Sibling and environmental correlates of adolescents’ perceptions of family environments: Ethnic group differences

Abstract

Hierarchical regression analyses and response surfaces were used in an investigation of relationships between sibling variables and adolescents’ perceptions of their family environments, after the impact on the perceptions of earlier family measures was taken into account. The analyses involved Australian adolescents and included 260 Anglo‐Australian, 120 Greek, and 90 Southern Italian families. Regression models included terms to test for possible linear, interaction, and curvilinear associations between the sibling and family environment variables. The analysis suggested the propositions that: (a) parents from different ethnic groups create different learning environments for their children and that there are ethnic‐group variations in how children perceive their family environments, (b) there are ethnic‐group variations in relationships between sibling variables and adolescents’ perceptions of their parents’ support for learning, and (c) within ethnic groups the relationships between sibling variables and perceived parental support for learning differ, depending on whether the support of fathers or mothers is being considered.     

Will granny save me? Birth status,survival, and the role of grandmothers in historical Finland

Grandmothers play a crucial role in families enhancing grandchild wellbeing and survival but their effects can be context-dependent, and the children born in poor conditions are most likely to benefit from the investments made by helping grandmothers. In this study, we examined, for the first time, whether grandmothers' presence modified associations between adverse birth status and survival up to 5 years of age. In detail, we verified, whether (i) firstborns, (ii) twins, (iii) children born within 24 months after their sibling, and (iv) children followed by short interval (i.e. their younger sibling was born within 24 months) survived better when either their maternal, paternal, or both grandmothers were present. Moreover, we evaluated whether illegitimate children survived better when the maternal grandmother was present. We used an extensive and largely pre-industrial demographic dataset collected from parish population registers kept by the Lutheran Church of Finland from years 1730–1895. We show that although grandmother presence cannot mitigate adverse effects of many poorer birth conditions, grandchildren whose next sibling was born after a short interval survived better when the maternal grandmother was present. Taken together, these findings highlight an important role of grandmothers in compensating the mother's investment in the new baby, thus enabling overall faster successful reproductive rate of mothers. Whilst the opportunity for grandmothers to mitigate the risks of adverse birth statuses is limited, this study does show - through the beneficial effect on survival for those with a short subsequent birth interval - that grandmothers can increase their daughters' and their own reproductive success.     

Does experience with competition matter? Effects of source competitive environment on mean and plastic trait expression in Erodium cicutarium

Interspecific competition is likely to act as an agent for selection on local scales, although evidence in plants is sparse so far. We hypothesize that in annual shade-avoiding grassland species, heterogeneity in the intensity of aboveground competition for light may shape patterns of genetic variation and induce phenotypic plasticity in traits affecting competitive ability. We collected maternal seed families of Erodium cicutarium from replicated high and low competition environments and exposed them to different levels of aboveground competition in a glasshouse. We examined effects of seed source and competition treatment on expression of plant traits related to competitive ability and fitness. Source environments with high levels of competition were significantly more heterogeneous in competition intensity at both intermediate (approx. 10 m) and small (approx. 0.1 m) spatial scales. Seed source and competition treatment both had highly significant effects on trait expression. Greater intensity of competition experienced by maternal plants was coupled with lower vegetative biomass production and slower growth rates, and at the same time lower abortion rates in the offspring. We interpret these findings as an indication of greater reproductive efficiency in the next generation, in response to competition experienced by parents. There was higher total phenotypic variability in the plants from high competition source sites, but equivalent levels of phenotypic plasticity across source-site competition levels; no costs of phenotypic plasticity were detected. We concluded that differences in competition intensity can lead to trait differentiation in the next generation. For E. cicutarium, experience with competition matters: it leads to substantial phenotypic differences and more total variability in the offspring generation.     

The patterning function of purines in the brine shrimp Artemia

In two Artemia wild-type sibling species originating from the Old and New Worlds, the processes underlying the construction of the naupliar body during embryonic development and the construction of the adult body during postembryonic development are disrupted by specific nutritional deficiencies and/or the administration of metabolic inhibitors. The species-specific phenotypic outcomes of these experimental disruptions on the construction of segments and the establishment of their identity, permit us to outline a model in which Hox genes would act as intermediary cogwheels fastened to a mechanism put in gear upstream by purine-mediated processes which would trigger downstream folic acid-mediated processes. The prevalent view that Hox genes can select for different developmental programmes, is challenged by this model whose relevancy is analysed in the context of our present knowledge on the master functions ascribed to Hox genes in developmental and evolutionary processes.     

Variation and covariation among life-history traits in Rumex acetosella from a successional old-field gradient

In this study morphological variation and the potential for competition to affect biomass and seedling selection of the families of five populations of Rumex acetosella L. sampled along a successional old-field gradient have been investigated. Seeds from 25 families were submitted to four competitive regimes: no competition (one plant per pot), medium competition (two plants/ pot taking plants from the same population), high within-population competition (four individuals from the same population in a pot) and high between-population competition (four individuals from two different populations in a pot). Eight traits were analysed after 3 months of growth for variation among families within populations. A significant difference among families within the two older populations was recorded for sexual biomass and related components. High sensitivity of these traits to density was observed in all populations except the youngest, suggesting specialization to particular environmental conditions in late successional populations, and a good adaptive capacity to buffer environmental variation in the pioneer population. Little significant interaction between competitive regimes and families within populations was found, i.e. genotypes within each population showed little variation in their response to environmental variation. Genotypic variance decreased with increasing competitive conditions for the majority of the traits. However, the percentage of variance in sexual reproduction explained by family was stable among treatments. Tradeoffs between vegetative reproduction and sexual reproduction were recorded at the population level along the successional gradient, with increasing competitive conditions. As succession proceeds, we observed a decrease in sexual reproduction and an increase in vegetative reproduction. At the family level, correlation among traits were similar when plants were grown in the absence of competition and at high density, with a significant negative correlation between sexual reproduction and vegetative reproduction. For both sprout number and sexual biomass, the performance of families grown under all the treatments was positively correlated. Together these results indicate allocational constraints on the reproductive biology of R. acetosella that may be favoured by natural selection and have influenced population differentiation along the successional gradient. However, they also revealed that the potential exists for evolutionary specialization through plasticity, in response to variation in environmental conditions.     

Effects of spatial pattern and relatedness in an experimental plant community

Many plant species show limited dispersal resulting in spatial and genetic substructures within populations. Consequently, neighbours are often related between each other, resulting in sibling competition. Using seed families of the annuals Capsella bursa-pastoris and Stachys annua we investigated effects of spatial pattern (i.e. random versus aggregated) on total and individual performance at the level of species and seed families under field conditions. At the level of species, we expected that inferior competitors increase, while superior competitors decrease their performance within neighbourhoods of conspecifics. Thus, we expected a species by spatial pattern interaction. Sibling competition, however, might reduce the performance of competitors, when genetically related, rather than non-related individuals are competing. Therefore, aggregations at the level of seed families could decrease the performance of competitors. Alternatively, if the opposite outcome would be observed, kin selection might be hypothesized to have occurred in the past. Because heavy seeds are expected to disperse less than light seeds, we further hypothesized that kin selection might be more likely to occur in superior competitors with heavy, locally dispersed seeds (e.g. Stachys) compared to inferior competitors with light, more distantly dispersed seeds (e.g. Capsella). We found a significant species by spatial pattern interaction. Indeed, the inferior competitor, Capsella, showed increased reproductive biomass production in aggregated compared to random patterns. Whereas, the performance of the superior competitor, Stachys, was to some extent decreased by intraspecific aggregation. Although statistically not significant, effects of intrafamily aggregations tended to be rather negative in Capsella but positive in Stachys. Our results confirmed that spatial patterns affect growth and reproduction of plant species promoting coexistence in plant communities. Although, we could not provide strong evidence for sibling competition or kin selection, our results suggested that competition among relatives was more severe for Capsella (lighter seeds) compared to Stachys (heavier seeds).     

Inferring Diffusion Dynamics from FCS in Heterogeneous Nuclear Environments

Fluorescence correlation spectroscopy (FCS) is a noninvasive technique that probes the diffusion dynamics of proteins down to single-molecule sensitivity in living cells. Critical mechanistic insight is often drawn from FCS experiments by fitting the resulting time-intensity correlation function, G(t), to known diffusion models. When simple models fail, the complex diffusion dynamics of proteins within heterogeneous cellular environments can be fit to anomalous diffusion models with adjustable anomalous exponents. Here, we take a different approach. We use the maximum entropy method to show—first using synthetic data—that a model for proteins diffusing while stochastically binding/unbinding to various affinity sites in living cells gives rise to a G(t) that could otherwise be equally well fit using anomalous diffusion models. We explain the mechanistic insight derived from our method. In particular, using real FCS data, we describe how the effects of cell crowding and binding to affinity sites manifest themselves in the behavior of G(t). Our focus is on the diffusive behavior of an engineered protein in 1) the heterochromatin region of the cell’s nucleus as well as 2) in the cell’s cytoplasm and 3) in solution. The protein consists of the basic region-leucine zipper (BZip) domain of the CCAAT/enhancer-binding protein (C/EBP) fused to fluorescent proteins.     

Resource allocation during ontogeny is influenced by genetic,developmental and ecological factors in the horned beetle,Onthophagus taurus

Resource allocation trade-offs arise when developing organs are in competition for a limited pool of resources to sustain growth and differentiation. Such competition may constrain the maximal size to which structures can grow and may force a situation in which the evolutionary elaboration of one structure may only be possible at the expense of another. However, recent studies have called into question both the consistency and evolutionary importance of resource allocation trade-offs. This study focuses on a well-described trade-off between the horns and eyes of Onthophagus beetles and assesses the degree to which it is influenced by genetic, developmental and ecological conditions. Contrary to expectations, we observed that trade-off signatures (i) were mostly absent within natural populations, (ii) mostly failed to match naturally evolved divergences in horn investment among populations, (iii) were subject to differential changes in F₁ populations derived from divergent field populations and (iv) remained largely unaffected by developmental genetic manipulations of horn investment. Collectively, our results demonstrate that populations subject to different ecological conditions exhibit different patterns of, and differential plasticity in, resource allocation. Further, variation in ecological conditions, rather than canalized developmental mechanisms, may determine whether and to what degree morphological structures engage in resource allocation trade-offs.     

Adaptive developmental plasticity in growing nestlings: sibling competition induces differential gape growth

Sibling competition has been shown to affect overall growth rates in birds. However, growth consists on the coordinated development of a multitude of structures, and there is ample scope for developmental plasticity and trade-offs among these structures. We would expect that the growth of structures that are used in sibling competition, such as the gape of altricial nestlings, should be prioritized under intense competition. We conducted an experiment in the spotless starling (Sturnus unicolor), cross-fostering nestlings to nests with different levels of sibling competition. We predicted that nestlings subjected to higher levels of sibling competition should develop larger gapes than control birds. We found that, halfway through the nestling period, overall size (a composite index of mass, wing, tarsus and bill) was reduced in nests with intense sibling competition, whereas gape width remained unaffected. At the end of the nestling period, experimental nestlings had wider gapes than controls. Additionally, a correlative study showed that nestling gape width increased when feeding conditions worsened and overall size decreased. These patterns could either be due to increased growth of gape flanges or to delayed reabsorption of this structure. Our results show that birds can invest differentially in the development of organs during growth, and that the growth of organs used in sibling competition is prioritized over structural growth.     

CHARACTERIZING SELECTION ON PHENOTYPIC PLASTICITY IN RESPONSE TO NATURAL ENVIRONMENTAL HETEROGENEITY

Adaptive genetic differentiation and adaptive phenotypic plasticity can increase the fitness of plant lineages in heterogeneous environments. We examine the relative importance of genetic differentiation and plasticity in determining the fitness of the annual plant, Erodium cicutarium, in a serpentine grassland in California. Previous work demonstrated that the serpentine sites within this mosaic display stronger dispersal‐scale heterogeneity than nonserpentine sites. We conducted a reciprocal transplant experiment among six sites to characterize selection on plasticity expressed by 180 full‐sibling families in response to natural environmental heterogeneity across these sites. Multivariate axes of environmental variation were constructed using a principal components analysis of soil chemistry data collected at every experimental block. Simple linear regressions were used to characterize the intercept, and slope (linear and curvilinear) of reaction norms for each full‐sibling family in response to each axis of environmental variation. Multiple linear regression analyses revealed significant selection on trait means and slopes of reaction norms. Multivariate analyses of variance demonstrated genetic differentiation between serpentine and nonserpentine lineages in the expression of plasticity in response to three of the five axes of environmental variation considered. In all but one case, serpentine genotypes expressed a stronger adaptive plastic response than nonserpentine genotypes.     

Increased sibling competition does not increase testosterone or corticosterone levels in nestlings of the spotless starling (Sturnus unicolor)

Nestling begging in passerine birds is a complex behaviour that is shaped by a multitude of ecological factors and could be physiologically mediated by varying levels of steroid hormones. Previous research has shown links between sibling competition and testosterone and corticosterone in several bird species. The spotless starling (Sturnus unicolor) is a medium sized passerine in which nestlings compete intensively for resources, often resulting in marked size hierarchies that can have profound effects on their fitness. We tested the hypothesis that an increase in sibling competition levels would result in increases in testosterone and corticosterone in this species. To this end we conducted a brood size manipulation, creating small, medium and large broods. This manipulation had the expected effect on morphology: nestling size and mass decreased with increasing brood size. Androgen levels varied in response to brood size manipulation but, contrary to expectations, the largest concentrations were found in reduced brood sizes. Corticosterone levels increased with increasing brood size, but this effect disappeared when we corrected for the time taken to process nestlings. Cell-mediated immune response was found to decrease with increasing brood size and testosterone levels. The results suggest that the proposed link between testosterone and corticosterone and sibling competition does not hold in this species, and underlines the diversity of species-specific responsiveness to steroids.     

No evidence for competition between cytotoxic T-lymphocyte responses in HIV-1 infection

Strong competition between cytotoxic T-lymphocytes (CTLs) specific for different epitopes in human immunodeficiency virus (HIV) infection would have important implications for the design of an HIV vaccine. To investigate evidence for this type of competition, we analysed CTL response data from 97 patients with chronic HIV infection who were frequently sampled for up to 96 weeks. For each sample, CTL responses directed against a range of known epitopes in gag, pol and nef were measured using an enzyme-linked immunospot assay. The Lotka–Volterra model of competition was used to predict patterns that would be expected from these data if competitive interactions materially affect CTL numbers. In this application, the model predicts that when hosts make responses to a larger number of epitopes, they would have diminished responses to each epitope and that if one epitope-specific response becomes dramatically smaller, others would increase in size to compensate; conversely if one response grows, others would shrink. Analysis of the experimental data reveals results that are wholly inconsistent with these predictions. In hosts who respond to more epitopes, the average epitope-specific response tends to be larger, not smaller. Furthermore, responses to different epitopes almost always increase in unison or decrease in unison. Our findings are therefore inconsistent with the hypothesis that there is competition between CTL responses directed against different epitopes in HIV infection. This suggests that vaccines that elicit broad responses would be favourable because they would direct a larger total response against the virus, in addition to being more robust to the effects of CTL escape.     

Reproductive strategies of Datura ferox, an abundant invasive weed in agro-ecosystems from central Argentina

Crop weeds develop in highly modified environments and are one of the most severe threats to agriculture worldwide, because their invasive nature determines competition for resources with crops and at the same time they can be hosts for pests and diseases. The information provided in this work is relevant both in scientific and technical terms, contributing to the design of effective strategies for the control of Datura ferox (Solanaceae). The aims of this work were to: (a) evaluate the reproductive strategies of D. ferox relative to fruit and seed production, (b) analyze the relationship between reproductive traits and persistence of these populations in agro-ecosystems of central Argentina, and (c) discuss different strategies to control crop weeds based on the knowledge of their reproductive ecology. D. ferox presented a great reproductive capacity that would not be constrained by limited pollen availability or pollinators in the populations studied. Flowers were pollinated by sphingids, coleopterans and Apis mellifera. The populations were self-compatible and autogamous; however, they exhibited higher fruiting percentages by natural pollination. Fruits produced by autogamy and geitonogamy had larger size and lower seed number and mass than those derived from natural pollination and xenogamy. D. ferox has combinations of traits (i.e., two flowering peaks, interactions with different pollinators, seed production after autogamy or xenogamy) that provide ecological advantages for establishment and survival processes in agro-ecosystems, hindering the species’ control. Control strategies might be improved if D. ferox abundance would be reduced before flowering to avoid fruit and seed production. This management strategy should be consistent over several years because the soil seed bank would allow population recovery in subsequent years.     

Fluctuating food resources influence developmental plasticity in wild boar

To maximize long-term average reproductive success, individuals can diversify the phenotypes of offspring produced within a reproductive event by displaying the ‘coin-flipping’ tactic. Wild boar (Sus scrofa scrofa) females have been reported to adopt this tactic. However, whether the magnitude of developmental plasticity within a litter depends on stochasticity in food resources has not been yet investigated. From long-term monitoring, we found that juvenile females produced similar-sized fetuses within a litter independent of food availability. By contrast, adult females adjusted their relative allocation to littermates to the amount of food resources, by providing a similar allocation to all littermates in years of poor food resources but producing highly diversified offspring phenotypes within a litter in years of abundant food resources. By minimizing sibling rivalry, such a plastic reproductive tactic allows adult wild boar females to maximize the number of littermates for a given breeding event.     

Evolutionary ecology along invasion fronts of the annual grass Aegilops triuncialis

Over the last two decades, Aegilops triuncialis (barbed goatgrass) has rapidly spread into many annual grassland and serpentine soil sites within California, USA. The capacity of this species to invade edaphically stressful serpentine soil is especially unusual. It is unclear whether genetic differentiation, phenotypic plasticity, or both have allowed A. triuncialis to invade competitive (i.e. high productivity non-serpentine annual grassland) and edaphically stressful (i.e. low productivity serpentine) environments. We used a reciprocal transplant field experiment to examine the effects of plasticity and genetic variation on A. triuncialis phenology and demography along invasion fronts associated with interspecific competition and edaphic gradients. We reciprocally transplanted seeds collected behind invasion fronts (core subpopulations) and along invasion fronts (edge subpopulations). For both gradient types we measured higher reproduction and population growth at invasion front edges. This was true for both edge and core subpopulation seed sources, suggesting that phenotypic plasticity may facilitate invasive spread. Consistent planting site effects indicated that phenotypic plasticity is a primary contributor to A. triuncialis demographic responses along interspecific competition gradients. In contrast, significant seed source effects suggest genetic differentiation along invasion fronts in serpentine edaphic gradients. Although persistent maternal environmental effects cannot be ruled out entirely, seed source effects suggest genetic differences between serpentine subpopulations located behind and beyond the invasion fronts for plant survival, plant size, total seed production, and individual seed size. Rapid expansion of A. triuncialis in California may reflect an evolutionary capacity in this species for both phenotypic plasticity and genetic differentiation.     

Developmental plasticity of thermal tolerances in temperate and subtropical populations of Drosophila melanogaster

Variation in temperature imposes selection pressures on organisms. In variable environments, organisms must adopt fixed or plastic strategies that enable persistence over a broad range of temperatures. In coarse-grained environments, where the thermal variation among generations exceeds that within generations, selection should favor developmental plasticity. Here, we compare the degree of developmental plasticity of thermal tolerances between populations of Drosophila melanogaster from environments with relatively high (Marlton, NJ, USA) and relatively low (Miami, FL, USA) variance in temperature among generations. We predicted that flies from Marlton would exhibit a greater plasticity of thermal tolerances than would flies from Miami. Flies from both populations were reared in three ecologically relevant treatments, after which we assessed knockdown and chill-coma recovery times. Flies from both populations responded plastically to temperature, but flies from New Jersey did not exhibit greater plasticity. Our results complement previous comparative studies and indicate that selection favors plasticity of thermal tolerances equally in these populations.     

Optimal root proliferation strategies: the roles of nutrient heterogeneity, competition and mycorrhizal networks

Background and Aims Plants proliferate roots in order to acquire nutrients, typically contending with heterogeneous resources and competing neighbours. A mathematical model was developed to identify optimal root proliferation strategies in patchy nutrient environments. The impact of joining mycorrhizal networks was also assessed. Methods A simple model of growth and competition in one spatial dimension was implemented within a genetic algorithm to obtain optimal proliferation strategies under different scenarios of resource distribution, and in the presence or absence of local competition and large-scale mycorrhizal networks. Results A strong proliferation response emerged for isolated plants in heterogeneous environments with low resources, and also for plants growing in competition. Even in statistically homogeneous environments, the presence of competition conferred a selective advantage to plants proliferating in the direction of the most recently acquired patch. In the presence of mycorrhizal networks, the optimal strategy switched from symbiosis to proliferation driven growth as the relative cost of acquiring resources through the networks increased. Conclusions The optimal proliferation response in a given scenario was governed by a hierarchy of factors: resource levels and distribution; the presence or absence of competition; and the marginal benefit of obtaining resources via symbiotic relationships with mycorrhizas.     

Inter- and intraspecific variability in the chemical composition of the mineral phase of cements from several tube-building polychaetes

Several species of marine polychaetes reside in individual protective tubes. These tubes may be agglomerated in patches of varied sizes with very high densities, or form massive reef-like mounds which can be stretch over several kilometers. These polychaetes can thus be considered as the most important building organisms after corals in coastal environments. We especially focused on several species belonging to the families of Sabellariidae, Terrebeliidae and Pectinariidae. Tubes grains are glued together with biomineralized cement secreted from a building organ connected to specialized glands. Different methods of micro-analysis were used to analyze the biomineral components of these cements for four varyingly gregarious tube-building polychaetes: Lanice conchilega, Pectinaria koreni, Sabellaria alveolata and Phragmatopoma caudata. The aim of this study is to describe and compare the inter- and the intraspecific variability in the main biomineral components of cement at local, regional and continental scales. Scanning Electron Microscopy confirms an identical structure of the cement within species of Sabellariidae in Europe and America. Electron Probe Micro-Analysis (EPMA) confirms the presence of calcium, phosphorus, and magnesium plus traces of manganese in all cements, with varying concentrations of these elements at different locations for the same species or for different species at the same location. Finally, our dataset is compared with previous studies from literature.