Community assembly through adaptive radiation in Hawaiian spiders.
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Communities arising through adaptive radiation are generally regarded as unique, with speciation and adaptation being quite different from immigration and ecological assortment. Here, I use the chronological arrangement of the Hawaiian Islands to visualize snapshots of evolutionary history and stages of community assembly. Analysis of an adaptive radiation of habitat-associated, polychromatic spiders shows that (i) species assembly is not random; (ii) within any community, similar sets of ecomorphs arise through both dispersal and evolution; and (iii) species assembly is dynamic with maximum species numbers in communities of intermediate age. The similar patterns of species accumulation through evolutionary and ecological processes suggest universal principles underlie community assembly. (+info)
The interpretation of biological surveys.
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Biological surveys provide the raw material for assembling ecological patterns. These include the properties of parameters such as range, abundance, dispersion, evenness and diversity; the relationships between these parameters; the relationship between geographical distributions and landscape structure; and the co-occurrence of species. These patterns have often been used in the past to evaluate the role of ecological processes in structuring natural communities. In this paper, I investigate the patterns produced by simple neutral community models (NCMs) and compare them with the output of systematic biological surveys. The NCM generates qualitatively, and in some cases quantitatively, the same patterns as the survey data. It therefore provides a satisfactory general theory of diversity and distribution, although what patterns can be used to distinguish neutral from adaptationist interpretations of communities, or even whether such patterns exist, remains unclear. (+info)
Global analysis of river systems: from Earth system controls to Anthropocene syndromes.
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Continental aquatic systems from rivers to the coastal zone are considered within two perspectives: (i) as a major link between the atmosphere, pedosphere, biosphere and oceans within the Earth system with its Holocene dynamics, and (ii) as water and aquatic biota resources progressively used and transformed by humans. Human pressures have now reached a state where the continental aquatic systems can no longer be considered as being controlled by only Earth system processes, thus defining a new era, the Anthropocene. Riverine changes, now observed at the global scale, are described through a first set of syndromes (flood regulation, fragmentation, sediment imbalance, neo-arheism, salinization, chemical contamination, acidification, eutrophication and microbial contamination) with their related causes and symptoms. These syndromes have direct influences on water uses, either positive or negative. They also modify some Earth system key functions such as sediment, water, nutrient and carbon balances, greenhouse gas emissions and aquatic biodiversity. Evolution of river syndromes over the past 2000 years is complex: it depends upon the stages of regional human development and on natural conditions, as illustrated here for the chemical contamination syndrome. River damming, eutrophication and generalized decrease of river flow due to irrigation are some of the other global features of river changes. Future management of river systems should also consider these long-term impacts on the Earth system. (+info)
Integrated management of land and water resources based on a collective approach to fragmented international conventions.
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Interlinked crises of land degradation, food security, ecosystem decline, water quality and water flow depletion stand in the way of poverty reduction and sustainable development. These crises are made worse by increased fluctuations in climatic regimes. Single-purpose international conventions address these crises in a piecemeal, sectoral fashion and may not meet their objectives without greater attention to policy, legal, and institutional reforms related to: (i) balancing competing uses of land and water resources within hydrologic units; (ii) adopting integrated approaches to management; and (iii) establishing effective governance institutions for adaptive management within transboundary basins. This paper describes this global challenge and argues that peace, stability and security are all at stake when integrated approaches are not used. The paper presents encouraging results from a decade of transboundary water projects supported by the Global Environment Facility in developing countries that test practical applications of processes for facilitating reforms related to land and water that are underpinned by science-based approaches. Case studies of using these participative processes are described that collectively assist in the transition to integrated management. A new imperative for incorporating interlinkages among food, water, and environment security at the basin level is identified. (+info)
Evo-Devo: the long and winding road.
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Evolutionary developmental biology (Evo-Devo) aims to unveil how developmental processes and mechanisms become modified during evolution and how from these changes the past and present biodiversity arose. The first wave of Evo-Devo identified a conserved set of toolkits common to most metazoans. The present second wave has changed gear and aims to identify how genes and modules were used differently through evolution to build the past and present morphological diversity. The burgeoning third wave is introducing experimental testing of predictions drawn from the first and second waves. Here we review some of the hottest topics, contributions and insights of present Evo-Devo related to basic concepts and paradigms of evolutionary research. Future directions of Evo-Devo are also highlighted; in other words, Quo Vadis, Evo-Devo? (+info)
48,000 years of climate and forest change in a biodiversity hot spot.
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A continuous 48,000-year-long paleoecological record from Neotropical lower montane forest reveals a consistent forest presence and an ice-age cooling of approximately 5 degrees to 9 degrees C. After 30,000 years of compositional stability, a steady turnover of species marks the 8000-year-long transition from ice-age to Holocene conditions. Although the changes were directional, the rates of community change were no different during this transitional period than in the preceding 30,000-year period of community stability. The warming rate of about 1 degrees C per millennium during the Pleistocene-Holocene transition was an order of magnitude less than the projected changes for the 21st century. (+info)
Biodiversity of exopolysaccharides produced by Streptococcus thermophilus strains is reflected in their production and their molecular and functional characteristics.
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Twenty-six lactic acid bacterium strains isolated from European dairy products were identified as Streptococcus thermophilus and characterized by bacterial growth and exopolysaccharide (EPS)-producing capacity in milk and enriched milk medium. In addition, the acidification rates of the different strains were compared with their milk clotting behaviors. The majority of the strains grew better when yeast extract and peptone were added to the milk medium, although the presence of interfering glucomannans was shown, making this medium unsuitable for EPS screening. EPS production was found to be strain dependent, with the majority of the strains producing between 20 and 100 mg of polymer dry mass per liter of fermented milk medium. Furthermore, no straightforward relationship between the apparent viscosity and EPS production could be detected in fermented milk medium. An analysis of the molecular masses of the isolated EPS by gel permeation chromatography revealed a large variety, ranging from 10 to >2,000 kDa. A distinction could be made between high-molecular-mass EPS (>1,000 kDa) and low-molecular-mass EPS (<1,000 kDa). Based on the molecular size of the EPS, three groups of EPS-producing strains were distinguished. Monomer analysis of the EPS by high-performance anion-exchange chromatography with amperometric detection was demonstrated to be a fast and simple method. All of the EPS from the S. thermophilus strains tested were classified into six groups according to their monomer compositions. Apart from galactose and glucose, other monomers, such as (N-acetyl)galactosamine, (N-acetyl)glucosamine, and rhamnose, were also found as repeating unit constituents. Three strains were found to produce EPS containing (N-acetyl)glucosamine, which to our knowledge was never found before in an EPS from S. thermophilus. Furthermore, within each group, differences in monomer ratios were observed, indicating possible novel EPS structures. Finally, large differences between the consistencies of EPS solutions from five different strains were assigned to differences in their molecular masses and structures. (+info)
Darwin's abominable mystery: Insights from a supertree of the angiosperms.
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Angiosperms are among the major terrestrial radiations of life and a model group for studying patterns and processes of diversification. As a tool for future comparative studies, we compiled a supertree of angiosperm families from published phylogenetic studies. Sequence data from the plastid rbcL gene were used to estimate relative timing of branching events, calibrated by using robust fossil dates. The frequency of shifts in diversification rate is largely constant among time windows but with an apparent increase in diversification rates within the more recent time frames. Analyses of species numbers among families revealed that diversification rate is a labile attribute of lineages at all levels of the tree. An examination of the top 10 major shifts in diversification rates indicates they cannot easily be attributed to the action of a few key innovations but instead are consistent with a more complex process of diversification, reflecting the interactive effects of biological traits and the environment. (+info)