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Wells CP, Lyon BE, Thow CM, Stair T, Jones M, Hinton M, Eadie JM. Limited evidence of biased offspring sex allocation in a cavity-nesting conspecific brood parasite. Behav Ecol 2024; 35:arae024. [PMID: 39372888 PMCID: PMC11453106 DOI: 10.1093/beheco/arae024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2023] [Revised: 03/08/2024] [Accepted: 03/27/2024] [Indexed: 10/08/2024] Open
Abstract
Sex allocation theory predicts that mothers should bias investment in offspring toward the sex that yields higher fitness returns; one such bias may be a skewed offspring sex ratio. Sex allocation is well-studied in birds with cooperative breeding systems, with theory on local resource enhancement and production of helpers at the nest, but little theoretical or empirical work has focused on birds with brood parasitic breeding systems. Wood ducks (Aix sponsa) are a conspecific brood parasite, and rates of parasitism appear to increase with density. Because female wood ducks show high natal philopatry and nest sites are often limiting, local resource competition (LRC) theory predicts that females should overproduce male offspring-the dispersing sex-when competition (density) is high. However, the unique features of conspecific brood parasitism generate alternative predictions from other sex allocation theory, which we develop and test here. We experimentally manipulated nesting density of female wood ducks in 4 populations from 2013 to 2016, and analyzed the resulting sex allocation of >2000 ducklings. In contrast to predictions we did not find overproduction of male offspring by females in high-density populations, females in better condition, or parasitic females; modest support for LRC was found in overproduction of only female parasitic offspring with higher nest box availability. The lack of evidence for sex ratio biases, as expected for LRC and some aspects of brood parasitism, could reflect conflicting selection pressures from nest competition and brood parasitism, or that mechanisms of adaptive sex ratio bias are not possible.
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Affiliation(s)
- Caitlin P Wells
- Department of Fish, Wildlife, and Conservation Biology; Colorado State University, 901 Amy Van Dyken Way, Fort Collins, CO 80523, USA
- Department of Wildlife, Fish, and Conservation Biology; University of California, 1088 Academic Surge, Davis, CA 95616, USA
| | - Bruce E Lyon
- Department of Ecology and Evolution; University of California, UCSC/Coastal Biology Building 130 McAllister Way, Santa Cruz, CA 95060, USA
| | - Caroline M Thow
- Department of Ecology and Evolution; University of California, UCSC/Coastal Biology Building 130 McAllister Way, Santa Cruz, CA 95060, USA
| | - Tez Stair
- Department of Wildlife, Fish, and Conservation Biology; University of California, 1088 Academic Surge, Davis, CA 95616, USA
| | - Melissa Jones
- Department of Wildlife, Fish, and Conservation Biology; University of California, 1088 Academic Surge, Davis, CA 95616, USA
| | - Mitch Hinton
- Department of Wildlife, Fish, and Conservation Biology; University of California, 1088 Academic Surge, Davis, CA 95616, USA
| | - John M Eadie
- Department of Wildlife, Fish, and Conservation Biology; University of California, 1088 Academic Surge, Davis, CA 95616, USA
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2
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Weerawansha N, Wang Q, He XZ. A haplodiploid mite adjusts fecundity and sex ratio in response to density changes during the reproductive period. EXPERIMENTAL & APPLIED ACAROLOGY 2022; 88:277-288. [PMID: 36242724 PMCID: PMC9732065 DOI: 10.1007/s10493-022-00749-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Accepted: 10/04/2022] [Indexed: 06/16/2023]
Abstract
Population density is one of the main socio-environmental factors that have critical impacts on reproduction of animals. Consequently, they need to adjust their reproductive strategies in response to changes of local population density. In this study we used a haplodiploid spider mite, Tetranychus ludeni Zacher (Acari: Tetranychidae), to test how population density dynamics during the reproductive period altered female reproductive performance. We demonstrate that females produced fewer eggs with a significantly higher female-biased sex ratio in dense populations. Reducing fecundity and increasing daughter production in a dense environment could be an advantageous strategy to minimise the intensity of local food competition. However, females also reduced their fecundity after arrival in a new site of larger area from a dense population, which may be associated with higher web production costs because females need to produce more webs to cover the larger area. There was no trade-off between egg number and size, and egg size had little impact on reproductive fitness. Therefore, T. ludeni females could adapt to the shift of population density during their reproductive period by manipulating the fecundity and offspring sex ratio but not the egg size.
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Affiliation(s)
- Nuwan Weerawansha
- School of Agriculture and Environment, Massey University, Private Bag 11222, Palmerston North, New Zealand
- Faculty of Animal Science and Export Agriculture, Uva Wellassa University of Sri Lanka, Passara Road, Badulla, 90000, Sri Lanka
| | - Qiao Wang
- School of Agriculture and Environment, Massey University, Private Bag 11222, Palmerston North, New Zealand
| | - Xiong Zhao He
- School of Agriculture and Environment, Massey University, Private Bag 11222, Palmerston North, New Zealand.
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Driver R, Ferretti V, Burton ES, McCoy MW, Duerr KC, Curry RL. Spatiotemporal variation in hatching success and nestling sex ratios track rapid movement of a songbird hybrid zone. Am Nat 2022; 200:264-274. [DOI: 10.1086/720207] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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BARTLOW ANDREWW, JANKOWSKI MARKD, HATHCOCK CHARLESD, RYTI RANDALLT, RENEAU STEVENL, FAIR JEANNEM. Sex ratio of Western Bluebirds Sialia mexicana is mediated by phenology and clutch size. THE IBIS 2021; 163:977-989. [PMID: 35801167 PMCID: PMC9257600 DOI: 10.1111/ibi.12935] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Accepted: 01/25/2021] [Indexed: 06/15/2023]
Abstract
Mothers may produce more of one sex to maximize their fitness if there are differences in the cost of producing each sex or there are differences in their relative reproductive value. Breeding date and clutch size are known to influence offspring sex ratios in birds through sex differences in dispersal, social behaviours, differential mortality, and available food resources. We tested if breeding date, clutch size and drought conditions influenced offspring sex ratios in a sexually size-monomorphic species, the Western Bluebird, by interrogating a 21-year dataset. After controlling for differential mortality, we found that hatch dates late in the breeding season were associated with the production of more females, suggesting that the value of producing males declines as the breeding season progresses. When clutch size was taken into account, small clutches yielded significantly more females late in the breeding season compared to the early and middle parts of the breeding season that produced significantly more males. Large clutches early in the season tended to produce more females, although this was not significant. Drought severity was not correlated with sex ratio adjustment. We propose and discuss several explanations for these patterns, including male offspring, but not female offspring, acting as helpers, increased female nestling provisioning late in the breeding season, differences in food abundance, and egg-laying order. Future work will help to uncover the mechanisms leading to these patterns. Identifying patterns and mechanisms of sex ratio skew from long-term datasets is important for informing predictions regarding life-history trade-offs in wildlife populations.
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Affiliation(s)
- ANDREW W. BARTLOW
- Los Alamos National Laboratory, Biosecurity and Public Health, Mailstop M888, Los Alamos, NM 87545, USA
| | - MARK D. JANKOWSKI
- Laboratory Services and Applied Science Division, U.S. Environmental Protection Agency, 1200 6 Avenue, Suite 900, Seattle, WA 98101, USA
| | - CHARLES D. HATHCOCK
- Los Alamos National Laboratory, Environmental Stewardship, Los Alamos, NM 87545, USA
| | - RANDALL T. RYTI
- Neptune and Company, Inc., 1505 15th St #B, Los Alamos, NM 87544, USA
| | - STEVEN L. RENEAU
- Los Alamos National Laboratory, PO Box 1663, Los Alamos, NM 87545
| | - JEANNE M. FAIR
- Los Alamos National Laboratory, Biosecurity and Public Health, Mailstop M888, Los Alamos, NM 87545, USA
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Firman RC, Tedeschi JN, Garcia-Gonzalez F. Sperm sex ratio adjustment in a mammal: perceived male competition leads to elevated proportions of female-producing sperm. Biol Lett 2020; 16:20190929. [PMID: 32486939 DOI: 10.1098/rsbl.2019.0929] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
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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Affiliation(s)
- Renée C Firman
- Centre for Evolutionary Biology, School of Biological Sciences (M092), The University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009, Australia
| | - Jamie N Tedeschi
- Centre for Evolutionary Biology, School of Biological Sciences (M092), The University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009, Australia
| | - Francisco Garcia-Gonzalez
- Centre for Evolutionary Biology, School of Biological Sciences (M092), The University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009, Australia.,Estacion Biológica de Doñana, CSIC, Sevilla, Spain
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Firman RC. Exposure to high male density causes maternal stress and female-biased sex ratios in a mammal. Proc Biol Sci 2020; 287:20192909. [PMID: 32370673 PMCID: PMC7282911 DOI: 10.1098/rspb.2019.2909] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Accepted: 04/14/2020] [Indexed: 12/29/2022] Open
Abstract
A shift from the traditional perspective that maternal stress is invariably costly has instigated recent interest into its adaptive role in offspring sex allocation. Stress generated by social instability has been linked to offspring sex ratio biases that favour the production of female offspring, which converges with the theoretical prediction that mothers in the poor condition are better off investing in daughters rather than sons. However, previous research has failed to disentangle two different processes: the passive consequence of maternal stress on sex-specific mortality and the adaptive effect of maternal stress at the time of conception. Here, I show that exposure to high male density social conditions leads to elevated stress hormone levels and female-biased in utero offspring sex ratios in house mice (Mus musculus domesticus), and identify that sex-specific offspring production-not sex-specific mortality-is the mechanism accounting for these sex ratio skews. This outcome reflects the optimal fitness scenario for mothers in a male-dominated environment: the production of daughters, who are guaranteed high mate availability, minimizes male-male competition for their sons. Overall, this study supports the idea that maternal stress has the potential to be adaptive and advances our understanding of how exposure to different social conditions can influence sex allocation in mammals.
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Affiliation(s)
- Renée C. Firman
- Centre for Evolutionary Biology, School of Biological Sciences, University of Western Australia, 35 Stirling Hwy, Crawley, Western Australia 6009, Australia
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Zhang J, King AJ, Fürtbauer I, Wang YW, He YQ, Zhang ZW, Wan DM, Yin JX. Facilitative effects of social partners on Java sparrow activity. Anim Behav 2020. [DOI: 10.1016/j.anbehav.2019.12.017] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Lavoie MD, Tedeschi JN, Garcia‐Gonzalez F, Firman RC. Exposure to male-dominated environments during development influences sperm sex ratios at sexual maturity. Evol Lett 2019; 3:392-402. [PMID: 31388448 PMCID: PMC6675145 DOI: 10.1002/evl3.123] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Revised: 04/15/2019] [Accepted: 05/21/2019] [Indexed: 11/18/2022] Open
Abstract
Different stages during development are important when it comes to phenotypic adjustments in response to external stimuli. Critical stages in mammals are the prenatal phase, where embryos are exposed to a milieu of sex steroid hormones, and the early-postnatal phase, where littermates interact and experience their incipient social environment. Further, the postmaternal environment will influence the development of traits that are linked to reproductive success in adulthood. Accumulated evidence of male-driven sex allocation establishes the currently untested hypothesis that the sperm sex ratio is a plastic trait that can be mediated to align with prevailing social conditions. Here, we used natural variation in the maternal environment and experimentally manipulated the postmaternal environment to identify the importance of these developmental phases on sperm sex ratio adjustments in wild house mice (Mus musculus domesticus). We found that male density in both environments was predictive of sperm sex ratios at sexual maturity: males from more male-biased litters and males maturing under high male density produced elevated levels of Y-chromosome-bearing sperm. Our findings indicate that the sperm sex ratio is a variable phenotypic trait that responds to the external environment, and highlight the potential that these adjustments function as a mechanism of male-driven sex allocation.
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Affiliation(s)
- Misha D. Lavoie
- School of Biological Sciences (M092), Centre for Evolutionary BiologyThe University of Western AustraliaCrawleyWA6009Australia
| | - Jamie N. Tedeschi
- School of Biological Sciences (M092), Centre for Evolutionary BiologyThe University of Western AustraliaCrawleyWA6009Australia
| | - Francisco Garcia‐Gonzalez
- School of Biological Sciences (M092), Centre for Evolutionary BiologyThe University of Western AustraliaCrawleyWA6009Australia
- Estacion Biológica de DoñanaCSICSevillaSpain
| | - Renée C. Firman
- School of Biological Sciences (M092), Centre for Evolutionary BiologyThe University of Western AustraliaCrawleyWA6009Australia
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