scholarly journals Reproducing lizards modify sex allocation in response to operational sex ratios

2006 ◽  
Vol 3 (1) ◽  
pp. 47-50 ◽  
Author(s):  
Daniel A Warner ◽  
Richard Shine
Keyword(s):  
Sex Allocation ◽  
Sex Ratios ◽  
Operational Sex Ratio ◽  
Sexual Competition ◽  
Amphibolurus Muricatus ◽  
Offspring Sex ◽  
Sex Allocation Theory ◽  
Experimental Trials ◽  
Direction Opposite ◽  
Operational Sex Ratios

Sex-allocation theory suggests that selection may favour maternal skewing of offspring sex ratios if the fitness return from producing a son differs from that for producing a daughter. The operational sex ratio (OSR) may provide information about this potential fitness differential. Previous studies have reached conflicting conclusions about whether or not OSR influences sex allocation in viviparous lizards. Our experimental trials with oviparous lizards ( Amphibolurus muricatus ) showed that OSR influenced offspring sex ratios, but in a direction opposite to that predicted by theory: females kept in male-biased enclosures overproduced sons rather than daughters (i.e. overproduced the more abundant sex). This response may enhance fitness if local OSRs predict survival probabilities of offspring of each sex, rather than the intensity of sexual competition.

scholarly journals Male-biased sex allocation in ageing parents; a longitudinal study in a long-lived seabird

2016 ◽  
Vol 12 (8) ◽  
pp. 20160260 ◽  
Author(s):  
Oscar Vedder ◽  
Sandra Bouwhuis ◽  
María M. Benito ◽  
Peter H. Becker
Keyword(s):  
Sex Allocation ◽  
Sex Ratios ◽  
Individual Change ◽  
Parental Age ◽  
Frequency Dependent ◽  
Specific Strength ◽  
Offspring Sex ◽  
Sex Allocation Theory ◽  
Per Se ◽  
Ageing Parents

Optimal sex allocation is frequency-dependent, but senescence may cause behaviour at old age to be suboptimal. We investigated whether sex allocation changes with parental age, using 16 years of data comprising more than 2500 molecularly sexed offspring of more than 600 known-age parents in common terns ( Sterna hirundo ), slightly sexually size-dimorphic seabirds. We decomposed parental age effects into within-individual change and sex allocation-associated selective (dis)appearance. Individual parents did not differ consistently in sex allocation, but offspring sex ratios at fledging changed from female- to male-biased as parents aged. Sex ratios at hatching were not related to parental age, suggesting sons to outperform daughters after hatching in broods of old parents. Our results call for the integration of sex allocation theory with theory on ageing and demography, as a change in sex allocation with age per se will cause the age structure of a population to affect the frequency-dependent benefits and the age-specific strength of selection on sex allocation.

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.

scholarly journals Sex allocation theory reveals a hidden cost of neonicotinoid exposure in a parasitoid wasp

2015 ◽  
Vol 282 (1807) ◽  
pp. 20150389 ◽  
Author(s):  
Penelope R. Whitehorn ◽  
Nicola Cook ◽  
Charlotte V. Blackburn ◽  
Sophie M. Gill ◽  
Jade Green ◽  
...  
Keyword(s):  
Sex Allocation ◽  
Evolutionary Ecology ◽  
Parasitoid Wasp ◽  
Reproductive Behaviour ◽  
Fitness Costs ◽  
Offspring Sex ◽  
Hidden Cost ◽  
Sex Allocation Theory ◽  
First Time ◽  
Fecundity Reduction

Sex allocation theory has proved to be one the most successful theories in evolutionary ecology. However, its role in more applied aspects of ecology has been limited. Here we show how sex allocation theory helps uncover an otherwise hidden cost of neonicotinoid exposure in the parasitoid wasp Nasonia vitripennis . Female N. vitripennis allocate the sex of their offspring in line with Local Mate Competition (LMC) theory. Neonicotinoids are an economically important class of insecticides, but their deployment remains controversial, with evidence linking them to the decline of beneficial species. We demonstrate for the first time to our knowledge, that neonicotinoids disrupt the crucial reproductive behaviour of facultative sex allocation at sub-lethal, field-relevant doses in N. vitripennis . The quantitative predictions we can make from LMC theory show that females exposed to neonicotinoids are less able to allocate sex optimally and that this failure imposes a significant fitness cost. Our work highlights that understanding the ecological consequences of neonicotinoid deployment requires not just measures of mortality or even fecundity reduction among non-target species, but also measures that capture broader fitness costs, in this case offspring sex allocation. Our work also highlights new avenues for exploring how females obtain information when allocating sex under LMC.

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

1998 ◽  
Vol 88 (1) ◽  
pp. 37-45 ◽  
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.

scholarly journals Sex allocation theory aids species conservation

2006 ◽  
Vol 2 (2) ◽  
pp. 229-231 ◽  
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.

Sex ratio variation in the yuma bat (Myotis yumanensis)

1993 ◽  
Vol 71 (5) ◽  
pp. 937-940 ◽  
Author(s):  
Barry N. Milligan ◽  
R. Mark Brigham
Keyword(s):  
British Columbia ◽  
Sex Ratio ◽  
Maternal Age ◽  
Sex Allocation ◽  
Sex Ratios ◽  
Ratio Variation ◽  
Sex Allocation Theory

Sex allocation theory predicts that monomorphic species should produce natal sex ratios near unity. We measured natal sex ratios in a maternity colony of approximately 1600 yuma bats (Myotis yumanensis) near Squilax, British Columbia, during June and July 1991. Overall, the natal sex ratio did not differ from unity but the sex ratio did vary significantly throughout the summer. Variation appears to be related to an interaction between maternal age and date of birth. This evidence suggests that facultative manipulation of the sex of the offspring by individual females may occur within the population.

Female mountain bluebirds (Sialia currucoides) paired to more colourful males produce male-biased broods

Behaviour ◽  
2016 ◽  
Vol 153 (3) ◽  
pp. 367-386 ◽  
Author(s):  
Erica S. Bonderud ◽  
Nancy J. Flood ◽  
Jonathan D. Van Hamme ◽  
Cameron A. W. Boyda ◽  
Matthew W. Reudink
Keyword(s):  
Sex Allocation ◽  
Reproductive Value ◽  
First Year ◽  
Reproductive Decisions ◽  
Offspring Sex ◽  
Sialia Currucoides ◽  
Sex Allocation Theory ◽  
Mountain Bluebirds ◽  
Breeding Seasons ◽  
Signalling Systems

Sex allocation theory predicts that females should bias the sex ratio of their offspring in response to differences in the reproductive value of sons versus daughters. Consistent with this prediction, females of many species appear to bias offspring sex ratios in response to mate attractiveness and condition. Male mountain bluebirds (Sialia currucoides) display full body UV-blue structural plumage colouration, which is associated with attractiveness, condition, and reproductive success. Over four breeding seasons, we found females paired with more colourful males produced increasingly male-biased broods and provisioned offspring at a higher rate. Surprisingly, however, we also found females with duller plumage and those mated to first-year males produced more male-biased broods. These results provide support for sex allocation in mountain bluebirds and suggest female reproductive decisions may be influenced by the attractiveness of her mate. However, this system is clearly complex and more work is needed to understand the roles of male age and female colouration in the signalling systems of mountain bluebirds.

The effect of operational sex ratio on sex allocation and neonate phenotype in a viviparous lizard Eremias multiocellata

2012 ◽  
Vol 33 (3-4) ◽  
pp. 485-493 ◽  
Author(s):  
Xiao-Long Tang ◽  
Feng Yue ◽  
De-Jiu Zhang ◽  
Xue-Feng Yan ◽  
Ying Xin ◽  
...  
Keyword(s):  
Sex Ratio ◽  
Sex Allocation ◽  
Animal Species ◽  
Field Experiments ◽  
Maternal Investment ◽  
Tail Length ◽  
Operational Sex Ratio ◽  
Sex Allocation Theory ◽  
Female Investment ◽  
Eremias Multiocellata

Maternal investment in the production of male versus female neonates was approximately equal in most animal species. However, sex allocation theory predicts that under certain conditions, selection may favor the females’ ability to adjust the sex ratio of their offspring, which females tend to use more for an investment of the rare sex. The mechanism of operational sex ratio (OSR) influence on sex allocation is still unclear, and recent studies conducted on lizards have reached conflicting conclusions. Here, we selected a viviparous lizard Eremias multiocellata to test whether pregnant females could adjust the sex ratio of their offspring in response to OSRs. Our results showed that mothers did not adjust the sex ratios or phenotypes of neonates in the laboratory and field-based experiments, except tail length. However, the OSRs subsequently affected growth in both mass and SVL of the offspring in laboratory experiments; whereas only the mass was affected in the semi-nature field experiments. Our results, thus, contradict the predictions of sex allocation theory and challenge the idea that female investment in the scarcity sex might serve as a mechanism which is used for adjusting the population sex ratio.

scholarly journals Solving the sex ratio scandal in Melittobia wasps

2020 ◽  
Author(s):  
Jun Abe ◽  
Ryosuke Iritani ◽  
Koji Tsuchida ◽  
Yoshitaka Kamimura ◽  
Stuart A. West
Keyword(s):  
Sex Ratio ◽  
Sex Allocation ◽  
Laboratory Experiments ◽  
Sex Ratios ◽  
Local Mate Competition ◽  
Mate Competition ◽  
Offspring Sex ◽  
Local Mate ◽  
Close Relatives

AbstractThe scandalous sex ratio behaviour of Melittobia wasps has long posed one of the greatest problems for the field of sex allocation. In contrast to the predictions of theory, and the behaviour of numerous other organisms, laboratory experiments have found that Melittobia females do not produce less female-biased offspring sex ratios when more females lay eggs on a patch. We resolve this scandal, by showing that, in nature, females of M. australica have sophisticated sex ratio behaviour, where their strategy also depends upon whether they have dispersed from the patch where they emerged. When females have not dispersed, they will be laying eggs with close relatives, which keeps local mate competition high, even with multiple females, and so they are selected to produce consistently female-biased sex ratios. Laboratory experiments mimic these conditions. In contrast, when females disperse, they will be interacting with non-relatives, and so they adjust their sex ratio depending upon the number of females laying eggs. Consequently, females appear to use dispersal status as an indirect cue of relatedness, and whether they should adjust their sex ratio in response to the number of females laying eggs on the patch.

Effects of parental condition and nesting habitat on sex allocation in the mountain chickadee

Behaviour ◽  
2017 ◽  
Vol 154 (11) ◽  
pp. 1101-1121 ◽  
Author(s):  
Erica S. Bonderud ◽  
Ken A. Otter ◽  
Brent W. Murray ◽  
Kristen L.D. Marini ◽  
Theresa M. Burg ◽  
...  
Keyword(s):  
Habitat Quality ◽  
Sex Allocation ◽  
Breeding Habitat ◽  
Reproductive Value ◽  
Urban Habitat ◽  
Habitat Gradient ◽  
Offspring Sex ◽  
Sex Allocation Theory ◽  
Mountain Chickadee ◽  
Mountain Chickadees

When the reproductive value of sons vs. daughters differs, sex allocation theory predicts females should bias the sex ratio of their broods towards the higher-value sex. Females in numerous bird species appear to bias offspring sex in response to self and mate condition, and breeding habitat quality. Over three breeding seasons, we monitored mountain chickadees breeding along a rural to urban habitat gradient. We did not find female condition or the condition of the putative father or true genetic father to influence offspring sex. We found marginal evidence for sex allocation in relation to habitat urbanization, though opposite to our predictions. In urban habitat, offspring were more likely to be female as the degree of habitat urbanization increased. We suggest habitat quality may be influential in mountain chickadee reproductive decisions; however, the ecology of mountain chickadees may not fulfill the assumptions of sex allocation theory.

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