La sélection de la parentèle est le concept actuellement le plus fréquemment avancé pour justifier l’évolution et le maintien d'une caste ouvrière stérile chez les Hyménoptères sociaux. La fourmi méditerranéenne Cataglyphis cursor possède plusieurs traits biologiques qui font de cette espèce un modèle particulièrement intéressant pour tester les prédictions de la théorie de la sélection de la parentèle, le plus important d'entre eux étant la capacité des ouvrières, qui ne s'accouplent jamais, à produire une descendance mâle (haploïde) par parthénogenèse arrhénotoque, ou femelle (diploïde) par parthénogenèse thélytoque. Nos analyses génétiques, basées sur des marqueurs microsatellites développés au préalable pour cette espèce, ont révélé que les reines utilisent la reproduction sexuée et asexuée respectivement pour la production de la caste ouvrière et reproductrice. L'analyse du pedigree des reproductrices issues de la reproduction asexuée nous a permis d'identifier le mécanisme cytologique de la parthénogenèse thélytoque et d'estimer la proportion de reines issues de la reproduction des ouvrières au sein de la population. De plus, bien que les reines soient capables de produire une descendance diploïde (femelle) par parthénogenèse thélytoque, elles ont conservé la reproduction sexuée pour la caste ouvrière et s'accouplent avec plusieurs mâles. Ceci indique que la reproduction sexuée a une fonction importante au niveau de la colonie, et nous avons testé certaines des hypothèses avancées pour justifier l'évolution de la polyandrie. Finalement, nous avons étudié l'impact des stratégies de dispersion de cette espèce sur le sex-ratio de la descendance sexuée. Ces résultats confirment l'intérêt que représente l'étude des stratégies reproductrices chez les Hyménoptères sociaux pour tester les prédiction de diverses théories en biologie évolutives et ouvrent également de nouvelles perspectives de recherche, tant chez C. cursor que chez d'autres espèces appartenant au genre Cataglyphis. / Kin selection is, to date, the most widely accepted theory to justify the evolution of a sterile worker caste among social Hymenoptera. The Mediterranean ant Cataglyphis cursor represents an interesting biological model for several reasons, the most important of them being the ability for unmated workers to produce haploid (male) offspring, through arrhenotokous parthenogenesis, and diploid (female) offspring, through thelytokous parthenogenesis. Our genetic analyses, based on microsatellite loci developed for this purpose, revealed that queens selectively use sexual and asexual reproduction to produce workers and sexuals, respectively. Pedigree analyses allowed us to identify the cytological mechanism involved in thelytokous parthenogenesis and to estimate the proportion of worker-produced queens in the study population. Although C. cursor queens do not require mating to produce diploid offspring, they have retained sexual reproduction and mate multiply with up to 8 males. This suggests that sexual reproduction has important benefits for colony function, and we tested several hypotheses accounting for the evolution of polyandry. Eventually, we studied the effect of dispersal strategies on sex-ratio of the sexual brood. These results confirm the interest of investigating the reproductive strategies of social Hymenoptera to test the predictions of diverse theories in the field of evolutionary biology, and open new research perspectives in C. cursor and other ants of the Cataglyphis genera. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

The most speciose group of fishes in the Gulf of Mexico is the dragonfishes (Family: Stomiidae). These fishes are dominant mesopelagic predators occurring throughout the world’s oceans, including the Antarctic seas. Little is known regarding their reproductive ecology, a consequence attributed to insufficient sample sizes of mature adults due to inadequacies of sampling gear; larger, sexually mature stomiid adults are more adept at net avoidance, thereby obfuscating synoptic reproductive biology studies. Between 2010-2011, the Offshore Nekton Sampling and Analysis Program was initiated in the northern Gulf of Mexico over all four seasons using a discrete-depth sampling system (MOCNESS) and a large, commercial-sized midwater trawl (Irish herring trawl). Gonads were dissected from 714 individuals belonging to 47 species of stomiids, of which the most 12 abundant species were subjected to detailed analysis. Female ovaries possessed an asynchronous oocyte development, suggesting that females are iteroparous. Males exhibited a similar pattern. Chauliodus sloani had an overall sex ratio that favored females, and was the only species in which the overall sex ratio significantly differed from the expected 1:1 ratio (male:female) (P < 0.05). Considering just mature specimens, Aristostomias xenostoma, Malacosteus niger, Eustomias fissibarbis, and Eustomias schmidti had sex ratios that favored males, and were the only species in which the sex ratio significantly differed from even (P < 0.05). Eustomias hypopsilus was the only species in which mean biomass significantly differed between sexes. Histological analysis and binomial regression indicated that females of the 12 most abundant species matured at larger lengths than males. Generally, only females were present in the larger size classes, suggesting that females also become larger than males. Size distribution plots by gear type to assess gear selectivity revealed two patterns: the MOCNESS caught fewer specimens per species than the Irish herring trawl, and the MOCNESS caught predominantly smaller specimens. These data are essential for ecosystem-based modeling of global deep-pelagic ecosystems, which contain the overwhelming majority of Earth’s fish biomass.

Magister Philosophiae - MPhil / In many countries, an enumeration of all household members remains the most important source of population statistics. According to Statistics South Africa, two population censuses and quite a few household surveys have taken place across the country. The quality of data recorded varies according to the operation. Despite great improvement in data collection and analysis capacities,some of the demographic data provided have not been assessed in terms of quality. The aim of this study was to ascertain the accuracy of demographic data on age and sex collected and the coverage during the population census 2001, General Household Surveys (2004 and 2007), Labour Force Surveys (2005 and 2007) and Community survey 2007 in South Africa. Two methods were applied to assess the quality of data. First, the direct method consists of checking the content and coverage (errors during enumeration, errors of exploitation, concordance in questionnaire). Second, the indirect method lies in the calculation of some indexes, age ratios,sex ratios, graphing of population pyramids and sex ratios curves. The indexes are Whipple’s index, Myer’s index and the Combined index of United Nations. Therefore, the main variables of interest are age, sex, place of residence and ethnic groups. Differentials in the quality according to declaration on age by gender, by ethnic group, by place of residence have been explored. This study has identified some variations in different indexes between 2001 and 2007 and has also evaluated the ethnic, gender and regional differentials. Comparison between indexes of each instrument has been done to measure some variations over years. Also, time-space comparisons were conducted across indexes of different instruments. The quality of data on age was better at national level compared to provincial level. Therefore, based on the measurements and patterns observed in the census and surveys data, the study has made some recommendations on the need for an integrated approach to reduce the gap and improve the quality of declarations on age and sex.

By controlling the inheritance of sex, the sex determination mechanism constrains sex allocation strategies and sex ratio adaptation; however, sex ratio selection also influences the evolution of sex determination mechanisms. Much of the sex determination literature focuses on how sex determination mechanisms transition between genetic and environmental factors (i.e. GSD vs. ESD), and if genetic sex factors are involved, how many (e.g. chromosomal vs polygenic systems). The study of sex allocation largely focuses on deviations in sex ratio from a theoretically 1:1 evolutionarily stable strategy, such as when sex ratios reflect ‘cost’ differences between the sexes. Tigriopus californicus is a tidepool copepod with polygenic sex determination, and shows wide variability in sex ratios in the field and lab that cannot be explained by genetic and stochastic processes alone, which suggests that an environmental variable might influence sex ratio. Females and their offspring were fed diets of different nutritional quality in a crossed design, and the sex ratio of each clutch was recorded for up to 8 clutches from a given female: this design allowed the influence of female diet vs. that of her offspring to be distinguished. The clutch sex ratio changed over the laying order according to the offspring’s diet, which is evidence for environmental sex determination in this species. Sex ratio also showed the influence of maternal diet, consistent with sex allocation theory. While dietary carotenoids showed no association with sex ratio or clutch size, long chain polyunsaturated fatty acids (particularly EPA and DHA) were implicated as the agent of sex ratio effect, providing a direction for future studies. The situation of T. californicus at the intersection of major themes in sex evolution makes this system an ideal model for selection studies. / Graduate / 2018-09-13

Environmental constraints can limit a population to a certain size, which is usually called the carrying capacity of a habitat. Besides to this 'external' factor, which is mainly determined by the limitation of resources, we investigate here another set of population-intrinsic factors that can limit a population size significantly below the maximum sustainable size. Firstly, density-independent mortality is a prominent factor in all organisms that show age-related and/or accidental death. Secondly, in sexually reproducing organisms the sex ratio and the success of pairing is important for finding reproductive partners. Using a simple model, we demonstrate how sex ratio, mating success and gender-specific mortality can strongly affect the speed of population growth and the maximum population size. In addition, we demonstrate that density-independent mortality, which is often neglected in population models, adds a very important feature to the system: it strongly enhances the negative influence of unbiased sex ratios and inefficient pairing to the maximum sustainable population size. A decrease of the maximum population size significantly affects a population's survival chance in inter-specific competition. Thus, we conclude that the inclusion of density-independent mortality is crucial, especially for models of species that reproduce sexually. We show that density-independent mortality, together with biased sex ratios, can significantly lower the abilities of a population to survive in conditions of strong inter-specific competition and due to the Allee effect. We emphasize that population models should incorporate the sex ratio, male success and density-independent mortality to make plausible predictions of the population dynamics in a gender-structured population. We show that the population size is limited by these intrinsic factors. This is of high ecological significance, because it means that there will always be resources available in any habitat that allows other species (e.g., invaders) to use these resources and settle successfully, if they are sufficiently adapted.

Two important relationships in parasitoid evolutionary ecology are those between adult size and fitness and between host quality and sex ratio. Sexually differential size-fitness relationships underlie predicted sex-ratio relationships. Despite each relationship receiving considerable attention, they have seldom been studied simultaneously or using field data. Here we report the biology of Anoplius viaticus paganus Dahlbom, a little known parasitoid of spiders, using field and laboratory data. We found that larger foraging females were able to select larger host spiders from the field, thus identifying a relatively novel component of the size-fitness relationship. Larger offspring developed from larger hosts and, in agreement with the prediction of the host quality model of sex allocation, were generally female. Data on the size-fitness relationship for males are lacking and, in common with many prior studies, we could not evaluate sexually differential size-fitness relationships as an explanation for the observed sex-ratio patterns. Nonetheless, A. v. paganus exhibited one of the strongest relationships between host size and offspring sex ratio yet reported.

The observation that more boys were born than girls was noted in the late 1660’s. Recent studies suggest the secondary sex ratio (SSR) is declining in industrialized countries. SSR is proposed as a sentinel for reproductive health. Declining SSR may reflect environmental factors or other influences of reproductive outcomes. We evaluated maternal age, birth order and SSR in the Old Order Amish (OOA), a homogenous sub-group with large family sizes. We used data from the Anabaptist Genealogy Database consisting of records for live births from 1696-2003. We used t-tests to compare mean maternal age and birth order by offspring sex, ANOVA to evaluate whether SSR has changed over time, and logistic regression for multivariable models. We evaluated clustering of SSR within families using random effects models and likelihood ratio tests of random effects. Maternal age was not associated with SSR (OR=1.003 [95% CI, 0.995-1.010), even after adjusting for birth order (AOR=1.000 [95% CI, 0.989-1.012). Similarly, we did not find an association between birth order and SSR in both unadjusted models (OR=1.007 [95% CI, 0.991-1.022), and those adjusted for maternal age (AOR= 1.006 [95% CI, 0.982-1.032]). The proportion of male births varied, however, there was no significant trend overtime. Lastly, we found a significant random effect (P<0.05), which may provide indication that having male births is heritable in families. Conclusions: Neither maternal age nor birth order is associated with the sex of an offspring. These findings suggest that decreases in SSR are unrelated to demographic factors, and rather may be related to other factors such as environmental exposures or other xenobiotic chemicals. These results may be relevant in providing information to the leading indicators to the decline in SSR.

Many management strategies are available to fishery managers to improve the sustainability of a fishery; however, it is not always clear how implemented strategies interact with the demographics of the exploited species. Management decisions are often made in order to maximize egg production and recruitment or to preserve specific size classes to increase reproductive output. Consequences of these strategies could include variation from a natural size structure of the population, exaggerated sexual dimorphism, skewed sex ratios, and suboptimal mating conditions. To examine the possibility of these consequences, I ran a series of deterministic models to simulate the fished and unfished population dynamics of two clawed lobster species, American lobster (Homarus americanus) and European lobster (Homarus gammarus), under a variety of management strategies. Protection of ovigerous females takes two forms in this model. The American fishery in the Gulf of Maine requires fishers to v-notch ovigerous females for up to four years of protection from fishing. The European fishery in southern Norway bans the harvest of ovigerous females, which translates to one year of protection. I compared the relative impact of the two levels of ovigerous female protections on factors that may be important for reproductive success: size structure, dimorphism, sex ratio, and egg production for both species. I then considered a case study on European lobster to evaluate the interaction of a no-take marine protected area with a slot limit to compare relative impacts to egg production, overall size structure and dimorphism. Results showed that American lobster females benefitted greatly from strict protections such as v-notching in terms of mean size increase and egg production, but mean size dimorphism and the overall proportion of females also increased with higher fishing pressure. European lobster females also benefitted from protections, but less dramatically than American lobsters, and with lower size dimorphism. In the case study, European lobsters benefited most from the implementation of a no-take marine protected area in combination with a slot limit to preserve the largest individuals of both sexes which improved overall egg production. By taking a simulation approach to evaluate these different management strategies on two closely related species of lobster, this thesis provides a basis for understanding how fishery decisions can achieve their sustainability goals in addition to quantifying some of the unintended impacts of management on parameters that may be important to overall reproductive success. / Master of Science / Fishery managers make decisions about a fishery based on the species' biology to optimize catch while also ensuring that enough individuals remain to keep the population alive for years to come. However, it is not always clear what types of unintended consequences these decisions may have. Management decisions are often made in order to maximize egg production, to keep small individuals alive until they can reproduce, or to preserve the large individuals that have high reproductive potential. Some consequences of these strategies could include a reduction in the number of large individuals with high fishing pressure, increased female body size compared to males, unequal numbers of females and males, and less optimal conditions for mating. To examine the possibility of these consequences, I ran a series of models to simulate the fished and unfished populations of two clawed lobster species, American lobster (Homarus americanus) and European lobster (Homarus gammarus), under a variety of management strategies. The American lobster fishery in the Gulf of Maine requires a practice known as v-notching, which protects egg-bearing females for up to four years. The Norwegian fishery for European lobster bans the harvest of egg-bearing females, which is protection that lasts for one year. I compared the impact of the two types of egg-bearing female protections on factors that may be important for reproductive success: abundance of large lobsters, unequal numbers of females and males, difference in size between females and males, and overall production of eggs for both species. I then considered a case study on European lobster to test how a no-take marine protected area and a slot limit (minimum and maximum harvest size limits) affected those same factors. Results showed that American lobster females benefited greatly from longer lasting protections by growing to larger sizes and producing more eggs, but the average size difference between females and males and the overall proportion of females also increased as fishing became more intense. European lobster females also benefitted from protections, but less dramatically than American lobsters, and with lower mean differences in size between females and males. In the case study, European lobsters benefitted most from the no-take marine protected area in combination with a slot limit to preserve the largest individuals of both sexes which improved overall egg production. Using a simulation makes it easier to tease apart the effects of these different management strategies on two closely related species of lobster. This thesis helps managers see how fishery decisions affect lobsters in both desired and unintended ways. With this information, managers can better improve the sustainability of the fishery through considering what a specific species needs to improve reproductive success.

This thesis studies the relationship between a skewed sex ratio and female empowerment in India. The study uses cross-sectional survey data from 2015-16, defining empowerment with an index that compiles questions directed toward women regarding if they have been subjected to violence and violations by their husbands or partners. We investigate if there is a negative relationship between sex ratio and the empowerment index by examining previous studies as well as conducting a multivariable regression analysis. The results show a statistically significant negative relationship at the 5% significance level when controlling for son preference, wealth index, education, habit of reading the news, and identification as Hindu and Muslim respectively. Furthermore, we find that a negative correlation persists when separately performing the regression for the wealth index levels “middle” and “richer”. Although statistically significant, the coefficients are relatively small and the economic significance of the results is hence debatable.

The Trivers-Willard hypothesis predicts a sex ratio bias contingent on maternal condition in species characterized by variation in male reproductive success. A male-biased sex ratio among mothers in good condition, and a female-biased sex ratio among mothers in poor condition is expected. Studies in humans have thus far provided mixed answers to the question of whether or not sex ratio is affected by maternal condition. The present study assessed whether or not the introduction of a western cash economy influenced the observed secondary sex ratio in Nepal's Khumbu region. Because acculturated villages provided better access to the cash economy and to health facilities, residence in an acculturated village was used as a proxy for "good" maternal condition. I analyzed demographic data gathered by survey in 1971 and 1982. The sample included 734 children from the 1971 survey and 1598 children from the 1982 survey. Using Poisson regression I analyzed the extent to which the sex ratios in age-stratified groups differed between the acculturated and unacculturated villages. In the 1971 dataset, the younger women in the acculturated villages displayed a significantly higher (p=.014) proportion of male offspring. It is likely that older women were subjected to minimal acculturation effects during their child-bearing years and among these data there was a lack of significant deviation between acculturated and unacculturated post-menopausal women. The rapid overall increase in acculturation between 1971 and 1982 likely made conditions in the two sets of villages much more similar by 1982. The results of this study underscore the impact that the transition to a market economy had on women in Nepal's Khumbu region. / Anthropology