NVGRP 1.0). This panel provides an assessment of the standing genetic variation for sex ratio in the study population. Using the NVGRP, we discovered a cluster of 18 linked SNPs, encompassing 9 annotated loci associated with sex ratio variation. Furthermore, we found evidence that sex ratio has a shared genetic basis with clutch size on three different chromosomes.ConclusionsOur approach provides a thorough description of the quantitative genetic basis of sex ratio variation in Nasonia at the genome level and reveals a number of inter-related candidate loci underlying sex allocation regulation.

scholarly journals Consistent sex ratio bias of individual female dragon lizards

2006 ◽  
Vol 2 (4) ◽  
pp. 569-572 ◽  
Author(s):  
Tobias Uller ◽  
Beth Mott ◽  
Gaetano Odierna ◽  
Mats Olsson
Keyword(s):  
Genetic Variation ◽  
Sex Ratio ◽  
Incubation Temperature ◽  
Sex Ratios ◽  
Phenotypic Traits ◽  
Female Size ◽  
Offspring Sex Ratio ◽  
Phenotypic Differences ◽  
Sex Ratio Bias ◽  
Offspring Sex

Sex ratio evolution relies on genetic variation in either the phenotypic traits that influence sex ratios or sex-determining mechanisms. However, consistent variation among females in offspring sex ratio is rarely investigated. Here, we show that female painted dragons ( Ctenophorus pictus ) have highly repeatable sex ratios among clutches within years. A consistent effect of female identity could represent stable phenotypic differences among females or genetic variation in sex-determining mechanisms. Sex ratios were not correlated with female size, body condition or coloration. Furthermore, sex ratios were not influenced by incubation temperature. However, the variation among females resulted in female-biased mean population sex ratios at hatching both within and among years.

scholarly journals The effects of X-rays on quantitative characters

1964 ◽  
Vol 5 (3) ◽  
pp. 410-422 ◽  
Author(s):  
G. A. Clayton ◽  
Alan Robertson
Keyword(s):  
Genetic Variation ◽  
Population Size ◽  
Effective Population Size ◽  
Artificial Selection ◽  
Inbred Lines ◽  
X Rays ◽  
Effective Population ◽  
Outbred Population ◽  
Culture Bottle ◽  
Quantitative Characters

1. The rate of production by X-rays of new genetic variation in two quantitative characters in Drosophila melanogaster (sternital and sternopleural bristles) has been investigated, using ‘plateaued’ populations which had reached the limit under artificial selection and, for sternital bristles only, populations which had been made genetically invariant by inbreeding. The genetic variation was always measured by the response of the population to selection. The X-rays dose given in any generation was always 1800 r. to adults.2. Seven plateaued lines had eight cycles of alternate irradiation and selection, each with its non-irradiated control. All the responses were small but in three lines they were significantly greater after irradiation.3. Selection was applied to three different inbred lines, genetically marked to detect contamination, after varying periods of irradiation. At the same time, the inbred lines and lines derived from them which had been mass mated in bottles were selected. The irradiated populations showed a greater response. The new genetic variance produced by the irradiation was approximately 10−5 units/r. The estimate of the dose required to introduce new variation equal to that in a standard outbred population was 500,000 r.4. The effective population size was an important factor in the interpretation of some of these results on the long-term effects of radiation. By observing the variation between replicate lines in the frequency of a gene with a visible effect under these culture conditions (i.e. in a single culture bottle) the effective population size was estimated at sixty. Outbred populations kept under these conditions for many generations showed a reduction of genetic variability in agreement with this value.5. To investigate the possibility that the deleterious genes produced by irradiation would interfere with the response to artificial selection, a standard outbred population was irradiated and selected. In spite of the observed high frequency of recessive lethals produced, the response to selection was very similar to that of the standard population.

scholarly journals The comparative biology of genetic variation for conditional sex ratio behavior in a parasitic wasp, Nasonia vitripennis.

Genetics ◽  
1991 ◽  
Vol 127 (3) ◽  
pp. 583-599 ◽  
Author(s):  
S H Orzack ◽  
E D Parker ◽  
J Gladstone
Keyword(s):  
Sex Ratio ◽  
Group Size ◽  
Evolutionarily Stable Strategy ◽  
Sex Ratios ◽  
Parasitic Wasp ◽  
Nasonia Vitripennis ◽  
Reasonable Evidence ◽  
Ess Model ◽  
Isofemale Strains ◽  
Evolutionarily Stable

Abstract Using genetic markers, we tracked the sex ratio behavior of individual females of the parasitic wasp, Nasonia vitripennis, in foundress groups of size 1, 2, 4, 8 and 16. Comparison of 12 isofemale strains extracted from a natural population reveals significant between-strain heterogeneity of sex ratios produced in all sizes of foundress group. Under simple assumptions about population structure, this heterogeneity results in heterogeneity of fitnesses. The strains differ in their conditional sex ratio behavior (the sex ratio response of a female to foundress groups of different sizes). Females of some strains produce more males as foundress group size increases (up to size eight). Females of another strain produce more males when not alone but do not respond differentially to group size otherwise. Females of two other strains show no conditional sex ratio behavior. Females of only two strains behave differently in foundress groups of size 8 and 16. Correlation and regression analyses indicate that the strains differ significantly in their fit to the predictions of an evolutionarily stable strategy (ESS) model of conditional sex ratio behavior. Such heterogeneity contradicts the notion that females of this species possess conditonal sex ratio behavior that is optimal in the ESS sense. The results imply that this ESS model is useful but not sufficient for understanding the causal basis of the evolution of this behavior in this species. This is the first report on the sex ratio behavior of individual females in multiple foundress groups in any species of parasitic wasp. Data of this type (and not foundress group or "patch" sex ratios) are essential for testing evolutionary models that predict the sex ratio behaviors of individuals. We suggest that a test for an ESS model include the answers to two important questions: 1) is the model quantitatively accurate? and 2) is there reasonable evidence to indicate that natural selection has caused individuals to manifest the ESS behavior?

scholarly journals Heritability of Directional Asymmetry in Drosophila melanogaster

2009 ◽  
Vol 2009 ◽  
pp. 1-7 ◽  
Author(s):  
Ashley J. R. Carter ◽  
Elizabeth Osborne ◽  
David Houle
Keyword(s):  
Drosophila Melanogaster ◽  
Genetic Variation ◽  
Artificial Selection ◽  
Natural Variation ◽  
The Other ◽  
Directional Asymmetry ◽  
Consistent Difference ◽  
Selection Experiment ◽  
Response To Selection ◽  
Powerful Technique

Directional asymmetry (DA), the consistent difference between a pair of morphological structures in which the same side is always larger than the other, presents an evolutionary mystery. Although many paired traits show DA, genetic variation for DA has not been unambiguously demonstrated. Artificial selection is a powerful technique for uncovering selectable genetic variation; we review and critique the limited number of previous studies that have been performed to select on DA and present the results of a novel artificial selection experiment on the DA of posterior crossvein location in Drosophila wings. Fifteen generations of selection in two genetically distinct lines were performed and none of the lines showed a significant response to selection. Our results therefore support and reconfirm previous findings; despite apparent natural variation and evolution of DA in nature, DA remains a paradoxical trait that does not respond to artificial selection.

scholarly journals Quantitative genetics of sex ratio traits in the parasitic wasp, Nasonia vitripennis.

Genetics ◽  
1994 ◽  
Vol 137 (1) ◽  
pp. 211-220
Author(s):  
S H Orzack ◽  
J Gladstone
Keyword(s):  
Sex Ratio ◽  
Sex Ratios ◽  
Parasitic Wasp ◽  
Genetic Correlations ◽  
Nasonia Vitripennis ◽  
Narrow Sense Heritability ◽  
First Sex ◽  
Second Sex ◽  
Study Population ◽  
Almost All

Abstract We detected significant parent-offspring regressions for the first sex ratio (the sex ratio produced by a female in a fresh host) and the second sex ratio (the sex ratio produced by a female in a previously parasitized host) in the parasitic wasp, Nasonia vitripennis. For both traits, estimates of the narrow-sense heritability range from approximately 0.05 to approximately 0.15 (depending on how the data are analyzed). The study population was derived from isofemale strains created from wasps captured in a single bird nest. The same population exhibited no significant parent-offspring regression for the brood sizes associated with the first and second sex ratios. There may be a significant negative parent-offspring regression for diapause proportion in the first sex ratio broods. The estimates of the genetic correlations between first and second sex ratios are positive although almost all are not significantly different from 0.0. To our knowledge, this study is the first "fine-scale" analysis of genetic variation for sex ratio traits in any species of insect. Such studies are an essential part of the assessment of the validity of claims that sex ratio traits are locally optimal.

Effect of inbreeding on sex ratio in the apple snail Pomacea canaliculata

2019 ◽  
Vol 85 (3) ◽  
pp. 348-353
Author(s):  
Natsumi Kumagai ◽  
Yoichi Yusa
Keyword(s):  
Sex Ratio ◽  
Sex Ratios ◽  
Empirical Support ◽  
Freshwater Snail ◽  
Inbred Lines ◽  
Pomacea Canaliculata ◽  
Apple Snail ◽  
Terrestrial Vertebrates ◽  
Average Proportion ◽  
Invasive Capacity

ABSTRACT Female-biased sex ratios are adaptive in populations founded by a small number of individuals and are mainly due to local mate competition (the haystack model). However, little empirical support for this theory exists and, with the exception of terrestrial vertebrates and arthropods, very little is known about the possible mechanisms for biased sex ratios under this model in animals. The highly invasive freshwater snail Pomacea canaliculata usually reproduces in small temporary water bodies and is characterized by genetically based variable brood sex ratios. We conducted a mating experiment to test the prediction that sex ratio is biased towards females in inbred populations. Inbred lines (pairing of a male and a female from the same brood) and outcrossed lines (pairing of a male and a female from different broods) were reared in the lab, and sex ratios were compared between these two breeding types for three generations (the F1 generation was produced by outcrossing only). As predicted, the sex ratios of the inbred lines showed greater bias towards females (average proportion of males per generation was 0.38–0.40) than the outcrossed lines (0.45–0.55). The female-biased sex ratios of P. canaliculata may facilitate rapid population growth and may thus enhance the invasive capacity of this snail. Female-biased sex ratios under metapopulation structures, as predicted by the haystack models, may be more common than previously considered.

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