Ratio Bias Research Articles

Do errors on classic decision biases happen fast or slow? Numeracy and decision time predict probability matching, sample size neglect, and ratio bias

Higher numeracy is associated with better comprehension and use of numeric information as well as reduced susceptibility to some decision biases. We extended this line of work by showing that increased numeracy predicted probability maximizing (versus matching) as well as a better appreciation of large sample sizes. At the same time, we replicated the findings that the more numerate were less susceptible to the ratio bias and base rate neglect phenomena. Decision time predicted accuracy for the ratio bias, probability matching, and sample size scenarios, but not the base rate scenarios. Interestingly, this relationship between decision time and accuracy was positive for the ratio bias problems, but negative for the probability matching and sample size scenarios. Implications for research on cognitive ability and decision biases are discussed.

Triple-oxygen isotopes of stony micrometeorites by secondary ion mass spectrometry (SIMS): Olivine, basaltic glass and iron oxide matrix effects for sensitive high-mass resolution ion microprobe-stable isotope (SHRIMP-SI).

Micrometeorites are extraterrestrial particles smaller than ~2mm in diameter, most of which melted during atmospheric entry and crystallised or quenched to form 'cosmic spherules'. Their parentage among meteorite groups can be inferred from triple-oxygen isotope compositions, for example, by secondary ion mass spectrometry (SIMS). This method uses sample efficiently, preserving spherules for other investigations. While SIMS precisions are improving steadily, application requires assumptions about instrumental mass fractionation, which is controlled by sample chemistry and mineralogy (matrix effects). We have developed a generic SIMS method using sensitive high-mass resolution ion micro probe-stable isotope (SHRIMP-SI) that can be applied to finely crystalline igneous textures as in cosmic spherules. We correct for oxygen isotope matrix effects using the bulk chemistry of samples obtained by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and model bulk chemical compositions as three-component mixtures of olivine, basaltic glass and Fe-oxide (magnetite), finding a unique matrix correction for each target. Our first results for cosmic spherules from East Antarctica compare favourably with established micrometeorite groups defined by precise and accurate but consumptive bulk oxygen isotope methods. The Fe-oxide content of each spherule is the main control on magnitude of oxygen isotope ratio bias, with effects on δ18O up to ~6‰. Our main peak in compositions closely coincides with so-called 'Group 1' objects identified by consumptive methods. The magnitude of SIMS matrix effects we find is similar to the previous intraspherule variations, which are now the limiting factor in understanding their compositions. The matrix effect for each spherule should be assessed quantitatively and individually, especially addressing Fe-oxide content. We expect micrometeorite triple-oxygen isotope compositions obtained by SIMS to converge on the main clusters (Groups 1 to 4) after correction firstly for magnetite content and secondarily for other phases (e.g., basaltic glass) in each target.

Testing secondary sex ratio bias hypotheses in white-tailed deer in Mississippi, USA.

Natural selection favors individuals with the highest inclusive fitness (i.e., total number of descendants). In cases where one sex is more productive, one or both parents may maximize their inclusive fitness by investing in the offspring of the more prolific sex. Such preferential production can lead to skewed sex ratios at various life history stages, including at birth, resulting in secondary sex ratio bias. Several competing hypotheses have been proposed to explain observed variation in secondary sex ratios including Fisher's frequency dependence and two hypotheses related to maternal condition: Trivers-Willard and the local resource hypotheses. Although it has been shown that maternal condition can influence the number of offspring produced in white-tailed deer, there is no consensus as to which of the hypotheses drives sex ratio bias in wild populations. Using a spatiotemporally extensive dataset of pregnant white-tailed deer from Mississippi, USA, we examined fetal sex ratio in relation to the Fisherian frequency-dependence hypothesis and hypotheses related to maternal condition. While there was a male-sex ratio bias in pregnant females that reduced in intensity with the number of offspring, there was no support for condition-related hypotheses. Instead, secondary sex ratios for white-tailed deer in Mississippi were nearly consistent with Fisherian frequency dependence. Our findings add to the body of literature on secondary sex biases in white-tailed deer and help inform sex bias ratios for a southern population of a cervid of management importance in the US.

Analysis of the synergetic effect of process parameters of hydrogenated amorphous carbon deposition in plasma-enhanced chemical vapor deposition using machine learning

The synergetic effects of process parameters on hydrogenated amorphous carbon (a-C:H) films properties were quantitatively analyzed in plasma-enhanced chemical vapor deposition. Predictive models, created from experimental datasets and machine learning, indicate a synergetic effect between the H2 ratio and ion energy impacting on the substrate. At a H2 ratio of 75 %, etch rates of 200 nm/min were predicted, regardless of radio frequency (RF) bias. These rates decreased to 120–140 nm/min at lower H2 ratios, primarily depending on RF bias. Quadrupole mass spectrometry and Raman scattering were used to investigate the underlying mechanisms. High H2 ratios led to a greater presence of low-mass hydrogen-rich molecules in the plasma. The C2H3 radical intensity at a 75 % H2 ratio was 15 times greater than that at 0 % at an RF bias of 50 W, and similar trends were observed for other low-mass neutrals. The synergetic effects of H2 ratio and RF bias decreased the film's hydrogen content. Machine learning and those diagnostics revealed that ion bombardment induces dehydrogenation of a-C:H, influenced by hydrogen-rich species. This study demonstrates that machine learning can uncover complex plasma processes and optimize material synthesis.

Offspring sex ratio in a communal breeding bird is male‐biased when pre‐breeding rainfall is low

Offspring sex ratios may deviate from parity when the fitness benefits of producing male or female offspring vary. We tested for sex ratio bias in smooth‐billed anis Crotophaga ani, a communal laying cuckoo with low within‐group relatedness and high offspring dispersal. One male group member performs nocturnal incubation and sires more offspring than other males in the group, suggesting males may have greater reproductive variance than females. We hypothesized that pre‐breeding rainfall influences food availability and offspring sex ratio, predicting that breeding females skew production towards the sex with higher reproductive variance (males) in high food years. Females may also adjust sex ratio across the hatching order to increase survival of the more competitive sex, especially when clutches are larger and within‐brood competition is higher. As adults, male smooth‐billed anis are larger than females, so we assumed male nestlings are more competitive than females and predicted a male‐bias in first hatched chicks in larger broods. Contrary to our first prediction, offspring sex ratio was male biased when pre‐breeding rainfall was lower. In partial support of our second prediction, marginally more first hatched chicks were male in larger broods. To our knowledge, this is the first evidence of offspring sex ratio bias in a communal laying bird species. Future work in this system will attempt to uncover the mechanisms by which co‐breeding females adjust offspring sex ratio and test alternative hypotheses to explain male‐biased offspring sex ratios under different conditions.

Vertical distribution of Lake Superior cisco (Coregonus artedi) spawning aggregations and implications for population monitoring

Cisco (Coregonus artedi) support an evolving commercial roe fishery in Wisconsin waters of Lake Superior. To monitor trends in spawning cisco abundance, fishery managers recently began estimating adult biomass and exploitation using fall hydroacoustic surveys, which were combined with gill net surveys to inform apportionments of acoustic data. The gill net survey design consisted of paired top-suspended and bottom-set gill nets, but only the sex ratios from top nets are currently used with the hydroacoustic surveys due to an assumption that cisco in Lake Superior are pelagic spawners. However, the vertical sex distribution of cisco during spawning aggregations has been described as dynamic, with males becoming more bottom-oriented throughout the spawning season. We used multilevel aggregated binomial regressions to: 1) determine if there is bias between top and bottom gill net catches of cisco for either sex and if it changes throughout the spawning season, 2) evaluate how the vertical distribution of males and females may create bias in sex ratios used to estimate exploitation, and 3) explore the effect that maturity (i.e., gonadal development) has on vertical distribution during spawning aggregations. We identified sex-specific bias in vertical catch location that has the potential to bias estimates of sex ratio, and the source of this bias may be attributable to maturity driven changes in behavior. These findings highlight a need for caution when relying on gill nets to apportion cisco sex ratios during spawning aggregations and provide support for a non-pelagic alternative hypothesis of spawning behavior.

Epidemiological studies likely need to consider PM2.5 composition even if total outdoor PM2.5 mass concentration is the exposure of interest.

Outdoor fine particulate air pollution, <2.5 µm (PM2.5) mass concentrations can be constructed through many different combinations of chemical components that have varying levels of toxicity. This poses a challenge for studies interested in estimating the health effects of total outdoor PM2.5 (i.e., how much PM2.5 mass is present in the air regardless of composition) because we must consider possible confounders of the version of treatment-outcome relationships. We evaluated the extent of possible bias in mortality hazard ratios for total outdoor PM2.5 by examining models with and without adjustment for sulfate and nitrate in PM2.5 as examples of potential confounders of version of treatment-outcome relationships. Our study included approximately 3 million Canadians and Cox proportional hazard models were used to estimate hazard ratios for total outdoor PM2.5 adjusting for sulfate and/or nitrate and other relevant covariates. Hazard ratios for total outdoor PM2.5 and nonaccidental, cardiovascular, and respiratory mortality were overestimated due to the confounding version of treatment-outcome relationships, and associations for lung cancer mortality were underestimated. Sulfate was most strongly associated with nonaccidental, cardiovascular, and respiratory mortality suggesting that regulations targeting this specific component of outdoor PM2.5 may have greater health benefits than interventions targeting total PM2.5. Studies interested in estimating the health impacts of total outdoor PM2.5 (i.e., how much PM2.5 mass is present in the air) need to consider potential confounders of the version of treatment-outcome relationships. Otherwise, health risk estimates for total PM2.5 will reflect some unknown combination of how much PM2.5 mass is present in the air and the kind of PM2.5 mass that is present.

Adjustment for sparse data bias in odds ratios: Significance to appraisal of risk of diabetes due to occupational trichlorfon insecticide exposure

BackgroundBias away from the null in odds ratios (OR), aggravated by low power, is a well-known phenomenon in statistics (sparse data bias). Such bias increases in presence of selection of “significant” results on the basis of null hypothesis testing (effect size magnification, ESM). ObjectivesWe seek to illustrate these issues and adjust for suspected sparse data bias in the context of a reported more than doubling of the odds of new onset type 2 diabetes in presence of occupational trichlorfon insecticide exposure reported in the Agricultural Health Study. MethodsWe performed ESM analysis on the crude ORs extracted from the contingency table in the published report, which is done by simulating selected OR given a posited true OR. Next, we applied easily accessible methods that adjust for sparse data bias to the extracted contingency tables, including data augmentation, bootstrap, Firth's regression, and Bayesian methods with weakly informative priors. ResultsDuring the ESM analysis, we observed that there was a reasonable chance that a “statistically significant” OR of around 2.5–2.6 would be observed for true OR of 1.2. Adjustment for sparse data bias revealed that Bayesian methods outperformed alternative approaches in terms of yielding more precise inference, while not making unjustified distributional assumptions about estimates of OR. The OR in the original paper of about 2.5–2.6 was reduced on average to OR of 1.9 to 2.2, with 95% (Bayesian) credible intervals that included the null. DiscussionIt is reasonable to adjust ORs for sparse data bias when the reported association has societal importance, because policy must be informed by the least biased estimates of the effect. We think that such adjustment would lead to a more appropriate evaluation of the extent of evidence on the contribution of occupational exposure to trichlorfon pesticide to risk of new onset diabetes.

P-148 Humid versus dry culture: impact on euploidy, live birth sex ratio and clinical outcomes

Abstract Study question Does humidity have an impact on top-quality blastocyst rate, ploidy, live birth sex ratio and clinical outcomes? Summary answer Humid culture conditions in time-lapse incubators may enhance clinical outcomes, particularly in autologous cycles, without biasing euploidy or newborn sex. What is known already Recent advances in assisted reproductive technology have focused on improving embryo culture conditions and incubators are becoming more sophisticated. Although culture conditions such as oxygen and temperature are well-studied, the optimal humidity level remains uncertain. Dry atmospheres favour higher evaporation of culture media compared to humid conditions, increasing its osmolality. This appears to be detrimental to several animal model embryos: developmental arrest, changes in gene expression and epigenetic alterations in the embryos. Previous studies have shown than incubator humidification improves clinical outcomes and embryonic development. However, other studies showed no significant improvements. Study design, size, duration A single center retrospective study was performed. Data included a total of 793 cycles of IVF/ICSI between January 2019 and May 2023. Participants/materials, setting, methods 793 cycles of IVF/ICSI from 734 patients were studied. Study population was categorized in autologous (n = 544) and egg-donation (n = 249) cycles. A total of 5909 embryos were included in the study. Patients were randomly distributed in two distinct cohorts at the moment of their treatment: dry condition (DC) and humid condition (HC). Blastocyst quality (BR), biochemical pregnancy (BPR), implantation rate (IR), live birth rate (LBR) were studied. Ploidy rate and LB sex ratio was also studied. Main results and the role of chance In egg donation cycles, no differences were observed between HC and DC groups in the rates of top-quality blastocysts (61.5 HC vs 64.4% DC), BPR, (71.1% HC vs 71.2% DC), IR (53.8% HC vs. 59.2% DC) or LBR (51.9% HC vs. 44.8% DC). However, autologous cycles showed an improvement when humid conditions were used. BR and IR were higher in humid conditions (BR: 58.8% HC vs. 55,6% DC, p-value 0.03; IR:57.1% HC vs. 39.7% DC, p-value 0.011)). Humid and dry culture conditions yielded similar rates of BPR (65.0% HC vs 53.0% DC, p-value: 0.11) and live birth rate (44.3% HC vs 34.5% DC, p-value: 0.16). Although there is a tendency towards a 20% of benefit in presence of humidity in both rates, no significance was reached. No differences were found in euploidy between dry and humid groups. When stratifying patients by age, all age groups met the ploidy expected rates in both culture conditions. Humid culture conditions enhance clinical outcomes, particularly in autologous cycles. Donated oocytes may take advantage of their better quality to compensate the detrimental effect of dry ambients. Our study, moreover, demonstrates that humidity does not introduce any bias towards chromosomal alterations or newborn sex. Limitations, reasons for caution This is a retrospective study and should be further confirmed with a prospective randomized study. Sample size should be increased, especially for ploidy Specific humidity values could also be tested. Wider implications of the findings Humid culture conditions may highly improve ART outcomes for particular groups of patients. If tested with stratified groups by age, a specific age group might be especially benefited of humidity, without any bias in sex ratios when best embryo is transferred in fresh cycles. Trial registration number not applicable

Female‐biased population sex ratios caused by genetic rather than ecological mechanisms in dwarf willow (Salix herbacea L.)

Abstract Biased sex ratios among reproductive individuals are common in plants, but the underlying mechanisms, as well as the evolutionary consequences, are not well understood. The classical theory of Düsing and Fisher predicts an equal primary sex ratio at seed production, based on the selective advantage of the rare sex. Biased sex ratios among reproductive plants can arise from sexual dimorphism in survival and flowering. Sex ratio biases can also be present from the seed stage; in these cases, assumptions of Düsing's and Fisher's theory, for example, random mating or demographic equilibrium, are thought to be violated. We investigated mechanisms leading to female‐biased sex ratios in the arctic‐alpine dwarf willow Salix herbacea L. We studied sex ratios in three natural populations over 3 years as well as in 29 crosses (full‐sib families) under controlled conditions over four growth periods. We tested whether sex ratio was associated with habitat parameters (elevation and snowmelt time), or with germination, survival or flowering, and whether females and males differed in size or flowering that may cause observation bias. We detected a strong and consistent female bias, both in natural populations (sex ratio [proportion of females]: 0.71–0.82) and in our controlled experiment (overall sex ratio: 0.70–0‐72). Female bias became more pronounced with increasing elevation. Our data did not support sexual dimorphism in size or flowering. Family sex ratios varied largely (from 0.25 to 1), including many female‐biased families, unbiased families and two male‐biased families. Families with lower germination, seedling establishment, survival or flowering did not have stronger female bias, indicating that intrinsically higher survival or flowering in females does not explain overall female bias. Synthesis. Our results suggest that sex ratio bias in S. herbacea is already present in seeds and does not arise through intrinsic differences between sexes. Candidate mechanisms that can lead to both overall female bias and variation in sex ratio among families are meiotic drive or cyto‐nuclear interactions. The pioneer habit of Salix may lead to non‐equilibrium population dynamics that allow for the long‐term persistence of variable genetic sex ratio distortion systems that arise from genetic conflict.

Early‐life demographic processes do not drive adult sex ratio biases and mating systems in sympatric coucal species

Abstract Sex differences in early‐life survival can drive skewed adult sex ratios (ASR), which play an important role in mating tactics and parental sex roles. Among birds, cuckoos exhibit the largest diversity in mating systems and thus represent an interesting system to study sex‐specific demography. Here we investigate the early‐life survival pathways shaping ASR using long‐term field data and sex‐ and stage‐specific demographic modelling of black coucals and white‐browed coucals—two sympatric Centropus cuckoo species differing in mating system and the extent of sexual size dimorphism. We hypothesized that sexual size dimorphism would lead to differential juvenile mortality due to the greater energy demands and predation risk of the larger sex during maturation. We expected higher early‐life mortality among large‐bodied females in the sexually dimorphic and classically polyandrous black coucal, whereas no bias should exist in the less dimorphic and monogamous white‐browed coucal. Both species had balanced hatching sex ratios, but in black coucals, female survival (μ = 0.64 ± 0.061 SD) was lower during the ‘groundling’ phase (i.e. a flightless 3‐week period following nest departure) than male survival (0.70 ± 0.066). Yet, this sex difference in survival was not strong enough to account for the species' male‐biased ASR where 70% of the adult population is male. In white‐browed coucals, survival during maturation exhibited high inter‐individual variation but lacked clear sex differences, reflecting the emergence of a balanced ASR. In summary, we found no evidence that the strongly male‐biased ASR of black coucals is driven by sex‐specific survival during maturation. In black coucals, the male‐biased ASR must therefore stem from processes occurring later in life: possibly, larger females are more likely to die during migration and/or the recruitment of young females is delayed due to competitive exclusion by more experienced females. Our results differ from studies on shorebirds, in which sex‐specific mortality of precocial young is related to ASR and mating dynamics. Hence, early‐life sex biases in survival of precocial shorebirds cannot be generalized to other taxonomic groups. Factors other than early‐life sex biases in survival are likely to be important in shaping adult sex ratios and the associated mating dynamics and social behaviours in altricial coucals. Read the free Plain Language Summary for this article on the Journal blog.

Quantitative Analysis of the Impact of Sex Ratio Bias on Ecosystems: The Case of the Sea Lamprey

Quantitative Analysis of the Impact of Sex Ratio Bias on Ecosystems: The Case of the Sea Lamprey

Distributed multi‐station target tracking based on unscented particle filter and Dempster‐Shafer theory

AbstractIn a distributed multi‐station system, the observations received by local radar nodes for a single target will have a large signal‐to‐noise ratio (SNR) bias due to inconsistent radar cross‐sections from distinct angles, different distances from the target, various local interference such as harsh weather, and dissimilar background noise. Integrating heterogeneous information in dynamic and uncertain environments can be challenging for the fusion centre. Moreover, the particles in the basic particle filter (PF) may degrade after many iterations, making it difficult to achieve accurate target state estimation in the local tracking process. To address these issues, the authors propose a novel method named DS‐UPF based on the Dempster–Shafer (DS) theory and the unscented particle filter (UPF). By updating the important density function, the UPF efficiently suppresses particle degradation. The weighted Basic Probability Assignments (BPAs) are proposed and integrated under the new synthesis formula. The weight‐modified DS method restrains the impact of significant local estimation errors on weighted BPAs fusion result, improving robustness without local interference prior knowledge. The experimental results demonstrate that the DS‐UPF outperforms the unscented Kalman filter, PF, and UPF in tracking tasks under various local interference. This indicates that the proposed algorithm can improve estimation precision in dynamic and uncertain environments.

Should we care about pay ratios? Dealing with ISSP questions on actual and ideal wages from a comparative perspective

ABSTRACT Questions on actual and ideal wages of various occupations are distinctive features of ISSP Social Inequality modules which can be used to quantify respondents’ perceived and ideal wage inequality, by computing pay ratios ex-post. However, recent research has raised harsh criticism of pay ratios, emphasizing that they suffer from anchoring bias, ratio bias, and, more generally, low validity. This article investigates what adjustments can be made to improve the validity of pay ratios for comparative analyses. It is found that country comparisons are very sensitive to adjustments and have major limitations. Nevertheless, as attitudes expressed by word-based items do not measure the extent of inequalities that respondents are willing to tolerate, further research is needed to find out ways to fix problems with pay ratios at the level of data collection rather than of data analysis. The article concludes with some suggestions regarding data collection.

The hot sex: is there evidence for climate‐driven sex allocation in mammals?

Abstract Climate change predictions indicate that future conditions will be hotter and drier, and rainfall will be more variable. Climatic conditions can affect individual condition and shape offspring sex ratios. The implications that climate change have for mammalian sex allocation are vast but are currently poorly understood. There are several scenarios under which climate‐driven sex allocation responses might emerge. Here, I make predictions on the direction of offspring sex ratio biases under hypothetical situations of restricted resource availability and altered social/spatial structures that may result from hotter, drier conditions. I searched the literature for existing evidence of climate‐driven offspring sex ratio biases among individuals studied in wild populations. There was no strong, directional support for the production of sons or daughters under ‘good’ or ‘poor’ climatic conditions among the 30 studies had reported on climatic variables and offspring sex ratio. I also searched the literature for studies that assessed maternal condition and offspring sex ratio in natural populations (i.e. there is a link between climate, resource availability and maternal condition). Of the 27 investigations, half reported a bias in favour of sons born to mothers in ‘good’ condition (56%). I discuss how this outcome could be due to a publication bias, or that it may indicate that low resource availability has the potential to lead to mothers in poor condition and the production of fewer sons. I consider the conservation implications of climate‐driven offspring sex ratios skews being carried through to the population level. I discuss the challenge of being able to account for the multiple factors that influence offspring sex ratios in natural populations and emphasise the growing need for more research in this important area of mammalian evolutionary ecology.

Identifying social determinants of health from clinical narratives: A study of performance, documentation ratio, and potential bias

ObjectiveTo develop a natural language processing (NLP) package to extract social determinants of health (SDoH) from clinical narratives, examine the bias among race and gender groups, test the generalizability of extracting SDoH for different disease groups, and examine population-level extraction ratio. MethodsWe developed SDoH corpora using clinical notes identified at the University of Florida (UF) Health. We systematically compared 7 transformer-based large language models (LLMs) and developed an open-source package – SODA (i.e., SOcial DeterminAnts) to facilitate SDoH extraction from clinical narratives. We examined the performance and potential bias of SODA for different race and gender groups, tested the generalizability of SODA using two disease domains including cancer and opioid use, and explored strategies for improvement. We applied SODA to extract 19 categories of SDoH from the breast (n = 7,971), lung (n = 11,804), and colorectal cancer (n = 6,240) cohorts to assess patient-level extraction ratio and examine the differences among race and gender groups. ResultsWe developed an SDoH corpus using 629 clinical notes of cancer patients with annotations of 13,193 SDoH concepts/attributes from 19 categories of SDoH, and another cross-disease validation corpus using 200 notes from opioid use patients with 4,342 SDoH concepts/attributes. We compared 7 transformer models and the GatorTron model achieved the best mean average strict/lenient F1 scores of 0.9122 and 0.9367 for SDoH concept extraction and 0.9584 and 0.9593 for linking attributes to SDoH concepts. There is a small performance gap (∼4%) between Males and Females, but a large performance gap (>16 %) among race groups. The performance dropped when we applied the cancer SDoH model to the opioid cohort; fine-tuning using a smaller opioid SDoH corpus improved the performance. The extraction ratio varied in the three cancer cohorts, in which 10 SDoH could be extracted from over 70 % of cancer patients, but 9 SDoH could be extracted from less than 70 % of cancer patients. Individuals from the White and Black groups have a higher extraction ratio than other minority race groups. ConclusionsOur SODA package achieved good performance in extracting 19 categories of SDoH from clinical narratives. The SODA package with pre-trained transformer models is available at https://github.com/uf-hobi-informatics-lab/SODA_Docker.

Limited evidence of biased offspring sex allocation in a cavity-nesting conspecific brood parasite.

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.

Effects of ultraviolet light supplementation on hen behaviour and welfare during early lay

Poultry can see in the ultraviolet (UV) spectrum and supplementation of UVA has been shown to reduce laying hens’ fear and stress. The shorter wavelengths (UVB) also facilitate vitamin D3 production. However, UV spectrums are typically not included in indoor commercial poultry lighting which may result in less than optimum welfare of laying hens. This study predicted that UVA and UVA/B supplementation would increase desirable behaviours such as foraging and exploratory pecking and reduce measures of fear and stress. The effects of UV light supplementation were assessed on 252 ISA Brown hens during the period from 16 to 27 weeks of age. Birds were housed in eighteen pens (14 hens/pen) under three different light treatment groups each with six replications: (i) UV0: standard control lighting with LED white light, (ii) UVA: control lighting plus a supplemental ‘daylight’ avian bulb providing UVA, and (iii) UVA/B: control lighting plus a supplemental full spectrum reptile bulb containing both UVA and UVB wavelengths. Behavioural time budgets were assessed in the home pens at 18 and 24 weeks. At 20, 23, and 26 weeks, assessments included: individual behavioural tests of tonic immobility and open field, pen-level novel object tests and blood heterophil/lymphocyte (H/L) ratios. At 27 weeks the UV supplemental lights were turned off for 3 days as a ‘stressor’ with bird locations in the pen measured before and during the stressor, along with H/L ratio and attention bias test assessments. Results showed limited effects of the supplemental lights. At 26 weeks both UV light treatments reduced tonic immobility duration (P = 0.006) and vocalisations across time in the open field test (P = 0.0003), while the UVA/B hens had lower H/L ratios than the UV0 hens (P = 0.01). However, removing the treatment lights did not result in greater stress and anxiety and there were few differences observed in the home pen time budgets. Overall, these results align with complementary findings in the same birds showing minimal impact of the UV treatments on measures of egg production, egg quality, bone health, and circulating plasma P and Ca but with an increase in serum vitamin D (25(OH)D3) for the UVA/B hens. The supplemental UV lights in this study were only on one side of the pens which could have minimised their impacts. Similarly, effects may vary at different points in the production cycle than included in this study.

The haplolethal gene wupA of Drosophila exhibits potential as a target for an X-poisoning gene drive.

A synthetic gene drive that targets haplolethal genes on the X chromosome can skew the sex ratio toward males. Like an "X-shredder," it does not involve "homing," and that has advantages including the reduction of gene drive resistance allele formation. We examine this "X-poisoning" strategy by targeting 4 of the 11 known X-linked haplolethal/haplosterile genes of Drosophila melanogaster with CRISPR/Cas9. We find that targeting the wupA gene during spermatogenesis skews the sex ratio so fewer than 14% of progeny are daughters. That is unless we cross the mutagenic males to X^XY female flies that bear attached-X chromosomes, which reverses the inheritance of the poisoned X chromosome so that sons inherit it from their father, in which case only 2% of the progeny are sons. These sex ratio biases suggest that most of the CRISPR/Cas9 mutants we induced in the wupA gene are haplolethal but some are recessive lethal. The males generating wupA mutants do not suffer from reduced fertility; rather, the haplolethal mutants arrest development in the late stages of embryogenesis well after fertilized eggs have been laid. This provides a distinct advantage over genetic manipulation strategies involving sterility which can be countered by the remating of females. We also find that wupA mutants that destroy the nuclear localization signal of shorter isoforms are not haplolethal as long as the open reading frame remains intact. Like D. melanogaster, wupA orthologs of Drosophila suzukii and Anopheles mosquitos are found on X chromosomes making wupA a viable X-poisoning target in multiple species.

Identifying Offspring Sex Ratio Skews in Zoological Facilities Using Large Historical Datasets

The Fisher principle states that species should produce offspring at a ratio of 1:1 unless there are sex-specific differences in rearing costs. Research conducted across taxa has found that animals will vary the sex ratio of their offspring so as to maximize personal fitness in response to various ecological and biological variables. This phenomenon has been especially well studied within the Avian class. Professionally managed populations provide a useful framework within which to study the impacts of numerous variables on sex allocation strategies. Zoological facilities may be especially motivated to investigate this phenomenon due to corresponding conservation and welfare implications. We analyzed a large dataset containing the demographic data of over 1 million zoo-housed birds for species-specific offspring sex ratio biases. The offspring sex ratios of 19,867 zoo-hatched dams were calculated, and the median offspring sex ratio of 277 species from 25 orders was calculated across two 20-year time periods. We used a Wilcoxon signed rank tests with a Holm Bonferroni alpha criterion in order to determine if species medians differed from parity. Only one species in one time period displayed a significant species median offspring sex ratio. The limits of our dataset are discussed. We propose that future research should further explore the determinants of sex allocation strategies for species held within zoological facilities.