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.

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.

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.

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 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 Can an introduced predator select for adaptive sex allocation?

2021 ◽  
Vol 288 (1949) ◽  
Author(s):  
R. Heinsohn ◽  
J. Au ◽  
H. Kokko ◽  
M. H. Webb ◽  
R. M. Deans ◽  
...  
Keyword(s):  
Birth Order ◽  
Sex Allocation ◽  
Sex Ratios ◽  
Reproductive Value ◽  
Mate Competition ◽  
Female Mortality ◽  
Introduced Predators ◽  
Offspring Sex ◽  
Term Data

Most species produce equal numbers of sons and daughters, and sex differences in survival after parental care do not usually affect this pattern. Temporary overproduction of the scarcer sex can be adaptive when generations overlap, the sexes differ in life-history expectations, and parents can anticipate future mating opportunities. However, an alternative strategy of maximizing the competitiveness of the more abundant sex in these circumstances remains unexplored. We develop theory showing how mothers can maximize reproductive value when future mate competition will be high by producing more sons in the advantageous early hatching positions within their broods. Our model for optimal birth order was supported by long-term data of offspring sex in a parrot facing catastrophic female mortality caused by introduced predators. Swift parrots ( Lathamus discolor ) suffer high female mortality due to introduced sugar gliders ( Petaurus breviceps ) creating fluctuating male-biased adult sex ratios. Offspring hatched early within broods fledged in better condition, and in support of our model were more likely to be male in years with higher adult female mortality. We found a highly significant rank-order correlation between observed and predicted birth sex ratios. Our study shows the potential for mothers to maximize reproductive value via strategic biases in offspring sex depending on the advantages conferred by birth order and the predictability of future mate competition. Our long-term data support the predictions and appear to suggest that sex allocation strategies may evolve surprisingly quickly when anthropogenic pressures on populations are severe.

scholarly journals Extra-pair young in house wren broods are more likely to be male than female

2009 ◽  
Vol 276 (1665) ◽  
pp. 2285-2289 ◽  
Author(s):  
L. Scott Johnson ◽  
Charles F. Thompson ◽  
Scott K. Sakaluk ◽  
Markus Neuhäuser ◽  
Bonnie G.P. Johnson ◽  
...  
Keyword(s):  
Sex Ratio ◽  
Sex Allocation ◽  
House Wren ◽  
Cavity Nesting ◽  
Socially Monogamous ◽  
Pair Mating ◽  
Sex Allocation Theory ◽  
Breeding Seasons ◽  
Extra Pair Mating ◽  
The Relationship

Sex-allocation theory predicts that females should preferentially produce offspring of the sex with greater fitness potential. In socially monogamous animal species, extra-pair mating often increases the variance in fitness of sons relative to daughters. Thus, in situations where offspring sired by a female's extra-pair mate(s) will typically have greater fitness potential than offspring sired by the within-pair mate, sex-allocation theory predicts that females will bias the sex of offspring sired by extra-pair mates towards male. We examined the relationship between offspring sex and paternity over six breeding seasons in an Illinois population of the house wren ( Troglodytes aedon ), a cavity-nesting songbird. Out of the 2345 nestlings that had both sex and paternity assigned, 350 (15%) were sired by extra-pair males. The sex ratio of extra-pair offspring, 0.534, was significantly greater than the sex ratio of within-pair offspring, 0.492, representing an increase of 8.5 per cent in the proportion of sons produced. To our knowledge, this is the first confirmed report of female birds increasing their production of sons in association with extra-pair fertilization. Our results are consistent with the oft-mentioned hypothesis that females engage in extra-pair mating to increase offspring quality.

Age, stucture, growth rates and movements of sea mullet, Mugil cephalus L., and Yellow-eye Mullet, Aldrichetta forsteri (Valenciennes), in the Swan-Avon river system, Western Australia

1981 ◽  
Vol 32 (4) ◽  
pp. 605 ◽  
Author(s):  
CF Chubb ◽  
IC Potter ◽  
CJ Grant ◽  
RCJ Lenanton ◽  
J Wallace
Keyword(s):  
Growth Rates ◽  
River System ◽  
First Year ◽  
Length Frequency ◽  
Frequency Distributions ◽  
Using Data ◽  
The Times ◽  
First Year Of Life ◽  
Breeding Seasons ◽  
System 1

The age structure, growth rates and movements of M. cephalus and A forsteri in the Swan-Avon river system have been investigated using data obtained from beach seining and gill netting carried out between February 1977 and June 1980. Length-frequency data and scale readings show that the populations of both species consist predominantly of 0+ and 1 + fish. From the times when the smallest fry (20-30 mm) were present in the lower part of the river system, and from the condition of the gonads of older fish, the breeding seasons of the sea and yellow-eye mullets have been estimated as extending from March to September and from March to August respectively. The bimodality or polymodality exhibited by the length-frequency distributions for the 0 + year classes suggest that in both species groups of individuals spawn at slightly different times. The range of mean total lengths and weights of animals caught in May near the end of the first year of life was 178-222 mm and 64-119 gin M. cephalus and 136-154 mm and 19-30 g in A. forsteri, which shows that the growth of each of these two species of mullet is relatively very rapid in the Swan-Avon river system. 1 + and 2 + fish tend to leave the estuary for varying periods. Although 0+ fish of both species utilized the shallow banks of the estuary throughout the year. the sea mullet moved further upstream and were not as consistently abundant in the lower estuary. Since 0+ yellow-eye mullet 40-100 mm long were also abundant in marine coastal waters between January and May. and sea mullet of comparable age were rarely observed in these regions, it would appear that M. cephalus is the more estuarine-dependent of the two species. Commercial catches of M. cephalus were greater than those of A. forsteri. This feature can be related in part to the much faster growth rate of M. cephalus, which results in a larger proportion of its youngest year classes reaching the minimum legal size for capture prior to the time when they leave the estuary in large numbers.

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.

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