scholarly journals Genetic variation for sex ratio traits within a natural population of a parasitic wasp, Nasonia vitripennis.

Genetics ◽  
1990 ◽  
Vol 124 (2) ◽  
pp. 373-384 ◽  
Author(s):  
S H Orzack ◽  
E D Parker
Keyword(s):  
Population Structure ◽  
Sex Ratio ◽  
Natural Population ◽  
Sex Ratios ◽  
Parasitic Wasp ◽  
Nasonia Vitripennis ◽  
First Sex ◽  
Second Sex ◽  
Percent Difference ◽  
Isofemale Strains

Abstract By analyzing isofemale strains extracted from a natural population of Nasonia vitripennis, we detected variation for the sex ratios produced in fresh hosts (first sex ratios) and in previously parasitized hosts (second sex ratios). Under simple assumptions of population structure, this between-strain heterogeneity of first sex ratios results in heterogeneity of fitnesses. There is approximately ten percent difference in average fitnesses between the strains. (The fitnesses of second sex ratios are analyzed in the accompanying paper.) Average first and average second sex ratios are uncorrelated. There is significant between-female heterogeneity within some strains for first sex ratios but not for second sex ratios. In addition, the average direct-developing and diapause first sex ratios (but not second sex ratios) are significantly correlated. There are significant correlations between the direct-developing and diapause sex ratios produced by the same female. The strains differ in their effects on the sex ratio and size of another female's brood in the same host. Data on these types of variation for sex ratio traits are essential for further progress in the study of sex ratio evolution.

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.

scholarly journals The comparative biology of second sex ratio evolution within a natural population of a parasitic wasp, Nasonia vitripennis.

Genetics ◽  
1990 ◽  
Vol 124 (2) ◽  
pp. 385-396 ◽  
Author(s):  
S H Orzack
Keyword(s):  
Sex Ratio ◽  
Parasitic Wasp ◽  
Comparative Biology ◽  
Significant Heterogeneity ◽  
Regression Analyses ◽  
Nasonia Vitripennis ◽  
Second Sex ◽  
Sex Ratio Adjustment ◽  
Optimality Models ◽  
Isofemale Strains

Abstract Correlation and regression analyses indicate that isofemale strains extracted from a population of the parasitic wasp, Nasonia vitripennis, differ in the fit of their second sex ratios (those produced in previously parasitized hosts) to the predictions of the theory of optimal facultative sex ratio adjustment. Under the theory's simple assumptions about population structure, there is significant heterogeneity of fitnesses among the isofemale strains. The reasons underlying these types of heterogeneity must be understood before we can make statements about the nature of sex ratio evolution in this species. These results suggest that comparative analyses are essential for testing the qualitative predictions of optimality models.

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?

Cytogenetic analysis of the paternal sex ratio chromosome of Nasonia vitripennis

Genome ◽  
1993 ◽  
Vol 36 (1) ◽  
pp. 157-161 ◽  
Author(s):  
Kent M. Reed
Keyword(s):  
Sex Ratio ◽  
Silver Staining ◽  
Organizer Region ◽  
Parasitic Wasp ◽  
Nucleolus Organizer Region ◽  
B Chromosome ◽  
Nucleolus Organizer ◽  
Nasonia Vitripennis ◽  
C Banding ◽  
Paternal Sex Ratio

Paternal sex ratio (PSR) is a B chromosome found in the parasitic wasp Nasonia vitripennis. PSR has a unique etiology in that it destroys the paternal chromosomes of fertilized eggs, resulting in the production of all male families. This study examined structural aspects of PSR including size, C-banding, and silver staining. PSR was found to constitute approximately 5.7% of the genome of carrier males. C-banding confirmed the heterochromatic nature of PSR and the data suggest that PSR remains primarily condensed throughout the cell cycle. Examination of prometaphase spermatocytes revealed a secondary constriction on PSR. The constriction, however, did not stain positive for nucleolus organizer activity. During mitosis, PSR and the pericentromeric regions of the A chromosomes displayed a temporal pattern of silver staining, involving dense precipitation of silver prior to metaphase. This reaction is indicative of a protein complex specific to the heterochromatin of these regions. The implications of these findings to the origin of PSR are discussed.Key words: Nasonia vitripennis, paternal sex ratio, B chromosome, nucleolus organizer region, heterochromatin.

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 Sex-Ratio Drive in Drosophila simulans: Variation in Segregation Ratio of X Chromosomes From a Natural Population

Genetics ◽  
2002 ◽  
Vol 162 (3) ◽  
pp. 1221-1231 ◽  
Author(s):  
Catherine Montchamp-Moreau ◽  
Michel Cazemajor
Keyword(s):  
Sex Ratio ◽  
Natural Population ◽  
X Chromosome ◽  
Sex Ratios ◽  
Segregation Ratio ◽  
Drosophila Simulans ◽  
Chromosome Polymorphism ◽  
X Chromosomes ◽  
Clear Cut ◽  
Pattern Of Variation

Abstract The sex-ratio trait that exists in a dozen Drosophila species is a case of naturally occurring X chromosome drive that causes males to produce female-biased progeny. Autosomal and Y polymorphism for suppressors are known to cause variation in drive expression, but the X chromosome polymorphism has never been thoroughly investigated. We characterized 41 X chromosomes from a natural population of Drosophila simulans that had been transferred to a suppressor-free genetic background. We found two clear-cut groups of chromosomes, sex-ratio and standard. The sex-ratio X chromosomes differed in their segregation ratio (81-96% females in the progeny), the less powerful drivers being less stable in their expression. A sib analysis, using a moderate driver, indicated that within-X variation in drive expression depended on genetic (autosomal) or epigenetic factors and that the age of the males also affected the trait. The other X chromosomes produced equal or roughly equal sex ratios, but again with significant variation. The continuous pattern of variation observed within both groups suggested that, in addition to a major sex-ratio gene, many X-linked loci of small effect modify the segregation ratio of this chromosome and are maintained in a polymorphic state. This was also supported by the frequency distribution of sex ratios produced by recombinant X chromosomes.

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