Article

Sensitivity of leaf size and shape to climate: Global patterns and paleoclimatic applications

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Abstract

• Paleobotanists have long used models based on leaf size and shape to reconstruct paleoclimate. However, most models incorporate a single variable or use traits that are not physiologically or functionally linked to climate, limiting their predictive power. Further, they often underestimate paleotemperature relative to other proxies. • Here we quantify leaf-climate correlations from 92 globally distributed, climatically diverse sites, and explore potential confounding factors. Multiple linear regression models for mean annual temperature (MAT) and mean annual precipitation (MAP) are developed and applied to nine well-studied fossil floras. • We find that leaves in cold climates typically have larger, more numerous teeth, and are more highly dissected. Leaf habit (deciduous vs evergreen), local water availability, and phylogenetic history all affect these relationships. Leaves in wet climates are larger and have fewer, smaller teeth. Our multivariate MAT and MAP models offer moderate improvements in precision over univariate approaches (± 4.0 vs 4.8°C for MAT) and strong improvements in accuracy. For example, our provisional MAT estimates for most North American fossil floras are considerably warmer and in better agreement with independent paleoclimate evidence. • Our study demonstrates that the inclusion of additional leaf traits that are functionally linked to climate improves paleoclimate reconstructions. This work also illustrates the need for better understanding of the impact of phylogeny and leaf habit on leaf-climate relationships.

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... The patterns and adaptation mechanisms of plant functional traits across latitudinal gradients have attracted the attention of ecologists in recent years . Leaf functional traits are among the most sensitive to environmental changes and are closely related to plant growth and ecological adaptation strategies (Wright et al., 2004(Wright et al., , 2017Peppe et al., 2011). High leaf area and specific leaf area, for instance, indicates high photosynthesis, rapid growth, and competitiveness, whereas high leaf thickness and toughness indicate an adaptation advantage to natural enemies (Moles et al., 2011;Pearse and Hipp, 2012). ...
... A similar result was obtained for specific leaf area related to growth (Gallagher and Leishman, 2012;Tian et al., 2016;Wang et al., 2016;Luo et al., 2019;Zhang et al., 2019). Therefore, more research on the geographical variation in leaf functional traits and relevant environmental effects is needed to improve our understanding of how plants have and will adapt to climate change in the future (Moles et al., 2011;Peppe et al., 2011). ...
... There were limited research comparing the leaf growth and defense traits across latitude within its invasive and native ranges in the salt marsh (Minden et al., 2012), so our study provides new insights into the adaptation strategies of leaf functional traits of salt marsh plants along latitudinal gradients. The parallel response of leaf traits to latitude and climate can help us predict leaf morphological shifts and the evolutionary changes of invasive species in response to climate change (Peppe et al., 2011;Dong et al., 2020). ...
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The enemy release and pre-adaptation of alien species often drive their contemporary evolution across latitudinal gradients within its invasive and native ranges. Leaf functional traits constitute an important part of plant functional traits, reflecting their resource acquisition and usage. Thus, comparing the leaf functional traits (growth and defense traits) and latitude patterns of invasive and native plants could provide leading indicators of contemporary evolutionary and adaptative abilities that explain the success of invasive plants. Spartina alterniflora, a coastal wetland invasive plant native to the Atlantic coast and the Gulf of Mexico, has invaded China along the coast wetland (19–40 °N), similar to the United States (27–43 °N). To understand the leaf trait differences and variation across latitudes among continents of S. alterniflora within its invasive and native ranges and determine which factors drive leaf trait variation across latitudes, we investigated the relationship between leaf traits, related to growth (leaf area and specific leaf area), and defensive traits (leaf thickness and leaf toughness) at 10 invaded locations and 15 native locations. We identified correlations between leaf traits and abiotic conditions such as annual mean temperature, tide range, and soil salinity. Compared with native S. alterniflora, Chinese costal S. alterniflora has a larger leaf area and specific leaf area, less leaf thickness, and lower leaf toughness, suggesting that biosynthetic resources are transferred from defense to competitive traits, and indirectly supporting the Evolution of Increased Competitive Ability (EICA) hypothesis. The leaf area, specific leaf area, thickness, and toughness of S. alterniflora from both ranges had similar quadratic latitudinal relationships. Some of these relationships were stronger in the invasive range than the native range, indicating that the leaf traits of invasive S. alterniflora experienced pre-adaptation and had high phenotypic plasticity. Tide range, soil salinity, and especially temperature formed latitudinal gradients in different geographic regions. By analyzing indicators of leaf functional traits across geographical ranges, this study shows that the escape from natural enemies plays an important role in the successful invasion of S. alterniflora, while pre-adaptation and high phenotypic plasticity promote its rapid expansion along the latitudinal gradients.
... Leaf morphology, including the length, size, shape, and thickness of leaf, affects directly plants' ability for light interception and carbon acquisition (Milla and Reich, 2007;Peppe et al., 2011;Wright et al., 2017). The mechanism of leaf morphological formation in relation to adaptive value is generally believed to be related to a change in the balance of energy or water of the leaf (Niinemets et al., 2006;Peppe et al., 2011;Maire et al., 2015;Meng et al., 2015). ...
... Leaf morphology, including the length, size, shape, and thickness of leaf, affects directly plants' ability for light interception and carbon acquisition (Milla and Reich, 2007;Peppe et al., 2011;Wright et al., 2017). The mechanism of leaf morphological formation in relation to adaptive value is generally believed to be related to a change in the balance of energy or water of the leaf (Niinemets et al., 2006;Peppe et al., 2011;Maire et al., 2015;Meng et al., 2015). Typically, large and (or) broad leaves predominate in cool, humid, or shady environments because their thicker leaf margins induce greater resistance to transport of heat and substances (Ackerly et al., 2002;McDonald et al., 2003;Niinemets et al., 2006;Leigh et al., 2017), but small and (or) narrow leaves are considered advantageous in hot, dry, and high light habitats due to their ability of increasing leaf heat exchange, avoiding leaf damage, and maintaining leaf water content (Ackerly et al., 2002;Bragg and Westoby, 2002;Peppe et al., 2011). ...
... The mechanism of leaf morphological formation in relation to adaptive value is generally believed to be related to a change in the balance of energy or water of the leaf (Niinemets et al., 2006;Peppe et al., 2011;Maire et al., 2015;Meng et al., 2015). Typically, large and (or) broad leaves predominate in cool, humid, or shady environments because their thicker leaf margins induce greater resistance to transport of heat and substances (Ackerly et al., 2002;McDonald et al., 2003;Niinemets et al., 2006;Leigh et al., 2017), but small and (or) narrow leaves are considered advantageous in hot, dry, and high light habitats due to their ability of increasing leaf heat exchange, avoiding leaf damage, and maintaining leaf water content (Ackerly et al., 2002;Bragg and Westoby, 2002;Peppe et al., 2011). However, leaf size has also been found to decrease with temperature or irradiance gradient because low light and short growing season make against leaf carbon acquisition (McDonald et al., 2003;Wright et al., 2005Wright et al., , 2017Meng et al., 2015). ...
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Plant ecologists have long been interested in quantifying how leaf traits vary with climate factors, but there is a paucity of knowledge on these relationships given a large number of the relevant leaf traits and climate factors to be considered. We examined the responses of 11 leaf traits (including leaf morphology, stomatal structure and chemical properties) to eight common climate factors for 340 eastern Qinghai-Tibetan woody species. We showed temperature as the strongest predictor of leaf size and shape, stomatal size and form, and leaf nitrogen and phosphorus concentrations, implying the important role of local heat quantity in determining the variation in the cell- or organ-level leaf morphology and leaf biochemical properties. The effects of moisture-related climate factors (including precipitation and humidity) on leaf growth were mainly through variability in leaf traits (e.g., specific leaf area and stomatal density) related to plant water-use physiological processes. In contrast, sunshine hours affected mainly cell- and organ-level leaf size and shape, with plants developing small/narrow leaves and stomata to decrease leaf damage and water loss under prolonged solar radiation. Moreover, two sets of significant leaf trait-climate relationships, i.e., the leaf/stomata size traits co-varying with temperature, and the water use-related leaf traits co-varying with precipitation, were obtained when analyzing multi-trait relationships, suggesting these traits as good indicators of climate gradients. Our findings contributed evidence to enhance understanding of the regional patterns in leaf trait variation and its environmental determinants.
... Indeed, morphological variability of New Zealand plant phenotypes appears to be distinct, with, for example relatively high representation of woody species with leaves in the leptophyll-microphyll area range, or divaricate and/or heteroblastic growth forms (e.g. Burns and Dawson 2006;McGlone et al. 2010;Peppe et al. 2011;Kennedy et al. 2014). ...
... Studies that quantify the modern leaf morphology spectrum are often strongly dominated by Northern Hemisphere floras (e.g. Peppe et al. 2011;Yang et al. 2015) and results may differ from those in the Southern Hemisphere that have disparate floral compositions, influenced by a different tectonic (Boyden et al. 2011) and evolutionary history (Little et al. 2010;Kennedy et al. 2014). New Zealand's isolation since the late Cretaceous (Lee et al. 2001;Mortimer 2004;Schellart et al. 2006;Wallis and Trewick 2009;Prebble et al. 2021) presents an important opportunity to evaluate whether leaf trait responses to the environment are indeed universal, particularly those based on correlation and empirical observation, rather than a mechanistic understanding. ...
... The absence of a link between leaf teeth abundance and temperature in New Zealand highlights the influence of regional evolutionary history on this trait (Little et al. 2010) that is often assumed to be universally applicable as a paleoclimate proxy (e.g. Peppe et al. 2011;. A correlation between the occurrence of leaf teeth in woody dicots and rainfall was also identified in China (Li et al. 2016). ...
Article
Correlations of non-monocot woody angiosperm leaf traits to macroclimate are often used to reconstruct terrestrial paleoclimate under the assumption that macroclimate correlates with leaf phenotype are globally uniform, regardless of evolutionary history. Here, we evaluate if global trends in leaf trait variation with macroclimate are observed in the predominantly evergreen indigenous flora of New Zealand. A dataset of 557 indigenous woody dicot species and over 100,000 occurrences was employed to investigate community-level relationships of four leaf characters (leaf pubescence, margin teeth, area and length-to-width ratio) with geographic variation in temperature, precipitation, water deficit and solar radiation. Leaf area and the frequency of toothed leaves decline at higher latitudes in New Zealand. Variation in leaf pubescence and leaf teeth is associated primarily with measures of water availability, such as annual rainfall and annual water deficit; whereas leaf size is associated primarily with temperature. Variation in leaf length-to-width ratio was weakly correlated to climate parameters. The New Zealand relationship of leaf area with temperature aligns with global patterns, highlighting the importance of small leaves in limiting night-time chilling. The global negative correlation of leaf teeth with temperature is apparent in New Zealand trees and vines, but not in shrubs or all woody dicots combined. However, the primary correlate of leaf teeth in New Zealand is water availability, showing that the response of this trait to macroclimate is not globally uniform. The high occurrence of pubescent leaves in low rainfall and drought-prone environments in New Zealand suggests that the trait is associated with water retention in drier climates.
... Leaf shape is one of the most important features that have been used to study relationships with climate variables (Wilf et al. 1998; Baruch et al. 2017). Several studies have demonstrated significant changes in leaf shape and size along temperature and rainfall gradients, respectively (Wilf et al. 1998;Peppe et al. 2011;Wright et al. 2017). It has been shown that foliar area (FA) is one of the most useful biological parameters that is closely related to precipitation, as leaf size decreases with decreasing rainfall (Givnish 1979;Wilf et al. 1998;Wright et al. 2017;Gong et al. 2020). ...
... The contribution values of the P and FA variables were similar. Therefore, we chose the FA variable for cluster and discriminant analysis because it has been recognized as a valuable morphological variable and has been previously used in many studies (Royer et al. 2005;Peppe et al. 2011;Wright et al. 2017; among others). We selected 12 bioclimate indicators on the basis of the PCA and Spearman's correlation. ...
... Plant traits, especially leaf shape and size, possess intraspecific differences as a response to changes in environmental conditions (Peppe et al. 2011;Alcántara-Ayala et al. 2020). In this contribution we attempt to analyze plant morphological variations under different local climate conditions along a latitudinal gradient over a dryland domain. ...
Article
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Premise of research. Howvegetation adapts to environmental changes is one of the most important questions in plant science. Temperature and precipitation are considered the main climatic drivers of morphological variations in vegetation. Several studies have demonstrated that leaf morphology varies reliably with increasing latitude, and this is mostly attributed to changes in temperature and precipitation patterns. The morphological responses of plants to temperature and rainfall regimes in arid lands are still scarcely known and understood. We analyze the morphological variation in leaf traits (size and shape) as well as the internode distance in the species larrea divaricata and their relationship with bioclimatic variables along a latitudinal gradient in central western Argentina. Methodology. We combined a set of morphological features and bioclimatic indexes using multivariate statistics and detected six relevant regions with clear differences in both plant morphology and climatic variables. Pivotal results. The largest foliar areas were located in sites with higher seasonal precipitation. Leaf shape was influenced by temperature, and the internode distances were larger under semihumid conditions. Conclusions. The plant traits of L. divaricata were influenced by the latitudinal gradient and the predominant climate conditions of each recognized region. The study of foliar morphology allowed us to identify environmental factors that potentially influenced morphological responses in the studied species. As a preliminary stage in our research, our contribution attempts to recognize woody plant adaptations to climate influence. Other environmental variables must be included in future work for a more complete analysis.
... On the contrary, the remarkable homogeneity amongst the estimated MATs from Asian proxy records (ranging only from 14 to 19 • C) is somewhat puzzling, considering the fact that these 28 sites are spread between 18 and 52 • N in latitude and are located in various geographical settings, ranging from coastal regions to mountainous areas. A possible cause could be the application of modern temperature-vegetation relationships to palaeobotanical records, which might not prove fully adequate to reconstruct the warmer climates of the Eocene Peppe et al., 2011). ...
... Par exemple, les feuilles à bords dentelés sont assimilées à des plantes de climats tempérés, les feuilles de grande taille à des climats humides et celles de petite taille à des climats arides (pour des raisons d'optimisation de l'équilibre entre photosynthèse et évapotranspiration, notamment) [Chaloner and Creber, 1990;Peppe et al., 2011]. La méthode CLAMP est probable- Pour pallier à ces problèmes, Peppe et al. [2011] proposent par exemple une généralisation du traitement des traits physionomiques des feuilles par algorithme, afin de réduire la subjectivité de certaines interprétations, notamment celles concernant les méthodes portant sur l'analyse des bords de feuilles, de leur surface, mais également sur la méthode CLAMP. ...
... Par exemple, les feuilles à bords dentelés sont assimilées à des plantes de climats tempérés, les feuilles de grande taille à des climats humides et celles de petite taille à des climats arides (pour des raisons d'optimisation de l'équilibre entre photosynthèse et évapotranspiration, notamment) [Chaloner and Creber, 1990;Peppe et al., 2011]. La méthode CLAMP est probable- Pour pallier à ces problèmes, Peppe et al. [2011] proposent par exemple une généralisation du traitement des traits physionomiques des feuilles par algorithme, afin de réduire la subjectivité de certaines interprétations, notamment celles concernant les méthodes portant sur l'analyse des bords de feuilles, de leur surface, mais également sur la méthode CLAMP. ...
Thesis
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Les moussons régissent le climat d’une large partie de l’Asie depuis le subcontinent indien jusqu’à l’est de la Chine actuellement. Leur mise en place et leur évolution restent cependant débattues et sont régulièrement réévaluées grâce à l’acquisition de nouveaux indicateurs climatiques. Des données récentes suggèrent que le régime de mousson en Asie fonctionnait déjà il y a environ 40 Ma, à l’Éocène supérieur, dans un contexte climatique globalement plus chaud et dans une configuration paléogéographique très différente d’aujourd’hui. Le but de cette thèse est d’étudier les conditions d’une mise en place des moussons asiatiques au cours de la période 42-33 Ma, englobant la fin de l’Éocène et la transition climatique majeure de l’Éocène-Oligocène. Nous balayons les différents champs d’incertitudes persistantes pour cette époque (paléogéographie, pCO2, niveau marin) et les différentes sources de variabilité climatique (le forçage orbital essentiellement). Nous utilisons le modèle de système- Terre IPSL-CM5A2, récemment adapté à l’étude des paléoclimats. En utilisant une première paléogéographie tardi-Éocène et une pCO2 de 1120 ppm, nous montrons dans un premier temps que le modèle simule des précipitations extrêmement saisonnières en Asie, sans pour autant présenter la circulation atmosphérique caractéristique des moussons. La sensibilité du climat et du couvert végétal tardi-Éocène aux paramètres orbitaux est ensuite évaluée à travers différents tests de sensibilité. Nous démontrons que les variations orbitales ont pu être un forçage majeur de variabilité climatique et biologique en Asie. Les configurations favorisant des gradients thermiques inter-hémisphériques importants (via des obliquités fortes et/ou des précessions induisant des étés boréaux chauds), en provoquant une migration accrue des masses d’air équatoriales humides sur le continent, génèrent des climats saisonnièrement très humides en été sur le sud-est asiatique. Plus globalement, le couvert végétal semble également très sensible aux variations orbitales dans les subtropiques et aux hautes latitudes. Ces résultats ouvrent de nouvelles pistes de réflexion sur de possibles relations entre forçage orbital, climat et ouverture de corridors de dispersion des faunes asiatiques vers l’Europe et l’Amérique (phénomènes nommés Grande Coupure). Enfin, nous comparons les circulations atmosphériques générées par des reconstructions paléogéographiques alternatives de la région asiatique. Elles testent par exemple différentes altitudes du plateau tibétain et différentes morphologies de la phase initiale de collision entre l’Inde et l’Asie, ces deux aspects étant encore extrêmement débattus. Pour finir, ces résultats sont mis en perspective en les comparant à des simulations climatiques à ∼34, ∼20 et ∼10 Ma. Le climat simulé en Asie apparaît finalement très peu sensible aux changements locaux de la paléogéographie indo-tibétaine. À l’inverse, nous notons l’apparition progressive des champs de pressions et des vents caractéristiques des moussons à mesure que le retrait de la mer Paratéthys et de la fermeture de l’océan Néotéthys permet l’exondation de la péninsule arabique et de l’Asie centrale, augmentant ainsi fortement la continentalité de la région. Nous suggérons ainsi que les gradients thermiques induits par la continentalité asiatique sur une échelle de temps géologique, ou par des paramètres orbitaux favorables sur une échelle de temps de quelques milliers d’années constituent les forçages dominants du régime des moussons en Asie.
... For example, Leigh et al. [11] described leaf shape using measurements of leaf area and leaf dissection (leaf perimeter/area) in the context of plant hydraulics, and Royer et al. [12] used the same measure of leaf dissection to investigate the relationship between mean annual temperature and leaf shape. Measurements of such morphological features are often used to generate indices of leaf shape, such as compactness (perimeter 2 /area) and shape factor (4π × leaf area/ perimeter 2 ), which are used to summarize aspects of leaf shape and show how it relates to the environment or has changed through time [13][14][15][16]. Additionally, Shi et al. [17] found that the leaf shape of bamboo could be depicted by the simplified Gielis equation, while Li et al. [18] noted that leaf shape of two Michelia species followed the superellipse equation, and Shi et al. [19] developed a general formula for describing ovate leaf shape in plants. ...
... The inclusion of fossil leaves in this exploratory analysis (figure 6) indicates that both the PH framework and geometric methods based on elastic curves have potential application to evolutionary and palaeoecological problems that require data on leaf shape in the geological past (e.g. [7,10,[13][14][15][16]). Shape data derived from these approaches could also be used as classifiers in machine learning work to automate the classification of leaves in studies of modern and ancient plant diversity (cf. ...
... For angiosperms, 'leaf size and shape are selected by climate and are strongly correlated with climatic variables' ( [49], p. 266) and a clear next step is to apply our methods to angiosperm leaves in the context of climatic and palaeoclimatic analysis (e.g. [15]). In particular, given that our topological features measure the depth of indentations in the leaf margin, we are particularly interested to undertake quantitative analyses of angiosperm leaf margins. ...
Article
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Leaf shape is a key plant trait that varies enormously. The range of applications for data on this trait requires frequent methodological development so that researchers have an up-to-date toolkit with which to quantify leaf shape. We generated a dataset of 468 leaves produced by Ginkgo biloba , and 24 fossil leaves produced by evolutionary relatives of extant Ginkgo . We quantified the shape of each leaf by developing a geometric method based on elastic curves and a topological method based on persistent homology. Our geometric method indicates that shape variation in modern leaves is dominated by leaf size, furrow depth and the angle of the two lobes at the leaf base that is also related to leaf width. Our topological method indicates that shape variation in modern leaves is dominated by leaf size and furrow depth. We have applied both methods to modern and fossil material: the methods are complementary, identifying similar primary patterns of variation, but also revealing different aspects of morphological variation. Our topological approach distinguishes long-shoot leaves from short-shoot leaves, both methods indicate that leaf shape influences or is at least related to leaf area, and both could be applied in palaeoclimatic and evolutionary studies of leaf shape.
... Leaf morphology exhibits tremendous diversity between or within species, such as the broad leaves of poplars and needle leaves of conifers. Leaf size and shape are evolutionarily adapted to environmental changes in response to water and light stress [3,4], making it possible to reconstruct the paleoclimate [5,6]. In model systems, several genes and networks have been identified to affect initial leaf development and pattern formation [2,7,8] as well as leaf length and width [9][10][11] using the mutagenesis screening method. ...
... where y is a vector of trait values for n individuals; X is a design matrix of fixed effects; β is a vector of fixed effects; g is a vector of random genetic effects for each clone with g � Nð0; s 2 g I c Þ; Z is the coefficient matrix corresponding to the random vector g; e is the random residual vector with e � Nð0; s 2 e I n Þ. Moreover, we calculated the narrow heritability of a single trait as h 2 ¼ s 2 g =ðs 2 g þ s 2 e Þ without incorporating the fixed effects of SNPs in model (6). To calculate the restricted maximum likelihood (REML) estimates of genetic parameters, we applied the function emmremlMultivariate for the multivariate model (2) and emmreml for the univariate model (6) in the R package EMMREML (https://cran.r-project.org/web/ ...
... Moreover, we calculated the narrow heritability of a single trait as h 2 ¼ s 2 g =ðs 2 g þ s 2 e Þ without incorporating the fixed effects of SNPs in model (6). To calculate the restricted maximum likelihood (REML) estimates of genetic parameters, we applied the function emmremlMultivariate for the multivariate model (2) and emmreml for the univariate model (6) in the R package EMMREML (https://cran.r-project.org/web/ packages/EMMREML). ...
Article
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Leaf morphology exhibits tremendous diversity between and within species, and is likely related to adaptation to environmental factors. Most poplar species are of great economic and ecological values and their leaf morphology can be a good predictor for wood productivity and environment adaptation. It is important to understand the genetic mechanism behind variation in leaf shape. Although some initial efforts have been made to identify quantitative trait loci (QTLs) for poplar leaf traits, more effort needs to be expended to unravel the polygenic architecture of the complex traits of leaf shape. Here, we performed a genome-wide association analysis (GWAS) of poplar leaf shape traits in a randomized complete block design with clones from F 1 hybrids of Populus deltoides and Populus simonii . A total of 35 SNPs were identified as significantly associated with the multiple traits of a moderate number of regular polar radii between the leaf centroid and its edge points, which could represent the leaf shape, based on a multivariate linear mixed model. In contrast, the univariate linear mixed model was applied as single leaf traits for GWAS, leading to genomic inflation; thus, no significant SNPs were detected for leaf length, measures of leaf width, leaf area, or the ratio of leaf length to leaf width under genomic control. Investigation of the candidate genes showed that most flanking regions of the significant leaf shape-associated SNPs harbored genes that were related to leaf growth and development and to the regulation of leaf morphology. The combined use of the traditional experimental design and the multivariate linear mixed model could greatly improve the power in GWAS because the multiple trait data from a large number of individuals with replicates of clones were incorporated into the statistical model. The results of this study will enhance the understanding of the genetic mechanism of leaf shape variation in Populus . In addition, a moderate number of regular leaf polar radii can largely represent the leaf shape and can be used for GWAS of such a complicated trait in Populus , instead of the higher-dimensional regular radius data that were previously considered to well represent leaf shape.
... Leaf physiognomy (size and shape) is strongly correlated with mean annual temperature (MAT) [3][4][5][6][7][8][9][10] and mean annual precipitation (MAP) [11][12][13][14][15][16][17]. Based on these relationships, a variety of leaf physiognomic methods have been developed for reconstructing paleoclimate, including the famous univariate methods, leaf-margin analysis (LMA) [6,13] and leaf-area analysis (LAA) [18,19], and multivariate methods, Climate-Leaf Analysis Multivariate Program (CLAMP) [14,20] and digital leaf physiognomy (DLP) [8,21]. ...
... The DLP is also Sustainability 2022, 14, 4008 2 of 14 a multivariable method, mainly using continuous variables, which can be used to estimate 10 climatic factors [23], including the growing season precipitation (GSP) and mean annual range in temperature (MART). The DLP method has been tested several times, and it has shown its potential in paleoclimate estimation [10,25]. In the current DLP dataset, there are 92 natural or naturalized vegetation sites. ...
... An experiment about the effects of leaf physiognomy on temperature in five species also supported the view that the temperature effects on leaf shape are usually species-specific, so leafclimate models should take into account species-specific responses [26]. Studies [10,31] also showed that there were significant differences between individual climate and tooth size, shape, and number, Feret's diameter ratio and leaf size within evergreen than in deciduous species among woody taxa at individual sites. This also means that other patterns, not only the across-species mean of leaf physiognomy, may contribute useful information for estimating paleoclimate. ...
Article
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Paleobotanists have long built leaf climate models based on site mean of leaf physiognomic characteristics of woody dicotyledons species (WDS) for estimating past climate. To explore the potential of the order Ericales in estimating paleoclimate, we developed two linear models for each climatic factor. One is based on WDS, and the other is based on both WDS and leaf physiognomic characters of the order Ericales (WDS-E). We found that, compared with WDS models, WDS-E models improved greatly in mean annual precipitation (MAP), growing season precipitation (GSP) and mean annual range in temperature (MART). When the minimum species number of the order Ericales is three per site, the WDS-E models improved the r2 from 0.64 to 0.78 for MART, from 0.23 to 0.61 for ln(MAP), and from 0.37 to 0.64 for ln(GSP) compared with the WDS models. For mean annual temperature (MAT), the WDS-E model (r2 = 0.86) also exhibited a moderate improvement in precision over the WDS model (r2 = 0.82). This study demonstrates that other patterns, such as those of the order Ericales, can contribute additional information towards building more precise paleoclimate models.
... Leaf trait data ( Table 1) were collected from three sources, namely, the TRY database (Kattge et al., 2011), the China Plant Traits Database 1 , and published literature (a list of the data sources is presented in Supplementary Appendix A). The following criteria were used to ensure data quality and comparability: first, to minimize the effects of management disturbance, plant leaves were collected only from natural terrestrial ecosystems (excluding croplands, greenhouses, and laboratories); second, to reduce the confounding effects of ontogeny (Mason and Donovan, 2015), leaves were collected from healthy and mature plant individuals, while leaves in particular life stages (e.g., leaves from seedlings and expanding leaves) were excluded; third, leaves were sampled and measured according to the handbook for standardized measurement of plant functional traits (Perez-Harguindeguy et al., 2013); fourth, because plant ecological strategies may differ between native species and non-native species, leaves were collected only from the former (van Kleunen et al., 2010). Leaf samples were mostly collected during the peak of the growing season (June-August). ...
... Identifying the relationships between leaf traits and the environment variables is helpful for better understanding the impacts of environmental filtering on trait value selection and paleoclimate reconstruction (Peppe et al., 2011;Van Bodegom et al., 2012). Our results showed that environment variables explained the largest proportion of the variation in leaf traits, which was inconsistent with the results of a study by Yang et al. (2018), where the authors reported that environment variables exerted relatively weak effects on SLA and LDMC. ...
Article
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Leaf traits play key roles in plant resource acquisition and ecosystem processes; however, whether the effects of environment and phylogeny on leaf traits differ between herbaceous and woody species remains unclear. To address this, in this study, we collected data for five key leaf traits from 1,819 angiosperm species across 530 sites in China. The leaf traits included specific leaf area, leaf dry matter content, leaf area, leaf N concentration, and leaf P concentration, all of which are closely related to trade-offs between resource uptake and leaf construction. We quantified the relative contributions of environment variables and phylogeny to leaf trait variation for all species, as well as for herbaceous and woody species separately. We found that environmental factors explained most of the variation (44.4–65.5%) in leaf traits (compared with 3.9–23.3% for phylogeny). Climate variability and seasonality variables, in particular, mean temperature of the warmest and coldest seasons of a year (MTWM/MTWQ and MTCM/MTCQ) and mean precipitation in the wettest and driest seasons of a year (MPWM/MPWQ and MPDM/MPDQ), were more important drivers of leaf trait variation than mean annual temperature (MAT) and mean annual precipitation (MAP). Furthermore, the responses of leaf traits to environment variables and phylogeny differed between herbaceous and woody species. Our study demonstrated the different effects of environment variables and phylogeny on leaf traits among different plant growth forms, which is expected to advance the understanding of plant adaptive strategies and trait evolution under different environmental conditions.
... Leaf economic traits (Royer et al., 2007) and digital leaf physiognomy methods (Peppe et al., 2011;Royer et al., 2005) could not be performed because most of the leaves from this flora did not have petioles preserved, and the preservation did not occur in one plane, instead most leaves were undulated and fragmented due to the lack of rock lamination. ...
... Evidence of ancient TDFs around the globe is not abundant and mainly restricted to high-latitude macrofloras, such as the Paleocene-Eocene Bighorn Basin flora from Wyoming (Peppe et al., 2011;Wing and Currano, 2013), the middle Eocene of Africa (Jacobs and Herendeen, 2004) and the Middle Eocene Claiborne and Wilcox floras from Kentucky and Tennessee (Graham and Dilcher, 1995;Wang et al., 2013;Wolfe, 1978). Based on the palynological record, the earliest evidence of a TDF in the Neotropics comes from the middle to late Eocene of Panamá, in the Gatuncillo Formation (Graham, 1985;Graham and Dilcher, 1995). ...
Article
Movement toward our current climate state began in the middle Eocene to early Oligocene interval when the global temperature cooled and the first Antarctic ice sheet appeared. This dramatic climate change caused a significant global turnover in both marine and terrestrial biotas. The biotic response to this event at low latitudes remains mostly unexplored. Here, we studied a recently discovered Eocene fossil macro- and palynoflora from Esmeraldas Formation (Colombia). The Esmeraldas Flora consists of more than seven hundred macrofossil specimens found in two localities, including 15 morphotypes of leaves, seeds, cuticles, fruits, and flowers and > 5000 palynomorphs, that include 210 morphospecies. The Esmeraldas Formation is dominated by meandering river floodplain deposition, and was dated, using palynology and isotopic stratigraphy, as middle to late Eocene (~47.3 to ~33.9 Ma). Quantitative paleoclimatic calculations based on leaf physiognomy and coexistence analyses indicate a warm temperature and a seasonal precipitation within the range of modern tropical dry forests. Furthermore, the floristic composition that includes the presence of macrofossils of the Pterocarpus clade (Fabaceae), and pollen records of the subfamily Bombacoideae (Malvaceae), and Euphorbiaceae, could be indicative of a tropical dry forest. The overall paleobotanical record suggests that the Esmeraldas flora represents one of the earliest records of a tropical dry forest from low latitudes.
... In the investigation of leaf shape, the leaf roundness index (RI = ⁄ ) and leaf dissection index (DI = √ ⁄ ), where P is the leaf perimeter, are usually proposed and used as measures of leaf shape complexity (Kincaid & Schneider, 1983;Thomas & Bazzaz, 1996;Niinemets, 1998;Santiago & Kim, 2009;Peppe et al., 2011). However, the leaf RI only measures the deviation of a leaf"s shape from a standard circle. ...
... The leaf roundness index (RI) has long been regarded as a measure of the deviation of leaf shape from a standard circle (Niinemets, 1998;Peppe et al., 2011). It is effective for approximately round leaves. ...
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Plants have diverse leaf shapes that have evolved to adapt to the environments they have experienced over their evolutionary history. Leaf shape and leaf size can greatly influence the growth rate, competitive ability, and productivity of plants. However, researchers have long struggled to decide how to properly quantify the complexity of leaf shape. Prior studies recommended the leaf roundness index (RI = 4πA/P2) or dissection index (DI = ⁄ √ ), where P is leaf perimeter and A is leaf area. However, these two indices merely measure the extent of the deviation of leaf shape from a circle, which is usually invalid as leaves are seldom circular. In this study, we proposed a simple measure, named the ellipticalness index (EI), for quantifying the complexity of leaf shape based on the hypothesis that the shape of any oval leaf can be regarded as a variation from a standard ellipse. 2220 leaves from nine species of Magnoliaceae were sampled to check the validity of the EI. We also tested the validity of the Montgomery equation (ME), which assumes a proportional relationship between leaf area and the product of leaf length and width, because the EI actually comes from the proportionality coefficient of the ME. We also compared the ME with five other models of leaf area. The ME was found to be the best model for calculating leaf area based on consideration of the trade-off between model fit vs. complexity, which strongly supported the robustness of the EI for describing oval leaf shape. The new index can account for both leaf shape and size, and we conclude that it is a promising method for quantifying and comparing oval leaf shapes across species in future studies.
... PETM stratigraphic sections in the Bighorn Basin have been described from multiple outcrops and are typically 20-45 m thick and are composed of well-preserved alluvial channel sandstones and floodplain siltstones and mudstones that have undergone variable degrees of pedogenesis (Baczynski et al., 2017;Bowen et al., 2001Bowen et al., , 2015Koch et al., 1992;Kraus & Riggins, 2007). Before and after the PETM, Bighorn Basin floodplains supported mixed broad-leaved deciduous and evergreen forests composed of angiosperms and conifers whose living relatives are most diverse in humid, subtropical climates; leaf physiognomic proxies also suggest a warm, humid paleoclimate (Peppe et al., 2011;Wing & Greenwood, 1993;Wing & Currano, 2013;Wing et al., 1995). In contrast, fossil plants from the body of the negative carbon isotope excursion (CIE) associated with the PETM have living relatives that are most diverse in tropical dry climates; leaf physiognomic analyses, paleosol features, basin stratigraphy, and climate models support an increase of ∼5°C in mean annual temperature (MAT), a decrease in water availability (Currano et al., 2008;Kraus et al., 2013;Peppe et al., 2011;Wing & Currano, 2013;Wing et al., 2005), and enhanced seasonality of precipitation (Carmichael et al., 2018;Kraus et al., 2015;Rush et al., 2021;Shellito et al., 2003). ...
... Before and after the PETM, Bighorn Basin floodplains supported mixed broad-leaved deciduous and evergreen forests composed of angiosperms and conifers whose living relatives are most diverse in humid, subtropical climates; leaf physiognomic proxies also suggest a warm, humid paleoclimate (Peppe et al., 2011;Wing & Greenwood, 1993;Wing & Currano, 2013;Wing et al., 1995). In contrast, fossil plants from the body of the negative carbon isotope excursion (CIE) associated with the PETM have living relatives that are most diverse in tropical dry climates; leaf physiognomic analyses, paleosol features, basin stratigraphy, and climate models support an increase of ∼5°C in mean annual temperature (MAT), a decrease in water availability (Currano et al., 2008;Kraus et al., 2013;Peppe et al., 2011;Wing & Currano, 2013;Wing et al., 2005), and enhanced seasonality of precipitation (Carmichael et al., 2018;Kraus et al., 2015;Rush et al., 2021;Shellito et al., 2003). Fossil plants from the recovery phase of the CIE indicate a return to a cooler, wetter climate (Wing & Currano, 2013). ...
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Plain Language Summary The chemical breakdown of silicate minerals on continents promotes the withdrawal of CO2 from the ocean and atmosphere. This process is thought to be enhanced when CO2 rapidly enters the ocean and atmosphere, such as during past climate change events like the Paleocene‐Eocene Thermal Maximum (PETM). Although this enhancement of silicate weathering is found in global carbon cycle models and the chemistry of marine rocks, less terrestrial evidence exists for how, where, and to what extent silicate minerals weathered during the PETM. In this study, we measured the chemistry of bedrock and ancient floodplain sediment that span the PETM in the well‐studied Bighorn Basin, Wyoming (USA) to quantify changes in silicate weathering intensity. We find that silicate weathering intensity increases rapidly (within 7,000 years of the onset of the PETM) and remains elevated even as climate has begun to return to its pre‐perturbed state. We also determine that soils that formed farthest from ancient river channels underwent larger weathering changes than near‐channel soils, suggesting active weathering responses on floodplains. Alongside high CO2 contents and warmer temperatures, the simplest explanation for this weathering response relates to soil hydrology, where increased water flow through soils caused by fluctuating water tables enhanced weathering.
... Leaf structural and functional traits are generally correlated with each other and with the environment (Reich et al., 1997;Wright et al., 2004Wright et al., , 2005. Relationships of leaf morphology traits with climate have been well characterized for dicotyledons, allowing to reconstruct paleoclimate from fossil leaves in the geological past (Royer, 2012;Peppe et al., 2011Peppe et al., , 2014Soh et al., 2017). For example, the strong relationship between leaf teeth and temperature observed in extant woody dicotyledon can be used to estimate the paleotemperature (Royer, 2012). ...
Article
The end-Triassic mass extinction (ETME) is considered to be one of the five most severe extinction events in Earth history and caused the disappearance of ca. 80% of all species. The terrestrial ecosystems were also greatly affected by this extinction, but the severity of the land plant diversity loss is not well understood. Ferns are once a principal component of the terrestrial ecosystem from the late Paleozoic/early Mesozoic era and colonizers taxa commonly found in disturbed environments. In this study, we investigated the diversity and ecology of fern during the Triassic-Jurassic (Tr–J) transition in the Sichuan Basin of South China and focused for the first time on the impact of the end-Triassic mass extinction event on the fern communities. We assembled fern fossil records in 16 localities from the Rhaetian Xujiahe (XJH) Formation to the lowermost Jurassic Zhenzhuchong (ZZC) Formation. Our results indicate that no obvious mass extinctions of macro-microflora of ferns but a clear species turnover was recorded at ETME in the Sichuan Basin, reflected an appropriate response of plants in places far away from CAMP volcanism. The paleoecological analysis based on macroflora and microflora in the Sichuan Basin shows a warm and humid condition of tropical-subtropical climate during Rhaetian followed by an increase of specific dry-resistant taxa, indicating a dryer environment at the Earliest Jurassic. Additionally, multivariate statistical approaches (principal coordinates analysis, cluster analysis, network analysis) for fern macro-remains and spores data in the southeastern Sichuan Basin infer that the members of XJH and ZZC Formation cluster in three groups, corresponding to their environmental conditions, determined by humidity and temperature.
... Major contributions to the general collection are briefly listed here for paleobotanists, with additional taxonomic and occurrence references listed in Appendix 1. The fossils come from (1) a suite of latest Cretaceous (late Maastrichtian, Hell Creek Formation) and early Paleocene (early Danian, Fort Union Formation) sites from western North Dakota and South Dakota USA that have been used extensively for studies of the end-Cretaceous extinction (e.g., Johnson et al. 1989;Johnson 2002;Wilf and Johnson 2004); (2) the early Paleocene Salamanca Formation (early Danian) and Las Flores (late Danian) floras of Chubut, Argentina, known for diverse and well-preserved fossil plants and insect-feeding damage following the end-Cretaceous extinction (e.g., Iglesias et al. 2007Iglesias et al. , 2021Clyde et al. 2014;Donovan et al. 2017;Stiles et al. 2020); (3) the early Paleocene (Danian, Fort Union Formation) Mexican Hat site in southeastern Montana, USA, known for diverse insect herbivory traces preserved in its fossil leaves (Wilf et al. 2006;Winkler et al. 2010;Donovan et al. 2014); (4) the middle-late Paleocene (Selandian-Thanetian, Cerrejón Formation) Cerrejón flora from the Guajira Peninsula, Colombia and Bogotá Formation flora of Sabana de Bogotá, central Colombia, together preserving the remains of the oldest known Neotropical rainforests (e.g., Doria et al. 2008;Herrera et al. 2008Herrera et al. , 2019Gómez-Navarro et al. 2009;Wing et al. 2009;Carvalho et al. 2011Carvalho et al. , 2021aCarvalho et al. , 2021b; (5) a suite of sites spanning the late Paleocene (Fort Union Formation) through early Eocene (Wasatch Formation and Little Mountain locality of the Green River Formation) of southwestern and northwestern Wyoming that have been used in many studies of floristic and plant-insect associational responses to climate change (e.g., Gemmill and Johnson 1997;Wilf et al. 1998Wilf et al. , 2006Wilf and Labandeira 1999;Wilf 2000;Donovan et al. 2014); (6) the early Eocene Laguna del Hunco Lagerstätte in Chubut, Argentina (Huitrera Formation), known for its outstanding diversity of fossil plants and animals, varied biogeographic connections, and large number of unique taxon occurrences for South America (e.g., Wilf et al. 2003Wilf et al. , 2013Wilf et al. , 2019Gandolfo et al. 2011); (7) the late early Eocene flora of Republic, Washington (Wolfe and Wehr 1987;DeVore et al. 2005;Greenwood et al. 2016; Klondike Mountain Formation) and the middle Eocene Green River Formation flora (MacGinitie 1969;Smith et al. 2008) of Bonanza, Utah, specifically using images of field-censused collections at DMNH from both sites led by K. Johnson that were used previously for analyses of insect herbivory, fossil-leaf economics, and digital leaf physiognomy (Wilf et al. 2001(Wilf et al. , 2005bCariglino 2007;Royer et al. 2007;Peppe et al. 2011). ...
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Leaves are the most abundant and visible plant organ, both in the modern world and the fossil record. Identifying foliage to the correct plant family based on leaf architecture is a fundamental botanical skill that is also critical for isolated fossil leaves, which often, especially in the Cenozoic, represent extinct genera and species from extant families. Resources focused on leaf identification are remarkably scarce; however, the situation has improved due to the recent proliferation of digitized herbarium material, live-plant identification applications, and online collections of cleared and fossil leaf images. Nevertheless, the need remains for a specialized image dataset for comparative leaf architecture. We address this gap by assembling an open-access database of 30,252 images of vouchered leaf specimens vetted to family level, primarily of angiosperms, including 26,176 images of cleared and x-rayed leaves representing 354 families and 4,076 of fossil leaves from 48 families. The images maintain original resolution, have user-friendly filenames, and are vetted using APG and modern paleobotanical standards. The cleared and x-rayed leaves include the Jack A. Wolfe and Leo J. Hickey contributions to the National Cleared Leaf Collection and a collection of high-resolution scanned x-ray negatives, housed in the Division of Paleobotany, Department of Paleobiology, Smithsonian National Museum of Natural History, Washington D.C.; and the Daniel I. Axelrod Cleared Leaf Collection, housed at the University of California Museum of Paleontology, Berkeley. The fossil images include a sampling of Late Cretaceous to Eocene paleobotanical sites from the Western Hemisphere held at numerous institutions, especially from Florissant Fossil Beds National Monument (late Eocene, Colorado), as well as several other localities from the Late Cretaceous to Eocene of the Western USA and the early Paleogene of Colombia and southern Argentina. The dataset facilitates new research and education opportunities in paleobotany, comparative leaf architecture, systematics, and machine learning. Keywords Angiosperms, cleared leaves, data science, fossil leaves, leaf architecture, paleobotany
... Physiognomic techniques including CLAMP and leaf margin analysis (LMA; Wilf, 1997) were used to calculate mean annual air temperature. LMA uses the correlation between MAAT and the proportion of untoothed to total (untoothed + toothed) species in a local flora (Wolfe, 1979;Wilf, 1997;Wing and Greenwood, 1993;Peppe et al., 2011). See Allen (2017b) for additional reconstruction details based on floral assemblages. ...
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As atmospheric carbon dioxide (CO2) and temperatures increase with modern climate change, ancient hothouse periods become a focal point for understanding ecosystem function under similar conditions. The early Eocene exhibited high temperatures, high CO2 levels, and similar tectonic plate configuration as today, so it has been invoked as an analog to modern climate change. During the early Eocene, the greater Green River Basin (GGRB) of southwestern Wyoming was covered by an ancient hypersaline lake (Lake Gosiute; Green River Formation) and associated fluvial and floodplain systems (Wasatch and Bridger formations). The volcaniclastic Bridger Formation was deposited by an inland delta that drained from the northwest into freshwater Lake Gosiute and is known for its vast paleontological assemblages. Using this well-preserved basin deposited during a period of tectonic and paleoclimatic interest, we employ multiple proxies to study trends in provenance, parent material, weathering, and climate throughout 1 million years. The Blue Rim escarpment exposes approximately 100 m of the lower Bridger Formation, which includes plant and mammal fossils, solitary paleosol profiles, and organic remains suitable for geochemical analyses, as well as ash beds and volcaniclastic sandstone beds suitable for radioisotopic dating. New 40Ar / 39Ar ages from the middle and top of the Blue Rim escarpment constrain the age of its strata to ∼ 49.5–48.5 Myr ago during the “falling limb” of the early Eocene Climatic Optimum. We used several geochemical tools to study provenance and parent material in both the paleosols and the associated sediments and found no change in sediment input source despite significant variation in sedimentary facies and organic carbon burial. We also reconstructed environmental conditions, including temperature, precipitation (both from paleosols), and the isotopic composition of atmospheric CO2 from plants found in the floral assemblages. Results from paleosol-based reconstructions were compared to semi-co-temporal reconstructions made using leaf physiognomic techniques and marine proxies. The paleosol-based reconstructions (near the base of the section) of precipitation (608–1167 mm yr−1) and temperature (10.4 to 12.0 ∘C) were within error of, although lower than, those based on floral assemblages, which were stratigraphically higher in the section and represented a highly preserved event later in time. Geochemistry and detrital feldspar geochronology indicate a consistent provenance for Blue Rim sediments, sourcing predominantly from the Idaho paleoriver, which drained the active Challis volcanic field. Thus, because there was neither significant climatic change nor significant provenance change, variation in sedimentary facies and organic carbon burial likely reflected localized geomorphic controls and the relative height of the water table. The ecosystem can be characterized as a wet, subtropical-like forest (i.e., paratropical) throughout the interval based upon the floral humidity province and Holdridge life zone schemes. Given the mid-paleolatitude position of the Blue Rim escarpment, those results are consistent with marine proxies that indicate that globally warm climatic conditions continued beyond the peak warm conditions of the early Eocene Climatic Optimum. The reconstructed atmospheric δ13C value (−5.3 ‰ to −5.8 ‰) closely matches the independently reconstructed value from marine microfossils (−5.4 ‰), which provides confidence in this reconstruction. Likewise, the isotopic composition reconstructed matches the mantle most closely (−5.4 ‰), agreeing with other postulations that warming was maintained by volcanic outgassing rather than a much more isotopically depleted source, such as methane hydrates.
... Lobed leaves can be easily visualized even in the primary leaf stage, which can be used as an indicator trait for hybrid production [5,6]. Compared to unlobed-or serrated-leaf lines, plants with lobed leaves are better adapted to environmental stresses [7,8]. With improved heat transfer and light energy absorption, lobed leaves are advantageous for high-density planting and mechanized production [9]. ...
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Background Leaf shape is an important agronomic trait in ornamental kale (Brassica oleracea L. var. acephala). Although some leaf shape-related genes have been reported in ornamental kale, the detailed mechanism underlying leaf shape formation is still unclear. Here, we report a lobed-leaf trait in ornamental kale, aiming to analyze its inheritance and identify the strong candidate gene. Results Genetic analysis of F2 and BC1 populations demonstrate that the lobed-leaf trait in ornamental kale is controlled by a single dominant gene, termed BoLl-1 (Brassica oleracea lobed-leaf). By performing whole-genome resequencing and linkage analyses, the BoLl-1 gene was finely mapped to a 127-kb interval on chromosome C09 flanked by SNP markers SL4 and SL6, with genetic distances of 0.6 cM and 0.6 cM, respectively. Based on annotations of the genes within this interval, Bo9g181710, an orthologous gene of LATE MERISTEM IDENTITY 1 (LMI1) in Arabidopsis, was predicted as the candidate for BoLl-1, and was renamed BoLMI1a. The expression level of BoLMI1a in lobed-leaf parent 18Q2513 was significantly higher compared with unlobed-leaf parent 18Q2515. Sequence analysis of the parental alleles revealed no sequence variations in the coding sequence of BoLMI1a, whereas a 1737-bp deletion, a 92-bp insertion and an SNP were identified within the BoLMI1a promoter region of parent 18Q2513. Verification analyses with BoLMI1a-specific markers corresponding to the promoter variations revealed that the variations were present only in the lobed-leaf ornamental kale inbred lines. Conclusions This study identified a lobed-leaf gene BoLMI1a, which was fine-mapped to a 127-kb fragment. Three variations were identified in the promoter region of BoLMI1a. The transcription level of BoLMI1a between the two parents exhibited great difference, providing new insight into the molecular mechanism underlying leaf shape formation in ornamental kale.
... However, generalizing leaf size-environment patterns at a global scale is less straightforward than we might expect. Across >7000 species, Moles et al. (2014) found the correlation between leaf size and mean annual precipitation to be weaker than with mean annual temperature, whereas Wright et al. (2017) found that both temperature and rainfall were strong predictors, and rainfall is also strong for fossil leaves (Peppe et al., 2011). ...
... In addition, leaf morphology has been recognized as one of the key components of plant species adaptation to environmental conditions, influencing plant growth and productivity (Wang and Zhang 2012;Ren et al. 2020). Several studies have shown that spatial variation of leaf traits, including leaf size and shape are significantly related to climate (Peppe et al. 2011;Miljković et al. 2019;Jahdi et al. 2020), suggesting strong local adaptation. ...
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Key message Leaf shape in European beech provenances varies geographically, with narrower and longer lamina observed in southern provenances, indicating a direct selection favoring leaf shape that likely safeguards trees performances under less favorable growing conditions. AbstractSpatial and environmental patterns of European beech (Fagus sylvatica L.) leaf size and shape variations were studied using landmark-based geometric morphometrics. The study involved eight provenances originating from three biogeographic regions (i.e., Alpine, Continental, and Pannonian), spanning across six European countries (Bosnia and Herzegovina, Croatia, Germany, Hungary, Romania and Serbia). All specimens were cultivated in a common garden experiment. The symmetric component of leaf shape variation was analyzed by Procrustes ANOVA and multi‐variate analyses [principal component analysis and canonical variate analysis (CVA)], whereas MANOVA was used to examine asymmetry. Partial least square (PLS) analysis was used to assess the covariation between leaf shape and size, and geographical position and environmental variables at the sites of provenance origin, respectively. A highly observed phenotypic variation for the shape and size of leaf both within and among provenances, indicates a strong local adaptation of provenances within the species natural range. CVA revealed the existence of two clusters of provenances based on the leaf shape, i.e., the first group included provenances originating from Balkan Peninsula and Central Europe, while the second group consisted of two Romanian provenances and the northernmost provenance from Germany. Likewise, PLS evidenced that leaf shape was spatially structured along latitudinal (− 0.64) and longitudinal (0.60) gradients, with southern provenances having longer and narrower (ovate) lamina compared to the northern ones. In contrast, no correlation was found between centroid size and spatial and environmental variables. Results suggest the presence of direct selection favoring a leaf shape that likely safeguards trees from heat and water loses under less favorable growing conditions.
... Although a great deal of research has been devoted to the topic, our knowledge on LMTs is still mainly based on spatial comparisons across different gradients, which indicate that variations in LMTs are mainly driven by temperature and water availability (Peppe et al., 2011;Wright et al., 2017). In contrast, temporal variations in LMTs and their response to multiple drivers are still poorly understood, mainly owing to the scarcity of systematic measurements and foliar archives (e.g., Li et al., 2020). ...
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Leaf morphological traits (LMTs) of forest trees have been observed to vary across space and species. However, long-term records of LMTs are scarce, due to a lack of measurements and systematic leaf archives. This leaves a large gap in our understanding of the temporal dynamics and drivers of LMT variations, which may help us understand tree acclimation strategies. In our study, we used long-term LMT measurements from foliar material collections of European beech (Fagus sylvatica) and Norway spruce (Picea abies), performed every second year from 1995 to 2019 on the same trees within the Swiss Long-term Forest Ecosystem Research Program LWF. The 11 study plots (6 beech, 4 spruce, and 1 mixed) are distributed along gradients of elevation (485-1,650 m a.s.l.), mean annual precipitation (935-2142 mm), and mean annual temperature (3.2-9.8 • C). The investigated LMTs were (i) leaf or needle mass, (ii) leaf area or needle length, and (iii) leaf mass per area or needle mass per length. We combined this unique data set with plot variables and long-term data on potential temporal drivers of LMT variations, including meteorological and tree trait data. We used univariate linear regressions and linear mixed-effects models to identify the main spatial and temporal drivers of LMT variations, respectively. For beech LMTs, our temporal analysis revealed effects of mast year and crown defoliation, and legacy effects of vapor pressure deficit and temperature in summer and autumn of the preceding year, but no clear long-term trend was observed. In contrast, spruce LMTs were mainly driven by current-year spring conditions, and only needle mass per length showed a decreasing long-term trend over the study period. In temporal models, we observed that LMTs of both species were influenced by elevation and foliar nutrient concentrations, and this finding was partly confirmed by our spatial analyses. Our results demonstrate the importance of temporal analysis for determining less recognized drivers and legacy effects that influence LMTs, which are difficult to determine across space and species. The observed differences in the temporal drivers of beech and spruce LMTs suggest differences in the adaptation and acclimation potential of the two species.
... Leaf roundness index (RI) (Niinemets 1998;Peppe et al. 2011) and leaf ellipticalness index (EI) ) were used to measure the extent to which lamina geometry deviated from a circle or an ellipse using Eqs. 3 and 4: ...
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The shape of leaf laminae exhibits considerable diversity and complexity that reflects adaptations to environmental factors such as ambient light and precipitation as well as phyletic legacy. Many leaves appear to be elliptical which may represent a ‘default’ developmental condition. However, whether their geometry truly conforms to the ellipse equation (EE), i.e., ( x/a ) ² + ( y/b ) ² = 1, remains conjectural. One alternative is described by the superellipse equation (SE), a generalized version of EE, i.e., | x/a | n +| y/b | n = 1. To test the efficacy of EE versus SE to describe leaf geometry, the leaf shapes of two Michelia species (i.e., M. cavaleriei var. platypetala , and M. maudiae ), were investigated using 60 leaves from each species. Analysis shows that the majority of leaves (118 out of 120) had adjusted root-mean-square errors of < 0.05 for the nonlinear fitting of SE to leaf geometry, i.e., the mean absolute deviation from the polar point to leaf marginal points was smaller than 5% of the radius of a hypothesized circle with its area equaling leaf area. The estimates of n for the two species were ˂ 2, indicating that all sampled leaves conformed to SE and not to EE. This study confirms the existence of SE in leaves, linking this to its potential functional advantages, particularly the possible influence of leaf shape on hydraulic conductance.
... In this study, we aim to build several new leaf shape models that can describe ovate leaves and to find whether there is a best one relative to other candidate models. This work does not recommend a leaf shape index such as the leaf roundness index and leaf dissection index [16][17][18][19][20], because a leaf shape index cannot be used to fit the edge data of ovate leaves. Here, the mathematical model that we finally recommend can describe the ovate leaf shape with model parameters that can be well understood. ...
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Many plant species produce ovate leaves, but there is no general parametric model for describing this shape. Here, we used two empirical nonlinear equations, the beta and Lobry–Rosso–Flandrois (LRF) equations, and their modified forms (referred to as the Mbeta and MLRF equations for convenience), to generate bilaterally symmetrical curves along the x-axis to form ovate leaf shapes. In order to evaluate which of these four equations best describes the ovate leaf shape, we used 14 leaves from 7 Neocinnamomum species (Lauraceae) and 72 leaves from Chimonanthus praecox (Calycanthaceae). Using the AIC and adjusted root mean square error to compare the fitted results, the modified equations fitted the leaf shapes better than the unmodified equations. However, the MLRF equation provided the best overall fit. As the parameters of the MLRF equation represent leaf length, maximum leaf width, and the distance from leaf apex to the point associated with the maximum leaf width along the leaf length axis, these findings are potentially valuable for studying the influence of environmental factors on leaf shape, differences in leaf shape among closely related plant species with ovate leaf shapes, and the extent to which leaves are bilaterally symmetrical. This is the first work in which temperature-dependent developmental equations to describe the ovate leaf shape have been employed, as previous studies lacked similar leaf shape models. In addition, prior work seldom attempted to describe real ovate leaf shapes. Our work bridges the gap between theoretical leaf shape models and empirical leaf shape indices that cannot predict leaf shape profiles.
... Temperature is one of the critical drivers of leaf size and shape worldwide, generating giant leaves that have fewer, smaller teeth in tropical plants, and tiny ones with more numerous teeth in deserts (Peppe et al., 2011). Aridity limits leaf size as the risk of overheating during daytime maximum temperatures increases as they grow larger. ...
... As expected, specific leaf area declined with elevation, reflecting higher relative growth rate and photosynthetic activity at lower elevation (Pérez-Harguindeguy et al. 2013). Similarly, specific root length increased with elevation, reflecting a consistent pattern in root investment over elevation gradients (Bliss 1956;Körner and Renhardt 1987); and leaf dry matter content increased with elevation, potentially due to increases in leaf density (Körner 2003;Poorter et al. 2009;Peppe et al. 2011). Together, these trait differences suggest the emergence of different life history strategies in Nabalus plants at different elevations, which reflect the strategies typically seen in competitive low elevation habitats versus high elevation habitats, where stress tolerance is most important (Poorter et al. 2009). ...
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Species range limits often reflect niche limits, especially for ranges constrained along elevational gradients. In this study, we used elevational transplant experiments to test niche breadth and functional trait plasticity in early life stages of narrow-range Nabalus boottii and broad-range N. trifoliolatus plants to assess their climate change vulnerability and the applicability of the niche breadth-range size hypothesis to explain their range size differences. We discovered that the earliest life stage (seed germination) was the most vulnerable and the two alpine taxa, N. boottii and N. trifoliolatus var. nanus, were unable to establish at the warm low elevation site, however non-alpine N. trifoliolatus established at all three elevations, including at the high elevation (beyond-range) site. Niche limits in seed emergence may therefore contribute to range size in these taxa. In contrast, when seedlings were planted we found substantial functional trait plasticity in later life stages (average 44% across ten traits) that was highly similar for all Nabalus taxa, suggesting that differences in plasticity do not generate niche differences or restrict range size in the focal taxa. While this substantial plasticity may help buffer populations faced by climate change, the inability of the alpine taxa to establish at lower elevation sites suggests that their populations may still decline due to decreased seed recruitment under ongoing climate change. We therefore recommend monitoring alpine Nabalus populations, particularly globally rare N. boottii.
... Furthermore, correlating the species characteristics such as leaf characters to various climatic factors such as temperature, light intensity, RH, and rainfall will determine the differences in their growth responses in terms of morphological, physiological, and other parameters when planted in various locations. The physiognomy (sizes and shapes) of the leaves has been shown to have a strong correlation with temperature and moisture from global to local scales (reviewed in Peppe et al. 2011). Specifically, the site-mean leaf size typically is proportional with water availability and, to a lesser extent, temperature. ...
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Calophyllum inophyllum L. (bitaog), a native tree species in the Philippines that can be found growing in different locations (urban, coastal, and forest areas) with varying climatic conditions, were studied to compare the morphological and anatomical characters in relation to climatic factors. Nine leaf morphological characters (arrangement, apex, base, margin, shape, venation, texture, length, and width) were observed. The thicknesses of the epidermis, vascular tissues, and mesophyll were measured. One-way analysis of variance (ANOVA) was used to show significant differences in morphological and anatomical characters among locations. The linear mixed model was used to determine if leaf characters were affected by precipitation (PPT) and temperature (Temp) in each location. A significant difference in the quantitative morphological characters of C. inophyllum leaves was observed only in leaf length (LL), which was found negatively correlated with leaf width (LW) across locations. Palisade mesophyll (PM) and spongy mesophyll (SM) were found to have significant differences among locations. Leaves in the coastal area, which is the natural habitat of the species, had the thickest mesophyll. It was found out that C. inophyllum grows best in the coastal area and least in the urban area based on the quantitative measurement of leaf morphological characters such as LL and LW. On one hand, trees in the urban area have smaller LL, LW, PM, and SM as affected by the climatic variables. We, therefore, conclude that morphological and anatomical characteristics of C. inophyllum are altered once the species is grown outside of its natural habitat.
... Morphological traits alone or in combination with molecular markers have successfully differentiated Medicago species in several cases (Chen & al. 2021). The primarily driven factors behind the morphological variation, among populations across the geographical distribution range of a specific species, could be broadly classified into the ongoing environmental conditions within habitats, and previous historical processes and phylogenesis (Peppe & al. 2011;Thorpe 1987). The populations of the same species under various environmental conditions may respond differently to the selection pressures in their genetic and morphology. ...
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Medicago rigiduloides E. Small is a mostly Asian species that was recently separated from the extremely closely related, mostly European species, M. rigidula (L.) All. Medicago is a large genus of about 90 species, but there has never been a study of how any of these interact geographically where they meet. This, the first such study, documents the distribution ranges of the two species in Iran, based on 14 representative populations. The two species are extremely difficult to distinguish morphologically, so in addition to analysis of their morphology, molecular analysis of the internal transcribed spacer (ITS) region was conducted, and the degree of reliability of the diagnostic characters of the two taxa was assessed. Medicago rigidula, known to be mainly European, was found to have extended into Iran bordering the Caspian Sea. Medicago rigiduloides was found to be widely distributed in northwestern, western, southwestern, and central Iran, consistent with the hypothesis that the taxon is mainly Asian. Thus, the main distributions of the two taxa appear to be mainly parapatric, presumably related to different adaptations to the local ecology.
... Based on the shapes of leaf margins, leaf shape has been classified into three types: deeply lobed, entire, or serrated (Sinha 2004). Deeply lobed leaves seem to be more adapted to environmental stresses like strong winds and water stress due to improved heat transfer and light energy absorption (Semchenko and Zobel 2007;Vogel 2009;Peppe et al. 2011 In practice, crop plants with deeply lobed leaves are more suitable for high-density planting in mechanical production, as they can improve ventilation and allow more sunlight to reach the leaves under the canopy (Tu et al. 2013). Therefore, in crop breeding, a better understanding of the genetic mechanism and regulatory network of leaf shape variation, in particular, the formation of deeply lobed leaves may help the manipulation of leaf shape for better plant architecture and increase of crop productivity. ...
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Key message CpDll, encoding an HD-Zip I transcription factor, positively regulates formation of deeply lobed leaf shape in zucchini, Cucurbita pepo, which is associated with sequence variation in its promoter region. Abstract Leaf shape is an important horticultural trait in zucchini (Cucurbita pepo L.). Deeply lobed leaves have potential advantages for high-density planting and hybrid production. However, little is known about the molecular basis of deeply lobed leaf formation in this important vegetable crop. Here, we conducted QTL analysis and fine mapping of the deeply lobed leaf (CpDll) locus using recombinant inbred lines and large F2 populations developed from crosses between the deeply lobed leaf HM-S2, and entire leaf Jin-GL parental lines. We show that CpDll exhibited incomplete dominance for the deeply lobed leaf shape in HM-S2. Map-based cloning provided evidence that CpCll encodes a type I homeodomain (HD)- and Leu zipper (Zip) element-containing transcription factor. Sequence analysis between HM-S2 and Jin-GL revealed no sequence variations in the coding sequences, whereas a number of variations were identified in the promoter region between them. DUAL-LUC assays revealed significantly stronger promoter activity in HM-S2 than that in Jin-GL. There was also significantly higher expression of CpDll in the leaf base of deeply lobed leaves of HM-S2 compared with entire leaf Jin-GL. Comparative analysis of CpDll gene homologs in nine cucurbit crop species (family Cucurbitaceae) revealed conservation in both structure and function of this gene in regulation of deeply lobed leaf formation. Our work provides new insights into the molecular basis of leaf lobe formation in pumpkin/squash and other cucurbit crops. This work also facilitates marker-assisted selection for leaf shape in zucchini breeding.
... For ecometrics to work a trait-environment relationship needs to be identified through direct observations or identifying correlations based on underlying mechanical function. Examples of widely applied ecometrics based on observations are the relationship of gross leaf (Bailey and Sinnott, 1915;Greenwood et al., 2004;Peppe et al., 2011) and tooth (Liu et al., 2012;Fortelius et al., 2016;Oksanen et al., 2019) morphology to climate and body size to temperature (Hunt and Roy, 2006;L. Trip et al., 2014;Audzijonyte et al., 2020). ...
Thesis
Humans are changing the Earth. What is unknown is how biotic communities and ecosystems will react to this change on both short and long timescales. The fossil record can provide us with a means of investigating ecosystem responses to long-term climatic fluctuations which can act as baselines for future anthropogenic induced change. How we utilize the fossil record is therefore of critical Importance. The high spatial and temporal resolution of the planktonic foraminifera fossil record provides an ideal system to investigate ecosystem responses to climatic fluctuations at multiple scales and levels. The primary objective of this thesis is to measure and understand the relationship between planktonic foraminifera and their environment, to enable a more biologically informative assessment of the fossil record. I created a diversity record of planktonic foraminifera through the Middle Eocene Climatic Optimum comprising of 22,800 individuals classified to three taxonomic levels and investigated the responses of these assemblages using effective diversity: a novel approach for Palaeogene and deep-time systems (Chapter 2). The results from this study show that analytical size fraction choice is a key determinant of diversity signals in deep-time and furthermore it is small species that maintain ecological function during transient climatic events. I then investigated a key component of these assemblages, Subbotina, using individual morphological and geochemical measurements to link their traits to the environment and assess their persistence through the climatic fluctuations of the Middle Eocene (Chapter 3). I found that longevity of Subbotina is a result of morphological and geochemical trait plasticity resulting in a wide ecological niche which in turn allowed for continued persistence and dominance through the Middle Eocene whilst other groups faltered. Next, I explored the relationship between geochemistry and morphology within a relatively recent system to understand the relationship between geochemistry, size, and genetically identified species (Chapter 4). The results showed that fine resolution geochemical analyses can be used to unpick the drivers of intraindividual variability. However, more work is needed to understand the drivers of geochemistry at the individual level which is possible using the methods I advocate and explore in this thesis. Together, these discoveries expand our understanding of how planktonic foraminifera communities are linked to their environment and demonstrate that by using the appropriate analytical approaches we can investigate this relationship in a more biologically meaningful way. Future studies on planktonic foraminifera will require the application of traitbased approaches through the integration of geochemistry, morphology, and diversity measurements to further our understanding of how past communities responded to climatic perturbations with an aim to inform our understanding of biotic responses to current and future anthropogenic change
... Although not yet widely used in the community, this method arguably returns more consistent results than previous CA analyses (Grimm and Denk, 2012;Mosbrugger and Utescher, 1997;Punyasena, 2008;Thompson et al., 2012) and commonly used physiognomic climate reconstructions derived using vegetation (Peppe et al., 2011;Spicer et al., 2009;Wolfe, 1995). ...
Article
In their thoughtful paper entitled “An equable subtropical climate throughout China in the Miocene based on palaeofloral evidence”, Qing Wang, Yan Li, David K. Ferguson, Wen-Bo Mo, and Nan Yang (2021) imply that China exhibited negligible latitudinal mean annual precipitation (MAP) gradients and lacked arid regions during the Miocene. They also speculate that there was no abrupt change in elevation of the Tibetan Plateau, nor that the plateau attained its present altitude or orography during that period. These conclusions were derived mainly by using a co-existence approach (CA) and ‘incomplete data’. Here, we use CA with training data and also integrate a coexistence likelihood estimation, a pollen-MAP boundary, a desert-MAP boundary, and other newly published MAP data to show that Northwest China consistently exhibited drier conditions than South China and East China during the entire Miocene, with our new values being 300–500 mm lower than those of Wang et al. (2021). This implies that there were large spatial gradients of MAP in China during the Miocene, which may be directly linked with the growth of the Tibetan Plateau, the global cooling, as well as other factors. We recommend the comprehensive consideration of multiple methods and proxies for reconstructing past climate conditions as opposed to a single proxy.
... As reported and confirmed by numerous researchers, the leaf shape is a species-specific characteristic that is subjected to change by environmental or physiological processes (Du et al., 2007). Some reports have indicated that global warming has only changed the rate of leaf dentation and serration, and not the entire leaf shape (Peppe et al., 2011). Another study described that fluctuations in the availability of some macronutrients including nitrogen led to a negligible variation in the grapevine leaf shape aspect ratio (Kondou et al., 2002). ...
Article
The growth, development, and morphology of plants are extremely affected by many internal and external factors. In this regard, plant nourishing solutions take the most impact. Nowadays, the magnetization of nutrient solutions has been recommended as a promising eco-friendly approach for improving the growth and development of plants. This study was designed to explore the potential of magnetic nutrient solutions in altering morphometric characteristics as well as some physiological and nutritional attributes of Rasha grapevines. Magnetic treatments included magnetized nutrient solution (MagS) and pre-magnetized water completed with nutrients (MagW + S) at magnetic field intensities (0.1 and 0.2 T). According to the results, the most considerable changes in leaf shape and size as well as fresh and dry weights were observed in the plants treated with MagS at 0.2 T. Also, MagS 0.2 had a significant effect on increasing photosynthetic pigments, content of total soluble carbohydrates and protein, and activity of antioxidant enzymes. The content of TNK, K, P, Fe, and Cu was considerably amplified by MagW + S 0.2. Overall, the magnetic solutions had favorable influences on physiological, nutritional state, and leaf morphology of grapevines possibly through alerting water and solution properties, mineral solubility, and phytohormones signalling.
... Castle Rock (63.84 Ma; P-D1-West association) is notable for being an early example of a tropical rainforest (Johnson and Ellis, 2002;Johnson et al., 2003). Compared to most of the Denver Basin, Castle Rock had a low LMA (median = 64 g/m 2 ) and a high MAP (204 cm), in-line with many present-day tropical rainforests (Royer et al., 2007;Poorter et al., 2009;Peppe et al., 2011). We found a similarly low LMA (median = 59 g/m 2 ) at the older Baptist Road locality (∼66.5 Ma; P-D1-West; no MAP estimate), which is high in diversity but has never been classified as a rainforest. ...
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The Chicxulub bolide impact has been linked to a mass extinction of plants at the Cretaceous—Paleogene boundary (KPB; ∼66 Ma), but how this extinction affected plant ecological strategies remains understudied. Previous work in the Williston Basin, North Dakota, indicates that plants pursuing strategies with a slow return-on-investment of nutrients abruptly vanished after the KPB, consistent with a hypothesis of selection against evergreen species during the globally cold and dark impact winter that followed the bolide impact. To test whether this was a widespread pattern we studied 1,303 fossil leaves from KPB-spanning sediments in the Denver Basin, Colorado. We used the relationship between petiole width and leaf mass to estimate leaf dry mass per area (LMA), a leaf functional trait negatively correlated with rate of return-on-investment. We found no evidence for a shift in this leaf-economic trait across the KPB: LMA remained consistent in both its median and overall distribution from approximately 67 to 65 Ma. However, we did find spatio-temporal patterns in LMA, where fossil localities with low LMA occurred more frequently near the western margin of the basin. These western margin localities are proximal to the Colorado Front Range of the Rocky Mountains, where an orographically driven high precipitation regime is thought to have developed during the early Paleocene. Among these western Denver Basin localities, LMA and estimated mean annual precipitation were inversely correlated, a pattern consistent with observations of both fossil and extant plants. In the Denver Basin, local environmental conditions over time appeared to play a larger role in determining viable leaf-economic strategies than any potential global signal associated with the Chicxulub bolide impact.
... In addition to RWL, other leaf shape indices are available, i.e., the leaf roundness index and its reciprocal, the leaf dissection index (Kincaid and Schneider, 1983;Thomas and Bazzaz, 1996;Niinemets, 1998;Santiago and Kim, 2009;Peppe et al., 2011). However, an accurate quantification of many elliptical, oval, and oboval leaves significantly deviates from circular leaves. ...
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The Montgomery equation predicts leaf area as the product of leaf length and width multiplied by a correction factor. It has been demonstrated to apply to a variety of leaf shapes. However, it is unknown whether tree size (measured as the diameter at breast height) affects leaf shape and size, or whether such variations in leaf shape can invalidate the Montgomery equation in calculating leaf area. Here, we examined 60 individual trees of the alpine oak ( Quercus pannosa ) in two growth patterns (trees growing from seeds vs. growing from roots), with 30 individuals for each site. Between 100 and 110 leaves from each tree were used to measure leaf dry mass, leaf area, length, and width, and to calculate the ellipticalness index, ratio of area between the two sides of the lamina, and the lamina centroid ratio. We tested whether tree size affects leaf shape, size, and leaf dry mass per unit area, and tested whether the Montgomery equation is valid for calculating leaf area of the leaves from different tree sizes. The diameters at breast height of the trees ranged from 8.6 to 96.4 cm (tree height ranged from 3 to 32 m). The diameter at breast height significantly affected leaf shape, size, and leaf dry mass per unit area. Larger trees had larger and broader leaves with lower leaf dry mass per unit area, and the lamina centroid was closer to the leaf apex than the leaf base. However, the variation in leaf size and shape did not negate the validity of the Montgomery equation. Thus, regardless of tree size, the proportional relationship between leaf area and the product of leaf length and width can be used to calculate the area of the leaves.
... The dramatic linkage between venation architecture (including major vein density and the ratio of major to minor vein density) and leaf size in the subtropical forest community or at the global scale (Figures 1, 3, 4) provides a hydraulic mechanism for explaining the ecological or biogeographical distribution of leaf size. Small leaves are predominant in drier and more exposed habitats (Givnish, 1987;Peppe et al., 2011;Sack et al., 2012), while large leaves in moister and/or shaded habitats (Givnish, 1987;Fonseca et al., 2000). A spatially explicit model showed that the greatest impact for the increase of K leaf in the reticulate hierarchy system was from increases in major vein conductivity and in the minor vein density (McKown et al., 2010). ...
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Leaves are enormously diverse in their size and venation architecture, both of which are core determinants of plant adaptation to environments. Leaf size is an important determinant of leaf function and ecological strategy, while leaf venation, the main structure for support and transport, determines the growth, development, and performance of a leaf. The scaling relationship between venation architecture and leaf size has been explored, but the relationship within a community and its potential variations among species with different vein types and leaf habits have not been investigated. Here, we measured vein traits and leaf size across 39 broad-leaved woody species within a subtropical forest community in China and analyzed the scaling relationship using ordinary least squares and standard major axis method. Then, we compared our results with the global dataset. The major vein density, and the ratio of major (1° and 2°) to minor (3° and higher) vein density both geometrically declined with leaf size across different vein types and leaf habits. Further, palmate-veined species have higher major vein density and a higher ratio of major to minor vein density at the given leaf size than pinnate-veined species, while evergreen and deciduous species showed no difference. These robust trends were confirmed by reanalyzing the global dataset using the same major vein classification as ours. We also found a tradeoff between the cell wall mass per vein length of the major vein and the major vein density. These vein scaling relationships have important implications on the optimization of leaf size, niche differentiation of coexisting species, plant drought tolerance, and species distribution.
... However, it remains unclear as to whether the same trend holds at the intraspecific level in which a direct trade-off exists between the investments in mechanical support and photosynthetic tissues (Milla and Reich, 2007;Niklas et al., 2007). In addition, leaf size, shape, and vein density are affected significantly by environmental factors (e.g., temperature and precipitation) (Peppe et al., 2011;Zhu et al., 2011;Wright et al., 2017), which may lead to significant variations in leaf vein architecture across species . It is important therefore to compare leaves differing in size from the same species from plants growing in similar as well as different environments. ...
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Premise: Across species, main leaf vein density scales inversely with leaf area (A). Yet, minor vein density manifests no clear relationship with respect to A, despite having the potential to provide important insights into the trade-off among the investments in leaf mechanical support, hydraulics, and light interception. Methods: To examine this phenomenon, the leaves of nine Magnoliaceae leaves were sampled, and the scaling relationships among A and midrib length (ML), total vein length (TVL), total vein area (TVA), total areole area (TAA), and mean areole area (MAA) were determined. The scaling relationships between MAA and areole density (the number of areoles per unit leaf area) and between MAA and A were also analyzed. Results: For five of the nine species, A was proportional to ML2 . For eight of the nine species, TVL and TVA were both proportional to A. The numerical values of the scaling exponents for TAA vs. A were between 1.0 and 1.07 for eight species, i.e., as expected, TAA was isometrically proportional to A. There was no correlation between MAA and A, but MAA scaled inversely with respect to areole density for each species. Conclusions: The correlation between midrib "density" (i.e., ML/A) and A, and the lack of correlation between total leaf vein density and A result from the A ∝ ML2 scaling relationship and the proportional relationship between TVL and A, respectively. Leaves with the same size can have widely varying MAA. Thus, leaf size itself does not directly constrain leaf hydraulic efficiency and redundancy. This article is protected by copyright. All rights reserved.
... For example, when water resources are limited, plants have to reduce their transpiration rates (Gates, 1965) and therefore develop small leaves (Peppe et al., 2011;Poorter et al., 2010;Spasojevic et al., 2014;Wright et al., 2017) and small flowers (Paušič et al., 2019;Kuppler & Kotowska, 2021). In contrast, laurel forests are dominated by mild climate and continual humidity that might have offered ecological opportunity for niche differentiation (Rundell & Price, 2009). ...
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Functional traits can help us to elucidate biogeographical and ecological processes driving assemblage structure. We analysed the functional diversity of plant species of different evolutionary origins across an island archipelago, along environmental gradients and across geological age, to assess functional aspects of island biogeographical theory. Canary Islands, Spain. Spermatophytes. Present day. We collected data for four traits (plant height, leaf length, flower length and fruit length) associated with resource acquisition, competitive ability, reproduction and dispersal ability of 893 endemic, non‐endemic native and alien plant species (c. 43% of the Canary Island flora) from the literature. Linking these traits to species occurrences and composition across a 500 m × 500 m grid, we calculated functional diversity for endemic, non‐endemic native and alien assemblages using multidimensional functional hypervolumes and related the resulting patterns to climatic (humidity) and island biogeographical (geographical isolation, topographic complexity and geological age) gradients. Trait space of endemic and non‐endemic native species overlapped considerably, and alien species added novel trait combinations, expanding the overall functional space of the Canary Islands. We found that functional diversity of endemic plant assemblages was highest in geographically isolated and humid grid cells. Functional diversity of non‐endemic native assemblages was highest in less isolated and humid grid cells. In contrast, functional diversity of alien assemblages was highest in arid ecosystems. Topographic complexity and geological age had only a subordinate effect on functional diversity across floristic groups. We found that endemic and non‐endemic native island species possess similar traits, whereas alien species tend to expand functional space in ecosystems where they have been introduced. The spatial distribution of the functional diversity of floristic groups is very distinct across environmental gradients, indicating that species assemblages of different evolutionary origins thrive functionally in dissimilar habitats.
... The largest MP value described in was for Hydrocotyle vulgaris, a species that has oblate leaves and an MP value slightly smaller than π/4. It is not surprising that the estimates of MP for the three cicada In previous studies on leaf shapes, the leaf roundness index (RI = 4πA/P 2 ) and leaf dissection index (DI = P/2 √ A) (where P is the leaf perimeter and A is the leaf area) were frequently used to describe the complexity of leaf shapes (Kincaid & Schneider, 1983;Niinemets, 1998;Peppe et al., 2011;Santiago & Kim, 2009;Thomas & Bazzaz, 1996). Li, Quinn, Niinemets, et al. (2022) pointed out the shortcomings of RI and DI as parameters for de- ...
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Most insects engage in winged flight. Wing loading, that is, the ratio of body mass to total wing area, has been demonstrated to reflect flight maneuverability. High maneuverability is an important survival trait, allowing insects to escape natural enemies and to compete for mates. In some ecological field experiments, there is a need to calculate the wing area of insects without killing them. However, fast, nondestructive estimation of wing area for insects is not available based on past work. The Montgomery equation (ME), which assumes a proportional relationship between leaf area and the product of leaf length and width, is frequently used to calculate leaf area of plants, in crops with entire linear, lanceolate leaves. Recently, the ME was proved to apply to leaves with more complex shapes from plants that do not have any needle leaves. Given that the wings of insects are similar in shape to broad leaves, we tested the validity of the ME approach in calculating the wing area of insects using three species of cicadas common in eastern China. We compared the actual area of the cicadas' wings with the estimates provided by six potential models used for wing area calculation, and we found that the ME performed best, based on the trade-off between model structure and goodness of fit. At the species level, the estimates for the proportionality coefficients of ME for three cicada species were 0.686, 0.693, and 0.715, respectively. There was a significant difference in the proportionality coefficients between any two species. Our method provides a simple and powerful approach for the nondestructive estimation of insect wing area, which is also valuable in quantifying wing morphological features of insects. The present study provides a nondestructive approach to estimating the wing area of insects, allowing them to be used in mark and recapture experiments.
... Information on the modern relationships between climate and leaf size and dissection has been used in one specific field of application, to reconstruct climates of the deep geological past based on the leaf morphology of plants (e.g. Greenwood, 2005;Greenwood et al., 2004;Miller et al., 2006;Peppe et al., 2011;Royer, 2012;Uhl et al., 2003;Utescher et al., 2000), including a number of studies from different regions of China (e.g. Chen et al., 2014;Chen et al., 2019;Li et al., 2016;Su et al., 2010). ...
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1. Leaf morphological traits vary systematically along climatic gradients. However, recent studies in plant functional ecology have mainly analysed quantitative traits, while numerical models of species distributions and vegetation function have focused on traits associated with resource acquisition; both ignore the wider functional significance of leaf morphology. 2. A data set comprising 22 leaf morphological traits for 662 woody species from 92 sites, representing all biomes present in China, was subjected to multivariate analysis in order to identify leading dimensions of trait covariation (correspondence analysis), quantify climatic and phylogenetic contributions (canonical correspondence analysis with variation partitioning), and characterize co‐occurring trait syndromes (k‐means clustering) and their climatic preferences. 3. Three axes accounted for > 20% of trait variation in both evergreen and deciduous species. Moisture index, precipitation seasonality and growing‐season temperature explained 8–10% of trait variation; family 15–32%. Microphyll or larger, mid‐ to dark green leaves with drip‐tips in wetter climates contrasted with nanophyll or smaller glaucous leaves without drip‐tips in drier climates. Thick, entire leaves in less seasonal climates contrasted with thin, marginal dissected, aromatic, and involute/revolute leaves in more seasonal climates. Thick, involute, hairy leaves in colder climates contrasted with thin leaves with marked surface structures (surface patterning) in warmer climates. Distinctive trait clusters were linked to the driest and most seasonal climates, for example the clustering of picophyll, fleshy and succulent leaves in the driest climates and leptophyll, linear, dissected, revolute or involute, and aromatic leaves in regions with highly seasonal rainfall. Several trait clusters co‐occurred in wetter climates, including clusters characterised by microphyll, moderately thick, patent, and entire leaves or notophyll, waxy, dark green leaves. 4. Synthesis. The plastic response of size, shape, color and other leaf morphological traits to climate is muted, thus their apparent shift along climate gradients reflects plant adaptations to environment at a community‐level as determined by species replacement. Information on leaf morphological traits, widely available in floras, could be used to strengthen predictive models of species distribution and vegetation function.
... A. adenophora populations growing in high elevation range exhibited lower LL, LW, MLA, LA, SLA, LAR and were negatively correlated with elevation rise, representing the strategies of this invader to adapt in the harsh climatic conditions of high elevations. According to Givnish (1987), Singh and Singh (1987), Peppe et al. (2011) andLopez-Bernal et al. (2015), water stress, the main factor regulating leaf morphology was the output of limiting hydrating conditions and high solar irradiance at higher elevation, where low temperature results in increased water viscosity and reduced physiological activities inducing physiological water stress. Consistent with our findings, previous investigations on Quercus guyavifolia (Sun et al., 2016) and Metrosideros polymorpha (Cordell et al., 1998) also reported reduced leaf size at higher elevations Liu et al. (2020). ...
Article
Elevational gradients as well as habitat variability provide variation in environmental conditions enabling plants to alter their functional traits with respect to their surroundings on the way to sustain and better perform. Phenotypic plasticity has been suggested as one of the foremost mechanisms that invasive species implement to endure and invade wide geographical areas. The present study was performed to understand the leaf functioning and reproductive approaches adopted by the invasive weed Ageratina adenophora in response to different habitats of Kumaun Himalaya along elevational ranges. ANOVA showed significant effects of elevational ranges, habitats and their interactions on most of the investigated traits. A wide range in leaf area (367�1278 cm2/plant) and seed number (2803�12,240 seeds/plant) across the elevational zones indicated high plastic responses. Linear regression analysis revealed that the specific leaf area (r = -0.279; p < 0.05) and leaf area ratio (r = -0.255; p < 0.05) decreased significantly with increasing elevation. Reproductive traits like seed number (r = -0.284; p < 0.05) and reproductive index (r = -0.416; p < 0.05) also decreased significantly with increasing elevation. The results revealed that this species responds to heterogeneous environments via altering its leaf traits and reproductive performance. The large differences in trait values between habitats and elevations suggested a high degree of plasticity, which is leading to the successful encroachment and establishment of A. adenophora across an elevational gradient without undergoing adaptive evolution.
... All leaves were individually tagged with tree ID and leaf number, and sampled for carbon isotope analysis. The first subset of leaves (111) were photographed and weighed, in order to record leaf mass per area (LMA), as well as perimeter to determine shape factor and compactness, as previous studies have recorded changes to LMA and leaf shape relative to global climate and during past episodes of climate warming (Peppe et al., 2011;Bacon et al., 2013;Soh et al., 2017). However, an initial analysis yielded no discernible trends for these factors, and was not pursued further, but the data are provided in supplements for completeness (Tables S1 and S3). ...
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The Ginkgoales, including the ‘living fossil’ Ginkgo biloba, are an important group for stomata-based palaeo-pCO2 reconstructions, with long evolutionary lineages and an extensive, abundant fossil record. The stomatal proxy for palaeo-pCO2 can improve our understanding of the exact relationship between pCO2 and temperatures – Earth's climate sensitivity: a key measure of global warming by pCO2. However, pCO2 records from future climate analogues in the past, such as the mid-Miocene Climatic Optimum, seemingly underestimate pCO2 – climate models cannot simulate the past temperatures with the only moderately elevated pCO2 reconstructed by proxies. Either climate sensitivity must have been elevated, which has implications for future climate forecasts, or proxies underestimate pCO2 due to additional environmental factors. Here we tested whether climate conditions impact stomatal parameters and thus pCO2 reconstruction on a large global database of G. biloba leaves from all continents except Antarctica, spanning 12 climate zones. We reconstructed ambient pCO2 using three stomatal proxy methods (stomatal ratio, transfer functions, Franks gas exchange model) and one stomata-independent isotope-based proxy for comparison (C3 proxy). We found that the stomatal proxy methods reconstructed ambient pCO2 reasonably well and uniformly, but that the C3 proxy underestimated pCO2. All the investigated stomatal parameters displayed an unexpectedly large variability, but no significant relationship with temperature, precipitation, or seasonality. Based on these results, the stomatal proxy is not influenced by climate and specifically does not systematically underestimate pCO2 under high temperatures. Climate sensitivity was likely instead elevated during past global warming episodes, an urgent consideration in climate forecasts for our rapidly warming Earth.
... Environmental factors, especially moisture and light, have a strong effect on the leaf blade size. Plants growing in dry habitats tend to have smaller leaves, while plants in more humid areas have larger leaves (Peppe et al. 2011). Morphological analysis of the leaves showed that in more humid growing conditions, the size of the leaf blade is larger than in dry conditions. ...
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Aflatunia ulmifolia (Franch.) Vassilcz. is a rare, poorly studied species from the Rosaceae Juss family. Its natural distribution range is limited to Central Asia (Western Tien Shan, Pamir-Alay, Dzhungarskiy and Kirghiz Alatau). Information on the current state of natural plant communities with the participation of A. ulmifolia, the introduction potential, and the methods of conservation of the species is limited. The aim of our study was to improve information about A. ulmifolia, by verifying its current distribution range, both in natural habitats and in places where it is introduced, and analyze the major ecological, morphological and biological characteristics of the species. We produced the most up-to-date species distribution map showing both natural and introduced populations of A. ulmifolia. For the first time, we provide a comprehensive list of tree and shrub species co-occurring with A. ulmifolia in Tajikistan, Kyrgyzstan, and Kazakhstan. We present detailed information on the successful introduction of A. ulmifolia in nine European and Asian countries. Although the species is not of immediate conservation concern, it might become vulnerable to extinction if its distribution range continues to shrink because of anthropogenic impact and natural disturbances. We argue for the development of effective conservation strategies for A. ulmifolia in nature and for the creation of stable introduction populations of this species in botanical gardens and arboretums. ARTICLE HISTORY
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Premise: Reconstructing plant canopy light environment and architecture from the fossil record includes proxies derived from cell wall undulation, cell size, and carbon isotopes. All approaches assume that plant taxa will respond predictably to changes in light environments. However, most species-level studies looking at cell wall undulation only consider "sun" or "shade" leaves, therefore we lack a fully quantitative taxon-specific method. Methods: We quantify the response of cell wall undulation, cell size, and carbon isotopes of Platanus occidentalis using two different experimental setups: (1) two growth chambers at low and high light and (2) a series of outdoor growth experiments using green and black shade cloth at different densities. We then developed and applied a proxy for daily light integral (DLI) to fossil Platanites leaves from two early Paleocene floras from the San Juan Basin in New Mexico. Results: All traits responded to light environment. Cell wall undulation was the most useful trait for reconstructing DLI in the geological record. Median reconstructed DLI from early Paleocene leaves was ~44 mol m-2 d-1, with values ranging from 28 - 54 mol m-2 d-1. Conclusions: Cell wall undulation of P. occidentalis is a robust, quantifiable measurement of light environment that can be used to reconstruct paleo-light environment from fossil leaves. The distribution of high DLI values from fossil leaves may provide information on canopy architecture; indicating that either (1) most of the canopy mass is within the upper portion of the crown or (2) leaves exposed to more sunlight are preferentially preserved. This article is protected by copyright. All rights reserved.
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Leaf thermoregulation and consequent leaf-to-air temperature difference (ΔT) are tightly linked to plant metabolic rates and health. Current knowledge mainly focus on the regulation of environmental conditions on ΔT, while an accurate assessment of biotic regulations with field data remains lacking. Here, we used a trait-based model that integrates a coupled photosynthesis-stomatal conductance model with a leaf energy balance model to explore how six leaf traits (i.e. leaf width, emissivity, visible and near-infrared light absorptance, photosynthetic capacity—Vc,max25, and stomatal slope—g1) regulate ΔT variability across the diel timescale. We evaluated the model with field observations collected from temperate to tropical forests. Our results show that: (1) leaf traits mediate large ΔT variability, with the noon-time trait-mediated ΔT variability reaching c. 15.0 °C; (2) leaf width, Vc,max25, and g1 are the three most important traits and their relative importance in ΔT regulation varies strongly across the diel timescale; and (3) model-derived trait-ΔT relationships match field observations that were collected close to either midday or midnight. These findings advance our understanding of biotic controls of leaf-level ΔT variability, highlighting a trait-based representation of leaf energy balance that can improve simulations of diverse leaf thermoregulation strategies across species and physiological responses to climate change.
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This paper investigates leaf morphology variation of the strawberry tree (Arbutus unedo) within and between two natural contrasting populations of significant latitudinal difference (Kassandreia, Chalkidiki and Ancient Olympia, Peloponnese). This study employed 11 leaf size and shape parameters, recorded by image processing and analyzing software. The results showed that in the measurements of central tendency (parameter means) the northern population of Kassandreia presented the highest values, while in contrast the highest values in the measurements of spread were found in the southern population of Ancient Olympia. Moreover, statistically significant differences between populations were detected in leaf size, but not in leaf shape parameters. Results are discussed in the context of their value in studying quantitative population differentiation and laying the basis of more advanced studies.
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The isotopic composition of paleosol carbonate and organic matter were investigated in the Bighorn Basin, Wyoming, to explore changes in the carbon cycle and climate across the Paleocene-Eocene boundary. In three different measured sections, soil carbonate δ13C values change in phase with marine surface water carbonates on both long (∼7 m.y.) and short (∼100 k.y.) time scales. The carbon cycle perturbations at the Paleocene-Eocene Boundary Thermal Maximum (PETM) and the Eocene Warm Interval (EWI) are recorded in multiple sections, providing unambiguous links between marine and continental deposits. The PETM and EWI δ13C excursions in the Bighorn Basin are larger than those in the surface ocean, but the reasons for this amplification are unclear. Organic matter samples from the Bighorn Basin yield noisy δ13C records that do not mirror global changes, perhaps due to diagenetic alteration or postformational contamination. The δ18O values of soil carbonate are subject to multiple climatic influences that are often antagonistic. Although the δ18O shifts at the PETM and EWI are small, the shift at the PETM is statistically significant in two of the measured sections. Assuming a plausible range of values for the meteoric water δ18O/mean annual temperature relationship, the perturbation in soil carbonate δ18O at the PETM is consistent with an increase in meteoric water δ18O of ∼2% and changes in local temperature of 3-7 °C.
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Leaf size variation with respect to climate was studied at 35 sample sites reported in the literature from the Western Hemisphere. The variation in leaf size was analyzed by plotting the sample sites on Holdridge's (1967) life zone chart and comparing the percentage of species having large leaves (greater than 20.25 sq cm in area) in the different life zones. Four foliar belts were identified in the tropical basal and altitudinal belts. Three of these foliar belts were identified earlier in a field study carried out in Costa Rica (Dolph and Dilcher in press). The fourth foliar belt is not found in Costa Rica because it is confined to very dry basal belt life zones. It was concluded that leaf size cannot be used to identify specific life zones or climates in either extant or fossil floras.
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Global climate during the Mesozoic and early Cenozoic is thought to have been warmer than at present, but there is debate about winter temperatures. Paleontological data indicate mild temperatures even at high latitudes and in mid-latitude continental interiors, whereas computer simulations of continental paleoclimates produce winter temperatures closer to modern levels. Foliar physiognomy and floristic composition of 23 Eocene floras from the interior of North America and Australia indicate cold month means generally >2°C, even where the mean annual temperature (MAT) was <15°C. Reconstructed Eocene latitudinal gradients of MAT are curvilinear but are about 0.4°C per 1° of latitude in continental interiors of mid-latitudes, much less than the 0.8-1.0°C per 1° of latitude observed in eastern and central North America today, but similar to modern gradients in the Southern Hemisphere mid-latitudes and on the west coast of North America. -from Authors
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Estimates of past precipitation are of broad interest for many areas of inquiry, including reconstructions of past environments and topography, climate modeling, and ocean circulation studies. The shapes and sizes of living leaves are highly sensitive to moisture conditions, and assemblages of fossil leaves of flowering plants have great potential as paleoprecipitation indicators. Most quantitative estimates of paleoprecipitation have been based on a multivariate data set of morphological leaf characters measured from samples of living vegetation tied to climate stations. However, when tested on extant forests, this method has consistently overestimated precipitation. We present a simpler approach that uses only the mean leaf area of a vegetation sample as a predictor variable but incorporates a broad range of annual precipitation and geographic coverage into the predictor set. The significant relationship that results, in addition to having value for paleoclimatic reconstruction, refines understanding of the long-observed positive relationship between leaf area and precipitation. Seven precipitation estimates for the Eocene of the Western United States are revised as lower than previously published but remain far wetter than the same areas today. Abundant moisture may have been an important factor in maintaining warm, frost-free conditions in the Eocene because of the major role of water vapor in retaining and transporting atmospheric heat.
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Leaf teeth are conspicuous and often diagnostic features of many plant species. In mesic environments with sufficient nutrient resources, the percentage of toothed species in extant floras generally correlates negatively with temperature; consequently, fossil leaf teeth are widely used to estimate continental paleotemperatures. However, the function of leaf teeth with respect to climate is poorly understood. Here, we test the hypothesis that teeth enhance rates of carbon uptake at the beginning of the growing season when temperatures are limiting. We measure the seasonal patterns of leaf-margin photosynthesis and transpiration for 60 woody species from two temperate regions with differing climates (Pennsylvania and North Carolina). Three sig- nificant results are, first, physiological activity at leaf margins is greatest early in the growing season (first 30 d); second, toothed margins are more active with respect to photosynthesis and transpiration than untoothed mar- gins; finally, leaf margins are more active in species native to colder Pennsylvania. The toothed species increase transpiration and photosynthate production early in the growing season relative to untoothed species and do so more in the Pennsylvania sample, maximizing carbon gain when temperature is limiting but moisture and nutrient availability are not. This mechanism may provide a proportionally increasing selective advantage to toothed species with decreasing temperature that is reflected in empirical correlations used for paleo- temperature estimation.
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Leaf margin analysis (LMA), which is based on a correlation between the proportion of woody dicot species with nontoothed leaf margins and mean annual temperature, has been promoted as a tool for estimating mean annual temperature (MAT) from fossil-leaf assemblages. The original LMA calibration was based on East Asian mesic vegetation, and substantially the same relationship has been shown for other geographical regions, including Australian mesic vegetation. In this report, taphonomic effects are assessed using autochthonous samples from extant Australian forests for sites ranging from tropical lowland rainforest and monsoonal deciduous woodland to temperate rainforest with and without emergent Eucalyptus, and for parautochthonous and allochthonous (i.e., streambed) leaf accumulations. MAT was estimated within the binomial sampling error of the estimate for 27 of 30 (90%) of the test sites, and was found to underestimate MAT systematically when applied to streambed leaf assemblages. This result may reflect the stream side bias detected in recent studies of tropical forests in South America. Sites where MAT was overestimated are of low species richness (<10 spp.).
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Paleoecological studies enhance our understanding of biotic response to climate change because they consider timescales not accessible through laboratory or ecological studies. From 60 to 51 million years ago (Ma), global temperatures gradually warmed to the greatest sustained highs of the last 65 million years. Superimposed on this gradual warming is a transient spike of high temperature and pCO 2 (partial pressure of carbon dioxide in the atmosphere; the Paleocene-Eocene Thermal Maximum 55.8 Ma) and a subsequent short-term cooling event (∼54 Ma). The highly resolved continental fossil record of the Bighorn Basin, Wyoming, USA, spans this interval and is therefore uniquely suited to examine the long-term effects of temperature change on the two dominant groups in terrestrial ecosystems, plants and insect herbivores. We sampled insect damage on fossil angiosperm leaves at nine well-dated localities that range in age from 52.7 to 59 Ma. A total of 9071 leaves belonging to 107 species were examined for the presence or absence of 71 insect-feeding damage types. Damage richness, frequency, and composition were analyzed on the bulk floras and individual host species. Overall, there was a strong positive correlation between changes in damage richness and changes in estimated temperature, a weak positive relationship for damage frequency and temperature, and no significant correlation for floral diversity. Thus, insect damage richness appears to be more sensitive to past climate change than to plant diversity, although plant diversity in our samples only ranges from 6 to 25 dicot species. The close tracking of the richness of herbivore damage, a presumed proxy for actual insect herbivore richness, to both warming and cooling over a finely divided, extended time interval has profound importance for interpreting the evolution of insects and plant–insect associations in the context of deep time. Our results also indicate that increased insect herbivory is likely to be a net long-term effect of anthropogenic warming.
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The Eocene was the warmest part of the Cenozoic, when warm climates extended into the Arctic, and substantive paleobotanical evidence indicates broadleaf and coniferous polar forests. Paleontological temperature proxies provide a basis for understanding Arctic early Paleogene climates; however, there is a lack of corresponding proxy data on precipitation. Both leaf physiognomic analysis and quantitative analysis of nearest living relatives of an Arctic macroflora indicate upper microthermal to lower mesothermal moist climates (mean annual temperature ∼13–15 °C; cold month mean temperature ∼4 °C; mean annual precipitation >120 cm/yr) for Axel Heiberg Island in the middle Eocene. Leaf-size analysis of Paleocene and Eocene Arctic floras demonstrates high precipitation for the Paleogene western and eastern Arctic. The predicted enormous volume of freshwater entering the Arctic Ocean as a result of northward drainage of a significant region of the Northern Hemisphere under a high-precipitation regime would have strongly affected Arctic Ocean salinity, potentially supporting Arctic Ocean Azolla blooms. High Paleogene precipitation around the Arctic Basin is consistent with high atmospheric humidity, which would have contributed significantly to polar, and global, Eocene warming.
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Few South American macrofloras of Paleocene age are known, and this limits our knowledge of diversity and composition between the end-Cretaceous event and the Eocene appearance of high floral diversity. We report new, unbiased collections of 2516 compression specimens from the Paleocene Salamanca Formation (ca. 61.7 Ma) from two localities in the Palacio de los Loros exposures in southern Chubut, Patagonia, Argentina. Our samples reveal considerably greater richness than was previously known from the Paleocene of Patagonia, including 36 species of angiosperm leaves as well as angiosperm fruits, flowers, and seeds; ferns; and conifer leaves, cones, and seeds. The floras, which are from siltstone and sandstone channel-fills deposited on low-relief floodplain landscapes in a humid, warm temperate climate, are climatically and paleoenvironmentally comparable to many quantitatively collected Paleocene floras from the Western Interior of North America. Adjusted for sample size, there are >50% more species at each Palacio de los Loros quarry than in any comparable U.S. Paleocene sample. These results indicate more vibrant terrestrial ecosystems in Patagonian than in North American floodplain environments ˜4 m.y. after the end-Cretaceous extinction, and they push back the time line 10 m.y. for the evolution of high floral diversity in South America. The cause of the dis parity is unknown but could involve reduced impact effects because of greater distance from the Chicxulub site, higher latest Cretaceous diversity, or faster recovery or immigration rates.
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