Both phenotypic plasticity and genetic determination can be important for understanding how plants respond to environmental change. However, little is known about the plastic response of leaf teeth ...and leaf dissection to temperature. This gap is critical because these leaf traits are commonly used to reconstruct paleoclimate from fossils, and such studies tacitly assume that traits measured from fossils reflect the environment at the time of their deposition, even during periods of rapid climate change. We measured leaf size and shape in Acer rubrum derived from four seed sources with a broad temperature range and grown for two years in two gardens with contrasting climates (Rhode Island and Florida). Leaves in the Rhode Island garden have more teeth and are more highly dissected than leaves in Florida from the same seed source. Plasticity in these variables accounts for at least 6–19 % of the total variance, while genetic differences among ecotypes probably account for at most 69–87 %. This study highlights the role of phenotypic plasticity in leaf-climate relationships. We suggest that variables related to tooth count and leaf dissection in A. rubrum can respond quickly to climate change, which increases confidence in paleoclimate methods that use these variables.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The sizes and shapes (physiognomy) of fossil leaves are widely applied as proxies for paleoclimatic and paleoecological variables. However, significant improvements to leaf-margin analysis, used for ...nearly a century to reconstruct mean annual temperature (MAT), have been elusive; also, relationships between physiognomy and many leaf ecological variables have not been quantified. Using the recently developed technique of digital leaf physiognomy, correlations of leaf physiognomy to MAT, leaf mass per area, and nitrogen content are quantified for a set of test sites from North and Central America. Many physiognomic variables correlate significantly with MAT, indicating a coordinated, convergent evolutionary response of fewer teeth, smaller tooth area, and lower degree of blade dissection in warmer environments. In addition, tooth area correlates negatively with leaf mass per area and positively with nitrogen content. Multiple linear regressions based on a subset of variables produce more accurate MAT estimates than leaf-margin analysis (standard errors of ±2 vs. ±3°C); improvements are greatest at sites with shallow water tables that are analogous to many fossil sites. The multivariate regressions remain robust even when based on one leaf per species, and the model most applicable to fossils shows no more signal degradation from leaf fragmentation than leaf-margin analysis.
A case study of renal tubular dysfunction consistent with idiopathic Fanconi syndrome is reported in an 18‐month‐old Holstein heifer. The clinical, biochemical, and histopathological features are ...described. The heifer had clinical signs of growth retardation, wasting, and persistent diarrhea. Biochemical blood analysis identified hypokalemia, hyponatremia, and hypochloremia. Urinalysis identified glycosuria, proteinuria, and acidic pH. Histological examination of the kidney disclosed mild tubular necrosis with proteinaceous casts in the lumina of renal tubules. We performed LC‐HRMS on urine to confirm Fanconi syndrome. Using this technique, we identified severe generalized aminoaciduria suggestive of idiopathic renal Fanconi syndrome in this heifer.
Introduction
Collecting feces is easy. It offers direct outcome to endogenous and microbial metabolites.
Objectives
In a context of lack of consensus about fecal sample preparation, especially in ...animal species, we developed a robust protocol allowing untargeted LC-HRMS fingerprinting.
Methods
The conditions of extraction (quantity, preparation, solvents, dilutions) were investigated in bovine feces.
Results
A rapid and simple protocol involving feces extraction with methanol (1/3, M/V) followed by centrifugation and a step filtration (10 kDa) was developed.
Conclusion
The workflow generated repeatable and informative fingerprints for robust metabolome characterization.
Earth system climate sensitivity (ESS) is the long‐term (>103 year) response of global surface temperature to doubled CO2 that integrates fast and slow climate feedbacks. ESS has energy policy ...implications because global temperatures are not expected to decline appreciably for at least 103 year, even if anthropogenic greenhouse gas emissions drop to zero. We report provisional ESS estimates of 3 °C or higher for some of the Cretaceous and Cenozoic based on paleo‐reconstructions of CO2 and temperature. These estimates are generally higher than climate sensitivities simulated from global climate models for the same ancient periods (approximately 3 °C). Climate models probably do not capture the full suite of positive climate feedbacks that amplify global temperatures during some globally warm periods, as well as other characteristic features of warm climates such as low meridional temperature gradients. These absent feedbacks may be related to clouds, trace greenhouse gases (GHGs), seasonal snow cover, and/or vegetation, especially in polar regions. Better characterization and quantification of these feedbacks is a priority given the current accumulation of atmospheric GHGs.
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.
Premise of the study: Leaf-margin state (toothed vs. untoothed) forms the basis of several popular methods for reconstructing temperature. Some potential confounding factors have not been ...investigated with large data sets, limiting our understanding of the adaptive significance of leaf teeth and their reliability to reconstruct paleoclimate. Here we test the strength of correlations between leaf-margin state and deciduousness, leaf thickness, wood type (ring-porous vs. diffuse-porous), height within community, and several leaf economic variables. Methods: We assembled a trait database for 3549 species from six continents based on published and original data. The strength of associations between traits was quantified using correlational and principal axes approaches. Key results: Toothed species, independent of temperature, are more likely to be deciduous and to have thin leaves, a high leaf nitrogen concentration, a low leaf mass per area, and ring-porous wood. Canopy trees display the highest sensitivity between leaf-margin state and temperature; subcanopy plants, especially herbs, are less sensitive. Conclusions: Our data support hypotheses linking the adaptive significance of teeth to leaf thickness and deciduousness (in addition to temperature). Toothed species associate with the "fast-return" end of the leaf economic spectrum, providing another functional link to thin leaves and the deciduous habit. Accounting for these confounding factors should improve climate estimates from tooth-based methods.
The response of temperature to CO
2
change (climate sensitivity) in the geologic past may help inform future climate predictions. Proxies for CO
2
and temperature generally imply high climate ...sensitivities: ≥3 K per CO
2
doubling during ice-free times (fast-feedback sensitivity) and ≥6 K during times with land ice (Earth-system sensitivity). Climate models commonly underpredict the magnitude of climate change and have fast-feedback sensitivities close to 3 K. A better characterization of feedbacks in warm worlds raises climate sensitivity to values more in line with proxies and produces climate simulations that better fit geologic evidence. As CO
2
builds in our atmosphere, we should expect both slow (e.g., land ice) and fast (e.g., vegetation, clouds) feedbacks to elevate the long-term temperature response over that predicted from the canonical fast-feedback value of 3 K. Because temperatures will not decline for centuries to millennia, climate sensitivities that integrate slower processes have relevance for current climate policy.
Leaf gas-exchange models show considerable promise as paleo-CO2 proxies. They are largely mechanistic in nature, provide well-constrained estimates even when CO2 is high, and can be applied to most ...subaerial, stomata-bearing fossil leaves from C3 taxa, regardless of age or taxonomy. Here we place additional observational and theoretical constraints on one of these models, the “Franks” model. In order to gauge the model's general accuracy in a way that is appropriate for fossil studies, we estimated CO2 from 40 species of extant angiosperms, conifers, and ferns based only on measurements that can be made directly from fossils (leafδ13C and stomatal density and size) and on a limited sample size (one to three leaves per species). The mean error rate is 28 %, which is similar to or better than the accuracy of other leading paleo-CO2 proxies. We find that leaf temperature and photorespiration do not strongly affect estimated CO2, although more work is warranted on the possible influence of O2 concentration on photorespiration. Leaves from the lowermost 1–2 m of closed-canopy forests should not be used because the local air δ13C value is lower than the global well-mixed value. Such leaves are not common in the fossil record but can be identified by morphological and isotopic means.
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