Individual-based Approach Research Articles

Effects of Group-based versus Individual-based Spinal Stability Exercises (SSE) on Physical Health and Mental Wellbeing of Patients with Chronic Low Back Pain (LBP): A Randomized Controlled Trial (RCT)

Background: Several studies have demonstrated the efficacy of spinal stability exercises in physiotherapy management of back pain disorders. Physiotherapists traditionally can administer this exercise treatment either with the patient in group or one to one basis. There is dearth of information on the relative efficacy of group-based and individual-based spinal stabilisation exercise treatment approach. This raises the question of which method is more effective in symptom remediation and improvement in the health status of patients with chronic LBP? Purpose: The purpose of this study was to compare the effect of group-based and individual-based SSE on bodily pain, functional limitation, physical health and mental wellbeing of patients with chronic LBP. Method: Thirty-five participants with chronic LBP were randomly assigned to undergo a SSE twice weekly week for 8 consecutive weeks in a group setting, and 35 participants received the same SSE on an individual basis during the same period. Functional limitation was assessed with Rolland Morris Disability Questionnaires. Bodily pain, physical health and mental well-being were evaluated with Rand 36 questionnaire. Assessments were carried out preintervention, post-intervention and at 3-month follow up. Results: Significant improvement in bodily pain, functional limitation, physical health and mental well-being were found in both the group-based SSE and individual-based SSE post intervention (P=0.00). Functional limitation did not show significant difference between the two groups post intervention (P=0.497). Friedman ANOVA showed significant within-group differences over time in bodily pain, functional limitation. Physical health and mental well-being over time (P=0.00) that favoured the group-based SSE. Conclusion: Findings from this study showed that group-based spinal stabilisation exercise interventions, is more effective in reducing pain, improving physical health and mental well-being of patients with chronic LBP than individually-based programs.

Households with a stunted child and obese mother: trends and child feeding practices in a middle-income country, 1992-2008.

Middle-income countries in the intermediate stages of the nutrition transition are facing a complex picture of nutrition-related diseases with child stunting and maternal obesity coexisting within single households (SCOB). A debate exists as to whether SCOB is a true phenomenon or a statistical artefact. In this study, we examine time trends and determinants of SCOB in Egypt and test the hypothesis that increased child sugary snack consumption, and reduced fruit/vegetable consumption (markers of poor dietary diversity) are associated with SCOB. Data on 25,065 mothers and their children from the Egyptian Demographic and Health Surveys from 1992, 1995, 2005 and 2008 are used to examine trends in child stunting, maternal obesity and child–mother household type [normal/non-obese, stunted/non-obese, normal/obese, stunted/obese (SCOB)]. The association of child sugary snack and fruit/vegetable consumption with household type is also examined using multinomial logistic regression adjusting for maternal age, maternal education, child age, breastfeeding, household wealth and urban/rural residence. The prevalence of SCOB increased between the periods 1992/95 and 2005/08 despite reductions in stunting levels. This increase paralleled a rise in maternal obesity. Child sugary snack consumption was associated with higher odds (51 %) of belonging to a SCOB household compared with normal/non-obese households, while fruit/vegetable consumption was associated with lower odds (24 %). The results suggest the existence of a link between the rise in maternal obesity and an increase in SCOB, and an association between child sugary snack consumption and SCOB. Addressing SCOB may require a household—rather than individual-based approach to nutrition.Electronic supplementary materialThe online version of this article (doi:10.1007/s10995-014-1634-5) contains supplementary material, which is available to authorized users.

Sources of variation in innate immunity in great tit nestlings living along a metal pollution gradient: An individual-based approach

Excessive deposition of metals in the environment is a well-known example of pollution worldwide. Chronic exposure of organisms to metals can have a detrimental effect on reproduction, behavior, health and survival, due to the negative effects on components of the immune system. However, little is known about the effects of chronic sublethal metal exposure on immunity, especially for wildlife. In our study, we examined the constitutive innate immunity of great tit (Parus major) nestlings (N=234) living in four populations along a metal pollution gradient. For each nestling, we determined the individual metal concentrations (lead, cadmium, arsenic) present in the red blood cells and measured four different innate immune parameters (agglutination, lysis, haptoglobin concentrations and nitric oxide concentrations) to investigate the relationship between metal exposure and immunological condition. While we found significant differences in endogenous metal concentrations among populations with the highest concentrations closest to the pollution source, we did not observe corresponding patterns in our immune measures. However, when evaluating relationships between metal concentrations and immune parameters at the individual level, we found negative effects of lead and, to a lesser extent, arsenic and cadmium on lysis. In addition, high arsenic concentrations appear to elicit inflammation, as reflected by elevated haptoglobin concentrations. Thus despite the lack of a geographic association between pollution and immunity, this type of association was present at the individual level at a very early life stage. The high variation in metal concentrations and immune measures observed within populations indicates a high level of heterogeneity along an existing pollution gradient. Interestingly, we also found substantial within nest variation, for which the sources remain unclear, and which highlights the need of an individual-based approach.

High intraspecific variability in the functional niche of a predator is associated with ontogenetic shift and individual specialization.

Investigations on the functional niche of organisms have primarily focused on differences among species and tended to neglect the potential effects of intraspecific variability despite the fact that its potential ecological and evolutionary importance is now widely recognized. In this study, we measured the distribution of functional traits in an entire population of largemouth bass (Micropterus salmoides) to quantify the magnitude of intraspecific variability in functional traits and niche (size, position, and overlap) between age classes. Stable isotope analyses (δ13C and δ15N) were also used to determine the association between individual trophic ecology and intraspecific functional trait variability. We observed that functional traits were highly variable within the population (mean coefficient variation: 15.62% ± 1.78% SE) and predominantly different between age classes. In addition, functional and trophic niche overlap between age classes was extremely low. Differences in functional niche between age classes were associated with strong changes in trophic niche occurring during ontogeny while, within age classes, differences among individuals were likely driven by trophic specialization. Each age class filled only a small portion of the total functional niche of the population and age classes occupied distinct portions in the functional space, indicating the existence of ontogenetic specialists with different functional roles within the population. The high amplitude of intraspecific variability in functional traits and differences in functional niche position among individuals reported here supports the recent claims for an individual-based approach in functional ecology.

Modelling Hen Harrier Dynamics to Inform Human-Wildlife Conflict Resolution: A Spatially-Realistic, Individual-Based Approach

Individual-based models have gained popularity in ecology, and enable simultaneous incorporation of spatial explicitness and population dynamic processes to understand spatio-temporal patterns of populations. We introduce an individual-based model for understanding and predicting spatial hen harrier (Circus cyaneus) population dynamics in Great Britain. The model uses a landscape with habitat, prey and game management indices. The hen harrier population was initialised according to empirical census estimates for 1988/89 and simulated until 2030, and predictions for 1998, 2004 and 2010 were compared to empirical census estimates for respective years. The model produced a good qualitative match to overall trends between 1989 and 2010. Parameter explorations revealed relatively high elasticity in particular to demographic parameters such as juvenile male mortality. This highlights the need for robust parameter estimates from empirical research. There are clearly challenges for replication of real-world population trends, but this model provides a useful tool for increasing understanding of drivers of hen harrier dynamics and focusing research efforts in order to inform conflict management decisions.

Particle swarm optimization with dual-level task allocation

Particle swarm optimization (PSO) is a well-known algorithm for global optimization over continuous search spaces. However, this algorithm is limited by the intense conflict between exploration and exploitation search processes. This improper adjustment of exploration and exploitation search processes can introduce an inappropriate level of diversity into the swarm, thereby either decelerating the convergence rate of the algorithm (caused by the excessive diversity) or inducing premature convergence (as a result of insufficient diversity). To address this issue, we propose a new PSO variant, namely, the PSO with dual-level task allocation (PSO–DLTA). Two task allocation modules, that is, the dimension-level task allocation (DTA) and the individual-level task allocation (ITA) modules, are developed in PSO–DLTA to balance the exploration and exploitation search processes. Unlike existing population-based and individual-based task allocation approaches, the DTA module assigns different search strategies to different dimensional components of a particle. Meanwhile, the ITA module serves as an alternative learning phase to enhance the PSO–DLTA particle if it fails to improve in terms of fitness in the DTA module. To demonstrate the effectiveness and efficiency of PSO–DLTA, we compare it with several recently developed optimization algorithms on 25 benchmark and 2 engineering design problems. Experimental results reveal that the proposed PSO–DLTA is more competitive than its contenders in terms of searching accuracy, reliability, and efficiency with respect to most of the tested functions.

Effects of temperature and surface water availability on spatiotemporal dynamics of stream salamanders using pattern-oriented modelling

Ecological models are powerful tools for generating predictions about the viability of populations of endangered species, especially in landscapes where they may be subject to complex, cross-scale disturbances. Spatially explicit, individual-based approaches are particularly promising due to their ability to simulate the effect of landscape level changes in habitat on individual-level behaviour, thus predicting possible emergent responses from the bottom up. We apply this approach to modelling the movement behaviour and the complex life cycles of two species of stream-dwelling salamanders (the Allegheny Mountain Dusky Salamander, Desmognathus ochrophaeus, and the Northern Spring Salamander, Gyrinophilus porphyriticus) in response to a spatially and temporally varying environment. Despite the poor state of ecological knowledge about these species, our model provides reasonable predictions about life cycle, as well as the density and distribution of salamanders. When tested with a dynamic, drought prone environment, the model predicts viability levels that are biologically plausible. By simulating the cross-scale interactions between organisms and their environment, individual-based models such as we have developed here provide a new tool for in silico investigations of the expected impacts of varying landscape scenarios and environmental changes.

Stochastic spread models: A comparison between an individual-based and a lattice-based model for assessing the expansion of invasive termites over a landscape

Spatially-explicit simulation models can help state and local regulatory agencies to predict both the rate and direction of the spread of an invasive species from a set of surveyed locations. Such models can be used to develop successful early detection, quarantine, or eradication plans based on the predicted areas of infestation. Individual-based models (IBMs) are often used to replicate the dynamics of complex systems and are both able to incorporate individual differences and local interactions among organisms, as well as spatial details. In this work, we introduce a new stochastic lattice-based model for simulating the spread of invasive termites over a landscape and compare it to a recently published stochastic individual-based approach, based on the same ecological parameters, with the goal of improving its computational efficiency. The two modeling frameworks were tested over a homogeneous landscape with randomly located sources of infestation. Further, the setting of a case-study of an invasive termite, Nasutitermes corniger (Motschulsky), was used to simulate the spread of the species in Dania Beach, Florida, U.S.A., and the results of the proposed model were compared with an earlier application of the IBM over the same area. The results show that the extent of the infested areas predicted by the new lattice-based model is similar, thus comparable, to the individual-based model while improving the computation time significantly. The simulation presented in this work could be used by the regulatory authorities to draw one or more areas of intervention instead of wasting resources by randomly surveying unknown perimeters.

A Critical Systematic Review of Studies Regarding Resilience in Turkey: A Call for the Socio-ecology of Resilience Perspective

Even though international research has shifted from problem-driven to strength-based approach such as resilience, very little is known in a non-Western context, Turkey. As a result, this paper aims to fill research gaps in existing peer-reviewed literature by targeting to promote more effective interventions and programs with regard to resilience approach in Turkey. A critical systematic review of available literature was carried out based on peer-reviewed articles published in English and Turkish using PubMed, Ovid, EBSCO HOST, ERIC, ProQuest databases, and hand searching. Four hundred fifty-two articles were retrieved of which 34 met the inclusion criteria. Results depict that the majority of studies solely employed individual-based resilience approach. Even though international resilience research has begun to match resilience to socio-ecological perspective, Turkish scholars hardly do so. Only pointing out this gap in resilience research is addressed, will social workers be help enabling Turkish individuals to fuel resilience.

Pengembangan Motivasi dan Kompetensi Guru dalam Peningkatan Mutu Pembelajaran di Madrasah

<p><em>Expectations </em><em>to improv</em><em>ing</em><em> the quality o</em><em>f </em><em>teaching</em><em> process</em><em> and learning outcomes, has been a major challenge in providing education in </em><em>MTs/</em><em>Madrasah</em><em> (Islamic Junior High School)</em><em> at this time. Accordingly, as </em><em>the</em><em> educator</em><em>, teachers are</em><em> often seen as the main</em><em> and first</em><em> factors that determine the quality </em><em>of</em><em> learning. Teachers are required to have high motivation and adequate pedagogic competence in performing their duties. In fact, the fulfillment of qualifications and pedagogic competence of teachers is becoming the fundamental issues in education held at Madrasah. In general, the quality of </em><em>M</em><em>adrasah teachers is relatively lower than teachers in public schools. Besides, there are still many teachers in MTs in Bekasi whose motivation is low.</em><em> </em><em>Research focuses on assessing the motivation and pedagogic competence of teachers in order to improve the quality of learning in the Madrasah. In spesific, the purpose of research is to describe the characteristics of teacher motivation, pedagogic competence of teacher, </em><em>and</em><em> finding the motivation and pedagogic competence development strategy, in order to improve the quality of learning.</em><em> </em><em>The study was conducted using a descriptive approach to describe the reality of the empirical analysis is based on data and various sources. The experiment was conducted at the </em><em>Islamic J</em><em>unior </em><em>S</em><em>econdary </em><em>S</em><em>chool (MTs) in Bekasi District. The data obtained through interviews, document analysis, and questionnaires. Sources of research data </em><em>are</em><em> teacher</em><em>s</em><em>, principal </em><em>of MTs</em><em>, </em><em>MTs</em><em> supervisors, and leaders of </em><em>coaching </em><em>institutions </em><em>at</em><em> </em><em>the district </em><em>religious ministry office. Data obtained through the questionnaire were analyzed using descriptive techniques. Data from interviews and document analysis were analyzed through a process of data reduction, data presentation, and </em><em>taking</em><em> conclusions based on the findings and results of the verification.</em><em> </em><em>Based on the results of the study concluded that there was no significant difference between the teachers who have been trained by the training yet, </em><em>either for </em><em>motivation, pedagogic competence and quality of learning. Therefore we need a model of training that can improve motivation, pedagogic competence and quality of learning. Training model should include (1) the motivation of teachers needs to be improved in order to improve the quality of learning both in the aspect of performance of duties, self-development, or building relationships, (2) the pedagogic competence of teachers needs to be improved in order to greater quality of learning with an emphasis on pedagogical and social dimension, (3) development of motivation can be done by strengthening the intrinsic motivation to approach the job expansion and job enrichment and strengthening of extrinsic motivation through guidance, distribution of tasks and responsibilities, performance appraisal followed by providing feedback (reward and punishment), creating a conducive working atmosphere, and provide career development opportunities in accordance achievement. Pedagogic dompetence development can be done using an individual-based approach through the development of self and institution-based approaches through supervision, empowerment, </em><em>conducting </em><em>scientific activities, as well as fostering</em><em> and development of</em><em> discipline and ethics teacher profession.</em></p><p class="keywords">Keywords: Kompetensi Guru, Madrasah, Motivasi, Mutu Pembelajaran</p>

Refuge use by hatching-year ring-necked ducks: An individual-based telemetry approach

Many studies have quantified use of established refuges where hunting is not permitted by counting waterfowl or conducting behavioral observations on refuges during hunting season. However, refuge use by individually marked birds remains largely unexplored, along with arrival and departure times, lengths of stay, and nighttime use. We used radio-transmitters and telemetry receiving stations that continuously scanned at 14 waterfowl refuges to test predictions that refuge use would be greatest during hunting hours and on weekends when hunting intensity was expected to be greatest, and that departures would occur in the evening after hunting ended. Movements on and off refuges coincided with sunrise and sunset, which approximated hunting hours. The average length of refuge stay was 12.0 ± 0.5 hours, although some departing birds returned repeatedly to refuges, resulting in longer accumulative stays. Use during the day was greater than at night at most refuges (92.7 ± 18.1 vs. 56.1 ± 10.8 hr, P = 0.03) and was greater on weekends during hunting season than before hunting opened (0.36 ± 0.03 vs. 0.22 ± 0.05, P = 0.01). We also documented nighttime use at refuges with good or excellent food ratings by wildlife managers. Our findings are consistent with the use of refuges to avoid disturbance and suggest that many of these areas provide numerous benefits to ring-necked ducks during fall staging and migration in northern Minnesota. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.

Progress of theoretical modelling and empirical studies on collective motion

The study on the collective motion of the biological systems, such as flocks of birds and schools of fish, has attracted the attention of researchers from diverse disciplines whilst the relevant studies are still emerging. Here, we review the state-of-the-art of collective motion on two prospects, the theoretical modelling and the empirical analysis. In particular, the latest developments of the individual-based modelling approach for the collective motion are summarized. Meanwhile, the new phenomena observed from the empirical analysis of the biological swarm system is sorted and analyzed. Finally, a brief discussion is provided to outline the open problems and the possible research directions in collective motion.

Geographical and temporal body size variation in a reptile: roles of sex, ecology, phylogeny and ecology structured in phylogeny.

Geographical body size variation has long interested evolutionary biologists, and a range of mechanisms have been proposed to explain the observed patterns. It is considered to be more puzzling in ectotherms than in endotherms, and integrative approaches are necessary for testing non-exclusive alternative mechanisms. Using lacertid lizards as a model, we adopted an integrative approach, testing different hypotheses for both sexes while incorporating temporal, spatial, and phylogenetic autocorrelation at the individual level. We used data on the Spanish Sand Racer species group from a field survey to disentangle different sources of body size variation through environmental and individual genetic data, while accounting for temporal and spatial autocorrelation. A variation partitioning method was applied to separate independent and shared components of ecology and phylogeny, and estimated their significance. Then, we fed-back our models by controlling for relevant independent components. The pattern was consistent with the geographical Bergmann's cline and the experimental temperature-size rule: adults were larger at lower temperatures (and/or higher elevations). This result was confirmed with additional multi-year independent data-set derived from the literature. Variation partitioning showed no sex differences in phylogenetic inertia but showed sex differences in the independent component of ecology; primarily due to growth differences. Interestingly, only after controlling for independent components did primary productivity also emerge as an important predictor explaining size variation in both sexes. This study highlights the importance of integrating individual-based genetic information, relevant ecological parameters, and temporal and spatial autocorrelation in sex-specific models to detect potentially important hidden effects. Our individual-based approach devoted to extract and control for independent components was useful to reveal hidden effects linked with alternative non-exclusive hypothesis, such as those of primary productivity. Also, including measurement date allowed disentangling and controlling for short-term temporal autocorrelation reflecting sex-specific growth plasticity.

Weak isolation by distance in Diaperis boleti, a fungivorous saproxylic beetle.

Living in unstable habitats is expected to decrease the intensity of isolation by distance in populations through the need for frequent movements of individuals. Insects associated with fruiting bodies of fungi therefore are supposed to have weak spatial genetic structure of populations compared with those living in more stable habitats. With the use of an amplified fragment length polymorphism technique, this study investigated the isolation by distance, inbreeding, and genetic diversity in Diaperis boleti (L.) (Coleoptera: Tenebrionidae), a fungivorous saproxylic beetle that inhabits sporocarps of Laetiporus sulphureus (Bulliard) Murrill (Polyporales) on trees growing in highly-fragmented agricultural landscapes. Isolation by distance was tested with spatial autocorrelation analysis of kinship (individual-based approach) and correlating matrices of genetic and geographic distances with the Mantel test (population-based approach). These results were compared with the results obtained for saproxylic beetles living in the same landscape but differing in ecological preferences. It was shown that the species dependent on sporocarps of wooddecomposing fungi had higher variability, lower individual inbreeding, and less intensive isolation by distance pattern than saproxylic beetles living in tree hollows. It was also demonstrated that spatial autocorrelation analysis of kinship is a more sensitive approach for detecting finescale spatial genetic structure than the Mantel test.

Uniting statistical and individual-based approaches for animal movement modelling.

The dynamic nature of their internal states and the environment directly shape animals' spatial behaviours and give rise to emergent properties at broader scales in natural systems. However, integrating these dynamic features into habitat selection studies remains challenging, due to practically impossible field work to access internal states and the inability of current statistical models to produce dynamic outputs. To address these issues, we developed a robust method, which combines statistical and individual-based modelling. Using a statistical technique for forward modelling of the IBM has the advantage of being faster for parameterization than a pure inverse modelling technique and allows for robust selection of parameters. Using GPS locations from caribou monitored in Québec, caribou movements were modelled based on generative mechanisms accounting for dynamic variables at a low level of emergence. These variables were accessed by replicating real individuals' movements in parallel sub-models, and movement parameters were then empirically parameterized using Step Selection Functions. The final IBM model was validated using both k-fold cross-validation and emergent patterns validation and was tested for two different scenarios, with varying hardwood encroachment. Our results highlighted a functional response in habitat selection, which suggests that our method was able to capture the complexity of the natural system, and adequately provided projections on future possible states of the system in response to different management plans. This is especially relevant for testing the long-term impact of scenarios corresponding to environmental configurations that have yet to be observed in real systems.

Invited commentary: are there unrealized benefits of unemployment insurance among the employed?

Political statements about the relationship between the economy and health intensify during economic downturns and fade in times of prosperity. Population health researchers share this cyclical interest in that the numbers of peer-reviewed publications on this topic increase during and immediately after recessions. In this issue of the Journal, Cylus et al. (Am J Epidemiol. 2014;180(1):45-52) follow in the "economy and health" research tradition and examine the relationship between US unemployment rates and suicide mortality. Their work makes a novel contribution in that they examine whether generous unemployment insurance benefits attenuate the relationship between economic downturns and suicide mortality in the United States. In this commentary, I assess the internal validity of their analysis, call into question some assumptions of their approach, and place their contribution within the context of the broader literature. I then argue that population-based and individual-based approaches in the "economy and health" field often work in concert to create knowledge and inform policy-makers.

An individual-based modeling approach to simulate the effects of cellular nutrient competition on Escherichia coli K-12 MG1655 colony behavior and interactions in aerobic structured food systems

Traditional kinetic models in predictive microbiology reliably predict macroscopic dynamics of planktonically-growing cell cultures in homogeneous liquid food systems. However, most food products have a semi-solid structure, where microorganisms grow locally in colonies. Individual colony cells exhibit strongly different and non-normally distributed behavior due to local nutrient competition. As a result, traditional models considering average population behavior in a homogeneous system do not describe colony dynamics in full detail.To incorporate local resource competition and individual cell differences, an individual-based modeling approach has been applied to Escherichia coli K-12 MG1655 colonies, considering the microbial cell as modeling unit.The first contribution of this individual-based model is to describe single colony growth under nutrient-deprived conditions. More specifically, the linear and stationary phase in the evolution of the colony radius, the evolution from a disk-like to branching morphology, and the emergence of a starvation zone in the colony center are simulated and compared to available experimental data. These phenomena occur earlier at more severe nutrient depletion conditions, i.e., at lower nutrient diffusivity and initial nutrient concentration in the medium. Furthermore, intercolony interactions have been simulated. Higher inoculum densities lead to stronger intercolony interactions, such as colony merging and smaller colony sizes, due to nutrient competition.This individual-based model contributes to the elucidation of characteristic experimentally observed colony behavior from mechanistic information about cellular physiology and interactions.

How do animal territories form and change? Lessons from 20 years of mechanistic modelling.

Territory formation is ubiquitous throughout the animal kingdom. At the individual level, various behaviours attempt to exclude conspecifics from regions of space. At the population level, animals often segregate into distinct territorial areas. Consequently, it should be possible to derive territorial patterns from the underlying behavioural processes of animal movements and interactions. Such derivations are an important element in the development of an ecological theory that can predict the effects of changing conditions on territorial populations. Here, we review the approaches developed over the past 20 years or so, which go under the umbrella of ‘mechanistic territorial models’. We detail the two main strands to this research: partial differential equations and individual-based approaches, showing what each has offered to our understanding of territoriality and how they can be unified. We explain how they are related to other approaches to studying territories and home ranges, and point towards possible future directions.

Genome scans for detecting footprints of local adaptation using a Bayesian factor model.

There is a considerable impetus in population genomics to pinpoint loci involved in local adaptation. A powerful approach to find genomic regions subject to local adaptation is to genotype numerous molecular markers and look for outlier loci. One of the most common approaches for selection scans is based on statistics that measure population differentiation such as FST. However, there are important caveats with approaches related to FST because they require grouping individuals into populations and they additionally assume a particular model of population structure. Here, we implement a more flexible individual-based approach based on Bayesian factor models. Factor models capture population structure with latent variables called factors, which can describe clustering of individuals into populations or isolation-by-distance patterns. Using hierarchical Bayesian modeling, we both infer population structure and identify outlier loci that are candidates for local adaptation. In order to identify outlier loci, the hierarchical factor model searches for loci that are atypically related to population structure as measured by the latent factors. In a model of population divergence, we show that it can achieve a 2-fold or more reduction of false discovery rate compared with the software BayeScan or with an FST approach. We show that our software can handle large data sets by analyzing the single nucleotide polymorphisms of the Human Genome Diversity Project. The Bayesian factor model is implemented in the open-source PCAdapt software.

RIVERSCAPE GENETICS IDENTIFIES REPLICATED ECOLOGICAL DIVERGENCE ACROSS AN AMAZONIAN ECOTONE

Ecological speciation involves the evolution of reproductive isolation and niche divergence in the absence of a physical barrier to gene flow. The process is one of the most controversial topics of the speciation debate, particularly in tropical regions. Here, we investigate ecologically based divergence across an Amazonian ecotone in the electric fish, Steatogenys elegans. We combine phylogenetics, genome scans, and population genetics with a recently developed individual-based evolutionary landscape genetics approach that incorporates selection. This framework is used to assess the relative contributions of geography and divergent natural selection between environments as biodiversity drivers. We report on two closely related and sympatric lineages that exemplify how divergent selection across a major Amazonian aquatic ecotone (i.e., between rivers with markedly different hydrochemical properties) may result in replicated ecologically mediated speciation. The results link selection across an ecological gradient with reproductive isolation and we propose that assortative mating based on water color may be driving the divergence. Divergence resulting from ecologically driven selection highlights the importance of considering environmental heterogeneity in studies of speciation in tropical regions. Furthermore, we show that framing ecological speciation in a spatially explicit evolutionary landscape genetics framework provides an important first step in exploring a wide range of the potential effects of spatial dependence in natural selection.