Population Sex Ratio Research Articles

Morphological changes in female reproductive organs in the African monarch butterfly, host to a male-killing Spiroplasma.

Sexual selection and conflicts within and between sexes promote morphological diversity of reproductive traits within species. Variation in the morphology of diagnostic reproductive characters within species offer an excellent opportunity to study these evolutionary processes as drivers of species diversification. The African monarch, Danaus chrysippus (Linnaeus, 1758), is widespread across Africa. The species is polytypic, with the respective geographical ranges of the four colour morphs only overlapping in East Africa. Furthermore, some of the populations host an endosymbiotic bacterium, Spiroplasma, which induces son-killing and distorts the local host population sex-ratio, creating sexual conflicts between the females seeking to optimize their fecundity and the limited mating capacity of the rare males. We dissected females from Kenya, Rwanda and South Africa, where Spiroplasma vary in presence and prevalence (high, variable and absent, respectively), and conducted microscopy imaging of their reproductive organs. We then characterized the effect of population, female body size, and female mating status, on the size and shape of different genitalia characters of the D. chrysippus female butterflies. We showed that although the general morphology of the organs is conserved in D. chrysippus, female genitalia vary in size and shape between and within populations. The virgin females have smaller organs, while the same organs were expanded in mated females. Females from highly female-biased populations, where the male-killing Spiroplasma is prevalent, also have a larger area of their corpus bursae covered with signa structures. However, this pattern occurs because a larger proportion of the females remains virgin in the female-biased populations rather than because of male depletion due to the symbiont, as males from sex-ratio distorted populations did not produce significantly smaller nutritious spermatophores.

Density, structure, growth, and mortality of the population of Ocypode gaudichaudii H. Milne Edwards & Lucas, 1843 (Brachyura, Ocypodidae) in Salaverry, Peru

Abstract The northern coast of Peru includes a series of dissipative desert beaches with varying levels of human impact. One endemic species to these beaches is Ocypode gaudichaudii, which has been shown to be an indicator of ecosystem disturbance. We measured population density, sex ratio, and cephalothorax length of O. gaudichaudii on three beaches near Salaverry between September 2021 and February 2022. The average population density was 0.15 burrows/m2. There was a higher proportion of males (56%); and average cephalothorax length was 28.8 ± 5.6 mm. Population, length, and sex variations during the study may be explained by behaviour of O. gaudichaudii and by temperature-dependent breeding. We also calculated the Von Bertalanffy growth parameters (, , ) and estimated the instantaneous mortality rate to be 0.84/year. These data indicate a high level of disturbance in the ecosystem, with few specimens approaching .

X chromosome drive is constrained by sexual selection and influences ornament evolution.

Experimental evolution provides an integrative method for revealing complex interactions among evolutionary processes. One such interaction involves sex-linked selfish genetic elements and sexual selection. X-linked segregation distorters, a type of selfish genetic element, influence sperm transmission to increase in frequency and consequently alter the population sex ratio and the opportunity for sexual selection, while sexual selection may impact the spread of X-linked distorters. Here we manipulated sexual selection by controlling female mating opportunities and the presence of a distorting X chromosome in experimental lines of the stalk-eyed fly, Teleopsis dalmanni, over 11 generations. We find that removal of sexual selection leads to an increase in the frequency of the X-linked distorter and sex ratio across generations and that post-copulatory sexual selection alone is sufficient to limit the frequency of distorters. In addition, we find that male eyestalk length, a trait under pre-copulatory sexual selection, evolves in response to changes in the strength of sexual selection with the magnitude of the response dependent on X chromosome type and the frequency of distorting X chromosomes. These results reveal how a selfish X can interact with sexual selection to influence the evolution of sexually selected traits in multiple ways.

Egg provisioning explains the penetrance of symbiont-mediated sex allocation distortion in haplodiploids.

Maternally transmitted symbionts such as Wolbachia can alter sex allocation in haplodiploid arthropods. By biasing population sex ratios towards females, these changes in sex allocation may facilitate the spread of symbionts. In contrast to symbiont-induced cytoplasmic incompatibility (CI), the mechanisms that underpin sex allocation distortion remain poorly understood. Using a nuclear genotype reference panel of the haplodiploid mite Tetranychus urticae and a single Wolbachia variant that is able to simultaneously induce sex allocation distortion and CI, we unraveled the mechanistic basis of Wolbachia-mediated sex allocation distortion. Host genotype was an important determinant for the strength of sex allocation distortion. We further show that sex allocation distortion by Wolbachia in haplodiploid mites is driven by increasing egg size, hereby promoting egg fertilization. This change in reproductive physiology was also coupled to increased male and female adult size. Our results echo previous work on Cardinium symbionts, suggesting that sex allocation distortion by regulating host investment in egg size is a common strategy among symbionts that infect haplodiploids. To better understand the relevance that sex allocation distortion may have for the spread of Wolbachia in natural haplodiploid populations, we parametrized a model based on generated phenotypic data. Our simulations show that empirically derived levels of sex allocation distortion can be sufficient to remove invasion thresholds, allowing CI to drive the spread of Wolbachia independently of the initial infection frequency. Our findings help elucidate the mechanisms that underlie the widespread occurrence of symbionts in haplodiploid arthropods and the evolution of sex allocation.

A Slim Majority: The Influence of Sex Ratio on Women's Body Dissatisfaction and Weight Loss Motivations.

The current investigation examined whether women's perceptions of the sex ratio (ratio of women to men) in the local population influence their body dissatisfaction and weight loss motivations. A higher ratio of women to men in a given population signifies a relative abundance of same-sex mating competitors, intensifying female intrasexual competition. Five studies (N = 1,776) tested the hypotheses that women's perceptions of a female-skewed sex ratio would correspond to increased feelings of intrasexual competitiveness and perceptions of unfavorable mating prospects, which would, in turn, be associated with heightened body dissatisfaction and weight loss motivations. Among university and community women (Studies 1and 2), perceptions of a female-skewed sex ratio corresponded to greater intrasexual competitiveness, increased body dissatisfaction, and increased dieting inclinations. Among single women, assessments of a female-skewed sex ratio corresponded to perceptions of unfavorable mating prospects, increased romantic pressure to alter their appearance, and higher body dissatisfaction (Study 3). Studies 4 and 5 experimentally manipulated perceived sex ratio. Women in the female-skewed condition felt less satisfied with their weights and shapes, but only if they believed the manipulation (Study 4). In Study 5, using a within-subjects design, women who evaluated a male-skewed (vs. female-skewed) dating profile array subsequently desired to lose less weight. Findings suggest women's perceptions of their social environments may contribute to body image and dieting motivations.

A comparative study of cultured and field plants provides evidence for the shy male hypothesis in tropical genotypes of Bryum argenteum Hedw.

ABSTRACT Introduction The female-biased sex ratio is recurrently observed in bryophyte populations, although the sex ratio of spores is usually balanced. The results of several studies have suggested explanations for this observation, one of which is the shy male hypothesis. The shy male hypothesis predicts that the sex ratio of populations is balanced in the field, but due to a low or lack of sex expression of male plants, the populations present a female bias when the sex ratio is based on observations of sex-expressing plants. Methods We tested the shy male hypothesis using samples of the moss Bryum argenteum collected from Brazilian seasonally dry tropical forests and the Brazilian Atlantic Forest. Field sex ratios were determined by classifying shoots as male, female, or non–sex-expressing. Non–sex-expressing shoots were further analysed for sex expression after culture regeneration. Results and discussion Our results showed that populations of Bryum argenteum in the field had a low rate of sex expression, and that most of the shoots expressed were female. However, when shoots without sex expression were cultured, a greater number of male shoots were observed compared with in the field plants. Because more males appeared in the shoots cultured from non–sex-expressing field plants, our data for tropical B. argenteum tend to support the shy male hypothesis. Some genotypes from the wet forest were synoicous (i.e. had male and female gametangia in the same gametoecia), suggesting polyploidy.

Climate change consequences for differential adult survival and the mating system of a temperate breeding shorebird

AbstractManaging for the effects of climate change on species whose populations are currently imperiled requires detailed knowledge of the relationship between their demographic rates and climate variables. We sought this information for the West Coast breeding population of snowy plover (Charadrius nivosus), which was federally listed as threatened in 1993 due to substantial declines in the numbers of plovers breeding along the coast and in the number of sites occupied for breeding. Snowy plovers employ a serially polygamous breeding system in which the male typically tends chicks to independence. This unusual breeding system is favored by male‐biased sex ratios in local populations. As part of a multispecies study of the effect of climate change on population growth, we used mark–capture models to examine climate drivers of adult survival for 1219 snowy plovers banded at Monterey Bay over 38 years and known to overwinter on the surrounding north‐central California outer coast. Nonclimate variables, including sex and unmeasured annual mortality risks (e.g., predator abundance), were the primary factors affecting adult survival. However, there is evidence that cold weather, particularly extended cold snaps with daily low temperatures below 2°C and daily high temperatures below 10°C, decreases overwinter survival. Exceptionally cold winters had a particularly strong effect on adult female plovers, contributing to the male‐biased adult sex ratios. Future winter climate on the north‐central California coast is projected to be generally warmer with fewer and shorter cold snaps. Reduced mortality from cold winter weather may mitigate other threats faced by plovers, such as anthropogenically enhanced predator populations, habitat loss, and accelerated sea level rise, while altering the adult sex ratio and potentially shifting the evolutionary landscape maintaining the plover's unusual breeding system.

Adaptive Response to Gillnets Bycatch in a North Sardinia Mediterranean Shag (Gulosus aristotelis desmarestii) Population.

Mediterranean Shag (Gulosus aristotelis desmarestii) is a seabird endemic to the Mediterranean and Black Seas, recently included in the IUCN list of threatened Species. Most of the reproductive colonies are hosted in Sardinia and surrounding islets. Bycatch in fishing nets is one of the most significant threats for this population. Our work aimed to assess alterations in the sex ratio caused by bycatch and to study the adaptive response of the population to a skewed adult sex ratio. The sex ratio of Mediterranean Shags found drowned in the gillnets near the colonies and that of the nestlings of the Corcelli (northeast Sardinia) colony was determined using the sex-linked polymorphism of the gene Chromobox-Helicase-DNA-binding 1. The data of the shags found drowned in gillnets evidenced a high mortality rate (83.3%; p < 0.001) and a larger size of males (35% heavier than females, p < 0.05) compared to females, supporting the theory that heavier individuals are able to forage at great depths. With 64.8% of the nestlings being male, the sex ratio of nestlings was statistically different from parity (p < 0.05). Furthermore, it was related to the brood size. In one- and two-chick broods, 73% and 70% of nestlings, respectively, were males, while in three-chick broods, only 33% were males. Our data identify the higher rate of male shags drowned in gillnets as a factor causing an alteration of the sex ratio in the Mediterranean Shag population. According to the Sex Allocation Theory, an adaptive adjustment of sex made by adult females restores the Mendelian sex ratio in the population.

Freshwater turtle populations as bioindicators following an oil spill: Delayed demographic changes reveal long-term impacts

Chronic, long-term impacts of oil spill disasters on wildlife often exceed short-term, highly visible mass mortalities and widespread oiling of individuals. Species with long lifespans, late maturation, and low recruitment rates are particularly vulnerable to long-term population-level impacts but can be useful as indicator species for ecosystem recovery. In 2010, one of the largest freshwater oil spills in the U.S. occurred in the Kalamazoo River, MI, when 3.2 million L of spilled oil impacted 56 km of river and associated wildlife. During cleanup and restoration efforts in 2010–2011, thousands of northern map turtles (Graptemys geographica) were captured, cleaned, and released. During 2019–2020 northern map turtles were captured to evaluate changes in the population size, demography, and size classes nine to ten years later.Population demography shifts occurred in the first few years after the spill in a species that otherwise exhibits minimal demographic fluctuation under “normal” conditions. In comparing demographic parameters at the time of the oil spill to values ∼ 10 years post-spill, a nearly 30% reduction in population size was detected, distribution of body size shifted to smaller males and females, and there was a shift in the population sex ratio between 2011 and 2019. There were also signals of failed recruitment in cohorts that would have hatched during the years immediately before and after the oil spill. These data suggest that beyond the direct mortality caused by the spill, declines in the estimated population size and shifts in the size distribution of northern map turtles are likely indicative of negative demographic impacts incurred following the 2010 oil spill and resulting cleanup.

Dietary crude oil exposure during sex differentiation skewed adult sex ratio towards males in the zebrafish

Dietary crude oil exposure has detrimental morpho-physiological effects in fishes, including endocrine disruption. However, little is known about how it influences sex differentiation and its potential for skewing sex ratios of populations. Appropriate sex ratio is important for maintaining effective population size and structure. Deviations of these ratios can compromise population growth and maintenance and may induce changes in a species' evolutionary trajectory. We assessed the potential of dietary exposure to crude oil (6.5, 11.4, and 17.5 mg/kg food) to alter sex differentiation in the zebrafish (Danio rerio) (20–35 days post fertilization (dpf)) and subsequently skew the adult (90 dpf) sex ratio. Multiple health- and fitness-related phenotypic traits (i.e., body mass and length, condition factor, heart rate, oxygen consumption, and their capacity to cope with hypoxia) were also assessed to better understand the effects of dietary crude oil exposure. We showed that dietary exposure to crude oil during the process of sex differentiation skewed sex ratio towards males (up to 0.34:1 female to male ratio in the highest oil concentration). Remarkably, this effect occurred independently of affecting physiological variables and female gonad characteristics, thus highlighting just how subtle the effects of dietary crude oil exposure can be. Our results suggest that, although fish were in an apparently healthy state during experimentation, sex ratio was still impacted, potentially compromising the resilience of the population. Therefore, considering how complex chemical mixtures affect organisms at several levels (molecular-individual) in experimental designs is warranted to better understand the implications of the exposures and the hazards that populations face in the wild.

Variance components of sex determination in the copepod Tigriopus californicus estimated from a pedigree analysis.

Extensive theory exists regarding population sex ratio evolution that predicts equal sex ratio (when parental investment is equal). In most animals, sex chromosomes determine the sex of offspring, and this fixed genotype for sex has made theory difficult to test since genotypic variance for the trait (sex) is lacking. It has long been argued that the genotype has become fixed in most animals due to the strong selection for equal sex ratios. The marine copepod Tigriopus californicus has no sex chromosomes, multiple genes affecting female brood sex ratio, and a brood sex ratio that responds to selection. The species thus provides an opportune system in which to test established sex ratio theory. In this paper, we further our exploration of polygenic sex determination in T. californicus using an incomplete diallel crossing design for analysis of the variance components of sex determination in the species. Our data confirm the presence of extra-binomial variance for sex, further confirming that sex is not determined through simple Mendelian trait inheritance. In addition, our crosses and backcrosses of isofemale lines selected for biased brood sex ratios show intermediate phenotypic means, as expected if sex is a threshold trait determined by an underlying "liability" trait controlled by many genes of small effects. Furthermore, crosses between families from the same selection line had similar increases in phenotypic variance as crosses between families from different selection lines, suggesting families from artificial selection lines responded to selection pressure through different underlying genetic bases. Finally, we estimate heritability of an individual to be male or female on the observed binary scale as 0.09 (95% CI: 0.034-0.14). This work furthers our accumulating evidence for polygenic sex determination in T. californicus laying the foundation for this as a model species in future studies of sex ratio evolution theory.

Continuous Reproduction Causes Stable Population Structure of Antipatharian-Associated Shrimp Sandyella tricornuta (Decapoda: Palaemonidae)

Sandyella tricornuta (Hendrickx, 1990) is a small (<13 mm total length), obligate and highly specific ectosymbiont of the black coral Antipathes galapagensis Deichmann, 1941 with a remarkable morphology and body coloration that resembles black coral polyps. Sandyella tricornuta population structure was investigated to infer the reproductive periods evidenced with ovigerous females from monthly collection at Espíritu Santo Island (April 2009–March 2010) and along a latitudinal gradient of six islands (24–30° N, July 2009) located along the west coast of the Gulf of California, Mexico. A total of 2,899 S. tricornuta individuals were collected from 70 colonies of A. galapagensis with a mean density of 210 inds./m3 per black coral colony. Sea floor temperature of S. tricornuta/A. galapagensis habitat seasonally ranged between 21 and 30°C. Females constituted >60% of the entire S. tricornuta population and >59% of the collected females were ovigerous females, suggesting active reproduction throughout the year and along the latitudinal gradient investigated. Sandyella tricornuta population density and sex ratio was similar throughout the year indicating a seasonally stable population size. Total abundance of S. tricornuta was density independent of black coral colony size and weight indicating that S. tricornuta depends on A. galapagensis, but the black coral colony can grow and develop without S. tricornuta characteristic of a commensalism ectosymbiotic association.

The influence of habitat properties on sex determination in cavity-nesting Hymenoptera

Unravelling the relationships between insect population dynamics and habitat properties is often complex. Established theoretical concepts, which predict an influence of available resources on sex determination, have often not been tested with quantitative field data. Cavity-nesting Hymenoptera are suitable to assess the influence of habitat properties on reproductive parameters, as haplodiploidy enables direct responses to local conditions. We hypothesize that with increasing resource availability, the population sex ratio (share of females per site), sex allocation preference per individual offspring (the probability of producing either a male or a female offspring per brood cell) and resource allocation per individual offspring will be favouring towards females. We sampled offspring of Osmia cornuta, Osmia caerulescens and Trypoxylon figulus and their resource provisions using trap nests on 30 study sites in an agricultural landscape in southwest Germany, from March to August 2020. The potential influence of resource availability, landscape variables, temperature, seasonal progression, and nesting opportunities on sex and resource provisions was tested. Population sex ratio was not related to habitat properties. Sex allocation preference in the three species, however, depended on several variables including cavity size and seasonal progression, with pronounced differences amongst species. Individual resource provisioning mainly differed between sexes, as male larvae received less provisions than female larvae. As there was no influence of resource availability, we conclude that the sex ratio of established populations was balanced at the selected study sites by available resources in the landscape. At the individual scale, sex and resource allocation were influenced in species-specific ways. As such, sex determination and resource allocation are essential life history properties of sexually reproducing organisms.

Individuality matters in human–wildlife conflicts: Patterns and fraction of damage‐making brown bears in the north‐eastern Carpathians

Abstract Effective, evidence‐based management is required to ensure long‐term coexistence between people and wildlife in an increasingly humanized world. Although behavioural individuality is recognized as a key factor affecting evolutionary and ecological processes, it has rarely been explicitly assessed in relation to human–wildlife conflicts. The ‘problem individual’ paradigm states that some conspecifics within a given population have a disproportionately large contribution to conflicts. To the best of our knowledge, no studies have so far systematically tested this assumption in large carnivores. Here, we investigated the variation in conflict behaviour among brown bears Ursus arctos within the population inhabiting the Polish Eastern Carpathians. We inspected all sites notified as damaged by bears in 2014–2017 to determine the number and sex of the individuals involved. We conducted systematic noninvasive genetic sampling to estimate the size of the local population by spatially explicit capture–recapture models. We assessed the fraction and sex ratio of damage‐making bears in relation to the population, as well as the behavioural patterns by classifying and differentiating between occasional and repetitive damage‐makers. Approximately one‐third of the estimated 72 (95% CI 45.2–115.5) brown bears inhabiting the Polish Eastern Carpathians were responsible for damage occurrence in the region. The majority of damage‐makers were female (65% vs. 35% of male), which reflected the sex ratio of the local population (0.57). Thirty‐three per cent of the damage‐making bears (i.e. nine individuals) were classified as ‘problem individuals’, exhibiting repetitive conflict behaviour. Synthesis and applications. This study provides evidence of intraspecific differences in conflict behaviour in a large carnivore species, the brown bear, and indicates that damage‐making behaviour is not exhibited with the same frequency by all individuals within a population. Managers and policy‐makers should be aware that targeting individuals involved in conflicts without reference to the whole population may lead to misleading conclusions or an incomplete picture of the mechanisms underlying the conflicts, and thus, to mismanagement. Unravelling the behavioural patterns of individual engagement in damage through large‐scale and population‐wide studies is needed to accurately assess the magnitude of damage and enhance human–wildlife coexistence in areas experiencing conflicts.

Demographic monitoring of the invasive ladder snake on Formentera (Balearic Islands, Spain)

AbstractThe ladder snake Zamenis scalaris was first reported in 2006 in Formentera (Balearic Islands, Spain), until then a snake‐free Mediterranean island. Since 2016, intense control campaigns have been carried out and, for the first time, snake captures over 2017–2020 have been used to analyze the sex ratio, age, fat percentage, population density, and seasonality of this invasive population. The male‐biased sex ratio found in the present work could be the result of capture biases caused by different detection probabilities between sexes. A reduction of snake body length over time was observed, which could indicate a depletion of the larger snakes due to intense snake capture. The highest capture frequencies of both sexes were reported in May and June, coinciding with the mate searching period in the species native range and indicating that snakes increase their movements during this period. Size‐specific survivorship curves indicated a drop in survivorship at medium sizes, which suggested a survival cost associated with reproduction, presumably due to increased mortality during the mating season. Population density decreased from 1.812 snakes/ha in 2017 to 0.669 snakes/ha in 2020. Evidence obtained in the present work has allowed to evaluate the main ecological aspects of Z. scalaris and the current state of the population of this invasive snake on the island of Formentera. Results showed that the population is well established in Formentera, but prolonged control campaigns have caused its decline. This study becomes a starting point to improve the management and control programs of invasive snake populations in the Balearic Islands. Long‐term control as well as the improvement of the detection and capture of adult females are strongly recommended to attempt the eradication of Z. scalaris in Formentera.

Gone with the wind: Negative genetic and progeny fitness consequences of habitat fragmentation in the wind pollinated dioecious tree Brosimum alicastrum.

Habitat fragmentation negatively affects population size and mating patterns that directly impact progeny fitness and genetic diversity; however, little is known about the effects of habitat fragmentation on dioecious, wind pollinated trees. We assessed the effects of habitat fragmentation on population sex ratios, genetic diversity, gene flow, mating patterns and early progeny vigor in the tropical dioecious tree, Brosimum alicastrum. We conducted our study in three continuous and three fragmented forest sites in a Mexican tropical dry forest. We used eight microsatellite loci to characterize the genetic diversity, gene flow via pollen distances and mean relatedness of progeny. We compared early progeny vigor parameters of seedlings growing under greenhouse conditions. Sex ratios did not deviate from 1:1 between habitat conditions, except for one population in a fragmented habitat, which was female biased. The genetic diversity of adult trees and their offspring was similar in both habitat conditions. Pollen gene flow distances were similar across habitat types; however, paternity correlations were greater in fragmented than in continuous habitats. Germination rates did not differ between habitat conditions; however, progeny from fragmented habitats produced fewer leaves and had a lower foliar area, total height, and total dry biomass than progeny from continuous habitats. Changes in mating patterns, because of habitat fragmentation, have negative effects on early progeny vigor. We conclude that negative habitat fragmentation effects on mating patterns and early progeny vigor may be a serious threat to the long-term persistence of tropical dioecious trees. This article is protected by copyright. All rights reserved.

Predictive factors for degenerative lumbar spinal stenosis: a model obtained from a machine learning algorithm technique

BackgroundDegenerative lumbar spinal stenosis (DLSS) is the most common spine disease in the elderly population. It is usually associated with lumbar spine joints/or ligaments degeneration. Machine learning technique is an exclusive method for handling big data analysis; however, the development of this method for spine pathology is rare. This study aims to detect the essential variables that predict the development of symptomatic DLSS using the random forest of machine learning (ML) algorithms technique.MethodsA retrospective study with two groups of individuals. The first included 165 with symptomatic DLSS (sex ratio 80 M/85F), and the second included 180 individuals from the general population (sex ratio: 90 M/90F) without lumbar spinal stenosis symptoms. Lumbar spine measurements such as vertebral or spinal canal diameters from L1 to S1 were conducted on computerized tomography (CT) images. Demographic and health data of all the participants (e.g., body mass index and diabetes mellitus) were also recorded.ResultsThe decision tree model of ML demonstrate that the anteroposterior diameter of the bony canal at L5 (males) and L4 (females) levels have the greatest stimulus for symptomatic DLSS (scores of 1 and 0.938). In addition, combination of these variables with other lumbar spine features is mandatory for developing the DLSS.ConclusionsOur results indicate that combination of lumbar spine characteristics such as bony canal and vertebral body dimensions rather than the presence of a sole variable is highly associated with symptomatic DLSS onset.

Temporal and spatial variations in local sex ratios in a suburban population of the European green toad Bufotes viridis

BackgroundSex ratios of animal populations are important factors of population demographics. In pond-breeding amphibians, the operational sex ratio (OSR) among the breeding population is usually male-biased. Also, in European green toads (Bufotes viridis), males usually outnumber females at breeding sites, while the sex ratio of the total adult population (ASR) is assumed to be balanced. It has been suggested that sex-specific breeding behavior causes male-predominance at the breeding sites. We used a dataset of 5 years of street patrols to test this hypothesis. For this we analyzed local sex ratios of green toads in terrestrial habitats and at two artificial breeding ponds. We expected temporal and/or spatial changes of local sex ratios which would indicate sex dependent differences in breeding behavior.ResultsOverall observed ASR among 2111 green toads, counted in the course of street patrols from 2016 to 2020, was slightly male-biased (ASR = 0.56, annual ASRs = 0.49–0.63). Based on the data of 1631 toads (920 males, 711 females) captured within a radius of 300 m around nine main breeding sites, temporal and spatial variations in local ASRs were evaluated. Resulting values were compared to the calculated OSR at two artificial breeding ponds in 2021 (645 adult: 553 males, 92 females). Estimates predict more equally distributed females and males prior to the main breeding season. During breeding season, males predominated at both breeding sites (B1: 0.83, B2: 0.89), whereas females are estimated to outnumber males in terrestrial habitats. Proportions of females highly significantly increased with advancing time of the year and increasing distance to the breeding sites. While males tended to accumulate in proximity to water bodies, females dispersed soon after breeding to more distant areas.ConclusionsObserved sex ratios in the studied green toad population changed with time and sampling site, deviating from the population-wide sex ratio. Expanding sampling effort in amphibian conservation assessments in time and space, i.e., outside the main breeding season and away from the breeding sites, would be important to encompass such variations.

Genetics as a novel tool in mining impact assessment and biomonitoring of critically endangered western chimpanzees in the Nimba Mountains, Guinea

AbstractWestern chimpanzees (Pan troglodytes verus) are Critically Endangered and Guinea is a key stronghold for this subspecies. However, Guinea is also rich in minerals with some of the highest‐grade iron‐ore deposits in the world. Specifically, the Nimba Mountains, home to western chimpanzees, is one of the sites under consideration for mining activities. To assess the impact of mining activities in the area, we used non‐invasive genetic sampling to estimate chimpanzee population size, sex ratio, community composition, and range boundaries on the western flank of the massif. The level of genetic diversity and affinity between communities was estimated and recommendations for future genetic censusing provided. Between 2003 and 2018, we collected 999 fecal samples of which 663 were analyzed using a panel of 26 microsatellites. We identified a minimum of 136 chimpanzees in four communities, with evidence of migratory events, a high level of shared ancestry and genetic diversity. We assessed sampling intensities and capture rates for each community. Saturation was reached in two communities with sampling between 3.2 and 4.3 times the estimated number of chimpanzees. Our findings highlight the utility of genetic censusing for temporal monitoring of ape abundance, as well as capturing migratory events and gauging genetic diversity and population viability over time. We recommend genetic sampling, combined with camera trapping, for use in future Environmental and Social Impact Assessments, as these methods can yield robust baselines for implementing the mitigation hierarchy, future biomonitoring and conservation management.

Population dynamics of Arctica islandica off Long Island (USA): an analysis of sex-based demographics and regional comparisons

The boreal bivalve Arctica islandica is an important fishery in the United States (US), yet very little is known about the resiliency of this species to fishing activity due to limited understanding of localized population demographics. Demographics including age frequency, recruitment patterns, mortality rates, and sexual dimorphism were evaluated for a population sampled off Long Island (LI, 40.09658°N 73.01057°W) and compared with samples from Georges Bank (GB, 40.72767°N, 67.79850°W) collected in 2015 and 2017, where GB was described in a previous study. This study supports evidence that this species is sexually dimorphic. Earlier assumptions of prolonged lapses in recruitment were not substantiated for either the GB or LI populations; yearly cohorts were observed for the past century, and both populations presented recruitment pulses in approximately 8-y periods. Estimated ages from this study are older than previously reported for the US Mid-Atlantic with the oldest animal represented by a 310-year-old male collected from LI. Simulated total mortality was higher at GB than LI, and higher for GB females than GB males, with simulated mean longevity estimates greater at LI than GB. The population sex ratio at GB was 1:1.1 (female:male), whereas the LI ratio was 1:1.4 and relatively deficient in large females. Recruitment into the populations occurs routinely with substantial hiatuses being rare and substantive year classes occurring at least decadally with lesser, but contributing, recruitment in most years in between. Routine recruitment may insulate this species from risks posed by overfishing to an extent not typical for other long-lived species.