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The legacy of climate variability over the last century on populations' phenotypic variation in tree height
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.
... kurdica based on the PC1/PC2 derived from phenotypic traits. The two-letter symbols represent the populations, which are explained in Table 1 in response to local and regional environmental changes (Liu and El-Kassaby 2019;Vizcaíno-Palomar et al. 2020). Unfortunately, our results cannot distinguish the effects of genetic components from the effects of environmental components on the observed phenotypic variations, since commongarden experiments would be needed to do so. ...
... This pattern of population grouping may be interpreted as evidence for the occurrence of parallel acclimation or adaptation in populations clustered in the same group, indicating that similar environmental factors may exert similar adaptive, selective, or acclimative forces on phenotypic variations in populations from different geographical areas (Adams 2010). This result is in agreement with previous observations on three pine species, which show that tree height variation at the population level is mainly driven by climate variability that the populations experienced during their evolutionary history (Vizcaíno-Palomar et al. 2020). Functional traits such as LMA, and leaf and seed size dimensions are important traits widely used in ecological modeling for linking the forest trees' distribution and their Table 1 Fig . ...
... Page 14 of 22 adaptation to the local variation of environmental factors (El Zerey-Belaskri and Benhassaini 2016; Benavides et al. 2021aBenavides et al. , 2021bVizcaíno-Palomar et al. 2020). For example, LMA, the ratio between leaf dry mass and leaf area (in g m −2 ), is one of the important traits involved in the adaptation and acclimation of different plant species to environmental stresses (Nicotra et al. 2010). ...
Pistacia atlantica subsp. kurdica (PAK) is both an economically and ecologically keystone tree species of semi-mountainous and semi-arid forests in western and southern Iran; however, its standing genetic diversity is increasingly threatened by a range of pressures such as climate change and anthropogenic landscape degradation. To support the development of suitable conservation and management plans for this species, the geographic pattern of phenotypic and genetic variation of 33 populations (a total of 567 trees), along the climate gradient of the species natural distribution in Iran from the temperate to dry-warm forest, was examined using six phenotypic traits and 13 nuclear microsatellite markers. We found significant phenotypic variation in all traits and populations along with the shifting climate and observed smaller leaves but larger and heavier seeds in the dry-warm southern populations. Based on neutral SSRs analysis of genetic variation in the nuclear genome, although the current PAK populations have maintained moderate to high levels of genetic diversity (HE = 0.566–0.711) to date, the populations inhabiting degraded localities in southern Zagros forests maintained lower levels of genetic diversity statistics as compared to the germplasm from the northern landscape of these forests. In addition, populations have shown a high degree of genetic differentiation (FST = 0.291) which can mostly be explained by the scattered and fragmented patterns of PAK distribution in the Zagros forests and the geographical barriers to the genetic material exchange between populations. STRUCTURE analysis revealed a geographical genetic structure and clustered populations into five main clusters corresponding to the northern, central, and southern populations, demonstrating substantial variability across the species’ range in the values of environmental drivers shaping the composition of the populations’ genome. Finally, the Mantel tests for correlation among population matrices detected significant positive correlations between genetic and both geographic and climatic distances. These findings are expected to provide theoretical support for the management and conservation designs of the PAK genetic resources in the Zagros mountains.
... One of the most common ways to forecast the most likely effects of climate change on forest systems is by means of statistical models such as species distribution models (SDM), based on the spatial occurrence of tree species at geographic scale (Araújo and New 2007;Pecchi et al. 2019). Various statistical models have also been developed such as reaction norms or response functions (Rehfeldt et al. 1999;Marchi et al. 2022; and trait models (O'Neill et al. 2008;Vizcaíno-Palomar et al. 2020;Benito Garzón 2021;Hallingbäck et al. 2021), mostly when more detailed data are available (i.e. common garden experiments). All these techniques aim at modelling the explained or potential niche of the target species as a function of environmental drivers (mainly climate variables). ...
... This last tool was used in this study to downscale the main climatic variables with a monthly resolution (Tmin, Tmax and Precipitation) of CHELSA v2.1 (original spatial resolution is 1 km) up to 500 m and to create the 1991-2020 normal period for the whole Europe. Afterwards, the raw monthly variables were used to calculate a set of nine climatic indices widely used in previous studies (Isaac-Renton et al. 2014;Benito Garzón et al. 2019;Vizcaíno-Palomar et al. 2020;Hallingbäck et al. 2021;Marchi and Cocozza 2021;Ray et al. 2021;Marchi et al. 2022). Climatic indices are generally more adequate to be used as predictor variables in spatial. ...
... Moreover, a geographic extent larger than expected has been found to be suitable for the species. Although modelers warn about the extrapolation issues (Fréjaville et al. 2019;Vizcaíno-Palomar et al. 2020;Hallingbäck et al. 2021;Marchi et al. 2022) and refer to the potential biases when using models to predict values outside the observed range of variation, this study is not affected in such a. The pSDM simply analyzes the expressed ecological niche projected into the geographic space for a selected period (2041-2070 in our case). ...
Regions of provenance for forest reproductive materials are the basis for wise use of forest resources in a changing climate. In this work a modelling framework is proposed for silver fir (Abies alba Mill.) in Italy where genetic clusters described by nuclear microsatellites were combined with high-resolution climatic data. When the genetic clusters were too large or had an uncertain ecological niche expression, an additional subregion division-was evaluated according to a climatic assessment. Subsequently each genecological group (Region of Provenance, RoP) was projected in geographic space separately using species distribution modelling (SDM) procedure under current (1991–2020) and a future climate scenario derived from the 6th assessment report for the period 2041–2070. The final division into nine RoPs was able to explain 77.41% of the total climatic variance, a good trade-off between statistical significance and practical usability. The modelling steps then showed a large degree of ecological overlap between RoPs with some of them occurring in similar ecological environments but characterized by a different genetic structure. When projected at the continental scale, the Italian RoPs were found to be suitable for almost all the current European range of silver fir, with potential expansion in Nordic countries in the future, beyond the current distribution range. The study showed that the combination of genetic and ecological data can be a robust way to proceed in areas where a strong genetic differentiation between populations occurs, such as in Italy. New markers such as SNPs can then be used to detect adaptive traits and drive the selection of provenances for common garden experiments in areas where the SDM modelscurrently extrapolate potential sites outside the current natural range.
... Particularly, populations have diverged in growth habits (de la Mata et al., 2014;Vizcaino-Palomar et al., 2016), following climate gradients (Correia et al., 2010). Maritime pine growth is also highly plastic to environmental conditions, with plasticity largely varying across populations (Rodriguez-Garcia & Bravo, 2013;Vizcaino-Palomar et al., 2020). ...
... Recent meta-analyses using data from multi-environmental common-garden networks indicated that among-population variation in plasticity to macro-environmental variation is the norm in plants (Matesanz et al., 2019) as seen elsewhere (Voltas et al., 2018;Vizcaino-Palomar et al., 2020). ...
... Environmental differences across trials were thus strong enough to trigger relevant and divergent plastic responses in Maritime pine populations. These results confirmed that this species is highly plastic to environmental conditions, as previously suggested Vizcaino-Palomar et al., 2020). Furthermore, despite the Atlantic character of test sites, Mediterranean populations showed even increased competitive ability in the poorest sites (Fig. S3). ...
Phenotypic plasticity is a main mechanism for sessile organisms to cope with changing environments. Plasticity is genetically based and can evolve under natural selection so that populations within a species show distinct phenotypic responses to environment. An important question that remains elusive is whether the intraspecific variation in plasticity at different spatial scales is independent from each other.
To test whether variation in plasticity to macro‐ and micro‐environmental variation is related among each other, we used growth data of 25 Pinus pinaster populations established in seven field common gardens in NW Spain. Phenotypic plasticity to macro‐environmental variation was estimated across test sites while plasticity to micro‐environmental variation was estimated by using semivariography and kriging for modeling within‐site heterogeneity.
We provide empirical evidence of among‐population variation in the magnitude of plastic responses to both micro‐ and macro‐environmental variation. Importantly, we found that such responses were positively correlated across spatial scales.
Selection for plasticity at one scale of environmental variation may impact the expression of plasticity at other scales, having important consequences on the ability of populations to buffer climate change. These results improve our understanding of the ecological drivers underlying the expression of phenotypic plasticity.
... The idea that species diversity only is important for forest resilience, ignores or underestimates the role of intra-specific genetic diversity (Alberto et al., 2013;Ennos et al., 2019) phenotypic plasticity (Vizcaíno-Palomar et al., 2020) and the evolutionary potential of trees (Lefèvre et al., 2013) which help maintain fitness under environmental change. These genetic factors play a major role in maintaining tree, stand health and vigour under climatic stress. ...
... These genetic factors play a major role in maintaining tree, stand health and vigour under climatic stress. For some species, provenance, progeny, and clonal forest reproductive material (FRM) have been tested and phenotyped for different traits (Vizcaíno-Palomar et al., 2020), including the resistance to abiotic and biotic threats (Hurel et al., 2021) in common garden genetic trials across an environmental range. For some species tested material has been incorporated into seed orchards, to provide FRM with known traits, including the resistance and avoidance of biotic and abiotic threats (Haapanen and Ruotsalainen, 2021). ...
... The height growth of maritime pine, Corsican pine (Pinus nigra ssp. laricio) and stone pine across a network of 38 common garden trials in the Mediterranean basin were analysed (Vizcaíno-Palomar et al., 2020). A phenotypic plasticity index, based on the ratio of the difference of the highest phenotypic value (of height) measured for a local population and compared to the value for the climatic range of the species was measured. ...
Deciding how to establish woodland in forest restoration is not straightforward as different outcomes may be obtained from different establishment approaches, each with cost implications and degree of success limitations attached. Planning restoration requires knowledge of site conditions, including how sites are likely to respond under climate change. For objectives of production and high timber quality it is likely that ground preparation will be used, and planting with forest reproductive material (FRM) of known traits, such as: high survival and growth in establishment, drought tolerance adequate for climate projections, good resistance to pests and pathogens. For objectives associated with biodiversity, carbon sequestration, water supply protection, soil protection, natural regeneration could be a less costly solution with a limited amount of assisted translocation of selected FRM to improve resilience. If objectives are for rewilding forest areas, a degree of natural colonisation perhaps with translocation of some FRM could be a solution. Ignoring site conditions and suitability of available sources of FRM for forest restoration is likely to provide unexpected results with a mix of open ground, scrub and scattered trees resulting from climate, herbivore, and browsing impacts. The recent B4EST EU Horizon 2020 project examined progress in novel rapid approaches for testing the quality of FRM from existing genetic trials. Here we review the work of B4EST to show the opportunities from transformative tree breeding in forest restoration schemes, including: new climate projection ensembles at high temporal and spatial resolution to develop norms of reaction and transfer models with genetic components; multi-environment genotype-phenotype associations and multi-locus genotype-environment associations in identifying drivers of local adaptation; techniques for genomic selection using single nucleotide polymorphism (SNP) arrays to derive functional traits from polygenic associations; work on Frontiers in Forests and Global Change 01 frontiersin.org Ray et al. 10.3389/ffgc.2022.1005761 seed orchard site and climate specific FRM and zones for deployment; and work on some of the forest ecosystem service benefits derived at a landscape scale. We conclude that tree-breeding will provide robust forest restoration for planting, and rewilding (assisted natural regeneration), and if not "ignoring" but instead assisting natural colonisation processes-tree breeding may improve long-term forest resilience under environmental change.
... The idea that species diversity only is important for forest resilience, ignores or underestimates the role of intra-specific genetic diversity (Alberto et al., 2013;Ennos et al., 2019) phenotypic plasticity (Vizcaíno-Palomar et al., 2020) and the evolutionary potential of trees (Lefèvre et al., 2013) which help maintain fitness under environmental change. These genetic factors play a major role in maintaining tree, stand health and vigour under climatic stress. ...
... These genetic factors play a major role in maintaining tree, stand health and vigour under climatic stress. For some species, provenance, progeny, and clonal forest reproductive material (FRM) have been tested and phenotyped for different traits (Vizcaíno-Palomar et al., 2020), including the resistance to abiotic and biotic threats (Hurel et al., 2021) in common garden genetic trials across an environmental range. For some species tested material has been incorporated into seed orchards, to provide FRM with known traits, including the resistance and avoidance of biotic and abiotic threats (Haapanen and Ruotsalainen, 2021). ...
... The height growth of maritime pine, Corsican pine (Pinus nigra ssp. laricio) and stone pine across a network of 38 common garden trials in the Mediterranean basin were analysed (Vizcaíno-Palomar et al., 2020). A phenotypic plasticity index, based on the ratio of the difference of the highest phenotypic value (of height) measured for a local population and compared to the value for the climatic range of the species was measured. ...
Deciding how to establish woodland in forest restoration is not straightforward as different outcomes may be obtained from different establishment approaches, each with cost implications and degree of success limitations attached. Planning restoration requires knowledge of site conditions, including how sites are likely to respond under climate change. For objectives of production and high timber quality it is likely that ground preparation will be used, and planting with forest reproductive material (FRM) of known traits, such as: high survival and growth in establishment, drought tolerance adequate for climate projections, good resistance to pests and pathogens. For objectives associated with biodiversity, carbon sequestration, water supply protection, soil protection, natural regeneration could be a less costly solution with a limited amount of assisted translocation of selected FRM to improve resilience. If objectives are for rewilding forest areas, a degree of natural colonisation perhaps with translocation of some FRM could be a solution. Ignoring site conditions and suitability of available sources of FRM for forest restoration is likely to provide unexpected results with a mix of open ground, scrub and scattered trees resulting from climate, herbivore, and browsing impacts. The recent B4EST EU Horizon 2020 project examined progress in novel rapid approaches for testing the quality of FRM from existing genetic trials. Here we review the work of B4EST to show the opportunities from transformative tree breeding in forest restoration schemes, including: new climate projection ensembles at high temporal and spatial resolution to develop norms of reaction and transfer models with genetic components; multi-environment genotype-phenotype associations and multi-locus genotype-environment associations in identifying drivers of local adaptation; techniques for genomic selection using single nucleotide polymorphism (SNP) arrays to derive functional traits from polygenic associations; work on Frontiers in Forests and Global Change 01 frontiersin.org Ray et al. 10.3389/ffgc.2022.1005761 seed orchard site and climate specific FRM and zones for deployment; and work on some of the forest ecosystem service benefits derived at a landscape scale. We conclude that tree-breeding will provide robust forest restoration for planting, and rewilding (assisted natural regeneration), and if not "ignoring" but instead assisting natural colonisation processes-tree breeding may improve long-term forest resilience under environmental change.
... 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). ...
• Key message
The combination of structural equation modelling and linear mixed-effects models opens a new perspective to investigate trait adaptation syndromes through phenotypic integration prediction at large geographical scales, a necessary step to understand the future of organisms under climate change. In the case of Pinus caribaea Morelet, reproduction limits the species suitability, decreasing towards southernmost latitudes where dry conditions increase.ContextCaribbean pine is an ecologically and economically important species planted in all the tropical regions of the world, where it shows optimal growth and survival but low reproduction rates.AimsThis study investigates Caribbean pine fitness-related traits, accounting for phenotypic plasticity and local adaptation, to detect co-variation among traits and predict their relationship across the tropics.MethodsI re-analysed earlier data of survival, growth, reproduction, stem quality and development stage from 25 provenances of Caribbean pine planted in 16 trials in the tropical regions in a two-step modelling approach including (i) structural equation modelling (SEM) based on the current knowledge of the species and theoretical expectations coming from other species; (ii) mixed-effects model accounting for trait-relationships as defined by SEM and allowing for trait prediction.ResultsGrowth, survival and reproduction showed a slight but significant provenance effect indicating population differentiation and a positive co-variation between growth and reproduction, suggesting that trees reached optimal growth before they reproduced. Models predicted low reproduction rates of Caribbean pine across the tropics, decreasing towards southern latitudes where dry conditions increased.Conclusion
This study opens new perspectives to investigate trait adaptation syndromes through phenotypic integration prediction at large geographical scales.
... Although nutrients essential for plant growth are concentrated within this soil layer, soil drying due to drought reduces diffusivity and mass flow of nutrients (Ryel et al., 2008), and precipitation-induced nutrient pulses are only available to roots in contact with the surface layers (Hodge, 2004;Ryel et al., 2008). Thus, greater root plasticity at the recruitment stage could favour uptake of essential nutrients during periods of increased soil moisture (Vizcaíno-Palomar et al., 2020). Although we could not evaluate trait-associated differences in seedling survival because few seedlings died during our study, we found that root biomass plasticity, root length plasticity and root surface area plasticity were highest for seedlings from summer-wet environments, potentially allowing a faster growth response to infrequent resource pulses (Ushio et al., 2015;Vizcaíno-Palomar et al., 2020). ...
... Thus, greater root plasticity at the recruitment stage could favour uptake of essential nutrients during periods of increased soil moisture (Vizcaíno-Palomar et al., 2020). Although we could not evaluate trait-associated differences in seedling survival because few seedlings died during our study, we found that root biomass plasticity, root length plasticity and root surface area plasticity were highest for seedlings from summer-wet environments, potentially allowing a faster growth response to infrequent resource pulses (Ushio et al., 2015;Vizcaíno-Palomar et al., 2020). ...
Background and Aims
In dryland ecosystems, conifer species are threatened by more frequent and severe droughts, which can push species beyond their physiological limits. Adequate seedling establishment will be critical for future resilience to global change. We used a common garden greenhouse experiment to determine how seedling functional trait expression and plasticity varied among seed sources in response to a gradient of water availability, focusing on a foundational dryland tree species of the western United States, Pinus monophylla. We hypothesized that the expression of growth-related seedling traits would show patterns consistent with local adaptation, given clinal variation among seed source environments.
Methods
We collected P. monophylla seeds from 23 sites distributed across rangewide gradients of aridity and seasonal moisture availability. A total of 3,320 seedlings were propagated with 4 watering treatments representing progressively decreasing water availability. Aboveground and belowground growth-related traits of first-year seedlings were measured. Trait values and trait plasticity, here representing the degree of variation among watering treatments, were modeled as a function of watering treatment and environmental conditions at the seed source locations (i.e., water availability, precipitation seasonality).
Key Results
We found that, under all treatments, seedlings from more arid climates had larger aboveground and belowground biomass compared to seedlings from sites experiencing lower growing-season water limitation, even after accounting for differences in seed size. Additionally, trait plasticity in response to watering treatments was greatest for seedlings from summer-wet sites that experience periodic monsoonal rain events.
Conclusions
Our results show that P. monophylla seedlings respond to drought through plasticity in multiple traits, but variation in trait responses suggests that different populations are likely to respond uniquely to changes in local climate. Such trait diversity will likely influence the potential for future seedling recruitment in woodlands that are projected to experience extensive drought-related tree mortality.
... Our results show that the degree of phenotypic plasticity in growth of ponderosa pine populations was positively correlated with climate heterogeneity at the seed source locations. This is consistent with empirical (Gianoli, 2004;Gianoli & Gonzalez-Teuber, 2005;van Kleunen & Fischer, 2005) and theoretical studies (Alpert & Simms, 2002;Bradshaw & Hardwick, 1989;Matesanz et al., 2010) showing that phenotypic plasticity can be related to the environmental heterogeneity a population is subjected to, including conifer (Vizcaino-Palomar et al., 2020) and broadleaved (Balaguer et al., 2001) forest tree species. However, most of these previous studies focused on temporal, as opposed to spatial, variability as the source of heterogeneity, despite the fact that spatial variability adds environmental complexity (Scheiner, 2013), and in some cases, it has been shown to affect plasticity (Ernande & Dieckmann, 2004;Sultan & Spencer, 2002). ...
... These results are in line with prior studies in other plant species(Castillo et al., 2018;Kreyling et al., 2019) including the Mediterranean Stone pine (Pinus pinea L.;Vizcaino-Palomar et al., 2020). This pattern has been interpreted as a compensatory mechanism for the lack of genetic diversity to cope with environmental change. ...
Phenotypic plasticity is a main mechanism for organisms to cope with changing environments and broaden their ecological range. Plasticity is genetically based and can evolve under natural selection, such that populations within a species show distinct phenotypic responses to the environment if evolved under different conditions. Understanding how intraspecific variation in phenotypic plasticity arises is critical to assess potential adaptation to ongoing climate change. Theory predicts that plasticity is favored in more favorable but variable environments. Yet, many theoretical predictions about benefits, costs, and selection on plasticity remain untested. To test these predictions, we took advantage of three genetic trials in the northern Rocky Mountains, USA, which assessed 23 closely located Pinus ponderosa populations over 27 years. Mean environmental conditions and their spatial patterns of variation at the seed source populations were characterized based on six basic climate parameters. Despite the small area of origin, there was significant genetic variation in phenotypic plasticity for tree growth among populations. We found a significant negative correlation between phenotypic plasticity and the patch size of environmental heterogeneity at the seed source populations, but not with total environmental spatial variance. These results show that populations exposed to high microhabitat heterogeneity have evolved higher phenotypic plasticity and that the trigger was the grain rather than the total magnitude of spatial heterogeneity. Contrary to theoretical predictions, we also found a positive relationship between population plasticity and summer drought at the seed source, indicating that drought can act as a trigger of plasticity. Finally, we found a negative correlation between the quantitative genetic variance within populations and their phenotypic plasticity, suggesting compensatory adaptive mechanisms for the lack of genetic diversity. These results improve our understanding of the microevolutionary drivers of phenotypic plasticity, a critical process for resilience of long‐lived species under climate change, and support decision‐making in tree genetic improvement programs and seed transfer strategies.
... Similarly, European populations of P. sylvestris from low-altitude and high-latitude locations were reported to have lower height growth (Wachowiak et al. 2017). The local adaptation of population to climate variability is one of the main processes shaping morphological variation (Vizcaíno-Palomar et al. 2020), and the high correlations between trait variation and the geographical environment of origin were also observed in many studies. The tree height and radius of canopy showed highly significant differences among altitudinal ranges of Terminalia catappa in Indonesia (Marjenah and Putri 2017). ...
Pinus sylvestris var. mongolica plays a crucial role in the ecological restoration and industrial raw material production of arid and semiarid regions in northern China. The widespread degradation of its near‐mature plantation (over 30 years) is a significant concern, having been a topic of interest in recent decades. In this study, the genetic diversity and population genetic structure were assessed using 12 simple sequence repeat (SSR) markers within 11 native provenance populations and eight plantation populations. Additionally, variations in eight morphological traits of their offspring were evaluated at three sites in northern China. The results revealed high genetic diversity and weak genetic differentiation among the native provenance populations. The mean number of alleles (Na), allelic richness (Ar), expected heterozygosity (He), and Shannon–Wiener diversity index (I) were 5.492, 4.679, 0.550, and 1.120, respectively, and the genetic differentiation coefficient (FST) was 0.022. Significant population effects of tree height and height to live crown base (HCB), as well as interactions of population with site and block within site, were observed in tree height, HCB, stem diameter at breast height (DBH), stem volume (VOL), crown shape (CS), and disease grade (DG). The genetic diversity parameters based on SSR markers and breeding values of tree height, DBH, HCB, VOL, and stem form (SF) of plantation populations were found to be lower than those of native provenance populations. Significant positive correlations were identified between the mean effective number of alleles per locus (Ne) and VOL as well as He and crown width (CW). Furthermore, the maximum temperature of the warmest month (BIO5) and the silt content (T_SILT) were identified as significant factors influencing genetic diversity parameters and morphological variation, respectively. The findings provide scientific support for the reduction of plantation degradation, the effective restoration, and the sustainable management of forests for this species.
... Furthermore, analyses of existing data have been focused on identifying differences in performance in population means. Except for rare examples (Vizcaíno-Palomar et al., 2020), potential differences in plasticity between populations have seldom been studied, despite being important for determining a population's ability to withstand a changing climate (Valladares et al., 2014). ...
Climate change is expected to outpace the rate at which populations of forest trees can migrate. Hence, in forestry there is growing interest in intervention strategies such as assisted migration to mitigate climate change impacts. However, until now the primary focus when evaluating candidates for assisted migration has been mean or maximum performance. We explore phenotypic plasticity as a potentially new avenue to help maintain the viability of species and populations in the face of climate change. Capitalizing on large, multi-site international provenance trials of four economically and ecologically important forest tree species (Fagus sylvatica, Picea abies, Picea engelmannii, Pinus contorta), we quantify growth stability as the width of the response function relating provenance growth performance and trial site climate. We found significant differences in growth stability among species, with P. engelmannii being considerably more stable than the other three species. Additionally, we found no relationship between growth performance and growth stability of provenances, indicating that there are fast-growing provenances with a broad climate optimum. In two of the four species, provenances' growth stability showed a significant relationship with the climate of the seed source, the direction of which depends on the species. When taken together with data on growth performance in different climate conditions, a measure of growth stability can improve the choice of species and provenances to minimize future risks in forest restoration and reforestation.
... It has been shown that the evolutionary responses of perennial species can be constrained in unsuitable areas because adults produce maladapted offspring [49]. According to some expectations, the Atlantic area under study will increase its productivity [50] and future suitability, while in the southern range of the species the suitability will decrease [51]. Moreover, the predicted changes in the distribution of the species under future climatic conditions, indicate that the Atlantic area could be part of the ecological niche of southern genetic groups of the species [52,53]. ...
Background
Predicting the adaptability of forest tree populations under future climates requires a better knowledge of both the adaptive significance and evolvability of measurable key traits. Phenotypic plasticity, standing genetic variation and degree of phenotypic integration shape the actual and future population genetic structure, but empirical estimations in forest tree species are still extremely scarce. We analysed 11 maritime pine populations covering the distribution range of the species (119 families and 8 trees/family, ca. 1300 trees) in a common garden experiment planted at two sites with contrasting productivity. We used plant height as a surrogate of fitness and measured five traits (mean and plasticity of carbon isotope discrimination, specific leaf area, needle biomass, Phenology growth index) related to four different strategies (acquisitive economics, photosynthetic organ size, growth allocation and avoidance of water stress).
Results
Estimated values of additive genetic variation would allow adaptation of the populations to future environmental conditions. Overall phenotypic integration and selection gradients were higher at the high productivity site, while phenotypic integration within populations was higher at the low productivity site. Response to selection was related mainly to photosynthetic organ size and drought-avoidance mechanisms rather than to water use efficiency. Phenotypic plasticity of water use efficiency could be maladaptive, resulting from selection for height growth.
Conclusions
Contrary to the expectations in a drought tolerant species, our study suggests that variation in traits related to photosynthetic organ size and acquisitive investment of resources drive phenotypic selection across and within maritime pine populations. Both genetic variation and evolvability of key adaptive traits were considerably high, including plasticity of water use efficiency. These characteristics would enable a relatively fast micro-evolution of populations in response to the ongoing climate changes. Moreover, differentiation among populations in the studied traits would increase under the expected more productive future Atlantic conditions.
... This mainly stemmed from a lack of explicit hypothesis testing of these drivers when reanalyzing provenance trial data. Some studies evaluated a suite of climate variables and used a statistical process to select those variables with the highest contribution to explained trait variance (e.g., Gárate-Escamilla et al., 2019;Leites et al., 2019;Rehfeldt et al., 1999;Thomson et al., 2009;Vizcaíno-Palomar et al., 2020), whereas other studies fitted models using climate variables found to be important in previous studies (e.g., Carter, 1996;Onofrio et al., 2021). Nonetheless, of the 28 species in this search for which evidence of intraspecific genetic differentiation related to home climate has been found, 16 species ...
Intraspecific variation plays a critical role in extant and future forests responses to climate change. Forest tree species with wide climatic niches rely on the intraspecific variation resulting from genetic adaptation and phenotypic plasticity to accommodate spatial and temporal climate variability. A centuries-old legacy of forest ecological genetics and provenance trials has provided a strong foundation upon which to continue building on this knowledge, which is critical to maintain climate-adapted forests. Our overall objective is to understand forest trees intraspecific responses to climate across species and biomes, while our specific objectives are to describe ecological genetics models used to build our foundational knowledge, summarize modeling approaches that have expanded the traditional toolset, and extensively review the literature from 1994 to 2021 to highlight the main contributions of this legacy and the new analyzes of provenance trials. We reviewed 103 studies comprising at least three common gardens, which covered 58 forest tree species, 28 of them with range wide studies. Although studies using provenance trials data cover mostly commercially important forest tree species from temperate and boreal biomes, this synthesis provides a global overview of forest tree species adaptation to climate. We found that evidence for genetic adaptation to local climate is commonly present in the species studied (79%), being more common in conifers (87.5%) than in broadleaf species (67%). In 57% of the species, clines in fitness-related traits were associated with temperature variables, in 14% species with precipitation and in 25% of the species by both. Evidence of adaptation lags was found in 50% of the species with range wide studies. We conclude that ecological genetics models and analysis of provenance trials data provide excellent insights on intraspecific genetic variation, whereas the role and limits of phenotypic plasticity, which will likely determine the fate of extant forests, is vastly understudied.
... Several studies have shown that environmental variation promotes higher plasticity (e.g. Baythavong 2011;L azaro-Nogal et al. 2015;Vizcaino-Palomar et al. 2020). As such, plasticity related to drought tolerance, as well as resistance to invasive annual grasses, may enhance seedling establishment in the Great Basin. ...
Seed selection is critical for successful restoration in semiarid systems. In the Great Basin, drought and annual grass invasion are primary barriers to native perennial seedling establishment. Local seed sourcing is encouraged to overcome drought, as drier populations exhibit drought‐adapted traits. Whether drought‐adapted traits are also beneficial for resisting invasive annual grasses, however, is an outstanding question. Here, we evaluate seedling performance and trait expression of Sandberg bluegrass (Poa secunda), a native perennial grass commonly used in restoration, in a factorial experiment that crossed seed source (five populations collected along an aridity gradient), water treatment (wet and dry), and competition (with and without cheatgrass). Seeds from the wettest site had the highest mean seedling establishment rate and biomass compared to seeds from drier sites. Establishment rate was sensitive to drought but not to cheatgrass competition, whereas biomass was sensitive to both stressors. Watering and competition treatments had a significant interaction effect on seedling trait expression. Specifically, without cheatgrass competition P. secunda exhibited more resource‐conservative traits under drought, such as lower specific leaf area (SLA) and higher proportion of fine roots, whereas the relationship shifted such that with cheatgrass competition P. secunda exhibited more resource‐acquisitive traits under drought. Plasticity of seedling emergence and root length were negatively correlated with drought tolerance, which suggests no evidence for adaptive plasticity. As trait‐based approaches are increasingly used for seed selection in the Great Basin, our results highlight that the predictive power of traits for drought depends on the context of annual grass invasion. This article is protected by copyright. All rights reserved.
... 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. ...
The most common tool to predict future changes in species range are species distribution models. These models do, however, often underestimate potential future habitat, as they do not account for phenotypic plasticity and local adaptation, although being the most important processes in the response of tree populations to rapid climate change. Here, we quantify the difference in the predictions of future range for Norway spruce, by (i) deriving a classic, occurrence-based species distribution model (OccurrenceSDM), and (ii) analysing the variation in juvenile tree height and translating this to species occurrence (TraitSDM). Making use of 32 site locations of the most comprehensive European trial series that includes 1,100 provenances of Norway spruce originating from its natural and further beyond from its largely extended, artificial distribution, we fit a universal response function to quantify growth as a function of site and provenance climate. Both the OccurrenceSDM and TraitSDM show a substantial retreat towards the northern latitudes and higher elevations (−55 and −43%, respectively, by the 2080s). However, thanks to the species’ particularly high phenotypic plasticity in juvenile height growth, the decline is delayed. The TraitSDM identifies increasing summer heat paired with decreasing water availability as the main climatic variable that restricts growth, while a prolonged frost-free period enables a longer period of active growth and therefore increasing growth potential within the restricted, remaining area. Clear signals of local adaptation to climatic clines spanning the entire range are barely detectable, as they are disguised by a latitudinal cline. This cline strongly reflects population differentiation for the Baltic domain, but fails to capture the high phenotypic variation associated to the geographic heterogeneity in the Central European mountain ranges paired with the species history of postglacial migration. Still the model is used to provide recommendations of optimal provenance choice for future climate conditions. In essence, assisted migration may not decrease the predicted range decline of Norway spruce, but may help to capitalize on potential opportunities for increased growth associated with warmer climates.
... 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. ...
The cultivation of hybrid poplar clones is increasing worldwide. Hundreds of hectares of plantations now occur across Europe and other continents such as North America, using tested clones and novel genotypes. Research effort aims are to develop fast growing disease-and pest-resistant clones to improve production quality and quantity. In this study the phenotypic plasticity of poplar clones was tested across environmental and temporal gradients. The growth performance of 49 hybrid poplar clones recorded between 1980 and 2021 was analysed using a mixed-effects model with climatic data as a predictor variable. Clones were aggregated into two groups according to their breeding protocol (i.e., standard clone, and improved material) and their growth modelled for future climate scenarios of RCPs 2.6 and 8.5 using a downscaled version of the variants 01 and 21 of UKCP18 climate projections dataset for three 30-year normal period time-slices: 2030s, 2040s, 2050s. The fitted growth models showed highly significant results, explaining more than 85% of the variance, with a mean relative absolute error of approximately 2%. Improved material showed more resistance to warmer and drier climates and less sensitivity to the changing climate. While no unique pattern was found when comparing growth performances, new improved clones were more productive than older clones (e.g., 'I-214') with an additional benefit of resistance to rust and pests. Spatial predictions confirmed the Po valley as the most important geographic area for poplar cultivation in Italy, but zones in Central and Southern Italy show potential. However, the Po Valley is also where poplars are predicted to be suitable in the next decades with large uncertainties. The analysis identified the need for more research on the topic of poplar breeding. For example, models using the most extreme (warm and dry) climate projection, variant 01 of RCP8.5 of the UKCP18, exceeded the historic climate threshold, and predictions used model extrapolation, with associated statistical uncertainty. Therefore , predictions should be considered with care and more research effort is required to test clones over wider environmental conditions.
... 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). ...
Forests provide important ecosystem services and renewable materials. Yet, under a future climate, optimal conditions will likely shift outside the current range for some tree species. This will challenge the persistence of populations to rely on inherent plasticity and genetic diversity to acclimate or adapt to future uncertain conditions. An opportunity to study such processes is offered by Scots pine (Pinus sylvestris L.), a forest tree with a large distribution range including populations locally adapted to a wide variety of environments, which hinders a range-wide assessment of the species to climate change. Here we evaluate tree height growth uncertainty of Scots pine marginal populations in Spain and the Nordic countries linked to their genetic adaptation promoted by different climatic drivers. Our aims are to: (i) review the main climatic drivers of Scots pine adaptation across its range; (ii) undertake provenance-based modeling and prediction of tree height under current and future climate scenarios including four representative concentration pathways (RCPs) and five general circulation models (GCMs) at two extremes of its climatic niche; (iii) estimate uncertainty in population tree height linked to the main drivers of local adaptation that may change among RCPs and GCMs in the Nordic countries and Spain. Our models revealed that tree height adaptation is mostly driven by drought in Spain and by photoperiod in the Nordic countries, whereas the literature review also highlighted temperature as a climatic driver for the Nordic region. Model predictions for the Nordic countries showed an overall increase in tree height but with high uncertainty in magnitude depending on the RCPs and GCMs whereas predictions for Spain showed tree height to be maintained in the north and reduced in the south, but with similar magnitudes among RCPs and GCMs. Both models predicted tree height outside the data range used to develop the models (extrapolation). Predictions using higher emission RCPs resulted in larger extrapolated areas, constituting a further source of uncertainty. An expanded network of Scots pine field trials throughout Europe, facilitated by data collection and international research collaboration, would limit the need for uncertain predictions based on extrapolation.
Pinus is the largest genus of conifers with more than 120 species. Some of the most extended and relevant forest trees in the northern hemisphere are pines. About 30 pine species bear seeds large enough to be collected for human consumption. Those seed kernels, also known as pine nuts, are one of the first known foods of forest-dwelling humans in Eurasia, including Neanderthals. Similarly, ancient American people relied on local pine nuts as a seasonal staple food. This chapter highlights the origin, evolutionary and cultural history and genetic diversity of some of the most relevant ‘stone pines’, namely Pinus pinea from the Mediterranean, Pinus koraiensis from Northeast Asia, and the Mexican Pinus cembroides. Their contrastive history is an example of different evolutionary strategies adopted by tree species.
Maritime pine (Pinus pinaster Ait.) covers vast areas and is of economic importance in southwestern Europe, particularly in Galicia (NW Spain). Galicia is a heterogeneous region with an Atlantic climate in the coast and a Mediterranean-like climate in the inland, where forest reproductive materials (FRM) with proper adaptation, productivity and timber quality are not available. Thus, there is a need for tailored FRM recommendations for reforestation in this region. P. pinaster is particularly sensitive to environmental variation and shows significant intraspecific genetic variability in this sensitivity, so understanding population responses to environmental variation becomes crucial for proper selection of FRM. Taking advantage of volume growth and stem straightness 13 years after planting, assessed on c. 7500 trees from 25 P. pinaster populations established in seven common gardens across inland Galicia, we analyzed intraspecific variation in sensitivity to climate, geographic, edaphic and site quality factors. We used Mantel correlations and factorial regression models to distinguish the environmental parameters explaining the observed population × site interaction. We also estimated population phenotypic plasticity across sites and the existing genetic relationship between growth and stem straightness to define the optimal selection strategy for productivity purposes. Results showed a quantitatively significant population × site interaction for growth whereas it was almost negligible for stem straightness. In the case of growth, no specific environmental factor was able to explain the population relative performance across test sites, being site quality the only significant factor but with low power to describe the patterns found. Population differences were maximized in higher site quality conditions, where the largest gains from planting selected populations would be expected. Tree growth and straightness were not genetically correlated. Based on these results, subdividing inland Galicia for deployment of P. pinaster FRM throughout specific selections for each subregion is not recommended. Selecting FRM based on average growth and its phenotypic stability should be also avoided, as both properties were negatively correlated. We recommend selecting FRM based on the results from high quality sites, where Atlantic origin populations with high levels of genetic improvement showed the fastest growth. The inclusion of selection criteria based on stem straightness did not alter recommendations given that fast growing FRM showed intermediate or slightly above-average straightness. The limited explanatory power of climate factors for the population × site interaction prevents adjusting recommendations in light of the projected climate change.
Tasmania’s distinctive climate environment supports highly productive and carbon-dense tall eucalypt forests, but also a vulnerability to climate change. Measurements in Eucalyptus obliqua tall forest at the Warra SuperSite in southern Tasmania showed them to be very sensitive to warmer temperatures. Gross primary productivity (GPP) declines sharply when temperatures rise above the forest’s relatively low temperature optimum for GPP. Heatwaves (consecutive days of unusually high temperatures) cause the forest to switch from being a net carbon sink to a net carbon source. As the climate changes and heatwaves occur more often, the risk of severe adverse impacts to this important ecosystem increases. Our current understanding of why the Tasmanian E. obliqua tall forest is so sensitive to warmer temperatures, even if imperfect, can allow appropriate management interventions to be identified and enabling policy settings to be formulated. Tasmania’s climate environment was associated with several features of the unique response by the tall eucalypt forests to heatwaves. The high sensitivity of GPP to temperature in the forest was associated with a low temperature range – GPP sensitivity to temperature increased as temperature range experienced by the forest decreased. The decline of GPP during warm conditions was not associated with either moisture limitation or atmospheric dryness (high vapour pressure deficits), a likely reflection of the high rainfall environment in which tall eucalypt forests grow in Tasmania. Low winter radiation associated with Tasmania’s high latitude, contributes to a lack of seasonal temperature acclimation by the forest. Because the forest responses to heatwaves were associated with the local climate environment, enhanced natural selection of local genotypes is identified as the most prospective approach to help Tasmania’s tall eucalypt forests adapt to a new, warmer climate. Enhanced natural selection is only feasible to do in forests that are managed for wood production. Policy settings that allow for the continuation of native forest harvesting will be needed if enhanced natural selection is to supply future needs of climate-adapted seed for regeneration and restoration of tall eucalypt forest areas in Tasmania.
Climate change is favouring the northward shift of Mediterranean oaks which are expanding their ranges at their leading edges. However, Mediterranean oaks have recalcitrant seeds (desiccation sensitive) that do not form seed banks, depending on climate conditions after seed fall and interactions between genetic determinants to germinate. Here we investigate the potential adaptation of Quercus suber range-wide populations to increasing spring temperature in germination timing and rates. We sowed 701 acorns from 9 populations from 10 mother trees each, at 15, 20 and 25 °C and monitored germination daily during 90 days. We modelled germination timing through Cox’s proportional-hazards models, assessed populations’ adaptation to spring temperature transfer distances and quantified the effect of acorn mass and storage duration on germination probability and timing with fixed-effects models. We used the mixed-effects models to predict germination climatic niches under current and RCP 8.5 2080 scenarios. Differences in germination timing were due to both the population origin and temperature treatment; germination rates showed a sub-optimality towards warmer-than-origin temperatures. The timing of germination decreased along with spring temperatures increment, with germination in 2080 predicted to occur 12 days earlier than to date in central Iberia. Warmer spring temperatures significantly accelerate the germination of recalcitrant Mediterranean species, which could alter seedlings’ developmental environment and ultimately populations’ regeneration and species composition. As such, germination timing should receive more attention from scientists and stakeholders and should be included in forest vulnerability assessments and assisted migration programs aiming at long-term forest regeneration to adapt forests to climate change.
Population response functions based on climatic and phenotypic data from common gardens have long been the gold standard for predicting quantitative trait variation in new environments. However, prediction accuracy might be enhanced by incorporating genomic information that captures the neutral and adaptive processes behind intrapopulation genetic variation. We used five clonal common gardens containing 34 provenances (523 genotypes) of maritime pine (Pinus pinaster Aiton) to determine whether models combining climatic and genomic data capture the underlying drivers of height growth variation and thus improve predictions at large geographical scales. The plastic component explained most of the height growth variation, probably resulting from population responses to multiple environmental factors. The genetic component stemmed mainly from climate adaptation and the distinct demographic and selective histories of the different maritime pine gene pools. Models combining climate of origin and gene pool of the provenances as well as height-associated positive-effect alleles (PEAs) captured most of the genetic component of height growth and better predicted new provenances compared with the climate-based population response functions. Regionally selected PEAs were better predictors than globally selected PEAs, showing high predictive ability in some environments even when included alone in the models. These results are therefore promising for the future use of genome-based prediction of quantitative traits.
The persistence of species distribution ranges depends on the tolerance and adaptive capacity of populations to novel conditions created by a changing climate. In the particular case of Mediterranean pines, which realized climatic niches are largely influenced by temperature, expected warmer climates may push them to their ecophysiological limits. To understand the vulnerability of Mediterranean pines to climate change, we review the main drivers of local adaptation and phenotypic plasticity and their contribution to phenotypic variation in fitness-related traits across the distribution ranges of Mediterranean pines. We also provide some examples of species distribution models based on tree growth measured in common gardens. Overall, models based on the adaptive capacity and the tolerance of populations to climate change present a less alarming message than species distribution models based on trees’ occurrence about the future of Mediterranean pines. To fully understand the vulnerability of Mediterranean pines to climate change, the limits of phenotypic plasticity for drought-resistance traits need to be explored at large geographical scales.
In the Mediterranean basin, Pinus pinaster (maritime pine) and P. pinea (stone pine) are highly economically important pine species. These species provide raw material for forest-based industries (e.g., wood, paper, and resin), as well as of other economically relevant products, such as pine nuts (stone pine) and essential oils (EOs). Previous studies described a large genetic and phenotypic intra-species variability that ultimately hinders the comparison between reports. The present work reviews the available literature on P. pinaster and P. pinea EO composition and pinpoints the compounds that showed the highest variation. The chemical profiles of EOs extracted from the aerial parts were obtained from a total of 30 publications. Cluster analysis revealed a higher influence of geographic location on P. pinaster EO composition, than on P. pinea. A high degree of chemical variability was detected for these species. Specifically, the EO components that showed the highest variations were limonene, α-pinene, β-pinene, trans-β-caryophyllene, germacrene D, and β-myrcene for P. pinea, and α-pinene, β-pinene, trans-β-caryophyllene, germacrene D, and β-myrcene for P. pinaster. Thus, it is highly recommended that research performed in field or greenhouse conditions should first ascertain pine chemical variability.
Population response functions based on climatic and phenotypic data from common gardens have long been the gold standard for predicting quantitative trait variation in new environments. However, prediction accuracy might be enhanced by incorporating genomic information that captures the neutral and adaptive processes behind intra-population genetic variation. We used five clonal common gardens containing 34 provenances (523 genotypes) of maritime pine (Pinus pinaster Aiton) to determine whether models combining climatic and genomic data capture the underlying drivers of height-growth variation, and thus improve predictions at large geographical scales. The plastic component explained most of the height-growth variation, probably resulting from population responses to multiple environmental factors. The genetic component stemmed mainly from climate adaptation, and the distinct demographic and selective histories of the different maritime pine gene pools. Models combining climate-of-origin and gene pool of the provenances, and positive-effect height-associated alleles (PEAs) captured most of the genetic component of height-growth and better predicted new provenances compared to the climate-based population response functions. Regionally-selected PEAs were better predictors than globally-selected PEAs, showing high predictive ability in some environments, even when included alone in the models. These results are therefore promising for the future use of genome-based prediction of quantitative traits.
Key message
Climate change will induce a change in fire frequency in Mediterranean region and that could impact fire-adapted plant species. We showed that fire-related traits of some pine species are strongly related to other factors than fire but the recent fire history has nonetheless an impact on the variation of key traits for different fire adaptive strategies.
ContextIn fire-prone Mediterranean areas, climate change is expected to exacerbate the fire pressure on ecosystems, altering the current fire regime and threatening species if they cannot acclimate.AimsStudying intraspecific variations of some fire-related traits in relation to variation in recent fire activity is thus an important step to better understand if this acclimation is possible.Methods
We measured structural (bark thickness, shoot bulk density, self-pruning, leaf surface to volume ratio) and functional (serotiny level for Pinus halepensis only) traits in two pines species (Pinus halepensis and Pinus sylvestris) commonly found in southeastern France and that present different fire-adaptive strategies (resilience vs resistance, respectively). Populations were sampled according to different fire frequency modalities (0 vs 1 to 2 fires) along a geographical gradient, measuring numerous environmental and plant characteristics to be used cofactors in the analyses.ResultsAs expected, trait variation was strongly linked to environmental and tree characteristics as well as to ontogeny overriding the effect of fire modalities, even though using integrative models with random effect. However, fire modalities had an impact on the variance of some key fire-related traits of Pinus halepensis.Conclusion
This study will help to anticipate the future response of these Mediterranean pine species and further underlines the importance of investigating chemical traits, flammability, and genetic variation of highly heritable traits, such as serotiny.
Results from a decade of association studies in different organisms suggest that most complex traits are polygenic, that is, their genetic architectures are determined by numerous causal loci distributed across the genome each with small effect-size. Thus, determining the degree of polygenicity is a central goal to understand the genetic basis of phenotypic variation. Recently, multi-loci methods able to detect variants associated with a phenotype of interest despite the subtle allele frequency changes between populations usually observed have been developed. In this study, we applied two multi-loci methods to estimate the degree of polygenicity of fitness-related traits in a long-lived plant species (maritime pine) and to analyze how polygenicity changes across years and environments. For this purpose, we evaluated five categories of fitness related traits, such as, height, survival, phenology-related, biotic-stress resistance and functional traits in a clonal common garden network planted in contrasted environments. Most of the analyzed traits showed evidences of local adaptation. We observed a remarkably stable degree of polygenicity (average 6%) across traits, environments and years. Additionally, some of the measured traits showed evidences of negative selection that could explain the observed degree of polygenicity, as previously suggested in humans. The observed genetic architecture of fitness-related traits in maritime pine is in accordance with the polygenic adaptation model. Because polygenic adaptation can take place rapidly, our results can contribute to improve the predictions about the capacity of natural populations of forest trees to adapt to new environments, which is of special relevance in the current context of climate change.
How populations of long‐living species respond to climate change depends on phenotypic plasticity and local adaptation processes. Marginal populations are expected to have lags in adaptation (i.e. differences between the climatic optimum that maximises population fitness and the local climate) because they receive pre‐adapted alleles from core populations preventing them from reaching a local optimum in their climatically marginal habitat. Yet, whether adaptation lags in marginal populations are a common feature across phylogenetically and ecologically different species and how lags can change with climate change remain unexplored. To test for range‐wide patterns of phenotypic variation and adaptation lags of populations to climate we i) built model ensembles of tree height accounting for the climate of population origin and the climate of the site for 706 populations monitored in 97 common garden experiments covering the range of six European forest tree species; ii) estimated populations’ adaptation lags as the differences between the climatic optimum that maximises tree height and the climate of the origin of each population; iii) identified adaptation lag patterns for populations coming from the warm/dry and cold/wet margins and from the distribution core of each species range. We found that i) phenotypic variation is driven by either temperature or precipitation; ii) adaptation lags are consistently higher in climatic margin populations (cold/warm, dry/wet) than in core populations; iii) predictions for future warmer climates suggest adaptation lags would decrease in cold margin populations, slightly increasing tree height, while adaptation lags would increase in core and warm margin populations, sharply decreasing tree height. Our results suggest that warm margin populations are the most vulnerable to climate change, but understanding how these populations can cope with future climates depend on whether other fitness‐related traits could show similar adaptation lag patterns.
Key message
This datapaper collects individual georeferenced tree height data from Pinus nigra Arn., P. pinaster Aiton, and P. pinea L. planted in common gardens in France, Germany, Morocco, and Spain. The data can be used to assess genetic variation and phenotypic plasticity with further applications in biogeography and forest management. The three datasets are available at:
https://doi.org/10.5281/zenodo.3250704 (Vizcaíno-Palomar et al. 2018a),
https://doi.org/10.5281/zenodo.3250698 (Vizcaíno-Palomar et al. 2018b), and
https://doi.org/10.5281/zenodo.3250707 (Vizcaíno-Palomar et al. 2018c),
and the associated metadata are available at:
https://metadata-afs.nancy.inra.fr/geonetwork/srv/eng/catalog.search#/metadata/644682d3-78c6-4fcc-af26-b1a928be7b1b, https://metadata-afs.nancy.inra.fr/geonetwork/srv/eng/catalog.search#/metadata/535b8ad0-9315-4d78-80bd-d0f6cbb9d0ce and https://metadata-afs.nancy.inra.fr/geonetwork/srv/eng/catalog.search#/metadata/4cc0d2f0-00a9-42c8-aa34-fbbc647e3eb9
for P. nigra, P. pinaster and P. pinea, respectively.
URL of a full-text view-only version at https://rdcu.be/bMnfK
Improving our understanding of species ranges under rapid climate change requires application of our knowledge of the tolerance and adaptive capacity of populations to changing environmental conditions. Here, we describe an emerging modelling approach, ΔTraitSDM, which attempts to achieve this by explaining species distribution ranges based on phenotypic plasticity and local adaptation of fitness‐related traits measured across large geographical gradients. The collection of intraspecific trait data measured in common gardens spanning broad environmental clines has promoted the development of these new models – first in trees but now rapidly expanding to other organisms. We review, explain and harmonize the main findings from this new generation of models that, by including trait variation over geographical scales, are able to provide new insights into future species ranges. Overall, ΔTraitSDM predictions generally deliver a less alarming message than previous models of species distribution under new climates, indicating that phenotypic plasticity should help, to a considerable degree, some plant populations to persist under climate change. The development of ΔTraitSDMs offers a new perspective to analyse intraspecific variation in single and multiple traits, with the rationale that trait (co)variation and consequently fitness can significantly change across geographical gradients and new climates.
Phenotypic plasticity is important for species responses to global change and species coexistence. Phenotypic plasticity differs among species and traits and changes across environments. Here, we investigated phenotypic plasticity of the widespread grass Arrhenatherum elatius in response to winter warming and frost stress by comparing phenotypic plasticity of 11 geographically and environmentally distinct populations of this species to phenotypic plasticity of populations of different species originating from a single environment. The variation in phenotypic plasticity was similar for populations of a single species from different locations compared to populations of functionally and taxonomically diverse species from one environment for the studied traits (leaf biomass production and root integrity after frost) across three indices of phenotypic plasticity (RDPI, PIN, slope of reaction norm). Phenotypic plasticity was not associated with neutral genetic diversity but closely linked to the climate of the populations’ origin. Populations originating from warmer and more variable climates showed higher phenotypic plasticity. This indicates that phenotypic plasticity can itself be considered as a trait subject to local adaptation to climate. Finally, our data emphasize that high phenotypic plasticity is not per se positive for adaptation to climate change, as differences in stress responses are resulting in high phenotypic plasticity as expressed by common plasticity indices, which is likely to be related to increased mortality under stress in more plastic populations.
Plant biology is experiencing a renewed interest in the mechanistic underpinnings and evolution of phenotypic plasticity that calls for a re‐evaluation of how we analyse phenotypic responses to a rapidly changing climate. We suggest that dissecting plant plasticity in response to increasing temperature needs an approach that can represent plasticity over multiple environments, and considers both population‐level responses and the variation between genotypes in their response. Here, we outline how a random regression mixed model framework can be applied to plastic traits that show linear or nonlinear responses to temperature. Random regressions provide a powerful and efficient means of characterising plasticity and its variation. Although they have been used widely in other fields, they have only recently been implemented in plant evolutionary ecology. We outline their structure and provide an example tutorial of their implementation.
Species can respond to environmental pressures through genetic and epigenetic changes and through phenotypic plasticity, but few studies have evaluated the relationships between genetic differentiation and phenotypic plasticity of plant species along changing environmental conditions throughout wide latitudinal ranges. We studied inter‐ and intrapopulation genetic diversity (using simple sequence repeats and chloroplast DNA sequencing) and inter‐ and intrapopulation phenotypic variability of 33 plant traits (using field and common‐garden measurements) for five populations of the invasive cordgrass Spartina densiflora Brongn. along the Pacific coast of North America from San Francisco Bay to Vancouver Island. Studied populations showed very low genetic diversity, high levels of phenotypic variability when growing in contrasted environments and high intrapopulation phenotypic variability for many plant traits. This intrapopulation phenotypic variability was especially high, irrespective of environmental conditions, for those traits showing also high phenotypic plasticity. Within‐population variation represented 84% of the total genetic variation coinciding with certain individual plants keeping consistent responses for three plant traits (chlorophyll b and carotenoid contents, and dead shoot biomass) in the field and in common‐garden conditions. These populations have most likely undergone genetic bottleneck since their introduction from South America; multiple introductions are unknown but possible as the population from Vancouver Island was the most recent and one of the most genetically diverse. S. densiflora appears as a species that would not be very affected itself by climate change and sea‐level rise as it can disperse, establish, and acclimate to contrasted environments along wide latitudinal ranges.
We present EuMedClim, a new climate dataset, that provides high spatial and temporal resolution (30 arc sec including monthly, seasonal and yearly time steps) of gridded climatologies for the years 1901–2014 across Europe and the Mediterranean Basin. We used an anomaly approach to interpolate spatial yearly climate data of CRU TS (version 3.23) using the climate surfaces of WorldClim (version 1.4) at 1 km resolution. Evaluation of our downscaled data against individual weather station data show good agreement between EuMedClim and original databases (EuMedClim vs. WorldClim for spatial and EuMedClim vs. CRU for temporal) and weather observations, with a higher accuracy of EuMedClim for the temporal component. EuMedClim thus provides new perspectives for studying spatio-temporal patterns of ecological and evolutionary processes at high temporal and spatial resolution for Europe and the Mediterranean Basin.
Phenotypic plasticity, both within and across generations, is an important mechanism that organisms use to cope with rapid climate change. While an increasing number of studies show that plasticity across generations (transgenerational plasticity or TGP) may occur, we have limited understanding of key aspects of TGP, such as the environmental conditions that may promote it, its relationship to within-generation plasticity (WGP) and its role in evolutionary potential. In this review, we consider how the detection of TGP in climate change experiments is affected by the predictability of environmental variation, as well as the timing and magnitude of environmental change cues applied. We also discuss the need to design experiments that are able to distinguish TGP from selection and TGP from WGP in multigenerational experiments. We conclude by suggesting future research directions that build on the knowledge to date and admit the limitations that exist, which will depend on the way environmental change is simulated and the type of experimental design used. Such an approach will open up this burgeoning area of research to a wider variety of organisms and allow better predictive capacity of the role of TGP in the response of organisms to future climate change.
The growth response of trees to ongoing climate change has important implications for future forest dynamics, accurate carbon accounting, and sustainable forest management. We used data from black spruce (Picea mariana) and jack pine (Pinus banksiana) provenance trials, along with published data for three other northern conifers, to identify a consistent growth response to climate warming in which cold-origin populations are expected to benefit and warm-origin populations are expected to decline. Specifically, populations from across the geographic range of a species appear to grow well at temperatures characteristic of the southern portion of the range, indicating significant potential for a positive growth response to climate warming in cold-origin populations. Few studies have quantified and compared this pattern across multiple species using provenance data. We present a forest regeneration strategy that incorporates these anticipated growth responses to promote populations that are both local to the planting site and expected to grow well under climate change.
Climate-driven selection
Climate change will fundamentally alter many aspects of the natural world. To understand how species may adapt to this change, we must understand which aspects of the changing climate exert the most powerful selective forces. Siepielski et al. looked at studies of selection across species and regions and found that, across biomes, the strongest sources of selection were precipitation and transpiration changes. Importantly, local and regional climate change explained patterns of selection much more than did global change.
Science , this issue p. 959
Plant species aboveground allometry can be viewed as a functional trait that reflects the evolutionary trade-off between above-and belowground resources. In forest trees, allometry is related to productivity and resilience in different environments, and it is tightly connected with a compromise between efficiency safety and competitive ability. A better understanding on how this trait varies within and across species is critical to determine the potential of a spe-cies/population to perform along environmental gradients. We followed a hierarchical framework to assess tree height-diameter allometry variation within and across four common European Pinus species. Tree height-diameter allome-try variation was a function of solely genetic components –approximated by either population effects or clinal geographic responses of the population's site of origin– and differential genetic plastic responses –approximated by the interaction between populations and two climatic variables of the growing sites (temperature and precipitation)–. Our results suggest that, at the species level, climate of the growing sites set the tree height-diameter allometry of xeric and mesic species (Pinus halepensis, P. pinaster and P. nigra) apart from the boreal species (P. sylvestris), suggesting a weak signal of their phylogenies in the tree height-diameter allometry variation. Moreover, accounting for interpopulation variability within species for the four pine species aided to: (1) detect genetic differences among populations in allometry variation, which in P. nigra and P. pinaster were linked to gene pools –genetic diversity measurements–; (2) reveal the presence of differential genetic variation in plastic responses along two climatic gradients in tree allometry variation. In P. sylvestris and P. nigra, genetic variation was the result of adaptive patterns to climate, while in P. pinaster and P. halepensis, this signal was either weaker or absent, respectively ; and (3) detect local adaptation in the exponent of the tree height-diameter allometry relationship in two of the four species (P. sylvestris and P. nigra), as it was a function of populations' latitude and altitude variables. Our findings suggest that the four species have been subjected to different historical and climatic constraints that might have driven their aboveground allometry and promoted different life strategies.
The Mediterranean stone pine, Pinus pinea L., seems to be well adapted to the different climate zones of its distribution range that spans four thousand kilometres along the Northern shore of the Mediterranean Sea. But recent molecular studies revealed it to be extremely genetically depauperate for a widespread tree. In this context, a provenances trial should elucidate whether any differentiation in adaptative traits can be identified between 34 accessions covering its natural range. The presence of strong spatial autocorrelations throughout four test sites required iterative nearest-neighbours adjustments in their statistical analysis. No significant differences in survival or ontogeny were found between accessions, while height growth was slightly though significantly more vigorous in northern or inland provenances. But these differences were masked by a common, stable reaction norm in dependence on site and microsite. On the other hand, its strong developmental plasticity allows the stone pine to delay the heteroblastic phase change in order to survive in unfavourable conditions, a clear advantage in the limiting and unpredictable environments of Mediterranean ecosystems.
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.
The importance of intraspecific variation in plant functional traits for structuring communities and driving ecosystem processes is increasingly recognized, but mechanisms governing this variation are less studied. Variation could be due to adaptation to local conditions, plasticity in observed traits, or ontogeny. We investigated 1) whether abiotic stress caused individuals, maternal lines, and populations to exhibit trait convergence, 2) whether trait variation was primarily due to ecotypic differences or trait plasticity, and 3) whether traits varied with ontogeny. We sampled three populations of Hypochaeris radicata that differed significantly in rosette diameter and specific leaf area (SLA). We grew nine maternal lines from each population (27 lines total) under three greenhouse conditions: ambient conditions (control), 50% drought, or 80% shade. Plant diameter and relative chlorophyll content were measured throughout the experiment, and leaf shape, root∶shoot ratio, and SLA were measured after five weeks. We used hierarchical mixed-models and variance component analysis to quantify differences in treatment effects and the contributions of population of origin and maternal line to observed variation. Observed variation in plant traits was driven primarily by plasticity. Shade significantly influenced all measured traits. Plant diameter was the only trait that had a sizable proportion of trait variation (30%) explained by population of origin. There were significant ontogenetic differences for both plant diameter and relative chlorophyll content. When subjected to abiotic stress in the form of light or water limitation, Hypochaeris radicata exhibited significant trait variability. This variation was due primarily to trait plasticity, rather than to adaptation to local conditions, and also differed with ontogeny.
Species are the unit of analysis in many global change and conservation biology studies; however, species are not uniform entities but are composed of different, sometimes locally adapted, populations differing in plasticity. We examined how intraspecific variation in thermal niches and phenotypic plasticity will affect species distributions in a warming climate. We first developed a conceptual model linking plasticity and niche breadth, providing five alternative intraspecific scenarios that are consistent with existing literature. Secondly, we used ecological niche-modeling techniques to quantify the impact of each intraspecific scenario on the distribution of a virtual species across a geographically realistic setting. Finally, we performed an analogous modeling exercise using real data on the climatic niches of different tree provenances. We show that when population differentiation is accounted for and dispersal is restricted, forecasts of species range shifts under climate change are even more pessimistic than those using the conventional assumption of homogeneously high plasticity across a species' range. Suitable population-level data are not available for most species so identifying general patterns of population differentiation could fill this gap. However, the literature review revealed contrasting patterns among species, urging greater levels of integration among empirical, modeling and theoretical research on intraspecific phenotypic variation.
There is an increasing interest in understanding the role of epigenetic variability in forest species and how it may contribute to their rapid adaptation to changing environments. In this study we have conducted a genome-wide analysis of cytosine methylation pattern in Pinus pinea, a species characterized by very low levels of genetic variation and a remarkable degree of phenotypic plasticity. DNA methylation profiles of different vegetatively propagated trees from representative natural Spanish populations of P. pinea were analyzed with the Methylation Sensitive Amplified Polymorphism (MSAP) technique. A high degree of cytosine methylation was detected (64.36% of all scored DNA fragments). Furthermore, high levels of epigenetic variation were observed among the studied individuals. This high epigenetic variation found in P. pinea contrasted with the lack of genetic variation based on Amplified Fragment Length Polymorphism (AFLP) data. In this manner, variable epigenetic markers clearly discriminate individuals and differentiates two well represented populations while the lack of genetic variation revealed with the AFLP markers fail to differentiate at both, individual or population levels. In addition, the use of different replicated trees allowed identifying common polymorphic methylation sensitive MSAP markers among replicates of a given propagated tree. This set of MSAPs allowed discrimination of the 70% of the analyzed trees.
Six Pinus pinea stands growing under the Mediterranean type climate in Italy along the Tyrrhenian and Sardinian coasts.
To identify the main climatic factors driving variability in growth responses to contrasting climate conditions at local and regional scales using tree-ring analysis.
Common growth patterns in tree rings were explored with clustering techniques. Local and regional growth responses to climate were examined using a dendroclimatic analysis. To remove the age-dependent trend we decomposed the tree ring width data into age-bands, thereafter standardized and recombined into a single mean site chronology.
The main grouping of tree ring series reflected climate-driven growth patterns, with a clear separation between stands from wetter and drier sites. The most interesting results were found at a seasonal scale and showed i) a shift of the main precipitation inputs from previous autumn-winter to current early-spring period, and ii) a bimodal pattern of sensitivity to water availability, when increasing drought conditions.
Our findings suggest that water deficit limits P. pinea growth also during late summer months in drier sites.
In view of the projected increases in the frequency and duration of summer droughts in the Mediterranean basin, detecting differences in growth responses to site-specific climate patterns may allow selection of more appropriate mitigation and conservation strategies across most of its present range.
One challenge of evolutionary ecology is to predict the rate and mechanisms of population adaptation to environmental variations. The variations in most life history traits are shaped both by individual genotypic and by environmental variation. Forest trees exhibit high levels of genetic diversity, large population sizes, and gene flow, and they also show a high level of plasticity for life history traits. We developed a new Physio-Demo-Genetics model (denoted PDG) coupling (i) a physiological module simulating individual tree responses to the environment; (ii) a demographic module simulating tree survival, reproduction, and pollen and seed dispersal; and (iii) a quantitative genetics module controlling the heritability of key life history traits. We used this model to investigate the plastic and genetic components of the variations in the timing of budburst (TBB) along an elevational gradient of Fagus sylvatica (the European beech). We used a repeated 5 years climatic sequence to show that five generations of natural selection were sufficient to develop nonmonotonic genetic differentiation in the TBB along the local climatic gradient but also that plastic variation among different elevations and years was higher than genetic variation. PDG complements theoretical models and provides testable predictions to understand the adaptive potential of tree populations.
Past meta-analyses of the response of marine organisms to climate change
have examined a limited range of locations, taxonomic groups and/or
biological responses. This has precluded a robust overview of the effect
of climate change in the global ocean. Here, we synthesized all
available studies of the consistency of marine ecological observations
with expectations under climate change. This yielded a meta-database of
1,735 marine biological responses for which either regional or global
climate change was considered as a driver. Included were instances of
marine taxa responding as expected, in a manner inconsistent with
expectations, and taxa demonstrating no response. From this database,
81-83% of all observations for distribution, phenology, community
composition, abundance, demography and calcification across taxa and
ocean basins were consistent with the expected impacts of climate
change. Of the species responding to climate change, rates of
distribution shifts were, on average, consistent with those required to
track ocean surface temperature changes. Conversely, we did not find a
relationship between regional shifts in spring phenology and the
seasonality of temperature. Rates of observed shifts in species'
distributions and phenology are comparable to, or greater, than those
for terrestrial systems.
The response to drought of 20 open-pollinated families from four Pinus pinaster Ait. populations covering a latitudinal cline (France, Central and Southern Spain, and Morocco) was assessed. The seedlings
were cultivated in a greenhouse under controlled temperature and vapor pressure deficit for 120 days, and subjected to two
watering regimes for 60 days. Different biomass partitioning variables, pre-dawn water potential, and isotopic discrimination
of 13C in needles (Δ) as surrogate of long-term water use efficiency were estimated for each seedling at the end of the experiment.
In response to the imposed drought, there was no change in the root biomass partitioning, but the overall Δ values decreased
in response to water stress. All the families of the population from Morocco showed the highest investment in roots, regardless
of the watering regime imposed. Inter-family differences within populations were also significant for most parameters as confirmed
by the heritability values estimated (higher under the well-watered treatment). The studied P. pinaster populations showed different strategies of response to drought. This may represent an important mechanism by local populations
in facing future climatic change. The results could be of value in forest conservation and breeding programs of maritime pine
in the future.
Aim Trees are often observed to get shorter and more narrowly crowned in dry regions and at high elevations. We explore how this pattern is driven by two opposing factors: competition for light makes it advantageous to extend branches to their biomechanical limit, whereas under cold or arid conditions it is advantageous to have shorter branches, thereby reducing the length of the hydraulic transport system and embolism risk. Using data from 700,000 trees of 26 species, we quantify how environmental conditions influence the scaling of height and crown diameter (CD) with stem diameter (d.b.h.). We compare our predictions with those of metabolic scaling theory (MST), which suggests that allometry is invariant of environment.
Location 48,000 inventory plots that systematically sample mainland Spain, a region in which climate varies strongly.
Methods We fit d.b.h.–height and d.b.h.–CD functions using Bayesian methods, allowing comparison of within‐ and across‐species trends in allometry along gradients of temperature, precipitation, drought and competition for light (i.e. the basal area of taller trees).
Results The competitive environment had a strong influence on aboveground allometry, but all trees were far shorter than predicted by biomechanical models, suggesting that factors other than biomechanics are important. Species that dominate in arid and cold habitats were much shorter (for a given diameter) than those from benign conditions; but within‐species heights did not vary strongly across climatic gradients.
Main conclusions Our results do not support the MST prediction that d.b.h.–height and d.b.h.–CD allometries are invariant, or that biomechanical constraints determine height allometry. Rather, we highlight the role of hydraulic limitations in this region. The fact that intra‐specific adjustment in d.b.h.–CD – height allometry along environmental gradients was far weaker than across‐species changes may indicate genetic constraints on allometry which might contribute to niche differentiation among species.
Mediterranean Stone pine (Pinus pinea L.) is a native species of the Mediterranean region, widely used for reforestation. It is characterised by a low genetic variation both at phenotypic traits and molecular markers. In the early nineties, experimental plots were established in several countries bordering the Mediterranean Sea for studying the distribution of genetic variability among provenances in adaptative traits as survival, vegetative and reproductive phase change, phenology and growth. Here we report results of the first decade at seven trial sites in France and Spain. The survival, ontogeny and growth patterns were homogeneous among provenances but differed among sites. On the other hand, the phenotypic plasticity of the species and its sensitivity to microsite (soil) variation produced strong spatial autocorrelations of the response variables, both between and within sites, which masked greatly the variation between provenances. Nearest-neighbours adjustments that captured the spatial pattern
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.
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.
The capacity to rapidly expand root systems to increase soil foraging is key for the survival of tree seedlings in arid regions. Plants alter root growth dynamics and architecture in response to environmental changes and this plasticity in root development allows plants to maximize soil resource uptake. However, how variation in plant
physiological status, such as nutrient content, affects root growth dynamics and architecture is poorly understood. We assessed how variation in seedling nutrient status affects root growth dynamics and architecture in three closely related, yet ecologically distinct pine species: Pinus nigra J.F. Arnold, Pinus pinaster Ait., and Pinus
pinea L. Seedlings were cultivated under contrasting fertilization regimes to promote different levels of mineral nutrient content. Seedlings were then transplanted into rhizotrons to evaluate root growth dynamics and architecture over 10 weeks. Overall, increased seedling nutrient content enhanced root development, but species
showed distinct root growth patterns and architecture.Pinus pinaster, which inhabits moderate climatic stress environments, showed the greatest root growth plasticity with variation in seedling nutrient content. In contrast, root development was less plastic in the pines adapted to more stressful environments,P. pinea, which occurs in
sites with long and strong summer drought andP. nigra, which inhabits cold winter areas. High nutrient-content seedlings developed larger root systems by maintaining a greater number of growing roots rather than by increasing the elongation rate of individual roots, reflecting a strategy that likely improves soil foraging capacity. Nitrogen use efficiency for root growth (new root growth per unit of plant nitrogen content at planting) increased with increasing nutrient content inP. pinaster, yet the opposite effect occurred in the other two species.
New roots of high nutrient-content seedlings had lower specific root length than low content seedlings in all species, suggesting that internal seedling nutrient status determines specific root length. The means by which increased seedling nutrient content affects root development after transplanting in pine species seems to be related to species ecology and stress resistance physiology. With a surplus of mineral nutrients during nursery cultivation, pine species from high stressful environments have low flexibility in modifying root development, while species from moderate climatic stress environments prioritize root development.
Aim
Many studies use differences among plant populations to infer future plant responses, but these predictions will provide meaningful insights only if patterns of plasticity among populations are similar (i.e., in the absence of population‐by‐environment interaction, P × E ). In this study, we tested whether P × E is considered in climate change studies. Specifically, we evaluated whether population differentiation varies across environments and whether P × E is determined by aspects of the study system and experimental design.
Location
Global.
Methods
We conducted a literature search in the Thomson Reuters Web of Science database to identify studies assessing population differentiation in a climate change context. We quantified the occurrence of P × E and performed a meta‐analysis to calculate the percentage of traits showing P × E in the study cases.
Results
We identified 309 study cases (from 237 published articles) assessing population differentiation in 172 plant species, of which 64% included more than one test environment and tested P × E . In 77% of these studies, P × E was significant for at least one functional trait. The overall proportion of traits showing P × E was 33.4% (95% confidence interval 27.7–39.3). These results were generally consistent across life‐forms, ecoregions and type of experiment. Furthermore, population differentiation varied across test environments in 76% of cases. The overall proportion of traits showing environment‐dependent population differentiation was 53.7% (95% confidence interval 37.9–69.3).
Conclusions
Our findings revealed that differences in phenotypic plasticity among populations are common but are usually neglected in order to forecast population responses to climate change. Future studies should assess population differentiation in many test environments (accounting for P × E ) that realistically reflect future environmental conditions, assessing climate change drivers that are rarely considered (e.g., multifactor experiments incorporating higher CO2 levels). Our review also revealed the predominant focus of population studies on trees from temperate climates, identifying underexplored life‐forms (shrubs, annuals), phylogenetic groups (ferns, ancient gymnosperms) and ecoregions (tropical, arctic) that should receive more attention in future.
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.
Interannual variability in climatic conditions should be taken into account in climate change studies in semi‐arid ecosystems. It may determine differentiation in phenotypic plasticity among populations, with populations experiencing higher environmental heterogeneity showing higher levels of plasticity.
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 semi‐arid ecosystems.
Working with populations of the semi‐arid 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.
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.
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.
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.
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.
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.
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.
Location Continental Spain.
Methods We conducted a multivariate comparison of ecological characteristics in planted and natural stands of main Iberian native pine species ( Pinus halepensis , Pinus pinea , Pinus pinaster , Pinus nigra and Pinus sylvestris ). We fitted species‐specific statistical models of recruitment and woody species richness and analysed the response of natural and planted stands along ecological gradients.
Results Planted pine forests occurred on average on poorer soils and experienced higher anthropic disturbance rates (fire frequency and anthropic mortality) than natural pine forests. Planted pine forests had lower regeneration and diversity levels than natural pine forests, and these differences were more pronounced in mountain pine stands. The largest differences in recruitment – chiefly oak seedling abundance – and species richness between planted and natural stands occurred at low‐medium values of annual precipitation, stand tree density, distance to Quercus forests and fire frequency, whereas differences usually disappeared in the upper part of the gradients.
Main conclusions Structural characteristics and patterns of recruitment and species richness differ in pine planted forests compared to natural pine ecosystems in the Mediterranean, especially for mountain pines. However, management options exist that would reduce differences between these forest types, where restoration towards more natural conditions is feasible. To increase recruitment and diversity, vertical and horizontal heterogeneity could be promoted by thinning in high‐density and homogeneous stands, while enrichment planting would be desirable in mesic and medium‐density planted forests.
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.
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.
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
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
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.
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.
The use of both linear and generalized linear mixed‐effects models ( LMM s and GLMM s) 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’ ( R ² ) as a relevant summarizing statistic of mixed‐effects models, however, is rare, even though R ² is routinely reported for linear models ( LM s) and also generalized linear models ( GLM s). R ² 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, R ² can also be a quantity of biological interest.
One reason for the under‐appreciation of R ² for mixed‐effects models lies in the fact that R ² can be defined in a number of ways. Furthermore, most definitions of R ² for mixed‐effects have theoretical problems (e.g. decreased or negative R ² 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 R ² for mixed‐effects models. We first provide the common definitions of R ² for LM s and GLM s and discuss the key problems associated with calculating R ² for mixed‐effects models. We then recommend a general and simple method for calculating two types of R ² (marginal and conditional R ² ) for both LMM s and GLMM s, 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 R ² for a wide range of circumstances.
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.
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...
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.
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.
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 comparative 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 significantly correlated with 12 out of the 17 PP indices analysed. An index including the environmental range leading to the different phenotypes (environmentally standardized 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.
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.
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.
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.