Sex ratio elasticity influences the selection of sex ratio strategy

10.7287/peerj.preprints.2166v1 ◽

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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Cooperative interactions among females and even more extraordinary sex ratios

10.1101/2020.06.08.118786 ◽

2020 ◽

Cited By ~ 1

Author(s):

Ryosuke Iritani ◽

Stuart A West ◽

Jun Abe

Keyword(s):

Sex Ratio ◽

Sex Ratios ◽

Structured Populations ◽

Local Mate Competition ◽

Mate Competition ◽

Wasp Species ◽

Cooperative Interactions ◽

Competition Theory ◽

Local Mate ◽

Biased Sex Ratio

AbstractHamilton’s local mate competition theory provided an explanation for extraordinary female biased sex ratios in a range of organisms. When mating takes place locally, in structured populations, a female biased sex ratio is favoured to reduce competition between related males, and to provide more mates for males. However, there are a number of wasp species where the sex ratios appear to more female biased than predicted by Hamilton’s theory. We investigated theoretically the extent to which cooperative interactions between related females can interact with local mate competition to favour even more female biased sex ratios. We found that: (i) cooperative interactions between females can lead to sex ratios that are more female biased than predicted by local competition theory alone; (ii) sex ratios can be more female biased when the cooperative interactions are offspring helping parents before dispersal, rather than cooperation between siblings after dispersal. Our results can be applied to a range of organisms, and provide an explanation for the extreme sex ratio biases that have been observed in Sclerodermus and Melittobia wasps.

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Can the extremely female-biased sex ratio of the social spider mites be explained by Hamilton’s local mate competition model?

Ecological Entomology ◽

10.1111/j.1365-2311.2007.00908.x ◽

2007 ◽

Vol 32 (6) ◽

pp. 597-602 ◽

Cited By ~ 11

Author(s):

YUKIE SATO ◽

YUTAKA SAITO

Keyword(s):

Sex Ratio ◽

Spider Mites ◽

Competition Model ◽

Local Mate Competition ◽

Mate Competition ◽

Social Spider ◽

The Social ◽

Local Mate ◽

Biased Sex Ratio

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

10.21203/rs.3.rs-138286/v1 ◽

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.

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Male-biased sex ratio in Argulus canadensis Wilson, 1916 (Crustacea: Branchiura) ectoparasitic on sticklebacks

Canadian Journal of Zoology ◽

10.1139/z89-296 ◽

1989 ◽

Vol 67 (8) ◽

pp. 2078-2080 ◽

Cited By ~ 3

Author(s):

Robert Poulin ◽

Gerard J. FitzGerald

Keyword(s):

Salt Marsh ◽

Sex Ratio ◽

Laboratory Experiments ◽

Fish Predation ◽

Reproductive Behaviour ◽

Egg Deposition ◽

Alternative Hypotheses ◽

Biased Sex Ratio ◽

The Difference ◽

Fish Hosts

Females of the ectoparasitic crustacean Argulus canadensis must leave their fish hosts at least temporarily to deposit their eggs on the substrate. To test the hypothesis that this difference in reproductive behaviour between the two sexes could result in male-biased sex ratios on their stickleback hosts, we sampled sticklebacks in tide pools of a Quebec salt marsh from early July to early September 1986. During this period, fish harboured significantly more male than female A. canadensis. Laboratory experiments were done to test two alternative hypotheses offered to explain this biased sex ratio. The first hypothesis was that male A. canadensis were more successful than females in attacking their stickleback hosts; however, we found no differences in attack success on their hosts between the two parasite sexes. The second hypothesis was that sticklebacks ate more female than male A. canadensis. Although males were less vulnerable to fish predation than females, the difference was not significant. We conclude that sexual differences in reproductive behaviour, i.e., egg deposition behaviour of females, can account for the male-biased sex ratio of A. canadensis on sticklebacks.

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