For most species, a precise understanding of how climatic parameters determine the timing of seasonal life cycle stages is constrained by limited long‐term data. Further, most long‐term studies of ...plant phenology that have examined relationships between phenological timing and climate have been local in scale or have focused on single climatic parameters. Herbarium specimens, however, can expand the temporal and spatial coverage of phenological datasets. Using Trillium ovatum specimens collected over > 100 yr across its native range, we analyzed how seasonal climatic conditions (mean minimum temperature (Tₘᵢₙ), mean maximum temperature and total precipitation (PPT)) affect flowering phenology. We then examined long‐term changes in climatic conditions and in the timing of flowering across T. ovatum's range. Warmer Tₘᵢₙ advanced flowering, whereas higher PPT delayed flowering. However, Tₘᵢₙ and PPT were shown to interact: the advancing effect of warmer Tₘᵢₙ was strongest where PPT was highest, and the delaying effect of higher PPT was strongest where Tₘᵢₙ was coldest. The direction of temporal change in climatic parameters and in the timing of flowering was dependent on geographic location. Tₘᵢₙ, for example, decreased across the observation period in coastal regions, but increased in inland areas. Our results highlight the complex effects of climate and geographic location on phenology.
Warming experiments are increasingly relied on to estimate plant responses to global climate change. For experiments to provide meaningful predictions of future responses, they should reflect the ...empirical record of responses to temperature variability and recent warming, including advances in the timing of flowering and leafing. We compared phenology (the timing of recurring life history events) in observational studies and warming experiments spanning four continents and 1,634 plant species using a common measure of temperature sensitivity (change in days per degree Celsius). We show that warming experiments underpredict advances in the timing of flowering and leafing by 8.5-fold and 4.0-fold, respectively, compared with long-term observations. For species that were common to both study types, the experimental results did not match the observational data in sign or magnitude. The observational data also showed that species that flower earliest in the spring have the highest temperature sensitivities, but this trend was not reflected in the experimental data. These significant mismatches seem to be unrelated to the study length or to the degree of manipulated warming in experiments. The discrepancy between experiments and observations, however, could arise from complex interactions among multiple drivers in the observational data, or it could arise from remediable artefacts in the experiments that result in lower irradiance and drier soils, thus dampening the phenological responses to manipulated warming. Our results introduce uncertainty into ecosystem models that are informed solely by experiments and suggest that responses to climate change that are predicted using such models should be re-evaluated.
Quantifying the extent to which seed production is limited by the availability of pollen has been an area of intensive empirical study over the past few decades. Whereas theory predicts that pollen ...augmentation should not increase seed production, numerous empirical studies report significant and strong pollen limitation. Here, we use a variety of approaches to examine the correlates of pollen limitation in an effort to understand its occurrence and importance in plant evolutionary ecology. In particular, we examine the role of recent ecological perturbations in influencing pollen limitation and discuss the relation between pollen limitation and plant traits. We find that the magnitude of pollen limitation observed in natural populations depends on both historical constraints and contemporary ecological factors.
A central goal of comparative plant ecology is to understand how functional traits vary among species and to what extent this variation has adaptive value. Here we evaluate relationships between four ...functional traits (seed volume, specific leaf area, wood density, and adult stature) and two demographic attributes (diameter growth and tree mortality) for large trees of 240 tree species from Neotropical forests. We evaluate how these key functional traits are related to survival and growth and whether similar relationships between traits and demography hold across different tropical forests. There was a tendency for a trade-off between growth and survival across rain forest tree species. Wood density, seed volume, and adult stature were significant predictors of growth and/or mortality. Both growth and mortality rates declined with an increase in wood density. This is consistent with greater construction costs and greater resistance to stem damage for denser wood. Growth and mortality rates also declined as seed volume increased. This is consistent with an adaptive syndrome in which species tolerant of low resource availability (in this case shade-tolerant species) have large seeds to establish successfully and low inherent growth and mortality rates. Growth increased and mortality decreased with an increase in adult stature, because taller species have a greater access to light and longer life spans. Specific leaf area was, surprisingly, only modestly informative for the performance of large trees and had ambiguous relationships with growth and survival. Single traits accounted for 9—55% of the interspecific variation in growth and mortality rates at individual sites. Significant correlations with demographic rates tended to be similar across forests and for phylogenetically independent contrasts as well as for cross-species analyses that treated each species as an independent observation. In combination, the morphological traits explained 41% of the variation in growth rate and 54% of the variation in mortality rate, with wood density being the best predictor of growth and mortality. Relationships between functional traits and demographic rates were statistically similar across a wide range of Neotropical forests. The consistency of these results strongly suggests that tropical rain forest species face similar trade-offs in different sites and converge on similar sets of solutions.
Summary
Background
Neoangiogenesis occurs within days following laser treatment of port wine stains (PWS), and plays a central role in treatment failures. Topical use of timolol can significantly ...reduce the production of vascular endothelial growth factor in vitro, and in animal models.
Objectives
The aim of this study was to assess the efficacy of topical timolol in combination with pulsed dye laser (PDL) treatment, compared with PDL alone, for treating PWS.
Methods
This was a prospective multicenter controlled trial performed in children with PWS of the face who had not previously received laser treatment. After randomization, one group was treated with PDL alone, and the other with PDL followed by twice daily applications of timolol gel. Three laser sessions were performed at 1‐month intervals with fixed parameters. The evaluation was performed on standardized pictures by two independent physicians blinded to the treatment received. The primary endpoint was marked or complete improvement of the PWS Investigator Global Assessment (IGA) 3 or 4 1 month after the third session.
Results
Twenty‐two children were included. Two patients were lost to follow‐up. There was no difference in the success rate between the two groups (IGA 3 or 4 observed in one of 10 patients and two of 12 patients, for PDL alone, and for PDL associated with topical timolol, respectively; P = 1·0). No side‐effect related to the application of topical timolol was observed.
Conclusions
The addition of timolol gel for preventing neoangiogenesis failed to significantly improve the efficacy of PDL treatment of PWS.
What's already known about this topic?
Neoangiogenesis occurs within days following laser treatment of port wine stains (PWS).
The expression of vascular endothelial growth factor (VEGF) and its receptors has been shown to be increased in PWS lesions, and to play a key role in neoangiogenesis.
By acting on VEGF, timolol gel might be useful for preventing post‐laser angiogenesis.
What does this study add?
Topical use of twice daily applications of timolol gel showed good tolerance, but failed to significantly improve the efficacy of pulsed dye laser treatment of PWS.
Recent studies illustrate the emerging field of restoration genetics, which is a synthesis of restoration ecology and population genetics. The translocation of organisms during the restoration of ...native ecosystems has provoked new questions concerning the consequences of sampling protocols and of intraspecific hybridization between locally adapted and transplanted genotypes. Studies are now underway to determine both the extent of local adaptation among focal populations and the potential risks of introducing foreign genotypes, including founder effects, genetic swamping and outbreeding depression. Data are needed to delineate ‘seed transfer zones’, or regions within which plants can be moved with little or no consequences for population fitness. Here, we address the revival of transplant and common garden studies, the use of novel molecular markers to predict population genetic consequences of translocation, and their combined power for determining appropriate seed transfer zones in restoration planning for native plant populations.
Despite an increasing number of studies over the past decade examining the interactions between plants and engineered nanomaterials (ENMs), very few have investigated the influence of environmental ...conditions on ENM uptake and toxicity, particularly throughout the entire plant life cycle. In this study, soil-grown herbaceous annual plants (Clarkia unguiculata) were exposed to TiO2, CeO2, or Cu(OH)2 ENMs at different concentrations under distinct light and nutrient levels for 8 weeks. Biweekly fluorescence and gas exchange measurements were recorded, and tissue samples from mature plants were analyzed for metal content. During peak growth, exposure to TiO2 and CeO2 decreased photosynthetic rate and CO2 assimilation efficiency of plants grown under high light and nutrient conditions, possibly by disrupting energy transfer from photosystem II (PSII) to the Calvin cycle. Exposure Cu(OH)2 particles also disrupted photosynthesis but only in plants grown under the most stressful conditions (high light, limited nutrient) likely by preventing the oxidation of a primary PSII reaction center. TiO2 and CeO2 followed similar uptake and distribution patterns with concentrations being highest in roots followed by leaves then stems, while Cu(OH)2 was present at highest concentrations in leaves, likely as ionic Cu. ENM accumulation was highly dependent on both light and nutrient levels and a predictive regression model was developed from these data. These results show that abiotic conditions play an important role in mediating the uptake and physiological impacts of ENMs in terrestrial plants.
Phylogenetic conservatism in plant phenology Davies, T. Jonathan; Wolkovich, Elizabeth M.; Kraft, Nathan J. B. ...
The Journal of ecology,
November 2013, Letnik:
101, Številka:
6
Journal Article
Recenzirano
Odprti dostop
1. Phenological events - defined points in the life cycle of a plant or animal - have been regarded as highly plastic traits, reflecting flexible responses to various environmental cues. 2. The ...ability of a species to track, via shifts in phenological events, the abiotic environment through time might dictate its vulnerability to future climate change. Understanding the predictors and drivers of phenological change is therefore critical. 3. Here, we evaluated evidence for phylogenetic conservatism - the tendency for closely related species to share similar ecological and biological attributes - in phenological traits across flowering plants. We aggregated published and unpublished data on timing of first flower and first leaf, encompassing ~4000 species at 23 sites across the Northern Hemisphere. We reconstructed the phylogeny for the set of included species, first, using the software program Phylomatic, and second, from DNA data. We then quantified phylogenetic conservatism in plant phenology within and across sites. 4. We show that more closely related species tend to flower and leaf at similar times. By contrasting mean flowering times within and across sites, however, we illustrate that it is not the time of year that is conserved, but rather the phenological responses to a common set of abiotic cues. 5. Our findings suggest that species cannot be treated as statistically independent when modelling phenological responses. 6. Synthesis. Closely related species tend to resemble each other in the timing of their life-history events, a likely product of evolutionarily conserved responses to environmental cues. The search for the underlying drivers of phenology must therefore account for species' shared evolutionary histories.
Given that flower size and pigmentation can mediate plant-pollinator interactions, many studies have focused on pollinator-driven selection on these floral traits. However, abiotic factors such as ...precipitation, temperature, and solar radiation also contribute to geographic variation in floral color, pattern, and size within multiple species. Several studies have described an ecogeographic pattern within species in which high temperature, high ultraviolet (UV) radiation, low precipitation and/or low latitudes are associated with increased floral anthocyanin production, smaller flowers, and/or larger UV-absorbing floral patterns (nectar guides or bullseyes). However, latitude or elevation is often used as a proxy variable to study variation in floral traits associated with a wide range of climatic variables, making the proximate abiotic drivers of variation difficult to identify. In this study, we tested and corroborated several predictions for how the abiotic environment may directly or indirectly shape geographic patterns of floral color, pattern, and size in Clarkia unguiculata (Onagraceae). This study provides the first report of geographic variation in multispectral floral color and pattern in C. unguiculata, while also providing an experimental test of the putative protective role of UV absorption for pollen performance. We quantified geographic variation among greenhouse-raised populations in UV floral pattern size, mean UV petal reflectance, anthocyanin concentration, and petal area in C. unguiculata across its natural range in California and, using 30 year climate normals for each population, we identified climatic and topographic attributes that are correlated with our focal floral traits. In addition, we examined pollen performance under high and low UV light conditions to detect the protective function (if any) of UV floral patterns in this species. Contrary to our expectations, the nectar guide and the proportion of the petal occupied by the UV nectar guide were largest in low solar UV populations. Estimated floral anthocyanin concentration was highest in populations with high solar UV, which does support our predictions. The size of the UV nectar guide did not affect pollen performance in either of the light treatments used in this study. We conclude that, under the conditions examined here, UV-absorbing floral patterns do not serve a direct "pollen protection" function in C. unguiculata. Our results only partially align with expected ecogeographic patterns in these floral traits, highlighting the need for research in a wider range of taxa in order to detect and interpret broad scale patterns of floral color variation.
Determining whether seed production is pollen limited has been an area of intensive empirical study over the last two decades. Yet current evidence does not allow satisfactory assessment of the ...causes or consequences of pollen limitation. Here, we critically evaluate existing theory and issues concerning pollen limitation. Our main conclusion is that a change in approach is needed to determine whether pollen limitation reflects random fluctuations around a pollen-resource equilibrium, an adaptation to stochastic pollination environments, or a chronic syndrome caused by an environmental perturbation. We formalize and extend D. Haig and M. Westoby's conceptual model, and illustrate its use in guiding research on the evolutionary consequences of pollen limitation, i.e., whether plants evolve or have evolved to ameliorate pollen limitation. This synthesis also reveals that we are only beginning to understand when and how pollen limitation at the plant level translates into effects on plant population dynamics. We highlight the need for both theoretical and empirical approaches to gain a deeper understanding of the importance of life-history characters, Allee effects, and environmental perturbations in population declines mediated by pollen limitation. Lastly, our synthesis identifies a critical need for research on potential effects of pollen limitation at the community and ecosystem levels.
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