Reverse Sex-Ratio Adjustment in an Apparently Outbreeding Wasp, Bracon hebetor

Evolution ◽  
1989 ◽  
Vol 43 (2) ◽  
pp. 465 ◽  
Author(s):  
Karen S. Galloway ◽  
Bruce Grant
Keyword(s):  
Sex Ratio ◽  
Bracon Hebetor ◽  
Sex Ratio Adjustment

scholarly journals REVERSE SEX-RATIO ADJUSTMENT IN AN APPARENTLY OUTBREEDING WASP,BRACON HEBETOR

Evolution ◽  
1989 ◽  
Vol 43 (2) ◽  
pp. 465-468 ◽  
Author(s):  
Karen S. Galloway ◽  
Bruce Grant
Keyword(s):  
Sex Ratio ◽  
Bracon Hebetor ◽  
Sex Ratio Adjustment

scholarly journals Primary sex ratio adjustment to experimentally reduced male UV attractiveness in blue tits

2006 ◽  
Vol 17 (4) ◽  
pp. 539-546 ◽  
Author(s):  
Peter Korsten ◽  
C. (Kate) M. Lessells ◽  
A. Christa Mateman ◽  
Marco van der Velde ◽  
Jan Komdeur
Keyword(s):  
Sex Ratio ◽  
Primary Sex Ratio ◽  
Sex Ratio Adjustment ◽  
Blue Tits

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 Recruitment sex ratios in gray-tailed voles (Microtus canicaudus) in response to density, sex ratio, and season

2003 ◽  
Vol 81 (8) ◽  
pp. 1306-1311 ◽  
Author(s):  
Monica L Bond ◽  
Jerry O Wolff ◽  
Sven Krackow
Keyword(s):  
Population Density ◽  
Sex Ratio ◽  
Resource Competition ◽  
Sex Ratios ◽  
Female Offspring ◽  
High Population ◽  
Reproductive Value ◽  
High Population Density ◽  
Adult Sex Ratio ◽  
Sex Ratio Adjustment

We tested predictions associated with three widely used hypotheses for facultative sex-ratio adjustment of vertebrates using eight enclosed populations of gray-tailed voles, Microtus canicaudus. These were (i) the population sex ratio hypothesis, which predicts that recruitment sex ratios should oppose adult sex-ratio skews, (ii) the local resource competition hypothesis, which predicts female-biased recruitment at low adult population density and male-biased recruitment at high population density, and (iii) the first cohort advantage hypothesis, which predicts that recruitment sex ratios should be female biased in the spring and male biased in the autumn. We monitored naturally increasing population densities with approximately equal adult sex ratios through the spring and summer and manipulated adult sex ratios in the autumn and measured subsequent sex ratios of recruits. We did not observe any significant sex-ratio adjustment in response to adult sex ratio or high population density; we did detect an influence of time within the breeding season, with more female offspring observed in the spring and more male offspring observed in the autumn. Significant seasonal increases in recruitment sex ratios indicate the capacity of female gray-tailed voles to manipulate their offspring sex ratios and suggest seasonal variation in the relative reproductive value of male and female offspring to be a regular phenomenon.

scholarly journals The mechanism of sex ratio adjustment in a pollinating fig wasp

2008 ◽  
Vol 275 (1643) ◽  
pp. 1603-1610 ◽  
Author(s):  
Shazia Raja ◽  
Nazia Suleman ◽  
Stephen G Compton ◽  
Jamie C Moore
Keyword(s):  
Sex Ratio ◽  
Fig Wasp ◽  
Sex Ratio Adjustment

scholarly journals Sperm sex ratio adjustment in a mammal: perceived male competition leads to elevated proportions of female-producing sperm

2020 ◽  
Vol 16 (6) ◽  
pp. 20190929
Author(s):  
Renée C. Firman ◽  
Jamie N. Tedeschi ◽  
Francisco Garcia-Gonzalez
Keyword(s):  
Sex Ratio ◽  
Sex Allocation ◽  
Sex Ratios ◽  
Female Offspring ◽  
Male Competition ◽  
Offspring Sex ◽  
Sex Ratio Adjustment ◽  
Adaptive Adjustment ◽  
Male House

Mammal sex allocation research has focused almost exclusively on maternal traits, but it is now apparent that fathers can also influence offspring sex ratios. Parents that produce female offspring under conditions of intense male–male competition can benefit with greater assurance of maximized grand-parentage. Adaptive adjustment in the sperm sex ratio, for example with an increase in the production of X-chromosome bearing sperm (CBS), is one potential paternal mechanism for achieving female-biased sex ratios. Here, we tested this mechanistic hypothesis by varying the risk of male–male competition that male house mice perceived during development, and quantifying sperm sex ratios at sexual maturity. Our analyses revealed that males exposed to a competitive ‘risk’ produced lower proportions of Y-CBS compared to males that matured under ‘no risk’ of competition. We also explored whether testosterone production was linked to sperm sex ratio variation, but found no evidence to support this. We discuss our findings in relation to the adaptive value of sperm sex ratio adjustments and the role of steroid hormones in socially induced sex allocation.

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