scholarly journals Does pollen limitation limit plant ranges? Evidence and implications

2021 ◽  
Author(s):  
Emma Dawson-Glass ◽  
Anna L Hargreaves
Keyword(s):  
Sexual Reproduction ◽  
Pollen Limitation ◽  
Meta Analysis ◽  
Ecological Factors ◽  
Range Limits ◽  
Global Databases ◽  
Plant Distributions ◽  
Occurrence Data ◽  
The Rich ◽  
The Tropics

Range limits often involve declines in sexual reproduction, reducing fitness, dispersal, and adaptive potential at range edges. For plants, sexual reproduction is frequently limited by inadequate pollination. While case studies show that pollen limitation can limit plant distributions, the extent to which pollination commonly declines toward plant range edges is unknown. Here, we leverage global databases of pollen-supplementation experiments and plant occurrence data to test whether pollen limitation increases toward plant range edges, using a phylogenetically controlled meta-analysis. While there was significant pollen limitation across studies, we found little evidence that pollen limitation increases toward plant range edges. Pollen limitation was not stronger toward the tropics, nor at species' equatorward vs poleward range limits. Meta-analysis results are consistent with results from targeted experiments, in which pollen limitation increased significantly toward only 14% of 14 plant range edges, suggesting that pollination contributes to range limits less often than do other interactions. Together, these results suggest pollination is one of the rich variety of potential ecological factors that can contribute to range limits, rather than a generally important constraint on plant distributions.

scholarly journals Meta-analysis reveals severe pollen limitation for the flowering plants growing in East Himalaya-Hengduan Mountains region

BMC Ecology ◽  
2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Xianfeng Jiang ◽  
Yanping Xie
Keyword(s):  
Confidence Interval ◽  
Pollen Limitation ◽  
Meta Analysis ◽  
Flowering Plants ◽  
Biodiversity Hotspot ◽  
Clear Relationship ◽  
Hengduan Mountains ◽  
Independent Data ◽  
The World ◽  
Global Biodiversity

Abstract Background Pollen limitation occurs widely and has an important effect on flowering plants. The East Himalaya-Hengduan Mountains region is a global biodiversity hotspot. However, to our knowledge, no study has synthetically assessed the degree of pollen limitation in this area. The present study aims to reveal the degree of pollen limitation for the flowering plants growing on East Himalaya-Hengduan Mountains and to test whether the reproductive features or the elevation is closely correlated with the degree of pollen limitation in this area. Results We complied data from 76 studies, which included 96 species and 108 independent data records. We found that the flowering plants in this area undergo severe pollen limitation [overall Hedges’ d = 2.004, with a 95% confidence interval (1.3264, 2.6743)] that is much higher than that of the flowering plants growing in many other regions around the world. The degree of pollen limitation was tested to determine the correlation with the capacity for autonomous self-reproduction and with the pollination pattern (generalized vs. specialized pollination) of plants. In addition, we found a clear relationship between elevation and the degree of pollen limitation, which indicates that plants might undergo more severe pollen limitation in relatively high places. Conclusions This paper is the first to address the severe pollen limitation of the flowering plants growing in East Himalaya-Hengduan Mountains region. Moreover, we reveal the positive correlation between elevation and the degree of pollen limitation.

scholarly journals Evaluating the role of contracting and expanding rainforest in initiating cycles of speciation across the Isthmus of Panama

2012 ◽  
Vol 279 (1742) ◽  
pp. 3520-3526 ◽  
Author(s):  
Brian Tilston Smith ◽  
Amei Amei ◽  
John Klicka
Keyword(s):  
Bird Species ◽  
Tropical Regions ◽  
Isthmus Of Panama ◽  
Species Pairs ◽  
The Matrix ◽  
High Species Richness ◽  
The Rich ◽  
The Tropics ◽  
The Impact

Climatic and geological changes across time are presumed to have shaped the rich biodiversity of tropical regions. However, the impact climatic drying and subsequent tropical rainforest contraction had on speciation has been controversial because of inconsistent palaeoecological and genetic data. Despite the strong interest in examining the role of climatic change on speciation in the Neotropics there has been few comparative studies, particularly, those that include non-rainforest taxa. We used bird species that inhabit humid or dry habitats that dispersed across the Panamanian Isthmus to characterize temporal and spatial patterns of speciation across this barrier. Here, we show that these two assemblages of birds exhibit temporally different speciation time patterns that supports multiple cycles of speciation. Evidence for these cycles is further corroborated by the finding that both assemblages consist of ‘young’ and ‘old’ species, despite dry habitat species pairs being geographically more distant than pairs of humid habitat species. The matrix of humid and dry habitats in the tropics not only allows for the maintenance of high species richness, but additionally this study suggests that these environments may have promoted speciation. We conclude that differentially expanding and contracting distributions of dry and humid habitats was probably an important contributor to speciation in the tropics.

scholarly journals Sensitivities of the Madden–Julian oscillation forecasts to configurations of physics in the ECMWF global model

2021 ◽  
Vol 21 (6) ◽  
pp. 4759-4778
Author(s):  
Jun-Ichi Yano ◽  
Nils P. Wedi
Keyword(s):  
Forecast Model ◽  
Global Model ◽  
Madden Julian Oscillation ◽  
Forecast Performance ◽  
Theoretical Investigations ◽  
Forecast Models ◽  
Forecasting System ◽  
The Rich ◽  
The Tropics ◽  
Original Motivation

Abstract. The sensitivities of the Madden–Julian oscillation (MJO) forecasts to various different configurations of the parameterized physics are examined with the global model of ECMWF's Integrated Forecasting System (IFS). The motivation for the study was to simulate the MJO as a nonlinear free wave under active interactions with higher-latitude Rossby waves. To emulate free dynamics in the IFS, various momentum-dissipation terms (“friction”) as well as diabatic heating were selectively turned off over the tropics for the range of the latitudes from 20∘ S to 20∘ N. The reduction of friction sometimes improves the MJO forecasts, although without any systematic tendency. Contrary to the original motivation, emulating free dynamics with an operational forecast model turned out to be rather difficult, because forecast performance sensitively depends on the specific type of friction turned off. The result suggests the need for theoretical investigations that much more closely follow the actual formulations of model physics: a naive approach with a dichotomy of with or without friction simply fails to elucidate the rich behaviour of complex operational models. The paper further exposes the importance of physical processes other than convection for simulating the MJO in global forecast models.

scholarly journals Calotropis procera (Arka): A Tribal Herb of Utmost Significance

2021 ◽  
Vol 8 (3) ◽  
Author(s):  
Isha Kumari ◽  
Gitika Chaudhary
Keyword(s):  
Medicinal Plants ◽  
Review Article ◽  
Calotropis Procera ◽  
Pharmacological Properties ◽  
The Family ◽  
Anti Oxidant ◽  
Phytochemical Constituents ◽  
The Rich ◽  
The Tropics ◽  
Important Medicinal Plant

Nature has gifted humans a vast variety of medicinal plants, which are the rich source of bioactive compounds. Calotropis procera is an important medicinal plant that belongs to the family asclepiadaceae. It is commonly known as madar and milkweed plant in english and arka in hindi. It is mostly found in the tropics of asia and africa. Calotropis procera is a highly valued plant in the folk medication system. Each part of the plant is richly endowed with diverse nature of phytochemical constituents like alkaloids, proteins, vitamins, carbohydrates, saponins, terpenes, and flavonoids, etc. These phytochemicals are significantly associated with various therapeutic and pharmacological properties such as anti-microbial, anti-oxidant, anti-inflammatory, anti-ulcer, antifertility, anti-diarrheal, and spasmolytic. In this review article, the therapeutic and pharmacological value of this important plant has been summarized along with its utilization in the folklore and ayurvedic medicinal system.

scholarly journals Meta-Analysis of Pollen Limitation Reveals the Relevance of Pollination Generalization in the Atlantic Forest of Brazil

PLoS ONE ◽  
2014 ◽  
Vol 9 (2) ◽  
pp. e89498 ◽  
Author(s):  
Marina Wolowski ◽  
Tia-Lynn Ashman ◽  
Leandro Freitas
Keyword(s):  
Atlantic Forest ◽  
Pollen Limitation ◽  
Meta Analysis

scholarly journals Reviews and syntheses: Soil N<sub>2</sub>O and NO emissions from land use and land-use change in the tropics and subtropics: a meta-analysis

2015 ◽  
Vol 12 (23) ◽  
pp. 7299-7313 ◽  
Author(s):  
J. van Lent ◽  
K. Hergoualc'h ◽  
L. V. Verchot
Keyword(s):  
Land Use ◽  
Land Use Change ◽  
Nitrogen Availability ◽  
Meta Analysis ◽  
Forest Conversion ◽  
N2o Emissions ◽  
Emission Rates ◽  
Soil N ◽  
The Tropics ◽  
No Emissions

Abstract. Deforestation and forest degradation in the tropics may substantially alter soil N-oxide emissions. It is particularly relevant to accurately quantify those changes to properly account for them in a REDD+ climate change mitigation scheme that provides financial incentives to reduce the emissions. With this study we provide updated land use (LU)-based emission rates (104 studies, 392 N2O and 111 NO case studies), we determine the trend and magnitude of flux changes with land-use change (LUC) using a meta-analysis approach (44 studies, 135 N2O and 37 NO cases) and evaluate biophysical drivers of N2O and NO emissions and emission changes for the tropics. The average N2O and NO emissions in intact upland tropical forest amounted to 2.0 ± 0.2 (n = 90) and 1.7 ± 0.5 (n = 36) kg N ha−1 yr−1, respectively. In agricultural soils annual N2O emissions were exponentially related to N fertilization rates and average water-filled pore space (WFPS) whereas in non-agricultural sites a Gaussian response to WFPS fit better with the observed NO and N2O emissions. The sum of soil N2O and NO fluxes and the ratio of N2O to NO increased exponentially and significantly with increasing nitrogen availability (expressed as NO3− / [NO3−+NH4+]) and WFPS, respectively; following the conceptual Hole-In-the-Pipe model. Nitrous and nitric oxide fluxes did not increase significantly overall as a result of LUC (Hedges's d of 0.11 ± 0.11 and 0.16 ± 0.19, respectively), however individual LUC trajectories or practices did. Nitrous oxide fluxes increased significantly after intact upland forest conversion to croplands (Hedges's d = 0.78 ± 0.24) and NO increased significantly following the conversion of low forest cover (secondary forest younger than 30 years, woodlands, shrublands) (Hedges's d of 0.44 ± 0.13). Forest conversion to fertilized systems significantly and highly raised both N2O and NO emission rates (Hedges's d of 1.03 ± 0.23 and 0.52 ± 0.09, respectively). Changes in nitrogen availability and WFPS were the main factors explaining changes in N2O emissions following LUC, therefore it is important that experimental designs monitor their spatio-temporal variation. Gaps in the literature on N oxide fluxes included geographical gaps (Africa, Oceania) and LU gaps (degraded forest, wetland (notably peat) forest, oil palm plantation and soy cultivation).

Why is the Sea Blue?

2009 ◽  
Author(s):  
Thomas N. Sherratt ◽  
David M. Wilkinson
Keyword(s):  
Natural Habitat ◽  
Euphotic Zone ◽  
Scuba Divers ◽  
Light Levels ◽  
High School Physics ◽  
Rich Diversity ◽  
The Pacific ◽  
Great White Shark ◽  
The Rich ◽  
The Tropics

One answer to this chapter’s question is straightforward and based on high-school physics. The early SCUBA divers quickly discovered that if they took underwater colour photographs, even if they were only a few metres down, their pictures had a strong blue cast to them. However, if they illuminated their subjects with a flash, then a more colourful world emerged in their pictures—especially if they were photographing the rich diversity of highly coloured fish that can be found in some parts of the tropics. The reason for the blueness is that as sunlight passes through water the colours of the spectrum are absorbed at different rates, with the long wavelengths (e.g. red) absorbed first and the higher-energy shorter wavelengths (e.g. blue) penetrating deeper into the depths. It follows that underwater available light is predominantly blue and that any light reflected from within the water body is more likely to be from the bluer end of the spectrum of visible light. So, light coming from the sea to our eyes is mainly blue because these wavelengths are least absorbed; indeed oceanographers who have studied some of the cleanest waters describe them as looking ‘violet blue’. As biologists we are interested in a more ecological answer to the question, ‘Why is the sea blue’? The physics explanation only works if seawater is reasonably clear, and it is this clarity that biologists need to explain. Consider our opening quotation, which comes from Peter Matthiessen’s book describing early attempts to film the great white shark in its natural habitat. It raises an interesting ecological question—why can a SCUBA diver or snorkeler see where they are going in the ocean? Put another way, why is the sea blue rather than green? The upper layer of the ocean with enough light for photosynthesis is called the euphotic zone (defined as extending down to the point where only 1% of photosynthetically usable light is present compared with surface light levels); this is often only a few tens of metres deep, but in extremely clear water near Easter Island in the Pacific it has recently been found to extend down to 170 m depth.

Spatial Patterns of Precipitation Change in CMIP5: Why the Rich Do Not Get Richer in the Tropics

2013 ◽  
Vol 26 (11) ◽  
pp. 3803-3822 ◽  
Author(s):  
Robin Chadwick ◽  
Ian Boutle ◽  
Gill Martin
Keyword(s):  
Spatial Patterns ◽  
Mass Flux ◽  
Precipitation Change ◽  
Specific Humidity ◽  
Tropical Precipitation ◽  
Humidity Change ◽  
The Rich ◽  
Convergence Zones ◽  
The Tropics ◽  
Convective Mass Flux

Abstract Changes in the patterns of tropical precipitation (P) and circulation are analyzed in Coupled Model Intercomparison Project phase 5 (CMIP5) GCMs under the representative concentration pathway 8.5 (RCP8.5) scenario. A robust weakening of the tropical circulation is seen across models, associated with a divergence feedback that acts to reduce convection most in areas of largest climatological ascent. This is in contrast to the convergence feedback seen in interannual variability of tropical precipitation patterns. The residual pattern of convective mass-flux change is associated with shifts in convergence zones due to mechanisms such as SST gradient change, and this is often locally larger than the weakening due to the divergence feedback. A simple framework is constructed to separate precipitation change into components based on different mechanisms and to relate it directly to circulation change. While the tropical mean increase in precipitation is due to the residual between the positive thermodynamic change due to increased specific humidity and the decreased convective mass flux due to the weakening of the circulation, the spatial patterns of these two components largely cancel each other out. The rich-get-richer mechanism of greatest precipitation increases in ascent regions is almost negated by this cancellation, explaining why the spatial correlation between climatological P and the climate change anomaly ΔP is only 0.2 over the tropics for the CMIP5 multimodel mean. This leaves the spatial pattern of precipitation change to be dominated by the component associated with shifts in convergence zones, both in the multimodel mean and intermodel uncertainty, with the component due to relative humidity change also becoming important over land.

scholarly journals Biotic interactions are more important at species’ warm vs. cool range-edges: a synthesis

2021 ◽  
Author(s):  
Alexandra Paquette ◽  
Anna L. Hargreaves
Keyword(s):  
Abiotic Factors ◽  
Empirical Support ◽  
Ecological Factors ◽  
Biotic Interactions ◽  
High Elevation ◽  
Range Limits ◽  
Low Latitude ◽  
Comprehensive Literature Review ◽  
Mixed Support ◽  
Species Being

ABSTRACTPredicting which ecological factors constrain species distributions is a fundamental question in ecology and critical to forecasting geographic responses to global change. Darwin hypothesized that abiotic factors generally impose species’ high-latitude and high-elevation (typically cool) range limits, whereas biotic interactions more often impose species’ low-latitude/low-elevation (typically warm) limits, but empirical support has been mixed. Here, we clarify three predictions arising from Darwin’s hypothesis, and show that previously mixed support is partially due to researchers testing different predictions. Using a comprehensive literature review (886 range limits), we find that biotic interactions, including competition, predation, and parasitism, influenced species’ warm limits more often than species’ cool limits. At cool limits, abiotic factors were consistently more important than biotic interactions, but temperature contributed strongly to cool and warm limits. Our results suggest that most range limits will be sensitive to climate warming, but warm limit responses will depend strongly on biotic interactions. “When we travel southward and see a species decreasing in numbers, we may feel sure that the cause lies quite as much in other species being favored, as in this one being hurt. (Whereas)… the number of species, and therefore of competitors, deceases northwards; hence in going northward or in ascending a mountain, we far oftener meet with stunted forms, due to the directly injurious action of climate” –Darwin 1859

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