scholarly journals Linked supergenes underlie split sex ratio and social organization in an ant

2021 ◽  
Author(s):  
German Lagunas-Robles ◽  
Jessica Purcell ◽  
Alan Brelsford
Keyword(s):  
Sex Ratio ◽  
Sex Allocation ◽  
Empirical Studies ◽  
Population Level ◽  
Theoretical Work ◽  
Female Offspring ◽  
Genomic Region ◽  
Genomic Conflict ◽  
Theoretical Predictions ◽  
Formica Podzolica

AbstractSexually reproducing organisms usually invest equally in male and female offspring. Deviations from this pattern have led researchers to new discoveries in the study of parent-offspring conflict, genomic conflict, and cooperation. Some social insect species exhibit the unusual population-level pattern of split sex ratio, wherein some colonies specialize in the production of future queens and others specialize in the production of males. Theoretical work focused on the relatedness asymmetries emerging from haplodiploid inheritance, whereby queens are equally related to daughters and sons, but their daughter workers are more closely related to sisters than to brothers, led to a series of testable predictions and spawned many empirical studies of this phenomenon. However, not all empirical systems follow predicted patterns, so questions remain about how split sex ratio emerges. Here, we sequence the genomes of 138 Formica glacialis workers from 34 male-producing and 34 gyne-producing colonies to determine whether split sex ratio is under genetic control. We identify a supergene spanning 5.5 Mbp that is closely associated with sex allocation in this system. Strikingly, this supergene is adjacent to another supergene spanning 5 Mbp that is associated with variation in colony queen number. We identify a similar pattern in a second related species, Formica podzolica. The discovery that split sex ratio is determined, at least in part, by a supergene in two species opens a new line of research on the evolutionary drivers of split sex ratio.Significance StatementSome social insects exhibit split sex ratio, wherein some colonies produce future queens and others produce males. This phenomenon spawned many influential theoretical studies and empirical tests, both of which have advanced our understanding of parent-offspring conflicts and cooperation. However, some empirical systems did not follow theoretical predictions, indicating that researchers lack a comprehensive understanding of the drivers of split sex ratio. Here, we show that split sex ratio is associated with a large genomic region in two ant species. The discovery of a genetic basis for sex allocation in ants provides a novel explanation for this phenomenon, particularly in systems where empirical observations deviate from theoretical predictions.

scholarly journals Linked supergenes underlie split sex ratio and social organization in an ant

2021 ◽  
Vol 118 (46) ◽  
pp. e2101427118
Author(s):  
German Lagunas-Robles ◽  
Jessica Purcell ◽  
Alan Brelsford
Keyword(s):  
Sex Ratio ◽  
Population Level ◽  
Theoretical Work ◽  
Female Offspring ◽  
Future Research ◽  
Genomic Conflict ◽  
Theoretical Predictions ◽  
Empirical Tests ◽  
Formica Podzolica ◽  
Relatedness Asymmetry

Sexually reproducing organisms usually invest equally in male and female offspring. Deviations from this pattern have led researchers to new discoveries in the study of parent–offspring conflict, genomic conflict, and cooperative breeding. Some social insect species exhibit the unusual population-level pattern of split sex ratio, wherein some colonies specialize in the production of future queens and others specialize in the production of males. Theoretical work predicted that worker control of sex ratio and variation in relatedness asymmetry among colonies would cause each colony to specialize in the production of one sex. While some empirical tests supported theoretical predictions, others deviated from them, leaving many questions about how split sex ratio emerges. One factor yet to be investigated is whether colony sex ratio may be influenced by the genotypes of queens or workers. Here, we sequence the genomes of 138 Formica glacialis workers from 34 male-producing and 34 gyne-producing colonies to determine whether split sex ratio is under genetic control. We identify a supergene spanning 5.5 Mbp that is closely associated with sex allocation in this system. Strikingly, this supergene is adjacent to another supergene spanning 5 Mbp that is associated with variation in colony queen number. We identify a similar pattern in a second related species, Formica podzolica. The discovery that split sex ratio is determined, at least in part, by a supergene in two species opens future research on the evolutionary drivers of split sex ratio.

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 Effects of host and foundress density on reproductive strategy of Diaeretiella rapae

2012 ◽  
Vol 65 ◽  
pp. 294-294 ◽  
Author(s):  
R. Kant ◽  
M.A. Minor ◽  
S.A. Trewick ◽  
W.R.M. Sandanayaka
Keyword(s):  
Sex Ratio ◽  
Reproductive Strategy ◽  
Sex Allocation ◽  
Parasitic Wasp ◽  
Female Offspring ◽  
Reproductive Fitness ◽  
Brevicoryne Brassicae ◽  
Diaeretiella Rapae ◽  
Progeny Production ◽  
Total Parasitism

The reproductive fitness of a parasitoid depends on the oviposition decisions of a female in response to competition The present study investigated the oviposition and sex ratio of offspring produced by the parasitic wasp Diaeretiella rapae while competing with other conspecific females and at different host densities The number of Brevicoryne brassicae nymphs parasitised by female D rapae increased with the number of nymphs offered to them However the proportion of nymphs parasitised by the female decreased when nymph density was high The proportion of fertilised eggs oviposited by females decreased when nymph density increased An increase in the number of foundresses (females ovpositing together) increased the total parasitism but the contribution of each female (the number of nymphs each female parasitised) decreased Smaller proportions of female offspring were produced when females were competing for the same hosts The results of this study suggest that both host and foundress densities asymmetrically affect progeny production and sex allocation in this species

scholarly journals Maternal effects obscure condition-dependent sex allocation in changing environments

2019 ◽  
Vol 6 (4) ◽  
pp. 181885 ◽  
Author(s):  
A. M. Edwards ◽  
E. Z. Cameron ◽  
E. Wapstra ◽  
J. McEvoy
Keyword(s):  
Climate Change ◽  
Sex Ratio ◽  
Environmental Change ◽  
Maternal Effects ◽  
Sex Allocation ◽  
Good Condition ◽  
Physiological Changes ◽  
Temperature Dependent ◽  
Changing Environments ◽  
Theoretical Predictions

Climate change increases environmental fluctuations which thereby impact population demography. Species with temperature-dependent sex determination may experience more extreme sex ratio skews, but this has not been considered in species with chromosomally determined sex. However, anticipatory maternal effects cause lifelong physiological changes impacting sex ratios. Here we show, in mice, that more sons were born to mothers in good condition when their breeding environment matched their gestational environment, consistent with theoretical predictions, but mothers in mismatched environments have no condition–sex ratio relationship. Thus, the predicted effect of condition on sex ratio was obscured by maternal effects when the environment changed. This may explain extreme sex ratio skews in reintroduced or translocated populations, and sex ratio skews may become more common and less predictable with accelerating environmental change.

scholarly journals Caste development and sex ratio of the Ryukyu drywood termite Neotermes sugioi and its potential mechanisms

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Y. Miyaguni ◽  
A. Agarie ◽  
K. Sugio ◽  
K. Tsuji ◽  
K. Kobayashi
Keyword(s):  
Sex Ratio ◽  
Evolutionary Biology ◽  
Sex Allocation ◽  
Reproductive Value ◽  
Total Biomass ◽  
Theoretical Predictions ◽  
Total Investment ◽  
Biased Sex Ratio ◽  
Caste Development ◽  
Female Bias

AbstractSex allocation is one of the most studied traits in evolutionary biology because its theoretical predictions match the empirical data. Here, using the Ryukyu dry-wood termite Neotermes sugioi, we investigated several factors that could bias the sex allocation in three populations (Okinawa, Ishigaki/Iriomote, and Yonaguni). Our survey showed that there were more queen-only colonies than king-only colonies in these populations, suggesting a longer lifespan of the queens than that of the kings. In this condition, sex-asymmetric reproductive value (SRV) theory predicts female bias, because even after the short-lived kings die, the long-lived queens can continue reproduction with their sons. However, sex allocation in this species seemed to be biased toward males. Furthermore, we examined the possibility of intrasexual competition among siblings (ICS). If ICS is the cause of the bias, the allocation is expected to change depending on the total investment in sexual offspring. However, the biomass of both male and female alates increased linearly with the increase in the total biomass of the alates in these populations. Thus, neither the SRV nor the ICS theory could explain the male-biased sex ratio of N. sugioi. On the basis of these results, we discuss the remaining possibilities in this species.

scholarly journals Inferring individual-level processes from population-level patterns in cultural evolution

2017 ◽  
Vol 4 (9) ◽  
pp. 170949 ◽  
Author(s):  
Anne Kandler ◽  
Bryan Wilder ◽  
Laura Fortunato
Keyword(s):  
Cultural Change ◽  
Cultural Evolution ◽  
Empirical Studies ◽  
Population Level ◽  
Theoretical Work ◽  
Cultural Variation ◽  
Group Level ◽  
Individual Level ◽  
The One ◽  
Over Time

Our species is characterized by a great degree of cultural variation, both within and between populations. Understanding how group-level patterns of culture emerge from individual-level behaviour is a long-standing question in the biological and social sciences. We develop a simulation model capturing demographic and cultural dynamics relevant to human cultural evolution, focusing on the interface between population-level patterns and individual-level processes. The model tracks the distribution of variants of cultural traits across individuals in a population over time, conditioned on different pathways for the transmission of information between individuals. From these data, we obtain theoretical expectations for a range of statistics commonly used to capture population-level characteristics (e.g. the degree of cultural diversity). Consistent with previous theoretical work, our results show that the patterns observed at the level of groups are rooted in the interplay between the transmission pathways and the age structure of the population. We also explore whether, and under what conditions, the different pathways can be distinguished based on their group-level signatures, in an effort to establish theoretical limits to inference. Our results show that the temporal dynamic of cultural change over time retains a stronger signature than the cultural composition of the population at a specific point in time. Overall, the results suggest a shift in focus from identifying the one individual-level process that likely produced the observed data to excluding those that likely did not. We conclude by discussing the implications for empirical studies of human cultural evolution.

scholarly journals Sex allocation and field population sex ratio of Apanteles taragamae Viereck (Hymenoptera: Braconidae), a larval parasitoid of the cucumber moth Diaphania indica Saunders (Lepidoptera: Crambidae)

2021 ◽  
Vol 6 (1) ◽  
pp. 673-681
Author(s):  
Ihsan Nurkomar ◽  
Azru Azhar ◽  
Damayanti Buchori
Keyword(s):  
Sex Ratio ◽  
Brood Size ◽  
Sex Allocation ◽  
Natural Habitat ◽  
Adult Emergence ◽  
Female Offspring ◽  
Individual Level ◽  
Apanteles Taragamae ◽  
Larval Parasitoid ◽  
Biased Sex Ratio

Abstract Sex ratio is one of the most important biological characteristics of arthropods. In a parasitoid population, sex ratio can influence the suppression of host populations or the stability of host–parasitoid interactions in the field. In this study, a survey was carried out to determine the sex allocation through the sequence of male/female adult emergence and calculate the sex ratio of selected populations of Apanteles taragamae in their natural habitat. Assessment of sex ratio at the population and individual level (brood size per female) was examined. We found no difference in the likelihood that either sex would emerge before the other. Observations of sex ratio at the population and individual level reveal a females biased sex ratio. Analysis of the relationship between brood size and sex ratio of A. taragamae shows that brood size may influence the proportion of male to female offspring yielded. A male-biased sex ratio tends to be found in smaller brood size. However, sex ratio is shifted to female biased in larger brood size.

scholarly journals Are human natal sex ratio differences across the world adaptive? A test of Fisher's principle

2021 ◽  
Vol 17 (3) ◽  
Author(s):  
Mathieu Douhard ◽  
Stéphane Dray
Keyword(s):  
Sex Differences ◽  
Sex Ratio ◽  
Spatial Autocorrelation ◽  
Sex Allocation ◽  
Natural Variation ◽  
Population Level ◽  
Childhood Mortality ◽  
High Resource ◽  
Sex Allocation Theory ◽  
Fisher’S Principle

Fisher's principle states that natural selection favours an equal number of male and female births at the population level, unless there are sex differences in rearing costs or sex differences in mortality before the end of the period of parental investment. Sex differences in rearing costs should be more pronounced in low- than in high-resource settings. We, therefore, examined whether human development index and sex differences in child mortality contribute to the natural variation in human sex ratio at birth across the globe. As predicted by Fisher's principle, the proportion of male births increased with both increasing male-biased childhood mortality and level of development of each country. However, these relationships were absent after accounting for spatial autocorrelation in the residuals, which our inference is conditioned on. This work shows how the failure to account for residual spatial autocorrelation can lead to incorrect conclusions regarding support for predictions from sex allocation theory.

scholarly journals Inferring individual-level processes from population-level patterns in cultural evolution

2017 ◽  
Author(s):  
Anne Kandler ◽  
Bryan Wilder ◽  
Laura Fortunato
Keyword(s):  
Cultural Change ◽  
Cultural Evolution ◽  
Empirical Studies ◽  
Population Level ◽  
Theoretical Work ◽  
Cultural Variation ◽  
Group Level ◽  
Individual Level ◽  
The One ◽  
Over Time

AbstractOur species is characterized by a great degree of cultural variation, both within and between populations. Understanding how group-level patterns of culture emerge from individual-level behaviour is a long-standing question in the biological and social sciences. We develop a simulation model capturing demographic and cultural dynamics relevant to human cultural evolution, focusing on the interface between population-level patterns and individual-level processes. The model tracks the distribution of variants of cultural traits across individuals in a population over time, conditioned on different pathways for the transmission of information between individuals. From these data we obtain theoretical expectations for a range of statistics commonly used to capture population-level characteristics (e.g. the degree of cultural diversity). Consistent with previous theoretical work, our results show that the patterns observed at the level of groups are rooted in the interplay between the transmission pathways and the age structure of the population. We also explore whether, and under what conditions, the different pathways can be distinguished based on their group-level signatures, in an effort to establish theoretical limits to inference. Our results show that the temporal dynamic of cultural change over time retains a stronger signature than the cultural composition of the population at a specific point in time. Overall, the results suggest a shift in focus from identifying the one individual-level process that likely produced the observed data to excluding those that likely did not. We conclude by discussing the implications for empirical studies of human cultural evolution.

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