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"ecological genetics"
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Local adaptation occurs along altitudinal gradient despite the existence of gene flow in the alpine plant species Festuca eskia
1. Alpine plant species are particularly vulnerable to climate change. Therefore, estimating the adaptive potential of alpine species is of vital importance for determining their future viability. In alpine plants, adaptive potential depends on (i) altitudinal genetic differentiation among populations, combined with gene flow along an altitudinal gradient; (ii) phenotypic plasticity for the traits under selection and (iii) co-gradient variation between genetic and environmental influences on these traits. 2. The adaptive potential of Festuca eskia Ramond (Poaceae), a perennial alpine grass common in the Pyrenean Mountains, was examined in this study. A reciprocal transplant experiment involving 180 individuals along three altitudinal gradients (from 1500 to 2500 m) was established, and survival, functional and reproductive traits were recorded. In addition, four neutral sequence-tagged site and simple sequence repeat molecular markers were chosen to estimate gene flow among populations. 3. Genetic differentiation attributable to selection was detected in all traits between populations along the altitudinal gradient despite the existence of restricted gene flow. For traits directly related to fitness, local altitudinal adaptation was clearly evident. The patterns of local adaptation suggested that selection patterns differed along an altitudinal gradient. Selection for reproductive output was predominant at low altitudes, whereas differential survivorship was observed at higher altitudes. 4. Genetic differentiation with increasing altitude resulted in reduced plant stature and reproductive output but increased specific leaf area (SLA). This increased SLA at higher altitude is interpreted as a resource acquisition strategy. 5. Phenotypic plasticity was seen in all traits at the population level. Evidence of co-gradient variation between genetic differentiation and plastic response was found for all traits except SLA, suggesting that adaptive phenotypic plasticity operates in F. eskia. 6. Synthesis. Local adaptation occurs in F. eskia. It involves different adaptive traits according to the altitude. Such differentiation occurs at a small scale along altitudinal gradients despite the existence of gene flow and phenotypic plasticity. The coexistence of genetic differentiation, gene flow and phenotypic plasticity along altitudinal gradients provides an adaptive potential for F. eskia to successfully adapt to climate change.
Journal Article
Home site advantage in two long-lived arctic plant species: results from two 30-year reciprocal transplant studies
1. Reciprocal transplant experiments designed to quantify genetic and environmental effects on phenotype are powerful tools for the study of local adaptation. For long-lived species, especially those in habitats with short growing seasons, however, the cumulative effects of many years in novel environments may be required for fitness differences and phenotypic changes to accrue. 2. We returned to two separate reciprocal transplant experiments thirty years after their initial establishment in interior Alaska to ask whether patterns of differentiation observed in the years immediately following transplant have persisted. We also asked whether earlier hypotheses about the role of plasticity in buffering against the effects of selection on foreign genotypes were supported. We censused survival and flowering in three transplant gardens created along a snowbank gradient for a dwarf shrub (Dryas octopetala) and six gardens created along a latitudinal gradient for a tussock-forming sedge (Eriophorum vaginatum). For both species, we used an analysis of variance to detect fitness advantages for plants transplanted back into their home site relative to those transplanted into foreign sites. 3. For D. octopetala, the original patterns of local adaptation observed in the decade following transplant appeared even stronger after three decades, with the complete elimination of foreign ecotypes in both fellfield and snowbed environments. For E. vaginatum, differential survival of populations was not evident 13 years after transplant, but was clearly evident 17 years later. There was no evidence that plasticity was associated with increased survival of foreign populations in novel sites for either D. octopetala or E. vaginatum. 4. Synthesis. We conclude that local adaptation can be strong, but nevertheless remain undetected or underestimated in short-term experiments. Such genetically based population differences limit the ability of plant populations to respond to a changing climate.
Journal Article
Artificial selection on flowering time: influence on reproductive phenology across natural light environments
1. Flowering time is frequently under selection due to a combination of abiotic, biotic and intrinsic factors. Evolution in response to this selection is likely to have broad effects, altering not only flowering time but reproductive phenology and, potentially, traits throughout the life cycle. We know little about the broader phenotypic changes associated with evolutionary shifts in flowering time, and the extent to which expression of these changes depends on local environmental conditions. 2. After three generations of selection for early‐ and late‐flowering, we grew plants of the herb Campanulastrum americanum in contrasting light environments (light gap and understorey) in its home population. 3. Response to selection on flowering time and correlated responses in reproductive phenology were expressed across light environments with the reproduction of early‐flowering lines being over 2 weeks ahead of late‐flowering lines. Plants in the understorey delayed initiation of flowering but accelerated flower deployment, fruit maturation and the end of reproduction, resulting in a condensed reproductive period. 4. Timing of seed dispersal influences whether offspring grow as annuals or biennials in C. americanum. Because evolution of flowering time shifted reproductive phenology, it is likely to alter life history frequency. In contrast, understorey habitats both delayed flowering and accelerated reproductive phenology, yielding no expected life history change. 5. Synthesis. Evolution of flowering time altered the phenology of all subsequent reproductive traits and is also likely to affect offspring traits. This ripple effect of changes in flowering time indicates that it is essential to recognize genetic and functional linkages among traits to understand potential life cycle consequences of selection on a single character.
Journal Article
Why phylogenies do not always predict ecological differences
The merger of phylogenies with ecology has given rise to the field of \"community phylogenetics,\" predicated on the assumption that ecological differences among species can be estimated from phylogenetic relationships (the phylogenetic distance/ecological difference, or PDED, hypothesis). A number of studies have failed to find strong support for this assumption, thus challenging the utility of phylogenetic approaches. This gap might highlight the fact that the PDED relationship is not useful for community assembly, but it is difficult to know because the lack of a relationship might also be due to a number of biological or methodological reasons, including inappropriate phylogenies, skewed distributions of phylogenetic distances, the lack of consideration of models of trait evolution, or the absence of sufficient niche space in experimental and observational venues. Each of these limitations, separately or combined, may confound recent experimental or observational results that examine relationships between phylogenetic distance and ecological differences. Notably, common evolutionary models can support alternative conclusions about the relationship between evolutionary distances and ecological differences than typically assumed and can change interpretations of community-based phylogenetic analyses. Here we review a number of issues that may lead to confounded effects in community phylogenetic analyses. In light of these potential pitfalls, we provide a number of guidelines for researchers to follow and stress that they need to address methodological shortcomings before concluding that ecological differences are unrelated to phylogenetic distances.
Journal Article
Ecology in an anthropogenic biosphere
Humans, unlike any other multicellular species in Earth's history, have emerged as a global force that is transforming the ecology of an entire planet. It is no longer possible to understand, predict, or successfully manage ecological pattern, process, or change without understanding why and how humans reshape these over the long term. Here, a general causal theory is presented to explain why human societies gained the capacity to globally alter the patterns, processes, and dynamics of ecology and how these anthropogenic alterations unfold over time and space as societies themselves change over human generational time. Building on existing theories of ecosystem engineering, niche construction, inclusive inheritance, cultural evolution, ultrasociality, and social change, this theory of anthroecological change holds that sociocultural evolution of subsistence regimes based on ecosystem engineering, social specialization, and non-kin exchange, or \"sociocultural niche construction,\" is the main cause of both the long-term upscaling of human societies and their unprecedented transformation of the biosphere. Human sociocultural niche construction can explain, where classic ecological theory cannot, the sustained transformative effects of human societies on biogeography, ecological succession, ecosystem processes, and the ecological patterns and processes of landscapes, biomes, and the biosphere. Anthroecology theory generates empirically testable hypotheses on the forms and trajectories of long-term anthropogenic ecological change that have significant theoretical and practical implications across the subdisciplines of ecology and conservation. Though still at an early stage of development, anthroecology theory aligns with and integrates established theoretical frameworks including social-ecological systems, social metabolism, countryside biogeography, novel ecosystems, and anthromes. The \"fluxes of nature\" are fast becoming \"cultures of nature.\" To investigate, understand, and address the ultimate causes of anthropogenic ecological change, not just the consequences, human sociocultural processes must become as much a part of ecological theory and practice as biological and geophysical processes are now. Strategies for achieving this goal and for advancing ecological science and conservation in an increasingly anthropogenic biosphere are presented.
Journal Article
Phenotypic differentiation in a common garden reflects the phylogeography of a widespread Alpine plant
1. Glacial history has affected the phylogeographic structure of numerous Alpine plant species, but its impact on phenotypic differentiation has been little studied. Therefore, we asked whether phenotypic differentiation in a common garden reflects the phylogeographic structure of the widespread Alpine plant Geum reptans L. 2. We combined a molecular investigation with a common garden experiment and investigated genets from 16 populations of G. reptans sampled from the European Alps. Using neutral molecular markers (RAPDs) and Bayesian cluster analysis, we analysed the species’ genetic differentiation and phylogeographic structure. In the common garden, we measured the differentiation of phenotypic traits related to growth, reproduction and leaf morphology. 3. Molecular analysis partitioned the populations into three genetic groups, indicating pronounced phylogeographic structure. Regional molecular variation was correlated with regional phenotypic differentiation. 4. Quantitative trait differentiation (QST) differed from neutral molecular differentiation (GST) in 10 of 11 traits, indicating that selection has contributed to phenotypic differentiation. Significant negative correlations between biomass and precipitation records for site of origin are a further indication of adaptation. 5. Synthesis. The current study compared regional molecular variation and phenotypic differentiation among populations of a widespread species in the context of extreme range changes during glaciations in the Alps. Because the common garden phenotypic differentiation of G. reptans reflects its phylogeographic structure, we conclude that glacial history affected both genotypes and phenotypes. The results suggest that the present‐day phenotypic differentiation was caused by genetic drift and limited gene flow between populations in glacial refugia and during post‐glacial recolonization, as well as by adaptation to current climatic conditions. Our findings are relevant for understanding the adaptive potential of Alpine plants and predicting potential range shifts in response to future climate change.
Journal Article
EXAMINING THE FULL EFFECTS OF LANDSCAPE HETEROGENEITY ON SPATIAL GENETIC VARIATION: A MULTIPLE MATRIX REGRESSION APPROACH FOR QUANTIFYING GEOGRAPHIC AND ECOLOGICAL ISOLATION
Understanding the effects of landscape heterogeneity on spatial genetic variation is a primary goal of landscape genetics. Ecological and geographic variables can contribute to genetic structure through geographic isolation, in which geographic barriers and distances restrict gene flow, and ecological isolation, in which gene flow among populations inhabiting different environments is limited by selection against dispersers moving between them. Although methods have been developed to study geographic isolation in detail, ecological isolation has received much less attention, partly because disentangling the effects of these mechanisms is inherently difficult. Here, I describe a novel approach for quantifying the effects of geographic and ecological isolation using multiple matrix regression with randomization. I explored the parameter space over which this method is effective using a series of individual-based simulations and found that it accurately describes the effects of geographic and ecological isolation over a wide range of conditions. I also applied this method to a set of real-world datasets to show that ecological isolation is an often overlooked but important contributor to patterns of spatial genetic variation and to demonstrate how this analysis can provide new insights into how landscapes contribute to the evolution of genetic variation in nature.
Journal Article
Canopy closure shapes clonal diversity and fine-scale genetic structure in the dioecious understorey perennial Mercurialis perennis
1. The degree of canopy closure can shape the dynamics of understorey plant populations that rely on clonal and sexual recruitment. Populations are expected to undergo declines in clonal diversity under conditions where recruitment from seed is temporally and spatially restricted. Localized seedling recruitment in clonal populations may also affect spatial genetic structure due to the clumping of genetically related genets. 2. Our major objective was to determine the effect of the degree of canopy closure on clonal diversity and spatial genetic structure in the rhizomatous, dioecious forest perennial Mercurialis perennis. As the distribution of the male and female shoots has been shown to be influenced by canopy openings, we paid special attention to the mediating role of the varying sex ratio. 3. We used genome-wide AFLP markers to fingerprint six populations of M. perennis along a light penetration gradient. 4. The proportion of male shoots in a population increased from 0.51 to 0.81 and male genet diversity decreased from 0.72 to 0.21 with increasing site illumination, in agreement with earlier reports of superior male growth in canopy openings. The most illuminated population, with the highest proportion of male shoots, was dominated by a few outsized, largely aggregated male clones (largest clone spreading over 10 m). 5. Overall clonal diversity (G/N: 0.31-0.74; mean: 0.52) and evenness strongly declined in well-lit sites, suggesting reduced sexual recruitment and the vast vegetative spread of a few locally well-adapted male genets under canopy gaps. 6. Fine-scale genetic structure among genets was significant within all populations, but its degree tended to increase with an increased proportion of male shoots and reduced clonal diversity. Very localized recruitment due to a low seed dispersal capacity combined with the aggregated distribution of large gender-specific clones likely incurred this pattern. 7. Synthesis. Forest management practices such as the cutting and removal of trees and the establishment of paths decreased the degree of canopy closure. Many understorey herb populations flourish in these canopy gaps, reflected in a higher clonal diversity. We demonstrated, however, that increased illumination negatively affects genotypic and genetic diversity in the dioecious understorey herb M. perennis.
Journal Article