Environmental Sources Of Variation Research Articles

Elevated fish densities extend kilometres from oil and gas platforms.

Thousands of offshore oil and gas platforms have been installed throughout the world's oceans and more structures are being installed as part of the transition to renewable energy. These structures increase the availability of ecological niches by providing hard substrate in midwater and complex 3D habitat on the seafloor. This can lead to 'hotspots' of biodiversity, or increased densities of flora and fauna, which potentially spill over into the local area. However, the distances over which these higher densities extend (the 'range of influence') can be highly variable. Fish aggregate at such structures, but the range of influence and any implications for wider fish populations, are unclear. We investigated the relationship between fish and platform areal densities using high resolution fisheries acoustic data. Data were collected in the waters surrounding the vessel exclusions zones around 16 oil and gas platforms in the North Sea, and throughout the wider area. We estimated densities of schooling fish using echo-integration, and densities of non-schooling fish using echo-counting. At 10 platforms, non-schooling fish densities were elevated near the platform relative to background levels in the equivalent wider area. The range of influence, defined here as the range to which fish densities were elevated above background, varied from 0.8 to 23 km. In areas of high platform density, fish schools were encountered more often, and non-schooling fish densities were higher, when controlling for other sources of environmental variation. This is the first time such long-range effects have been identified; previously, ranges of influence have been reported in the order of just 10s-100s of metres. These findings suggest that the environmental impact of these structures may extend further than previously thought, which may be relevant in the context of upcoming management decisions around the decommissioning of these structures.

Impact of climate change on long-term damage detection for structural health monitoring of bridges

The effects of operational and environmental variability have been posed as one of the biggest challenges to transit structural health monitoring (SHM) from research to practice. To deal with that, machine learning algorithms have been proposed to learn from experience based on a reference data set. These machine learning algorithms work well if the operational and environmental conditions under which the bridge operates do not change over time. Meanwhile, climate change has been posed as one of the biggest concerns for the health of bridges. Although the uncertainty associated with the magnitude of the change is large, the fact that our climate is changing is unequivocal. Therefore, it is expected that climate change can be another source of environmental variability, especially the temperature. So, what happens if the mean temperature changes over time? Will it significantly affect the dynamics of bridges? Will the reference data set used for the training of algorithms become outdated? Are machine learning algorithms robust enough to deal with those changes? This is a pioneering work on the impact of climate change on the long-term damage detection in the context of bridge SHM. A classifier rooted in machine learning is trained using one-year data from the Z-24 Bridge in Switzerland and tested with current and future data. Three climate change scenarios are assumed, centered in three future periods, namely 2035, 2060, and 2085. This study concludes that climate change may be seen as another source of operational and environmental variability to be considered when using machine learning algorithms for long-term damage detection.

Early-life telomeres are influenced by environments acting atmultiple temporal and spatial scales.

An individual's telomere length early in life may reflect or contribute to key life-history processes sensitive to environmental variation. Yet, the relative importance of genetic and environmental factors in shaping early-life telomere length is not well understood as it requires samples collected from multiple generations with known developmental histories. We used a confirmed pedigree and conducted an animal model analysis of telomere lengths obtained from nestling house sparrows (Passer domesticus) sampled over a span of 22 years. We found significant additive genetic variation for early-life telomere length, but it comprised a small proportion (9%) of the total biological variation. Three sources of environmental variation were important: among cohorts, among-breeding attempts within years, and among nestmates. The magnitude of variation among breeding attempts and among nestmates also differed by cohort, suggesting that interactive effects of environmental factors across time or spatial scales were important, yet we were unable to identify the specific causes of these interactions. The mean amount of precipitation during the breeding season positively predicted telomere length, but neither weather during a given breeding attempt nor date in the breeding season contributed to an offspring's telomere length. At the level of individual nestlings, offspring sex, size and mass at 10 days of age also did not predict telomere length. Environmental effects appear especially important in shaping early-life telomere length in some species, and more focus on how environmental factors that interact across scales may help to explain some of the variation observed among studies.

Common genetic and environmental bases of the mental disorders and personality traits: Special focus on the hierarchical model of psychopathology and NEO-PI-R facets.

This study examined whether phenotypic correlations between psychopathological dimensions and personality traits of different hierarchical levels originate from common genetic and environmental sources of variance. Participants were 386 monozygotic and 204 dizygotic twins. The Psychiatric Diagnostic Screening Questionnaire (PDSQ) was applied along with the Revised NEO Personality Inventory (NEO-PI-R). The results of the CFA confirmed the hypothesis of the internalizing and externalizing dimensions underlying PDSQ scales. The results indicated a significantly greater role of genetic compared to environmental factors in the relationship between internalizing psychopathology and personality traits. Facets of neuroticism showed positive genetic links with internalizing disorders, while negative genetic links were shown for all facets of extraversion except excitement-seeking, competence, self-discipline, achievement striving, actions, and trust. Lower-order personality traits were shown to be associated with internalizing disorders more intensively than the broader domains to which they belong, both at the phenotypic and genetic levels. High neuroticism, together with several facets from the domain of extraversion and conscientiousness seems to represent an increased genetic susceptibility to the disorders from the internalizing spectrum. Results also suggest that specific environmental factors which are not shared with personality traits contribute to the internalizing symptoms.

Structure and Sources of Core Self-Evaluations: Construct Validation Using Multi-Rater and Genetically Informative Designs

Self-efficacy, internal locus of control, self-esteem and emotional stability are characterized by substantial theoretical overlap and empirical associations. In previous research, these four characteristics were frequently suggested to represent a common personality construct referred to as core self-evaluations (CSE). However, neither the structure of the construct CSE has been sufficiently validated nor its genetic and environmental sources examined, so far. The current study bridges this gap. Applying multitrait-multirater analyses of 2377 self- and 1176 informant-reports, we found substantial common variance beyond self-rater specificity, item specificity and random measurement error. Furthermore, using genetically informative data from 1146 twins, we investigated common and specific genetic and environmental sources of variance in the four characteristics. Common variance was substantially attributable to additive genetic and nonshared environmental influences, which were mediated by a higher-order latent variable. The results support the validity of the construct’s hierarchical structure with a common latent core trait accounting for the covariance between the four characteristics. Beyond nonshared environmental components specific to the four characteristics, nonadditive genetic sources accounted for common variance in self-efficacy and internal locus of control, whereas specific additive genetic factors explained variance in emotional stability, implying that these characteristics also include divergently valid aspects of personality.

Spatial variation in the evolutionary potential and constraints of basal metabolic rate and body mass in a wild bird.

An organism's energy budget is strongly related to resource consumption, performance, and fitness. Hence, understanding the evolution of key energetic traits, such as basal metabolic rate (BMR), in natural populations is central for understanding life-history evolution and ecological processes. Here we used quantitative genetic analyses to study evolutionary potential of BMR in two insular populations of the house sparrow (Passer domesticus). We obtained measurements of BMR and body mass (Mb ) from 911 house sparrows on the islands of Leka and Vega along the coast of Norway. These two populations were the source populations for translocations to create an additional third, admixed 'common garden' population in 2012. With the use of a novel genetic group animal model concomitant with a genetically determined pedigree, we differentiate genetic and environmental sources of variation, thereby providing insight into the effects of spatial population structure on evolutionary potential. We found that the evolutionary potential of BMR was similar in the two source populations, whereas the Vega population had a somewhat higher evolutionary potential of Mb than the Leka population. BMR was genetically correlated with Mb in both populations, and the conditional evolutionary potential of BMR (independent of body mass) was 41% (Leka) and 53% (Vega) lower than unconditional estimates. Overall, our results show that there is potential for BMR to evolve independently of Mb , but that selection on BMR and/or Mb may have different evolutionary consequences in different populations of the same species.

Testing the Gray Whale Strike Limit Algorithm (SLA): allowing environmental variability to influence population dynamics

The performance of the Gray Whale SLA is evaluated based on an operating model conditioned on available information for the eastern North Pacific stock of gray whales including: survey estimates of 1+ abundance; calf counts; strandings data; and the extent of sea-ice in the feeding grounds in the Bering Sea in the early season. Multiple scenarios are considered in the analyses to explore the impact of different sources of environmental variation, including scenarios in which future environmental forcing and episodic events are driven by the relationships between reproductive success and survival to sea ice. A variety of sources of uncertainty are considered, including parameter uncertainty, the uncertainty about the relationship between the extent of sea-ice and population dynamics, and observation error. The impact of these sources of uncertainty on the performance of the Gray Whale SLA is small. For all scenarios considered in the simulations, application of the SLA results in the stock being at or near carrying capacity at the end of a 92 year projection period for which sea-ice cover forecasts are available, while still satisfying the needs of aboriginal whalers.

Honoring the Complexity of Genetics: Exploring the Role of Genes and the Environment Using Real World Examples

Historically, undergraduate genetics courses have disproportionately focused on the impact of genes on phenotypes, rather than multifactorial concepts which consider how a combination of genes, the environment, and gene-by-environment interactions impacts traits. Updating the curriculum to include multifactorial concepts is important to align course materials to current understanding of genetics, and potentially reduce deterministic thinking, which is the belief that traits are solely controlled by genes. Currently there are few resources to help undergraduate biology instructors incorporate multifactorial concepts into their genetics courses, so we designed this lesson that centers on familiar, real-world examples. During this lesson, students learn how to distinguish between genetic and environmental sources of variation, and examine and interpret examples of how phenotypic variation can result from a combination of gene and environmental variation and interactions. This lesson, which is designed for both in-person and online classrooms, engages students in small group and large group discussion, figure interpretation, and provides questions that can be used for both formative and summative assessments. Results from assessment questions suggest that students found working through models depicting the interactions between genotypes and environments beneficial for their understanding of these complex topics. <em>Primary Image:</em>&nbsp;Mendel&rsquo;s laws of alternative inheritance of peas. A photo taken by W.F.R. Weldon of variation in color and texture of peas. Reprinted with permission from Biometrika (Weldon WFR. 1902. <em>Mendel&rsquo;s laws of alternative inheritance in peas</em>).

Partitioning variance in immune traits in a zooplankton host—Fungal parasite system

Host immune traits arise from both genetic and environmental sources of variation. When immune traits have a strong genetic basis, the presence and severity of disease in a population may influence the distribution of those traits. Our study addressed how two immune-related traits (gut penetrability and the hemocyte response) are shaped by genetic and environmental sources of variation, and how the presence of a virulent disease altered the relative frequency of these traits in natural populations. Daphnia dentifera hosts were sampled from five Indiana lakes between June and December 2017 before and during epidemics of their fungal pathogen, Metschnikowia bicuspidata. Collected Daphnia were experimentally exposed to Metschnikowia and assayed for their gut penetrability, hemocyte response, and multi-locus genotype. Mixed-effects models were constructed to partition variance in immune traits between genetic and environmental sources. We then isolated the genetic sources to produce genotype-specific estimates of immune traits for each multi-locus genotype. Finally, we assessed the relative frequency and dynamics of genotypes during epidemics and asked whether genotypes with more robust immune responses increased in frequency during epidemics. Although genotype was an important source of variation for both gut penetrability and the hemocyte response, environmental factors (e.g., resource availability, Metschnikowia prevalence, and co-infection) still explained a large portion of observed variation, suggesting a high degree of flexibility in Daphnia immune traits. Additionally, no significant associations were detected between a genotype's immune traits and its frequency in a population. Our study highlights the power of variance partitioning in understanding the factors driving variation in Daphnia traits and motivates further research on immunological flexibility and the ecological drivers of immune variation.

Nitrogen fertilization levels and timing affect the plasticity of yield components in bread wheat (Triticum aestivum L.)

The plasticity of grain yield components typically follows a hierarchy, with early-forming components having greater plasticity than late components (tiller number > spike number > grain number > grain weight). The first aim of this study was to assess the plasticity of two previously unexplored yield sub-components in wheat, i.e. spikelets per spike and grains per spikelet, and of other yield-related variables, i.e. straw mass, plant height, ovary mass and harvest index. The second aim was to test the potential limits of the phenotypic plasticity of yield components, and the relationships between them, by applying sudden strong changes in resource availability (via nitrogen fertilization)at different times during the crop cycle. Nitrogen (N) fertilization was applied only early (60 kg ha-1 of N, early tillering) or only late (120 kg ha-1, early stem elongation), very late (120 kg ha-1, late stem elongation) or extremely late (120 kg ha-1, pollination), never (N0) or multiple times (total of 300 kg ha-1) during the growth cycle of both a small-fruited (Bologna) and a large-fruited (Bora) bread wheat (Triticum aestivum L.) cultivar. Yield and grain number increased with fertilization levels in both cultivars, with the 300 kg N ha-1 treatment having the highest yield. Grain weight also increased with fertilization levels, but only when considering different N levels applied early.Delaying fertilization reduced yield, but increased grain weight, creating a tradeoff between yield (and grain number) and grain weight. Similarly, the relationships between other yield components and variables varied when considering N timing or levels. The plasticity of yield components, expressed as total variation of the trait over the trait value for the N0 (i.e. control) treatment, was 26.5%, 30.5%, 61%, 75% and 22%, respectively for tiller number, spike number, spikelets/spike, grains/spikelet and grain weight. The plasticity of grains/spike, grain number, yield, straw biomass, plant height, ovary mass and harvest index, was 174%, 236% and 268%, 417%, 54%, 54% and 36.5%, respectively. The results show that the plasticity of yield components (and other variables) may differ with different sources of environmental variation, explaining why, in the literature, two traits may be found to correlate both positively, negatively (tradeoff) or not at all. These results further our knowledge on the plasticity of, and the relationships among, yield components, and may be useful for further improvements of yield with agronomic intervention or breeding.

Towards a Model of Urban Evolution—Part III: Rules of Evolution

This paper develops a formal model of urban evolution in terms of (1) sources of variations; (2) principles of selection; and (3) mechanisms of retention. More specifically, regarding (1) it defines local and environmental sources of variation and identifies some of their generative processes, such as recombination, migration, mutation, extinction, and transcription errors. Regarding (2), it outlines a series of selection processes as part of an evolutionary ecology of urban forms, including density dependence, scope dependence, distance dependence, content dependence, and frequency dependence. Regarding (3), it characterizes retention as a combination of absorption and restriction of novel variants, defines mechanisms by which these can occur, including longevity, fidelity, and fecundity, and specifies how these processes issue in trajectories define by properties such as stability, pace, convergence, and divergence. A conclusion reviews the effort and looks forward to computer simulation and data-driven applications, as well as focused theoretical extensions of parts of the model. This paper builds on Parts I and II and is part of the Urban Genome Project, about which more information can be found here.

Opposing effects of spatiotemporal variation in resources and temporal variation in climate on density dependent population growth in seabirds.

Understanding how ecological processes combine to shape population dynamics is crucial in a rapidly changing world. Evidence has been emerging for how fundamental drivers of density dependence in mobile species are related to two differing types of environmental variation-temporal variation in climate, and spatiotemporal variation in food resources. However, to date, tests of these hypotheses have been largely restricted to mid-trophic species in terrestrial environments and thus their general applicability remains unknown. We tested if these same processes can be identified in marine upper trophic level species. We assembled a multi-decadal data set on population abundance of 10 species of colonial seabirds comprising a large component of the UK breeding seabird biomass, and covering diverse phylogenies, life histories and foraging behaviours. We tested for evidence of density dependence in population growth rates using discrete time state-space population models fit to long time-series of observations of abundance at seabird breeding colonies. We then assessed if the strength of density dependence in population growth rates was exacerbated by temporal variation in climate (sea temperature and swell height), and attenuated by spatiotemporal variation in prey resources (productivity and tidal fronts). The majority of species showed patterns consistent with temporal variation in climate acting to strengthen density dependent feedbacks to population growth. However, fewer species showed evidence for a weakening of density dependence with increasing spatiotemporal variation in prey resources. Our findings extend this emerging theory for how different sources of environmental variation may shape the dynamics and regulation of animal populations, demonstrating its role in upper trophic marine species. We show that environmental variation leaves a signal in long-term population dynamics of seabirds with potentially important consequences for their demography and trophic interactions.

Increased signal-to-noise ratios within experimental field trials by regressing spatially distributed soil properties as principal components.

Environmental variability poses a major challenge to any field study. Researchers attempt to mitigate this challenge through replication. Thus, the ability to detect experimental signals is determined by the degree of replication and the amount of environmental variation, noise, within the experimental system. A major source of noise in field studies comes from the natural heterogeneity of soil properties which create microtreatments throughout the field. In addition, the variation within different soil properties is often nonrandomly distributed across a field. We explore this challenge through a sorghum field trial dataset with accompanying plant, microbiome, and soil property data. Diverse sorghum genotypes and two watering regimes were applied in a split-plot design. We describe a process of identifying, estimating, and controlling for the effects of spatially distributed soil properties on plant traits and microbial communities using minimal degrees of freedom. Importantly, this process provides a method with which sources of environmental variation in field data can be identified and adjusted, improving our ability to resolve effects of interest and to quantify subtle phenotypes.

Variation in placental microRNA expression associates with maternal family history of cardiovascular disease.

In the United States, cardiovascular disease is the leading cause of death and the rate of maternal mortality remains among the highest of any industrialized nation. Maternal cardiometabolic health throughout gestation and postpartum is representative of placental health and physiology. Both proper placental functionality and placental microRNA expression are essential to successful pregnancy outcomes, and both are highly sensitive to genetic and environmental sources of variation. Placental pathologies, such as preeclampsia, are associated with maternal cardiovascular health but may also contribute to the developmental programming of chronic disease in offspring. However, the role of more subtle alterations to placental function and microRNA expression in this developmental programming remains poorly understood. We performed small RNA sequencing to investigate microRNA in placentae from the Rhode Island Child Health Study (n = 230). MicroRNA counts were modeled on maternal family history of cardiovascular disease using negative binomial generalized linear models. MicroRNAs were considered to be differentially expressed at a false discovery rate (FDR) less than 0.10. Parallel mRNA sequencing data and bioinformatic target prediction software were then used to identify potential mRNA targets of differentially expressed microRNAs. Nine differentially expressed microRNAs were identified (FDR < 0.1). Bioinformatic target prediction revealed 66 potential mRNA targets of these microRNAs, many of which are implicated in TGFβ signaling pathway but also in pathways involving cellular metabolism and immunomodulation. A robust association exists between familial cardiovascular disease and placental microRNA expression which may be implicated in both placental insufficiencies and the developmental programming of chronic disease.

Vocabulary and reading speed in the majority language are affected by maternal language proficiency and language exposure at home: a study of language minority bilingual children in Italy

ABSTRACT Environmental sources of variance in the Italian vocabulary and reading skills of bilingual primary school children from immigrant families (or language minority bilingual children (LMBC)) in Italy were investigated, and the LMBC’s skill levels were compared to those of their monolingual classmates. A total of 140 children from the first, third, and fifth grades were administered standardized tests of receptive vocabulary, word reading, and nonword reading skills. LMBC’s exposure to Italian at home and their mothers’ Italian proficiency were reported by mothers. Immigrant mothers’ Italian proficiency was a significant predictor of vocabulary and word reading speed but not of word accuracy or nonword reading. High levels of Italian exposure at home in combination with low levels of maternal Italian proficiency was a negative predictor of vocabulary; high exposure to Italian at home was positively associated with word reading speed and negatively associated with nonword reading speed. LMBC had lower vocabulary scores but did not differ from monolingual children in measures of reading skill. The findings underscore the importance of the quality of language exposure for language development and replicate findings that bilingual children show decoding skills on a par with monolingual children despite smaller vocabularies.

On the etiology of aesthetic chills: a behavioral genetic study

Aesthetic chills, broadly defined as a somatic marker of peak emotional-hedonic responses, are experienced by individuals across a variety of human cultures. Yet individuals vary widely in the propensity of feeling them. These individual differences have been studied in relation to demographics, personality, and neurobiological and physiological factors, but no study to date has explored the genetic etiological sources of variation. To partition genetic and environmental sources of variation in the propensity of feeling aesthetic chills, we fitted a biometrical genetic model to data from 14,127 twins (from 8995 pairs), collected by the Netherlands Twin Register. Both genetic and unique environmental factors accounted for variance in aesthetic chills, with heritability estimated at 0.36 ([0.33, 0.39] 95% CI). We found females more prone than males to report feeling aesthetic chills. However, a test for genotype x sex interaction did not show evidence that heritability differs between sexes. We thus show that the propensity of feeling aesthetic chills is not shaped by nurture alone, but it also reflects underlying genetic propensities.

Combining Therapeutic Drug Monitoring and Pharmacokinetic Modelling Deconvolutes Physiological and Environmental Sources of Variability in Clozapine Exposure.

Background: Clozapine is a key antipsychotic drug for treatment-resistant schizophrenia but exhibits highly variable pharmacokinetics and a propensity for serious adverse effects. Currently, these challenges are addressed using therapeutic drug monitoring (TDM). This study primarily sought to (i) verify the importance of covariates identified in a prior clozapine population pharmacokinetic (popPK) model in the absence of environmental covariates using physiologically based pharmacokinetic (PBPK) modelling, and then to (ii) evaluate the performance of the popPK model as an adjunct or alternative to TDM-guided dosing in an active TDM population. Methods: A popPK model incorporating age, metabolic activity, sex, smoking status and weight was applied to predict clozapine trough concentrations (Cmin) in a PBPK-simulated population and an active TDM population comprising 142 patients dosed to steady state at Flinders Medical Centre in Adelaide, South Australia. Post hoc analyses were performed to deconvolute the impact of physiological and environmental covariates in the TDM population. Results: Analysis of PBPK simulations confirmed age, cytochrome P450 1A2 activity, sex and weight as physiological covariates associated with variability in clozapine Cmin (R2 = 0.7698; p = 0.0002). Prediction of clozapine Cmin using a popPK model based on these covariates accounted for <5% of inter-individual variability in the TDM population. Post hoc analyses confirmed that environmental covariates accounted for a greater proportion of the variability in clozapine Cmin in the TDM population. Conclusions: Variability in clozapine exposure was primarily driven by environmental covariates in an active TDM population. Pharmacokinetic modelling can be used as an adjunct to TDM to deconvolute sources of variability in clozapine exposure.

Genetic and environmental influences on the progression from alcohol use disorder to alcohol-related medical conditions.

Medical conditions related to alcohol use disorders (AUD) represent a substantial public health concern. However, only a subset of individuals with AUD develop these conditions and the extent to which genetic and environmental factors that are shared with AUD, versus those distinct from it, contribute to this progression has not yet been determined. Using data from Swedish national registries for a cohort born from 1932 to 1970 (N=1,319,214, 48.9% women), we conducted twin-sibling biometric model fitting to examine the genetic and environmental sources of variance that contribute to the liability to alcohol-related medical conditions (AMC). Progression to AMC, determined using medical registry data, was contingent on an AUD registration, which was determined using medical and criminal registry data. We identified AUD registrations in 3.2% of women and 9.2% of men. Among individuals with an AUD registration, 14.4% of women and 15.4% of men had an AMC registration. In the final models, we constrained the beta pathway from AUD to AMC and the genetic and unique environmental paths to be equal across sexes. The beta path was estimated at 0.59. AMC was modestly heritable in women (A=0.32) and men (A=0.30). The proportion of total heritability unique to AMC was 39.6% among women and 41.3% among men. A higher proportion of total environmental variance was unique to AMC: 76.7% for women and 77.2% for men. In a sensitivity analysis limited to liver-related AMC, we observed similar results, with a slightly lower beta path from AUD to AMC (0.46) and higher proportions of AMC-specific genetic (70.0% in women; 71.7% in men) and environmental (84.5% in both sexes) variance. A moderate-to-substantial proportion of genetic and environmental variance that contributes to AMC risk is not shared with AUD, underscoring the need for additional gene identification efforts for AMC. Furthermore, the prominent influence of environmental factors specific to AMC provides a promising area for the identification of prevention targets. We did not observe significant sex differences in the etiology of AMC, although follow-up is warranted in other well-powered studies.

Yield and forage quality in maize (Zea mays L.) inbred lines

Objective: To analyze the genetic diversity (agronomic attributes, forage yield, and fiber content) of 100 maize inbred lines and to identify genotypes with potential for the breeding of plants with the said traits. Design/methodology/approach: One-hundred maize inbred lines were evaluated in two environments, in a 10 x 10 complete block experimental design, with two repetitions. Days to male flowering, days to female flowering, ear height, plant height, stem diameter, green forage yield, neutral detergent fiber, and acid detergent fiber data were recorded. Results: Significant differences were observed in the environmental sources of variation and genotypes for all the traits evaluated. The first four components account for 81% of the total variation observed and the first two account for 66% of the variation. The variables which have the highest absolute value and which strongly influence the dispersion of the genotypes, as well as the formation of groups, were: plant height, forage yield, and acid detergent fiber (component one) and days to female flowering and days to male flowering (component two). Consequently, the genotypes were dispersed in four groups. Study limitations/implications: It was not possible to conduct genetic diversity studies using molecular markers. Findings/conclusions: The grouping pattern of inbred lines shows the genetic diversity present; this can be an important tool in genetic improvement programs aimed at obtaining hybrids with specific characteristics.

Phenotypic responses to oil pollution in a poeciliid fish

Pollution damages ecosystems around the globe and some forms of pollution, like oil pollution, can be either man-made or derived from natural sources. Despite the pervasiveness of oil pollution, certain organisms are able to colonise polluted or toxic environments, yet we only have a limited understanding of how they are affected by it. Here, we analysed phenotypic responses to oil pollution in guppies (Poecilia reticulata) living in oil-polluted habitats across southern Trinidad. We analysed body-shape and life-history traits for 352 individuals from 11 independent populations, six living in oil-polluted environments (including the naturally oil-polluted Pitch Lake), and five stemming from non-polluted habitats. Based on theory of, and previous studies on, responses to environmental stressors, we predicted guppies from oil-polluted waters to have larger heads and shallower bodies, to be smaller, to invest more into reproduction, and to produce more but smaller offspring compared to guppies from non-polluted habitats. Contrary to most of our predictions, we uncovered strong population-specific variation regardless of the presence of oil pollution. Moreover, guppies from oil-polluted habitats were characterised by increased body size; rounder, deeper bodies with increased head size; and increased offspring size, when compared to their counterparts from non-polluted sites. This suggests that guppies in oil-polluted environments are not only subject to the direct negative effects of oil pollution, but might gain some (indirect) benefits from other concomitant environmental factors, such as reduced predation and reduced parasite load. Our results extend our knowledge of organismal responses to oil pollution and highlight the importance of anthropogenic pollution as a source of environmental variation. They also emphasise the understudied ecological heterogeneity of extreme environments.