scholarly journals Competitor-to-resource ratio, a general formulation of operational sex ratio, as a predictor of competitive aggression in Japanese medaka (Pisces: Oryziidae)

2000 ◽  
Vol 11 (6) ◽  
pp. 670-675 ◽  
Author(s):  
James W. A. Grant ◽  
Chantal L. Gaboury ◽  
Howard L. Levitt
Keyword(s):  
Sex Ratio ◽  
Operational Sex Ratio ◽  
Japanese Medaka

scholarly journals Effect of operational sex ratio on female–female versus male–male competitive aggression

2002 ◽  
Vol 80 (12) ◽  
pp. 2242-2246 ◽  
Author(s):  
James W.A Grant ◽  
Patricia E Foam
Keyword(s):  
Comparative Analysis ◽  
Sex Ratio ◽  
Systems Theory ◽  
Mating Systems ◽  
Operational Sex Ratio ◽  
Japanese Medaka ◽  
Sexually Active ◽  
Male Aggression ◽  
Intrasexual Aggression ◽  
Opposite Sex

We compared the patterns of female–female and male–male competition in Japanese medaka (Oryzias latipes) in response to changes in the operational sex ratio (OSR), the ratio of sexually active members of one sex to sexually active members of the opposite sex. As expected, courtship behaviour and intrasexual aggression were more frequent in males than in females. However, the overall patterns of female–female and male–male aggression were similar: intrasexual aggression increased with the OSR (female/male OSR for females and male/female OSR for males), consistent with predictions of mating-systems theory. A comparative analysis of our data and those from three other studies indicated that the rate of intrasexual aggression was greater in males than in females, but the patterns of intrasexual aggression were similar: the rate increased linearly and with a common slope with increasing OSR over a range of 0.4–3.

Operational sex ratio, mediated by synchrony of female arrival, alters the variance of male mating success in Japanese medaka

1995 ◽  
Vol 49 (2) ◽  
pp. 367-375 ◽  
Author(s):  
JAMES W.A. GRANT ◽  
MICHAEL J. BRYANT ◽  
CATHERINE E. SOOS
Keyword(s):  
Sex Ratio ◽  
Mating Success ◽  
Operational Sex Ratio ◽  
Japanese Medaka ◽  
Male Mating ◽  
Male Mating Success

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 Deer Indirectly Alter the Reproductive Strategy and Operational Sex Ratio of an Unpalatable Forest Perennial

2020 ◽  
Vol 195 (1) ◽  
pp. 56-69
Author(s):  
Lalasia Bialic-Murphy ◽  
Christopher D. Heckel ◽  
Robert M. McElderry ◽  
Susan Kalisz
Keyword(s):  
Sex Ratio ◽  
Reproductive Strategy ◽  
Operational Sex Ratio
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