scholarly journals Sex Ratio Is Synergistically Modulated by Local Resource Competition and Enhancement: the Case of a Primitively Eusocial Wasp Under Female Philopatry

2021 ◽  
Author(s):  
Koji Tsuchida ◽  
Norio Ishiguro ◽  
Fuki Saito-Morooka ◽  
Jun-Ichi Kojima ◽  
Philip Spradbery
Keyword(s):  
Sex Ratio ◽  
Resource Competition ◽  
Female Competition ◽  
Offspring Sex Ratio ◽  
Local Resource Competition ◽  
Local Resource ◽  
Female Philopatry ◽  
Primitively Eusocial Wasp ◽  
Before And After ◽  
Biased Sex Ratio

Abstract BackgroundIn animals, the offspring sex ratio is modulated by kin conflict and cooperation, and determining the ratio is a main concern in evolutionary biology. Male competition for access to local mates is predictive of a female-biased sex ratio in the offspring (local mate competition; LMC). Conversely, female competition for access to local resources is predictive of a male-biased sex ratio in the offspring (local resource competition; LRC). However, several factors other than competition should synergistically operate in real-world populations. In the Australian paper wasp Ropalidia plebeiana, LRC and local resource enhancement (LRE) may operate simultaneously. To determine whether this is the case, we evaluated colony sex ratios and examined whether competition and/or enhancement operates at the population level in this species. ResultsIn spring, many foundress queens started their colonies by comb-cutting, in which nest combs from the previous season were divided into several combs to be reused. Genetic relatedness among foundresses did not differ before and after comb-cutting. Relatedness among foundresses was 0.339, whereas relatedness among new foundresses was 0.589, revealing nearly functional monogyny. The global FST value calculated with mtDNA markers was higher than that calculated with microsatellite markers, even after we corrected for differences in effective population sizes between sexes. This finding indicates female philopatry, which was also confirmed by mark–release–recapture before and after the hibernation of new foundresses. The colony sex ratio of reproductives became slightly biased toward males in larger colonies. In addition, both the number of foundresses and number of workers were positively associated with the number of reproductives, which indicates that LRE was also operating.ConclusionsOur results suggest that although the population structure seems to meet the requirements of LRC, the sex ratio is not modulated solely by LRC. Instead, the availability of female helpers at the founding stage likely mitigates the sex ratio predicted by LRC through LRE. Thus, LRC at the founding stage and LRE at the reproductive stage synergistically modulate the colony sex ratio in R. plebeiana.

Sex Ratio in Primates: A Test of the Local Resource Competition Hypothesis

Oikos ◽  
1989 ◽  
Vol 56 (1) ◽  
pp. 132 ◽  
Author(s):  
Colin A. Chapman ◽  
Lauren J. Chapman ◽  
Karen S. Richardson
Keyword(s):  
Sex Ratio ◽  
Resource Competition ◽  
Local Resource Competition ◽  
Local Resource ◽  
Competition Hypothesis

Sex Ratio and Local Resource Competition

1981 ◽  
Vol 117 (5) ◽  
pp. 796-797 ◽  
Author(s):  
John L. Hoogland
Keyword(s):  
Sex Ratio ◽  
Resource Competition ◽  
Local Resource Competition ◽  
Local Resource

Local Resource Competition and Sex Ratio Variation in Birds

1995 ◽  
Vol 26 (2) ◽  
pp. 168 ◽  
Author(s):  
Patrick J. Weatherhead ◽  
Robert Montgomerie
Keyword(s):  
Sex Ratio ◽  
Resource Competition ◽  
Local Resource Competition ◽  
Local Resource ◽  
Ratio Variation

scholarly journals A Test of Sex-Ratio Biasing in the White-Throated Magpie-Jay, A Cooperative Breeder with Female Helpers

The Condor ◽  
2004 ◽  
Vol 106 (2) ◽  
pp. 299-308
Author(s):  
Elena C. Berg
Keyword(s):  
Sex Ratio ◽  
Resource Competition ◽  
Bird Species ◽  
Population Level ◽  
Offspring Sex Ratio ◽  
Local Resource ◽  
Offspring Sex ◽  
Local Resource Enhancement ◽  
Genetic Parents ◽  
Dna Microsatellite Analysis

Abstract Recent studies suggest that many bird species are able to vary the sex ratio of their young. Among cooperative breeders, in which adult helpers aid the genetic parents in the rearing of young, two models have been invoked to explain this variation. According to the local resource competition hypothesis, parents should bias offspring sex ratios toward the dispersing sex in order to minimize competition for local resources. In contrast, the local resource enhancement (or “production of helpers”) hypothesis states that parents should overproduce the nondispersing sex if the presence of relatives enhances reproductive success. I examined these models in a Costa Rican population of White-throated Magpie-Jays (Calocitta formosa), a cooperatively breeding corvid with female helpers. Using DNA microsatellite analysis, I sexed 135 offspring from 38 broods and 14 groups over 3 years. I tested for variation in offspring sex ratio at the population level and as a function of social group, helper number, breeding female, and season. Unlike studies of the Seychelles Warbler (Acrocephalus sechellensis), one of the few other avian species with primarily female helpers, I found no evidence for systematic sex-ratio bias supporting either hypothesis. This suggests that female-biased helping is not a sufficient condition for the evolution of offspring sex-ratio biasing. Estudio del Sesgo en el Cociente de Sexos en Calocitta formosa, una Reproductora Cooperativa con Ayudantes Hembras Resumen. Estudios recientes sugieren que muchas especies de aves pueden hacer variar el cociente de sexos de sus crías. Se han utilizado dos modelos teóricos para explicar esta variación en las aves que se reproducen en forma cooperativa, en las cuales los adultos ayudan a los padres genéticos con el cuidado de sus crías. Según la hipótesis de competencia por recursos locales, los padres deben sesgar el cociente de sexos de su prole en favor del sexo que se dispersa con el fin de minimizar la competencia por los recursos locales. Por el contrario, según la hipótesis de incremento de recursos locales (o “producción de ayudantes”), los padres deben sobreproducir el sexo que no se dispersa si la presencia de parientes favorece el éxito reproductivo. Yo estudié estos modelos en una población costarricense de urracas (Calocitta formosa), un córvido de reproducción cooperativa con ayudantes hembras. Utilicé análisis de ADN microsatelital para averiguar el sexo de 135 crías provenientes de 38 nidadas y 14 grupos a lo largo de un período de tres años. Documenté las variaciones en el cociente de sexos de las crías a nivel poblacional y como función del grupo social, la cantidad de ayudantes, la hembra reproductiva y la estación del año. A diferencia de lo encontrado para el caso de Acrocephalus sechellensis, una de las pocas especies de aves con ayudantes principalmente hembras, no encontré indicios de sesgo sistemático en el cociente de sexos que avalara ninguna de las dos hipótesis. Esto sugiere que la ayuda por parte de las hembras no constituye una condición que determine la evolución de un sesgo en el cociente de sexos de las crías.

scholarly journals Sex ratio elasticity influences the selection of sex ratio strategy

2016 ◽  
Author(s):  
Yaqiang Wang ◽  
Ruiwu Wang ◽  
Yaotang Li ◽  
Zhanshan (Sam) Ma
Keyword(s):  
Sex Ratio ◽  
Resource Competition ◽  
Mate Competition ◽  
Unified Theory ◽  
Local Resource Competition ◽  
Local Mate ◽  
Biased Sex Ratio ◽  
Plausible Mechanism ◽  
The Difference ◽  
Selection Of

There are three sex ratio strategies (SRS) in nature—male-biased sex ratio, female-biased sex ratio and, equal sex ratio depending on the proportion of male offspring being greater than, less than, or equal to ½. The problem was already noted in Darwin’s (1859) “Origin of Species,” and it was R. A. Fisher (1930) who first explained why most species in nature display a sex ratio of ½. Consequent SRS theories such as Hamilton’s (1967) local mate competition (LMC) and Clark’s (1978) local resource competition (LRC) separately explained the observed deviations from the seemingly universal 1:1 ratio. However, to the best of our knowledge, there is not yet a unified theory that accounts for the mechanisms of the three SRS. Here, we introduce the price elasticity theory in economics to define sex ratio elasticity (SRE), and present an analytical model that derives three SRSs based on the following assumption: simultaneously existing competitions for both resources and mates influence the level of SRE in both sexes differently. Consequently, it is the difference (between two sexes) in the level of their sex ratio elasticity that leads to three different SRS. Our analytical results demonstrate that the elasticity-based model not only reveals a highly plausible mechanism that explains the evolution of SRS in nature, but also offers a novel framework for unifying two major classical theories (i.e., LMC & LRC) in the field of SRS research.

scholarly journals Sex ratio elasticity influences the selection of sex ratio strategy

2016 ◽  
Author(s):  
Yaqiang Wang ◽  
Ruiwu Wang ◽  
Yaotang Li ◽  
Zhanshan (Sam) Ma
Keyword(s):  
Sex Ratio ◽  
Resource Competition ◽  
Mate Competition ◽  
Unified Theory ◽  
Local Resource Competition ◽  
Local Mate ◽  
Biased Sex Ratio ◽  
Plausible Mechanism ◽  
The Difference ◽  
Selection Of

There are three sex ratio strategies (SRS) in nature—male-biased sex ratio, female-biased sex ratio and, equal sex ratio depending on the proportion of male offspring being greater than, less than, or equal to ½. The problem was already noted in Darwin’s (1859) “Origin of Species,” and it was R. A. Fisher (1930) who first explained why most species in nature display a sex ratio of ½. Consequent SRS theories such as Hamilton’s (1967) local mate competition (LMC) and Clark’s (1978) local resource competition (LRC) separately explained the observed deviations from the seemingly universal 1:1 ratio. However, to the best of our knowledge, there is not yet a unified theory that accounts for the mechanisms of the three SRS. Here, we introduce the price elasticity theory in economics to define sex ratio elasticity (SRE), and present an analytical model that derives three SRSs based on the following assumption: simultaneously existing competitions for both resources and mates influence the level of SRE in both sexes differently. Consequently, it is the difference (between two sexes) in the level of their sex ratio elasticity that leads to three different SRS. Our analytical results demonstrate that the elasticity-based model not only reveals a highly plausible mechanism that explains the evolution of SRS in nature, but also offers a novel framework for unifying two major classical theories (i.e., LMC & LRC) in the field of SRS research.

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