Spatial Heterogeneity Effects on Meta-Community Stability of Annual Plants from a Coastal Dune Ecosystem.

Spatial heterogeneity affects plant community composition and diversity. It is particularly noticeable in annual plant communities, which vary in space and time over short distances and periods, forming meta-communities at the regional scale. This study was conducted at the coastal dune ecosystem in Nizzanim nature reserve, Israel. This study aimed to analyze the effect of the spatial heterogeneity, which is expressed in differences in the fixation levels of the dunes and patches outside and beneath the dominant Artemisia monosperma shrubs, on the characteristics of the annual plant meta-community and its temporal stability, considering the mechanisms that may affect it. Thirteen dunes were studied: three mobile, seven semi-fixed, and three fixed dunes. Data on the annual plants were collected during the spring seasons of 2006, 2007, 2009, 2014, 2015, and 2016. For each dune, 72 quadrats of 40×40 cm were sampled yearly, with 24 quadrats per slope aspect (windward, leeward, and crest), 12 under the shrub, and 12 in the open. The results indicate that the transition from mobile dunes through semi-fixed to fixed dunes is characterized by an increase in annual plant cover, species richness, species diversity, changes in plant communities, and stability driven by the asynchrony of species population fluctuations. Asynchrony affected the stability of the meta-community of this ecosystem in patches beneath the shrubs but not in the open patches.

Why do plants silicify?

Despite seminal papers that stress the significance of silicon (Si) in plant biology and ecology, most studies focus on manipulations of Si supply and mitigation of stresses. The ecological significance of Si varies with different levels of biological organization, and remains hard to capture. We show that the costs of Si accumulation are greater than is currently acknowledged, and discuss potential links between Si and fitness components (growth, survival, reproduction), environment, and ecosystem functioning. We suggest that Si is more important in trait-based ecology than is currently recognized. Si potentially plays a significant role in many aspects of plant ecology, but knowledge gaps prevent us from understanding its possible contribution to the success of some clades and the expansion of specific biomes.

Propagule size and seed development duration: high photosynthate allocation and growth allometry.

MAIN CONCLUSION: The divergences in propagule mass have been more consistently associated with divergences in seed development duration or fruit pedicel cross-sectional area than with divergences in any other biotic factors. Allometry and Corner's rule became an important theme in evolutionary biology of plant trait structure and function. Being one of the most widely noticed plant traits, propagule (seed and fruit) mass variation mechanism across species is still controversial. Here we examined correlations between propagule mass and seed development duration as well as other traits, such as cross-sectional area of fruit pedicel, life form, fruit type and leaf area over four census years, to test an important life history strategy for propagule biomass allocation. We investigated 491 species, belonging to 91 families and 320 genera, representing 95% of native wild species in Beijing Botanical Garden. The scaling correlations between propagule mass and seed development duration and the other traits were determined using phylogenetic generalized linear models. Results show a significant positive relationship among propagule mass and seed development duration, leaf area and pedicel cross-sectional area for all species and for each life form (except vines) regardless of phylogeny. The variation in seed mass has been more consistently associated with variation in seed development duration than with divergences in any other variable, such as growth form, fruit type, pedicel cross-sectional area and leaf area, whereas variation in fruit weight was found to be more associated with variation in pedicel cross-sectional area than the other. Biotic factors, such as seed development duration, pedicel cross-sectional area, growth form and leaf area, mediate propagule size variation, of which seed development duration or pedicel cross-sectional area is the most important. The results further supported a hypothesis that large-seeded species evolved owing to high photosynthate availability and growth allometry in plant body. A mechanistic mathematical model involving seed development duration was provided to expound propagule mass variations across species.

Silicon in the Soil-Plant Continuum: Intricate Feedback Mechanisms within Ecosystems.

Plants' ability to take up silicon from the soil, accumulate it within their tissues and then reincorporate it into the soil through litter creates an intricate network of feedback mechanisms in ecosystems. Here, we provide a concise review of silicon's roles in soil chemistry and physics and in plant physiology and ecology, focusing on the processes that form these feedback mechanisms. Through this review and analysis, we demonstrate how this feedback network drives ecosystem processes and affects ecosystem functioning. Consequently, we show that Si uptake and accumulation by plants is involved in several ecosystem services like soil appropriation, biomass supply, and carbon sequestration. Considering the demand for food of an increasing global population and the challenges of climate change, a detailed understanding of the underlying processes of these ecosystem services is of prime importance. Silicon and its role in ecosystem functioning and services thus should be the main focus of future research.

Silicon and Plant-Animal Interactions: Towards an Evolutionary Framework.

Herbivory is fundamental in ecology, being a major driver of ecosystem structure and functioning. Plant Si and phytoliths play a significant antiherbivory role, the understanding of which and of its evolutionary context will increase our understanding of this phenomenon, its origins, and its significance for past, extant, and future ecosystems. To achieve this goal, we need a superdisciplinary evolutionary framework connecting the role of Si in plant-herbivore interactions, in global processes, and in plant and herbivore evolution. To do this properly, we should acknowledge and incorporate into our work some basic facts that are too often overlooked. First, there is great taxonomic variance both in plant Si contents, forms, and roles, but also in herbivore responses, dietary preferences, and in fossil evidence. Second, species and their traits, as well as whole ecosystems, should be seen in the context of their entire evolutionary history and may therefore reflect not only adaptations to extant selective factors but also anachronistic traits. Third, evolutionary history and evolutionary transitions are complex, resulting in true and apparent asynchronisms. Fourth, evolution and ecology are multiscalar, in which various phenomena and processes act at various scales. Taking these issues into consideration will improve our ability to develop this needed theoretical framework and will bring us closer to gaining a more complete understanding of one of the most exciting and elusive phenomena in plant biology and ecology.

Extending the scope of Darwin's 'abominable mystery': integrative approaches to understanding angiosperm origins and species richness.

Background and aims: Angiosperms are the most species-rich group of land plants, but their origins and fast and intense diversification still require an explanation. Scope: Extending research scopes can broaden theoretical frameworks and lines of evidence that can lead to solving this 'abominable mystery'. Solutions lie in understanding evolutionary trends across taxa and throughout the Phanerozoic, and integration between hypotheses and ideas that are derived from multiple disciplines. Key Findings: Descriptions of evolutionary chronologies should integrate between molecular phylogenies, descriptive palaeontology and palaeoecology. New molecular chronologies open new avenues of research of possible Palaeozoic angiosperm ancestors and how they evolved during as many as 200Myr until the emergence of true angiosperms. The idea that 'biodiversity creates biodiversity' requires evidence from past and present ecologies, with changes in herbivory and resource availability throughout the Phanerozoic appearing to be particularly promising. Conclusions: Promoting our understanding of angiosperm origins and diversification in particular, and the evolution of biodiversity in general, requires more profound understanding of the ecological past through integrating taxonomic, temporal and ecological scopes.

Shift of fleshy fruited species along elevation: temperature, canopy coverage, phylogeny and origin.

Plant communities differ in their fruit type spectra, especially in the proportions of fleshy and non-fleshy fruit types. However, which abiotic and biotic factors drive this variability along elevation gradient and what drives the evolution of fruit type diversity still are puzzling. We analyzed the variations in proportions and richness of fleshy-fruited species and their correlations to various abiotic and biotic variables along elevation gradients in three mountains in the Beijing region, northeast China. Fleshy-fruited species, which are characterized by high fruit water contents, were found in great proportion and richness at relatively low elevations, where soil water content is low compared to high elevations. High temperatures in low elevations increase water availability for plants. Plants that grow in the shaded low-elevation thick-canopy forests are less exposed to evapotranspiration and thus possess water surpluses that can be invested in fleshy fruits. Such an investment in fleshy fruits is beneficial for these species because it makes the fruits more attractive to frugivores that act as seed dispersers in the close-canopied environments, where dispersion by wind is less effective. A hypothesis is proposed that plant internal water surpluses are the prerequisite conditions that permit evolution of fleshy fruits to occur.