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Abstract

Phenotypic plasticity and local adaptation are the two main processes underlying trait variability. Under rapid environmental change, phenotypic plasticity, if adaptive, could increase the odds for organisms to persist. However, little is known on how environmental variation has shaped plasticity across species ranges over time. Here, we assess whether the portion of phenotypic variation of tree populations linked to the environment is related to the inter-annual climate variability of the last century and how it varies among populations across species ranges and age. To this aim, we used 372,647 individual tree height measurements of three pine species found in low elevation forests in Europe: Pinus nigra Arnold, P. pinaster Aiton and P. pinea L. Measurements were taken in a network of 38 common gardens established in Europe and North Africa with 315 populations covering the distribution range of the species. We fitted linear mixed-effect models of tree height as a function of age, population, climate and competition effects. Models allowed us to estimate tree height response curves at the population level and indexes of populations' phenotypic variation, as a proxy of phenotypic plasticity, at 4, 8 and 16 years old, and relate these indexes to the inter-annual climate variability of the last century. We found that phenotypic variation in tree height was higher in young trees than in older ones. We also found that P. pinea showed the highest phenotypic variation in tree height compared with P. pinaster and P. nigra. Finally, phenotypic variation in tree height may be partly adaptive, and differently across species, as climate variability during the last century at the origin of the populations explained between 51 and 69% of the current phenotypic variation of P. nigra and P. pinea, almost twice of the levels of P. pinaster. Main conclusions Populations' phenotypic variation in tree height is largely explained by the climate variability that the populations experienced during the last century, which we attribute to the genetic diversity among populations.

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... Local adaptation involves evolutionary processes that generally occur over the long-term (Savolainen et al. 2007), with the disadvantage of generating population maladaptation if climate changes too fast (Fréjaville et al. 2020). Reaction norms (i.e. the expression of a genotype across different environments) are the usual way to explore the plasticity of a genotype, but they can be relaxed for range-wide approaches to populations' reaction norms (Gianoli and Valladares 2012;Vizcaíno-Palomar et al. 2020), reflecting hence the capacity of one population to adjust to different environments. As a consequence, new range-wide approaches grounded on populations reaction norms are estimated on fitness-related traits measured on common gardens to account for populations' capacity to adjust to new climates (Benito Garzón et al. 2011Garzón et al. , 2019Sáenz-Romero et al. 2017;Gárate Escamilla et al. 2019;Leites et al. 2019;Patsiou et al. 2020;Vizcaíno-Palomar et al. 2020;Gárate-Escamilla et al. 2020). ...
... Reaction norms (i.e. the expression of a genotype across different environments) are the usual way to explore the plasticity of a genotype, but they can be relaxed for range-wide approaches to populations' reaction norms (Gianoli and Valladares 2012;Vizcaíno-Palomar et al. 2020), reflecting hence the capacity of one population to adjust to different environments. As a consequence, new range-wide approaches grounded on populations reaction norms are estimated on fitness-related traits measured on common gardens to account for populations' capacity to adjust to new climates (Benito Garzón et al. 2011Garzón et al. , 2019Sáenz-Romero et al. 2017;Gárate Escamilla et al. 2019;Leites et al. 2019;Patsiou et al. 2020;Vizcaíno-Palomar et al. 2020;Gárate-Escamilla et al. 2020). These approaches have shown that broadleaf species tend to show higher levels of plasticity than conifers, at least for fitnessrelated traits (Benito Garzón et al. 2019). ...
... Second, I used mixed-effects models to predict Caribbean pine reproduction across the tropical regions of the world as a response to co-variating traits defined by SEM and the provenance and environmental effects. I tested the following hypothesis (i) the environmental effect is higher than the provenance effect in fitness-related traits, giving high flexibility to the phenotypes to adjust to climatic conditions outside the distribution range of the species (Gárate Escamilla et al. 2019;Vizcaíno-Palomar et al. 2020); (ii) reproduction increases along with tree size in optimal environmental conditions (Roff 2000) such as those where the trees were planted and (iii) tree stem quality and growth can show trade-offs for slow-growing populations (Mihai and Mirancea 2016). ...
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... Great advantage is their ability to predict the performance of any population growing in any climate (Wang et al., 2010). While URFs are basically linear models, several recent studies have extended this approach to the mixed model framework, which allows to consider the experimental design as random effects in modeling intraspecific variation in single (Fréjaville et al., 2020;Vizcaíno-Palomar et al., 2020) and multiple traits (Gárate-Escamilla et al., 2019). In this respect, Benito-Garzón et al. (2019) proposed the term TraitSDM to summarize all models considering phenotypic trait variation (e.g., survival, growth, and phenology) as key dimension in the response of populations to rapid environmental change. ...
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... The first and oldest group is represented by Species Distribution Modelling techniques (SDM), where the spatial distribution of a target species is considered as a proxy of its realised niche (Elith et al. 2006, Pecchi et al. 2019. While SDM techniques have been used widely across time and space (Isaac-Renton et al. 2014, Tang et al. 2020, their shortcomings have been recognised, such as the need to ac-count for phenotypic plasticity and genetic adaptation through phenotyping traits in genetic trials (Vizcaíno-Palomar et al. 2020). Actually the huge genetic variability and phenotypic plasticity of tree species is an important resource for species performance across ecological gradients (Matyas 1994), observed using common garden experiments and reciprocal transplanting activities. ...
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... Although field trials were originally planted for breeding purposes, they have proved to be a useful resource to understand the likelihood of survival under climate change (Mátyás, 1994) providing accurate indicators of plasticity and local adaptation of fitness-related traits among provenances. As such, field trials have been extensively used to improve breeding programs (Gray et al., 2016), quantify phenotypic plasticity (Matesanz and Ramírez-Valiente, 2019;Vizcaíno-Palomar et al., 2020), perform species range predictions accounting for local adaptation and phenotypic plasticity , and design assisted migration programs (Isaac-Renton et al., 2014). ...
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Chapter
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Editor: Adrienne Nicotra Premise of research. In the future, ecosystems will have to deal with climate warming in combination with increasing frequency and magnitude of extreme weather events such as drought. Adaptive phenotypic plasticity enables plants to respond to environmental variability and is likely to buffer impacts of climate change. Therefore, factors that influence the phenotypic plasticity of plant populations must be identified to assess climate change outcomes and support conservation measures. Genetic diversity in many temperate plant species is known to vary among regions and populations, largely as a result of their phylogeographic history during the late Pleistocene and Holocene. Here, we argue that high (neutral) genetic diversity of populations might represent increased probability of possessing alleles or allele combinations that are advantageous or more capable in terms of average response capacities to environmental change. Methodology. We test this idea for European beech (Fagus sylvatica) by investigating response patterns of plant growth and leaf phenology to drought and warming treatments in a common-garden experiment with seedlings of six populations from Bulgaria and Germany. Phenotypic plasticity of populations was assessed and correlated with allozyme diversity. Populations differed in their plasticity to warming with respect to timing of leaf unfolding and senescence as well as in their drought plasticity in terms of height increment (marginally not significant), with some populations showing consistently high plasticity among traits. Pivotal results. Measures of genetic diversity showed an interregional structure according to known phylogeographic patterns. Height increment plasticity showed a significant positive correlation with genetic variation (allelic diversity) at the population level. Conclusions. Our results suggest general differences in phenotypic plasticity among populations and a potential influence of genetic diversity on the average plasticity. Besides its evolutionary value, genetic diversity might thus be an important property of plant populations for their short-term response capability against adverse effects of climate change.
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Phenotypic plasticity has been suggested as the main mechanism for species persistence under a global change scenario, and also as one of the main mechanisms that alien species use to tolerate and invade broad geographic areas. However, contrasting with this central role of phenotypic plasticity, standard models aimed to predict the effect of climatic change on species distributions do not allow for the inclusion of differences in plastic responses among populations. In this context, the climatic variability hypothesis (CVH), which states that higher thermal variability at higher latitudes should determine an increase in phenotypic plasticity with latitude, could be considered a timely and promising hypothesis. Accordingly, in this study we evaluated, for the first time in a plant species (Taraxacum officinale), the prediction of the CVH. Specifically, we measured plastic responses at different environmental temperatures (5 and 20°C), in several ecophysiological and fitness-related traits for five populations distributed along a broad latitudinal gradient. Overall, phenotypic plasticity increased with latitude for all six traits analyzed, and mean trait values increased with latitude at both experimental temperatures, the change was noticeably greater at 20° than at 5°C. Our results suggest that the positive relationship found between phenotypic plasticity and geographic latitude could have very deep implications on future species persistence and invasion processes under a scenario of climate change.
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The widespread Mediterranean Pinus pinea showed exceptionally low genetic diversity and low differentiation between traits in the adult phase. We explored the adaptation potential of seedlings from four main Iberian provenances during their regeneration phase. We assessed the variability of shoot growth, allometry, physiological traits, and phenotypic plasticity to the interactive effect of light and water environments during 8-month moderate water-stress cycle and after one-week heat wave. The effect of shade and drought was mainly orthogonal whatever the provenance. The inland La Mancha provenance showed higher shoot growth and biomass compared to the southern coastal Depresión-del-Guadalquivir provenance. Following the heat wave, La Mancha presented higher net photosynthetic rates, a lower decrease in maximal quantum efficiency of PSII, and a higher accumulated relative height growth, thus, showing an adaptive advantage. The observed differences corroborated the ecological grouping of the provenances along latitudinal and inland–coastal gradients. We confirmed the high adaptive plasticity of Pinus pinea to the unpredictable Mediterranean environment.
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1.Interannual variability in climatic conditions should be taken into account in climate change studies in semiarid ecosystems. It may determine differentiation in phenotypic plasticity among populations, with populations experiencing higher environmental heterogeneity showing higher levels of plasticity.2.The ability of populations to evolve key functional traits and plasticity may determine the survival of plant populations under the drier and more variable climate expected for semiarid ecosystems.3.Working with populations of the semiarid Chilean shrub Senna candolleana along its entire distribution range, we assessed inter- and intra-population variation in functional traits as well as in their plasticity in response to water availability. We measured morphological and physiological traits related to drought resistance in both field conditions and in a greenhouse experiment, where drought response was evaluated under two water availability treatments.4.All populations responded plastically, but higher precipitation heterogeneity in dry-edge populations seemed to have selected for more plastic genotypes compared to populations growing at mesic sites and with more homogeneous environmental conditions.5.Synthesis: Our results suggest adaptive plasticity since higher levels of phenotypic plasticity were positively associated with plant performance. However, we did not find evidence for genetic variation for plasticity within populations. To the extent that phenotypic plasticity may play a key role in future persistence, populations at mesic sites may be more vulnerable to climate change due to their lower plasticity and their current limitations to evolve novel norms of reaction. Conversely, although Senna candolleana populations at the dry-edge are exposed to higher levels of stress, they may be less susceptible to climate change in view of their greater plasticity. We highlight the need to consider population differentiation in both mean traits and their plasticity to model realistic scenarios of species distribution under climate change.This article is protected by copyright. All rights reserved.
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Limitations of linear regression applied on ecological data. - Things are not always linear additive modelling. - Dealing with hetergeneity. - Mixed modelling for nested data. - Violation of independence - temporal data. - Violation of independence spatial data. - Generalised linear modelling and generalised additive modelling. - Generalised estimation equations. - GLMM and GAMM. - Estimating trends for Antarctic birds in relation to climate change. - Large-scale impacts of land-use change in a Scottish farming catchment. - Negative binomial GAM and GAMM to analyse amphibian road killings. - Additive mixed modelling applied on deep-sea plagic bioluminescent organisms. - Additive mixed modelling applied on phyoplankton time series data. - Mixed modelling applied on American Fouldbrood affecting honey bees larvae. - Three-way nested data for age determination techniques applied to small cetaceans. - GLMM applied on the spatial distribution of koalas in a fragmented landscape. - GEE and GLMM applied on binomial Badger activity data.
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Abstract Five population-specific response functions were developed from quadratic models for 110 populations of Pinus sylvestris growing at 47 planting sites in Eurasia and North America. The functions predict 13 year height from climate: degree-days > 5 °C; mean annual temperature; degree-days 5 °C to mean annual precipitation. Validation of the response functions with two sets of independent data produced for all functions statistically significant simple correlations with coefficients as high as 0.81 between actual and predicted heights. The response functions described the widely different growth potentials typical of natural populations and demonstrated that these growth potentials have different climatic optima. Populations nonetheless tend to inhabit climates colder than their optima, with the disparity between the optimal and inhabited climates becoming greater as the climate becomes more severe. When driven by a global warming scenario of the Hadley Center, the functions described short-term physiologic and long-term evolutionary effects that were geographically complex. The short-term effects should be negative in the warmest climates but strongly positive in the coldest. Long-term effects eventually should ameliorate the negative short-term impacts, enhance the positive, and in time, substantially increase productivity throughout most of the contemporary pine forests of Eurasia. Realizing the long-term gains will require redistribution of genotypes across the landscape, a process that should take up to 13 generations and therefore many years.
Article
Context Mediterranean pines share many common life-history traits. They are found at almost all altitudinal levels around the Mediterranean Basin, from sea level to high-elevation mountains, and from hot and dry to wet and cold bioclimates. Their distribution ranges from widespread to regional and narrow, and from dense extensive populations to small populations of scattered individuals. They have been extensively used by human civilizations for millennia. Aims I show which are the main phylogenetic, ecological, and climatic factors explaining the patterns of within and among-population genetic diversity in Mediterranean pines. Methods I use a narrative synthesis approach and multiple examples from the literature on pine species from the Mediterranean Basin and California. Results While Mediterranean pines have the highest levels of differentiation worldwide, their genetic diversity increases from west to east and is significantly reduced in low-elevation species. Factors such as ancestral adaptation to wildfire, reduction of effective population size during the Last Glacial Maximum, long distance dispersal during the Holocene, and more recent adaptation to patchy environmental conditions could explain these patterns. Conclusion Because of contrasted ecological, demographic, historical, and geographical processes, and despite their common biological attributes, pines of the Mediterranean Basin display complex biogeographic patterns at neutral gene level that can help retrace their evolutionary history. Although individual species often represent unique case studies that make generalizations risky, locating habitats of significantly high and low genetic diversity is key for detecting and understanding the major factors affecting gene diversity and may prove useful for profiling areas of high conservation value in the Mediterranean.
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Aim There is increasing concern regarding sustainable management and restoration of planted forests, particularly in the Mediterranean Basin where pine species have been widely used. The aim of this study was to analyse the environmental and structural characteristics of Mediterranean planted pine forests in relation to natural pine forests. Specifically, we assessed recruitment and woody species richness along climatic, structural and perturbation gradients to aid in developing restoration guidelines.
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Plant populations may show differentiation in phenotypic plasticity, and theory predicts that greater levels of environmental heterogeneity should select for higher magnitudes of phenotypic plasticity. We evaluated phenotypic responses to reduced soil moisture in plants of Convolvulus chilensis grown in a greenhouse from seeds collected in three natural populations that differ in environmental heterogeneity (precipitation regime). Among several morphological and ecophysiological traits evaluated, only four traits showed differentiation among populations in plasticity to soil moisture: leaf area, leaf shape, leaf area ratio (LAR), and foliar trichome density. In all of these traits plasticity to drought was greatest in plants from the population with the highest interannual variation in precipitation. We further tested the adaptive nature of these plastic responses by evaluating the relationship between phenotypic traits and total biomass, as a proxy for plant fitness, in the low water environment. Foliar trichome density appears to be the only trait that shows adaptive patterns of plasticity to drought. Plants from populations showing plasticity had higher trichome density when growing in soils with reduced moisture, and foliar trichome density was positively associated with total biomass.
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Organisms may respond to changing environments by evading the new conditions or by adapting to them. Recently, a large body of evidence has been collected indicating that phenotypic adaptation to climate change is widespread. Adaptation may be achieved by phenotypic adjustment or by changes in the genetic composition of populations. Both processes can assure the survival of populations in changing environments, but at different time scales and at different costs. Recent studies indicate that the mechanisms leading to adaptive phenotypic changes in birds may be complex, involving both plastic response and genetic change. Changes in the timing of breeding, for instance, seem to be predominantly caused by phenotypic adjustment to environmental conditions. Shifts in the genetic composition of populations have been demonstrated to be involved in recent changes in morphology and migratory behaviour. The presence of considerable amounts of additive genetic variation within and among avian populations, and examples of rapid evolutionary response to rare climatic events suggest that birds have a high potential for adaptive evolutionary change. However, it is presently unclear whether this is a general pattern, and which factors actually limit the adaptability of avian populations. Antagonistic genetic correlations and maladaptive phenotypic responses (evolutionary traps) are probably the most important constrains to microevolutionary change. Furthermore, the loss of genetic variation due to population declines, and gene flow in the presence of among-population variation in the response to climate change may limit the rate of adaptive evolution. Future research should try to identify the targets of selection and gauge the importance of constraints to microevolutionary change.
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A game-theoretical model of tree growth balances the advantages of height for light interception against height-related costs, such as increased maintenance respiration, that reduce the energy available for stem growth. The model predicts an evolutionarily stable strategy (ESS) for trees of even-aged stands. This ESS consists of a prolonged interval of height growth that terminates when the trees reach 87% of the theoretical break-even height, at which stem maintenance and root and leaf renewal costs require all available photosynthate, leaving none for wood production. Tests of the model with data from forest yield tables indicate that 1) average-sized trees of even-aged stands follow the predicted ESS until reaching at least 70-90% of their maximum height; 2) trees that are larger than average have thicker-than-expected trunks to withstand disproportionately greater wind forces in the upper canopy; 3) height growth may cease in very old stands, as predicted; and 4) height growth appears to cease gradually rather than suddenly. Features that are not in the model but might favor a gradual cessation of height growth include the greater wind exposure of the upper canopy and unpredictable environmental variation. The general success of the model suggests that competition for light is the primary factor responsible for the evolution and maintenance of the arboreal life form. -from Author
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At the boundary of the Mediterranean zone in southern France different woodland communities occur on N-facing and S-facing slopes. The regional climate is transitional between that of the Mediterranean zone with a well-marked summer drought and that of the cooler and moister mountains. Summer-green deciduous woodland with many species characteristic of central Europe (eg Fraxinus excelsior and Tilia cordata) occurs on steep N-facing slopes and in ravines. Woodland dominated by the evergreen Quercus ilex with many Mediterranean species (eg Cistus salvifolius and Lavandula stoechas) occurs on S-facing slopes. Preliminary studies in England show that Tilia cordata wilts, sheds leaves and has reduced growth when water potential of the shoots falls to -2.1 MPa. Quercus ilex shows no injury when water potential of the shoots falls to -3.5 MPa. Results demonstrate the primary importance of water supply in controlling both thet small- and large-scale pattern of distribution of T. cordata near its southern limit in Europe. -from Authors
Article
The assembly of Mediterranean pines in the sense ofMirov is inhomogeneous in respect to morphological, geographical and evolutionary affinities. Considering new or neglected characters (vegetative and particularly reproductive, cone scales, apophyses, mucros, seeds: Figs. 1–3) in extant populations and fossils, three groups are recognized. The group of coast and island pines extends from the Canary islands to the Himalaya region and is closely related to Caribbean and C. American taxa. This complex evidently has originated from haploxyl ancestors of sect.Parrya during the Mesozoic (Upper Jurassic/Lower Cretaceous) in the NW. Tethys area (Fig. 13).P. rzedowskii can be regarded as an extant survivor of this first phase of differentiation. The extremely variableP. canariensis (together withP. roxburghii in sect.Sula) marks a transitional phase towards the more advanced diploxyl species of sect.Pinea (withP. pinea, P. halepensis &P. brutia, and subsect.Oocarpae) and sect.Pinaster (withP. pinaster, etc.) (Figs. 4–12).—The second group consists of diploxyl mountain pines from the areas surrounding the Mediterranean. They are classified as members of the Eurasiatic sect.Pinus subsect.Sylvestres, have differentiated along the northern Parathetys area, and exhibit close links with E. Asiatic taxa. The third group includes the haploxyl mountain pinesP. cembra andP. peuce which can be regarded as western outposts of the circumpacific centred sect.Strobus with a pre-Tertiary origin.—As an appendix, an improved classification scheme is presented for the pine groups discussed.
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Climate change is inducing changes in the phenological timings of organisms. Genetic diversity could influence phenological responses to climate change, but empirical evidence is very limited. We estimated the regional variation across Japan in flowering and leaf budburst dates of plants based on a dataset of phenological timings from 1953 to 2005. The observed plants' genetic diversities varied according to human cultivation. The within-species variations of phenological response to temperature as well as regional variations were less in the plant populations with lower genetic diversity. Thus, genetic diversity influences the variation in phenological responses of plant populations. Under increased temperatures, low variation in phenological responses may allow drastic changes in the phenology of plant populations with synchronized phenological timings. Our findings indicate that we should pay attention to maintaining genetic diversity of populations to alleviate changes in phenology due to future climate change.
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The use of both linear and generalized linear mixed-effects models (LMMs and GLMMs) has become popular not only in social and medical sciences, but also in biological sciences, especially in the field of ecology and evolution. Information criteria, such as Akaike Information Criterion (AIC), are usually presented as model comparison tools for mixed-effects models. The presentation of variance explained' (R2) as a relevant summarizing statistic of mixed-effects models, however, is rare, even though R2 is routinely reported for linear models (LMs) and also generalized linear models (GLMs). R2 has the extremely useful property of providing an absolute value for the goodness-of-fit of a model, which cannot be given by the information criteria. As a summary statistic that describes the amount of variance explained, R2 can also be a quantity of biological interest. One reason for the under-appreciation of R2 for mixed-effects models lies in the fact that R2 can be defined in a number of ways. Furthermore, most definitions of R2 for mixed-effects have theoretical problems (e.g. decreased or negative R2 values in larger models) and/or their use is hindered by practical difficulties (e.g. implementation). Here, we make a case for the importance of reporting R2 for mixed-effects models. We first provide the common definitions of R2 for LMs and GLMs and discuss the key problems associated with calculating R2 for mixed-effects models. We then recommend a general and simple method for calculating two types of R2 (marginal and conditional R2) for both LMMs and GLMMs, which are less susceptible to common problems. This method is illustrated by examples and can be widely employed by researchers in any fields of research, regardless of software packages used for fitting mixed-effects models. The proposed method has the potential to facilitate the presentation of R2 for a wide range of circumstances.
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We lack information regarding the main factors driving growth responses to drought in tree species with different vulnerability against this stressor and considering sites with contrasting climatic conditions. In this paper, we identify the main drivers controlling growth response to a multi-scalar drought index (Standardized Precipitation Index, SPI) in eight tree species (Abies alba, Pinus halepensis, Quercus faginea, Pinus sylvestris, Quercus ilex, Pinus pinea, Pinus nigra, Juniperus thurifera). We sampled forests growing across a pronounced climatic gradient under Mediterranean conditions in north-eastern Spain. To summarize the patterns of growth responses to drought, we used principal component analysis (PCA). To determine the main factors affecting growth responses to drought, correlation and regression analyses were carried out using a set of abiotic (climate, topography, soil type) and biotic (Normalized Difference Vegetation Index, Enhanced Vegetation Index, tree-ring width, diameter at breast height) predictors and the PCs loadings as response variables. The PCA analysis detected two patterns of growth responses to drought corresponding to xeric and mesic sites, respectively. The regression analyses indicated that growth responses to drought in xeric forests were mainly driven by the annual precipitation, while in mesic sites the annual water balance was the most important driver. The management of Mediterranean forests under the forecasted warmer and drier conditions should focus on the main local factors modulating the negative impacts of drought on tree growth in xeric and mesic sites.
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Populations are locally adapted when populations have the highest relative fitness at their home sites, and lower fitness in other parts of the range. Results from the extensive experimental plantations of populations of forest trees from different parts of the range show that populations can survive and grow in broad areas outside the home site. However, intra- and interspecific competition limit the distribution of genotypes. For populations from large parts of the range, relative fitness, compared with the local population, is often highest at the home site. At the edges of the range, this local adaptation may break down. The extent of local adaptation is determined by the balance between gene flow and selection. Genetic differentiation and strong natural selection occur over a range of tens or hundreds of kilometers, but reliable measurements of gene flow are available only for much shorter distances. Current models of spatially varying selection could be made more realistic by the incorporation of st...
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The aim of the study was to assess the potential importance for Mediterranean plants of trade-offs in the response to irradiance and water availability at the regeneration stage. Survival and growth patterns across an experimentally imposed irradiance gradient (1, 6, 20 and 100% sunlight) were studied in seedlings of eight Mediterranean woody species, together with the impact of a simulated summer drought. We found evidence of some of the trade-offs previously reported for non-Mediterranean plant communities, such as between survival in the shade and relative growth rate (RGR) at high light, but no evidence for others, such as between shade and drought tolerances. The impact of drought on survival and RGR was stronger in high light than in deep shade. The observed species-specific differences in performance provide a mechanistic basis for niche differentiation at the regeneration stage, contributing to possible explanations of species coexistence in Mediterranean ecosystems.
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Research into interspecific variation in functional traits is important for our understanding of trade-offs in plant design and function, for plant functional type classifications and for understanding ecosystem responses to shifts in species composition. Interspecific rankings of functional traits are a function of, among other factors, ontogenetic or allometric development and environmental effects on phenotypes. For woody plants, which attain large size and long lives, these factors might have strong effects on interspecific trait rankings. This paper is the first to test and compare the correspondence of interspecific rankings between laboratory grown seedlings and field grown adult plants for a wide range of functional leaf and stem traits. It employs data for 90 diverse woody and semi-woody species in a temperate British and a (sub)Mediterranean Spanish flora, all collected according to a strict protocol. For 12 out of 14 leaf and stem traits we found significant correlations between the species ranking in laboratory seedlings and field adults. For leaf size and maximum stem vessel diameter > 50 % of variation in field adults was explained by that in laboratory seedlings. Two important determinants of plant and ecosystem functioning, specific leaf area and leaf N content, had only 27 to 36 and 17 to 31 % of variation, respectively, in field adults explained by laboratory seedlings, owing to subsets of species with particular ecologies deviating from the general trend. In contrast, interspecific rankings for the same traits were strongly correlated between populations of field adults on different geological substrata. Extrapolation of interspecific trait rankings from laboratory seedlings to adult plants in the field, or vice versa, should be done with great caution. Nomenclature: Castroviejo et al. (1986–2000); Stace (1991). Abbreviations: DM/SM = Leaf dry mass/saturated mass ratio; LD = leaf density; PAR = Photosynthetically active radiation; SLA = Specific leaf area; SSLM = Specific saturated leaf mass; SVDmax = Maximum stem vessel diameter.
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Global change and emerging concepts in ecology and evolution are leading to a growing interest in phenotypic plasticity (PP), the environmentally contingent trait expression observed in a given genotype. The need to quantify PP in a simple manner in com- parative ecological studies has resulted in the prevalence of various indices instead of the classic approaches, i.e. a comparison of slopes in the norms of reactions (trait vs. environment plots). The objectives of this study were: (i) to review the most common methods for quantitative estimation of PP; (ii) to apply them to a specific case study of growth and shoot–root allocation responses to irradiance in seedlings of four woody species grown at 1%, 6%, 20% and 100% full sunlight; and (iii) to propose new methods of estimating PP. The 17 different plasticity indices analysed rendered disparate results, with cross-overs in species PP rankings. Statistical comparisons of PP among species were not possible with most of the indices due to the lack of confidence intervals. The non-linear responses of the traits made the use of the slope of the reaction norm to quantify PP unrealistic, and raised awareness on values derived from studies that consider just two environments. We propose an alternative approach to quantify PP based on phenotypic distances among individuals of a given species exposed to different environments, which is summarized in a relative distance plasticity index (RDPI) that allows for statistical comparisons of PP between species (or populations within species). RDPI was signifi- cantly correlated with 12 out of the 17 PP indices analysed. An index including the environmental range leading to the different phenotypes (environmentally standard- ized plasticity index, ESPI), and thus expressing plasticity per unit of environmental change, is also proposed. The new indexes can statistically segregate and unambiguously rank species according to their PP, which can foster a better understanding of plant ecology and evolution, particularly when common protocols are used by different investigators.
Article
Phenotypic plasticity is traditionally defined as the capacity of a given genotype to render alternative phenotypes under different environmental conditions. Some studies focus on the individual genotype to study ‘true’ phenotypic plasticity, regardless of the level of ecological organization involved in each particular study. We argue that, depending on the research question and the scale, there are advantages of looking beyond the genetic identity of each individual phenotype when addressing phenotypic plasticity. This broad approach may simplify experimental designs, increase their statistical power, and allow a more inclusive estimation of the extent of phenotypic plasticity in natural populations. We also posit that when the focus is on the ecological significance of a given phenotype, the final ontogenetic stage and size of the experimental individuals whose plastic responses are compared should not be necessarily considered as confounding factors. A broad approach to the genotypic basis of phenotypic responses, focusing on the representativeness of the genotypic sample, together with the recognition that any environmentally-induced phenotypic change is legitimate plasticity (and potential target of natural selection), may contribute to the understanding of the ecological significance of phenotypic plasticity. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105, 1–7.
Article
Aim To assess the effect of local adaptation and phenotypic plasticity on the potential distribution of species under future climate changes. Trees may be adapted to specific climatic conditions; however, species range predictions have classically been assessed by species distribution models (SDMs) that do not account for intra-specific genetic variability and phenotypic plasticity, because SDMs rely on the assumption that species respond homogeneously to climate change across their range, i.e. a species is equally adapted throughout its range, and all species are equally plastic. These assumptions could cause SDMs to exaggerate or underestimate species at risk under future climate change.
Article
Aim The aims of this study were to assess the distribution of putative Mediterranean refugia of plants, to compare the locations of refugia and those of regional hotspots of plant biodiversity, and to provide a critical analysis of the Mediterranean refugium paradigm. Furthermore, we consider how biogeographical and genetic results can be combined to guide global conservation strategies. Location The Mediterranean region. Methods We started from a detailed analysis of the scientific literature (1993–2007) in order to identify refugia in the Mediterranean region, based on intra-specific phylogeographical studies of plant species. We used population locations together with gene-pool identity to establish the database, comparing patterns of phylogeographical concordance with the locations of Mediterranean refugia. We then tested the biogeographical congruence between two biodiversity components, namely phylogeographical refugia and regional hotspots. Results We identified 52 refugia in the Mediterranean bioclimatic region and confirmed the role played by the three major peninsulas, with a shared total of 25 refugia. We emphasize the importance of areas that have previously been attributed a lesser role (large Mediterranean islands, North Africa, Turkey, Catalonia). Of the 52 refugia identified, 33 are situated in the western Mediterranean Basin and 19 in the eastern part. The locations of the phylogeographically defined refugia are significantly associated with the 10 regional hotspots of plant biodiversity, with 26 of these refugia (i.e. 50%) occurring within the hotspots. Main conclusions The locations of refugia are determined by complex historical and environmental factors, the cumulative effects of which need to be considered because they have occurred since the Tertiary, rather than solely during the last glacial period. Refugia represent climatically stable areas and constitute a high conservation priority as key areas for the long-term persistence of species and genetic diversity, especially given the threat posed by the extensive environmental change processes operating in the Mediterranean region. The refugia defined here represent ‘phylogeographical hotspots’; that is, significant reservoirs of unique genetic diversity favourable to the evolutionary processes of Mediterranean plant species.
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The description of the collinearity diagnostics as presented in Belsley, Kuh, and Welsch's, Regression Diagnostics: Identifying Influential Data and Sources of Collinearity, is principally formal, leaving it to the user to implement the diagnostics and learn to digest and interpret the diagnostic results. This paper is designed to overcome this shortcoming by describing the different graphical displays that can be used to present the diagnostic information and, more importantly, by providing the detailed guidance needed to promote the beginning user into an experienced diagnostician and to aid those who wish to incorporate or automate the collinearity diagnostics into a guided-computer environment.