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Garamszegi L.Z.,CSIC - Donana Biological Station
Behavioral Ecology and Sociobiology | Year: 2011

Scientific thinking may require the consideration of multiple hypotheses, which often call for complex statistical models at the level of data analysis. The aim of this introduction is to provide a brief overview on how competing hypotheses are evaluated statistically in behavioural ecological studies and to offer potentially fruitful avenues for future methodological developments. Complex models have traditionally been treated by model selection approaches using threshold-based removal of terms, i. e. stepwise selection. A recently introduced method for model selection applies an information-theoretic (IT) approach, which simultaneously evaluates hypotheses by balancing between model complexity and goodness of fit. The IT method has been increasingly propagated in the field of ecology, while a literature survey shows that its spread in behavioural ecology has been much slower, and model simplification using stepwise selection is still more widespread than IT-based model selection. Why has the use of IT methods in behavioural ecology lagged behind other disciplines? This special issue examines the suitability of the IT method for analysing data with multiple predictors, which researchers encounter in our field. The volume brings together different viewpoints to aid behavioural ecologists in understanding the method, with the hope of enhancing the statistical integration of our discipline. © 2010 Springer-Verlag. Source


Edelaar P.,CSIC - Donana Biological Station | Bjorklund M.,Uppsala University
Molecular Ecology | Year: 2011

The comparison between neutral genetic differentiation (FST) and quantitative genetic differentiation (QST) is commonly used to test for signatures of selection in population divergence. However, there is an ongoing discussion about what FST actually measures, even resulting in some alternative metrics to express neutral genetic differentiation. If there is a problem with FST, this could have repercussions for its comparison with QST as well. We show that as the mutation rate of the neutral marker increases, FST decreases: a higher within-population heterozygosity (He) yields a lower FST value. However, the same is true for QST: a higher mutation rate for the underlying QTL also results in a lower QST estimate. The effect of mutation rate is equivalent in QST and FST. Hence, the comparison between QST and FST remains valid, if one uses neutral markers whose mutation rates are not too high compared to those of quantitative traits. Usage of highly variable neutral markers such as hypervariable microsatellites can lead to serious biases and the incorrect inference that divergent selection has acted on populations. Much of the discussion on FST seems to stem from the misunderstanding that it measures the differentiation of populations, whereas it actually measures the fixation of alleles. In their capacity as measures of population differentiation, Hedricks GST and Josts D reach their maximum value of 1 when populations do not share alleles even when there remains variation within populations, which invalidates them for comparisons with QST. © 2011 Blackwell Publishing Ltd. Source


1. Understanding how plants respond and adapt to varying environmental conditions has attracted the attention of plant ecologists for decades. To study this process, altitudinal gradients are used because of their inherent variation in environmental conditions. In the current scenario of global warming, altitudinal gradients may also represent a valuable resource to deepen our understanding about plant adaptive responses to predicted changes in environmental conditions. 2.Nowadays, the study of adaptive variation demands equal contributions from ecology and genetics. We need to assess the effects of selective pressures on phenotypic variation but also the genetic and molecular basis of phenotypic traits. The annual plant Arabidopsis thaliana represents a useful model system for investigating adaptive variation. Here, I characterized patterns of life cycle variation in natural A. thaliana populations along an altitudinal gradient to unravel how the species copes with different environmental conditions. 3.I periodically monitored thousands of plants from eight populations in NE Spain over 5years (2007-2011) to estimate survival and fecundity schedules for autumn- and spring-germinated plants. Data were used to estimate net reproductive rate for each life cycle type. Data were regressed against altitude to detect altitudinal climatic clines for life cycle variation. 4.Survival of spring-germinated A. thaliana plants was significantly higher than that of winter-germinated plants. Plants from both cohorts exhibited similar fecundity values. The net reproductive rate of spring-germinated plants was fourfold higher than that of autumn-germinated plants. The proportion of spring-germinated plants increased significantly with altitude. 5.Synthesis. Arabidopsis thaliana can behave as a winter or spring annual plant. Nevertheless, the spring annual life cycle is clearly relevant to maintain A. thaliana populations, particularly at high-elevation locations. It is suggested that germination timing represents one of the most relevant traits to focus our efforts to understand adaptive variation in A.thaliana. The results illustrate the potential of annual plants to adjust their life cycles to varying environmental conditions encountered along a climatic gradient, which could mitigate the effects of global warming on annual plant populations. Arabidopsis thaliana can behave as a winter or spring annual plant. Nevertheless, the spring annual life cycle is clearly relevant to maintain A. thaliana populations, particularly at high-elevation locations. It is suggested that germination timing represents one of the most relevant traits to focus our efforts to understand adaptive variation in A.thaliana. The results illustrate the potential of annual plants to adjust their life cycles to varying environmental conditions encountered along a climatic gradient, which could mitigate the effects of global warming on annual plant populations. © 2012 The Author. Journal of Ecology © 2012 British Ecological Society. Source


Garamszegi L.Z.,CSIC - Donana Biological Station
Malaria Journal | Year: 2014

Background: The major histocompatibility complex (MHC) is the most polymorphic genetic region in vertebrates, but the origin of such genetic diversity remains unresolved. Several studies have demonstrated at the within-population level that individuals harbouring particular alleles can be less or more susceptible to malaria, but these do not allow strong generalization. Methods. Here worldwide data on the frequencies of several hundred MHC alleles of the human leucocyte antigen (HLA) system in relation to malaria risk at the between-population level were analysed in a phylogenetic framework, and results for different alleles were quantitatively summarized in a meta-analysis. Results: There was an overall positive relationship between malaria pressure and the frequency of several HLA alleles indicating that allele frequencies increase in countries with strong malaria pressure. Nevertheless, considerable heterogeneity was observed across alleles, and some alleles showed a remarkable negative relationship with malaria risk. When heterogeneities were partitioned into different organization groups of the MHC, the strongest positive relationships were detected for alleles of the HLA-A and HLA-B loci, but there were also differences between MHC supertypes that constitute functionally distinct nucleotide sequences. Finally, the number of MHC alleles that are maintained within countries was also related to malaria risk. Conclusion: Therefore, malaria represents a key selection pressure for the human MHC and has left clear evolutionary footprints on both the frequencies and the number of alleles observed in different countries. © 2014 Garamszegi; licensee BioMed Central Ltd. Source


Edelaar P.,CSIC - Donana Biological Station | Edelaar P.,Pablo De Olavide University | Bolnick D.I.,Howard Hughes Medical Institute
Trends in Ecology and Evolution | Year: 2012

Dispersal is an important life-history trait involved in species persistence, evolution, and diversification, yet is one of the least understood concepts in ecology and evolutionary biology. There is a growing realization that dispersal might not involve the random sample of genotypes as is typically assumed, but instead can be enriched for certain genotypes. Here, we review and compare various sources of such non-random gene flow, and summarize its effects on local adaptation and resource use, metapopulation dynamics, adaptation to climate change, biological invasion, and speciation. Given the possible ubiquity and impacts of non-random gene flow, there is an urgent need for the fields of evolution and ecology to test for non-random gene flow and to more fully incorporate its effects into theory. © 2012 Elsevier Ltd. Source

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