What Fig Wasp Sex Ratios May or May Not Tell Us about Sex Allocation Strategies

<p>The application of sex allocation theory can provide useful insight into endangered rhinoceros biology to improve in situ and ex situ conservation efforts by understanding the factors that cause a female to produce one sex of calf. By decreasing the birth sex ratio (number of males born per number of females born) in a population it may be possible to increase population growth rates. The first aim was to determine if an environmentally cued sex allocation response occurred in black rhinos. By examining rainfall and calf sex records in a wild black rhino population, I identified that birth sex ratios increase in rainy seasons and rainy years. Mothers were more likely to be observed with male calves if they conceived during the wet season (57.3% male) than during the dry season (42.9% male). Mothers were more likely to raise male calves if they conceived during wet years (60.2% male) than during dry years (46.1% male). Next, I examined whether pulsatile or random variation in sex ratios of different magnitudes, as might occur under changes in climate patterns, would be detrimental to rhinoceros population growth. Results demonstrated that while random increases in the magnitude of birth sex ratio variation, in either direction, increased population survival probability up to 0.907, sequential pulsed years of birth sex ratio bias had the opposite effect on population performance down to a survival probability of 0.619. Furthermore, for both scenarios, populations of less than 50 animals are particularly vulnerable to extinction. Since the sex biases observed in the captive rhinoceros population were attributed to several factors, I used an information theoretic approach to evaluate the relative importance of different hypotheses for birth sex bias for predicting calf sex. The results demonstrated that none of the models tested were greatly predictive of calf sex. Suspecting that the mechanisms that were cueing calf sex occur close to the time of conception and were nutritionally cued, in the final experiment, I measured changes in blood glucose in white rhinos after they ate different meals. At 90 minutes, serum glucose levels in rhinos eating the 10 % lucerne hay diet were significantly lower than the 5% glucose and 10% glucose diets but not the 10% pellet nor 10% grass hay diets. This is the first time such an experiment has been published in a wildlife species and not only demonstrates the feasibility of training rhinos for successive blood draws but also that captive diets are low glycemic for white rhinos. Overall, my research confirmed that an environmentally cued sex allocation response does occur in African rhinos, and changes in the duration and magnitude of sex ratio patterns can decrease population growth and increase potential for extinction. Additionally, none of the previous hypotheses for the suspected male-sex bias in captive born rhinos were influential on calf sex, which shifts the focus of sex allocation research in rhinos to more acute signals around the time of conception, such as changes in diet and body condition.</p>

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Sex allocation conflict and sexual selection throughout the lifespan of eusocial colonies

10.1101/454512 ◽

2018 ◽

Author(s):

Piret Avila ◽

Lutz Fromhage ◽

Laurent Lehmann

Keyword(s):

Resource Allocation ◽

Sexual Selection ◽

Evolutionary Biology ◽

Sex Allocation ◽

Colony Growth ◽

Eusocial Insects ◽

Dynamic Resource ◽

Colony Ontogeny ◽

Allocation Decisions ◽

Allocation Strategies

AbstractModels of sex allocation conflict are central to evolutionary biology but have mostly assumed static decisions, where resource allocation strategies are constant over colony lifespan. Here, we develop a model to study how the evolution of dynamic resource allocation strategies is affected by the queen-worker conflict in annual eusocial insects. We demonstrate that the time of dispersal of sexuals affects the sex allocation ratio through sexual selection on males. Furthermore, our model provides three predictions that depart from established results of classic static allocation models. First, we find that the queen wins the sex allocation conflict, while the workers determine the maximum colony size and colony productivity. Second, male-biased sex allocation and protandry evolve if sexuals disperse directly after eclosion. Third, when workers are more related to new queens, then the proportional investment into queens is expected to be lower, which results from the interacting effect of sexual selection (selecting for protandry) and sex allocation conflict (selecting for earlier switch to producing sexuals). Overall, we find that colony ontogeny crucially affects the outcome of sex-allocation conflict because of the evolution of distinct colony growth phases, which decouples how queens and workers affect allocation decisions and can result in asymmetric control.

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Sex Allocation, Sex Ratios and Reproduction

Encyclopedia of Animal Behavior ◽

10.1016/b978-0-08-045337-8.00194-7 ◽

2010 ◽

pp. 146-151 ◽

Cited By ~ 1

Author(s):

I.C.W. Hardy

Keyword(s):

Sex Allocation ◽

Sex Ratios

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

Biology Letters ◽

10.1098/rsbl.2019.0929 ◽

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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Host size-dependent sex allocation behaviour in a parasitoid: implications forCatolaccus grandis(Hymenoptera: Pteromalidae) mass rearing programmes

Bulletin of Entomological Research ◽

10.1017/s0007485300041535 ◽

1998 ◽

Vol 88 (1) ◽

pp. 37-45 ◽

Cited By ~ 18

Author(s):

K.M. Heinz

Keyword(s):

Biological Control ◽

Sex Ratio ◽

Sex Allocation ◽

Sex Ratios ◽

Boll Weevil ◽

Mass Rearing ◽

Host Size ◽

Offspring Sex Ratio ◽

Offspring Sex ◽

Control Programmes

AbstractAn often encountered problem associated with augmentative and inundative biological control programmes is the high cost of producing sufficient numbers of natural enemies necessary to suppress pest populations within the time constraints imposed by ephemeral agroecosystems. In many arrhenotokous parasitoids, overproduction of males in mass-rearing cultures inflates costs (per female) and thus limits the economic feasibility of these biological control programmes. Within the context of existing production technologies, experiments were conducted to determine if the sex ratio ofCatolaccus grandis(Burks), an ectoparasitoid of the boll weevilAnthonomous grandisBoheman, varied as a function of boll weevil larval size. Results from natural and manipulative experiments demonstrate the following behavioural characteristics associated with C.grandissex allocation behaviour: (i) femaleC. grandisoffspring are produced on large size hosts and male offspring are produced on small hosts; (ii) whether a host is considered large or small depends upon the overall distribution of host sizes encountered by a female parasitoid; and (iii) female parasitoids exhibit a greater rate of increase in body size with host size than do male parasitoids. The observed patterns cannot be explained by sex-specific mortality of immature parasitoids developing on the different host size categories. In subsequent experiments, laboratory cultures ofC. grandisexposed daily to successively larger sizes ofA. grandislarvae produced successively greater female biased offspring sex ratios, cultures exposed daily to successively smaller sizes of host larvae produced successively greater male biased offspring sex ratios, and cultures exposed daily to equivalent host size distributions over time maintained a uniform offspring sex ratio. By increasing the average size ofA. grandislarval hosts exposed toC. grandisby 2.5 mg per day in mass rearing cultures, the percentage of male progeny can be reduced from 33% to 23% over a period of four consecutive exposure days.

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STABILIZING SELECTION AND VARIANCE IN FIG WASP SEX RATIOS

Evolution ◽

10.1111/j.1558-5646.1998.tb01647.x ◽

1998 ◽

Vol 52 (2) ◽

pp. 475-485 ◽

Cited By ~ 38

Author(s):

S. A. West ◽

E. A. Herre

Keyword(s):

Sex Ratios ◽

Stabilizing Selection ◽

Fig Wasp

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Sex allocation theory aids species conservation

Biology Letters ◽

10.1098/rsbl.2005.0430 ◽

2006 ◽

Vol 2 (2) ◽

pp. 229-231 ◽

Cited By ~ 60

Author(s):

Bruce C Robertson ◽

Graeme P Elliott ◽

Daryl K Eason ◽

Mick N Clout ◽

Neil J Gemmell

Keyword(s):

Sex Allocation ◽

Extinction Risk ◽

Sex Ratios ◽

Species Conservation ◽

Supplementary Feeding ◽

Intensive Management ◽

Maternal Condition ◽

Conservation Practice ◽

Individual Survival ◽

Sex Allocation Theory

Supplementary feeding is often a key tool in the intensive management of captive and threatened species. Although it can increase such parameters as breeding frequency and individual survival, supplementary feeding may produce undesirable side effects that increase overall extinction risk. Recent attempts to increase breeding frequency and success in the kakapo Strigops habroptilus using supplementary feeding inadvertently resulted in highly male-biased chick sex ratios. Here, we describe how the inclusion of sex allocation theory has remedied this conservation dilemma. Our study is the first to manipulate chick sex ratios in an endangered species by altering maternal condition and highlights the importance of incorporating evolutionary theory into modern conservation practice.

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Estimating the Frequency of Constrained Sex Allocation in Field Populations of Hymenoptera

Behaviour ◽

10.1163/156853990x00086 ◽

1990 ◽

Vol 114 (1-4) ◽

pp. 137-147 ◽

Cited By ~ 33

Author(s):

H.C.J. Godfray ◽

I.C.W. Hardy

Keyword(s):

Sex Ratio ◽

Sex Allocation ◽

Sex Ratios ◽

Parasitoid Species ◽

Ratio Bias ◽

Sex Ratio Bias ◽

Sex Ratio Theory

Abstract1) Sex ratio theory has assumed that females can produce offspring of both sexes. It has been suggested that some females in haplodiploid populations are only able to produce sons (constrained sex allocation), for example because they are virgin. The presence of such females influences the optimal sex ratio of unconstrained females. The relevance of these ideas to field sex ratios is largely untested. 2) The frequencies of constrained oviposition in three Drosophila parasitoid species are estimated. Constrained, ovipositing females were distinguished by the absence of sperm in the spermatheca. Constrained females were absent or rare in these species. 3) We review data from the literature that allow an estimate of the frequency of constrained females. 4) We conclude that the available evidence suggests that while constrained oviposition is uncommon, there are some species in which constrained females are sufficiently common to select for an observable sex ratio bias by unconstrained females.

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The maleness of larger angiosperm flowers

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1910631117 ◽

2020 ◽

Vol 117 (20) ◽

pp. 10921-10926 ◽

Cited By ~ 1

Author(s):

Gustavo Brant Paterno ◽

Carina Lima Silveira ◽

Johannes Kollmann ◽

Mark Westoby ◽

Carlos Roberto Fonseca

Keyword(s):

Sex Allocation ◽

Seed Set ◽

Limited Resource ◽

Male And Female ◽

Allocation Patterns ◽

Biomass Components ◽

Flower Evolution ◽

Primary Male ◽

Shed Light ◽

Allocation Strategies

Flower biomass varies widely across the angiosperms. Each plant species invests a given amount of biomass to construct its sex organs. A comparative understanding of how this limited resource is partitioned among primary (male and female structures) and secondary (petals and sepals) sexual organs on hermaphrodite species can shed light on general evolutionary processes behind flower evolution. Here, we use allometries relating different flower biomass components across species to test the existence of broad allocation patterns across the angiosperms. Based on a global dataset with flower biomass spanning five orders of magnitude, we show that heavier angiosperm flowers tend to be male-biased and invest strongly in petals to promote pollen export, while lighter flowers tend to be female-biased and invest more in sepals to insure their own seed set. This result demonstrates that larger flowers are not simple carbon copies of small ones, indicating that sexual selection via male–male competition is an important driver of flower biomass evolution and sex allocation strategies across angiosperms.

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