| 1. |
- Calatayud, Joaquín, et al.
(författare)
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Positive associations among rare species and their persistence in ecological assemblages
- 2020
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Ingår i: Nature Ecology & Evolution. - : Nature Publishing Group. - 2397-334X. ; 4:1, s. 40-45
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Tidskriftsartikel (refereegranskat)abstract
- According to the competitive exclusion principle, species with low competitive abilities should be excluded by more efficient competitors; yet, they generally remain as rare species. Here, we describe the positive and negative spatial association networks of 326 disparate assemblages, showing a general organization pattern that simultaneously supports the primacy of competition and the persistence of rare species. Abundant species monopolize negative associations in about 90% of the assemblages. On the other hand, rare species are mostly involved in positive associations, forming small network modules. Simulations suggest that positive interactions among rare species and microhabitat preferences are the most probable mechanisms underpinning this pattern and rare species persistence. The consistent results across taxa and geography suggest a general explanation for the maintenance of biodiversity in competitive environments. Analysing spatial association networks among >300 terrestrial and aquatic assemblages, the authors find that the majority of negative associations involve abundant species. In contrast, rare species form mostly positive associations, potentially explaining their persistence in natural communities.
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| 2. |
- Cavieres, Lohengrin A., et al.
(författare)
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Facilitative plant interactions and climate simultaneously drive alpine plant diversity
- 2014
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Ingår i: Ecology Letters. - : Wiley. - 1461-0248 .- 1461-023X. ; 17:2, s. 193-202
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Tidskriftsartikel (refereegranskat)abstract
- Interactions among species determine local-scale diversity, but local interactions are thought to have minor effects at larger scales. However, quantitative comparisons of the importance of biotic interactions relative to other drivers are rarely made at larger scales. Using a data set spanning 78 sites and five continents, we assessed the relative importance of biotic interactions and climate in determining plant diversity in alpine ecosystems dominated by nurse-plant cushion species. Climate variables related with water balance showed the highest correlation with richness at the global scale. Strikingly, although the effect of cushion species on diversity was lower than that of climate, its contribution was still substantial. In particular, cushion species enhanced species richness more in systems with inherently impoverished local diversity. Nurse species appear to act as a ‘safety net’ sustaining diversity under harsh conditions, demonstrating that climate and species interactions should be integrated when predicting future biodiversity effects of climate change.
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| 3. |
- Dengler, Juergen, et al.
(författare)
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GrassPlot - a database of multi-scale plant diversity in Palaearctic grasslands
- 2018
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Ingår i: Phytocoenologia. - : Schweizerbart. - 0340-269X. ; 48:3, s. 331-347
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Tidskriftsartikel (refereegranskat)abstract
- GrassPlot is a collaborative vegetation-plot database organised by the Eurasian Dry Grassland Group (EDGG) and listed in the Global Index of Vegetation-Plot Databases (GIVD ID EU-00-003). GrassPlot collects plot records (releves) from grasslands and other open habitats of the Palaearctic biogeographic realm. It focuses on precisely delimited plots of eight standard grain sizes (0.0001; 0.001;... 1,000 m(2)) and on nested-plot series with at least four different grain sizes. The usage of GrassPlot is regulated through Bylaws that intend to balance the interests of data contributors and data users. The current version (v. 1.00) contains data for approximately 170,000 plots of different sizes and 2,800 nested-plot series. The key components are richness data and metadata. However, most included datasets also encompass compositional data. About 14,000 plots have near-complete records of terricolous bryophytes and lichens in addition to vascular plants. At present, GrassPlot contains data from 36 countries throughout the Palaearctic, spread across elevational gradients and major grassland types. GrassPlot with its multi-scale and multi-taxon focus complements the larger international vegetationplot databases, such as the European Vegetation Archive (EVA) and the global database " sPlot". Its main aim is to facilitate studies on the scale-and taxon-dependency of biodiversity patterns and drivers along macroecological gradients. GrassPlot is a dynamic database and will expand through new data collection coordinated by the elected Governing Board. We invite researchers with suitable data to join GrassPlot. Researchers with project ideas addressable with GrassPlot data are welcome to submit proposals to the Governing Board.
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| 4. |
- Dwibedi, Chinmay Kumar, et al.
(författare)
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Long-range dispersal moved Francisella tularensis into Western Europe from the East
- 2016
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Ingår i: Microbial Genomics. - : Microbiology Society. - 2057-5858. ; 2:12
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Tidskriftsartikel (refereegranskat)abstract
- For many infections transmitting to humans from reservoirs in nature, disease dispersal patterns over space and time are largely unknown. Here, a reversed genomics approach helped us understand disease dispersal and yielded insight into evolution and biological properties of Francisella tularensis, the bacterium causing tularemia. We whole-genome sequenced 67 strains and characterized by single-nucleotide polymorphism assays 138 strains, collected from individuals infected 1947-2012 across Western Europe. We used the data for phylogenetic, population genetic and geographical network analyses. All strains (n= 205) belonged to a monophyletic population of recent ancestry not found outside Western Europe. Most strains (n= 195) throughout the study area were assigned to a star-like phylogenetic pattern indicating that colonization of Western Europe occurred via clonal expansion. In the East of the study area, strains were more diverse, consistent with a founder population spreading from east to west. The relationship of genetic and geographic distance within the F. tularensis population was complex and indicated multiple long-distance dispersal events. Mutation rate estimates based on year of isolation indicated null rates; in outbreak hotspots only, there was a rate of 0.4 mutations/genome/year. Patterns of nucleotide substitution showed marked AT mutational bias suggestive of genetic drift. These results demonstrate that tularemia has moved from east to west in Europe and that F. tularensis has a biology characterized by long-range geographical dispersal events and mostly slow, but variable, replication rates. The results indicate that mutation-driven evolution, a resting survival phase, genetic drift and long-distance geographical dispersal events have interacted to generate genetic diversity within this species.
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| 5. |
- Madrigal-Gonzalez, Jaime, et al.
(författare)
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Climate reverses directionality in the richness-abundance relationship across the World's main forest biomes
- 2020
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Ingår i: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- More tree species can increase the carbon storage capacity of forests (here referred to as the more species hypothesis) through increased tree productivity and tree abundance resulting from complementarity, but they can also be the consequence of increased tree abundance through increased available energy (more individuals hypothesis). To test these two contrasting hypotheses, we analyse the most plausible pathways in the richness-abundance relationship and its stability along global climatic gradients. We show that positive effect of species richness on tree abundance only prevails in eight of the twenty-three forest regions considered in this study. In the other forest regions, any benefit from having more species is just as likely (9 regions) or even less likely (6 regions) than the effects of having more individuals. We demonstrate that diversity effects prevail in the most productive environments, and abundance effects become dominant towards the most limiting conditions. These findings can contribute to refining cost-effective mitigation strategies based on fostering carbon storage through increased tree diversity. Specifically, in less productive environments, mitigation measures should promote abundance of locally adapted and stress tolerant tree species instead of increasing species richness. Correlations between tree species diversity and tree abundance are well established, but the direction of the relationship is unresolved. Here the authors use path models to estimate plausible causal pathways in the diversity-abundance relationship across 23 global forests regions, finding a lack of general support for a positive diversity-abundance relationship, which is prevalent in the most productive lands on Earth only
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| 6. |
- Tye, Matthew R., et al.
(författare)
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Assessing seed and microsite limitation on population dynamics of a gypsophyte through experimental soil crust disturbance and seed addition
- 2017
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Ingår i: Plant Ecology. - : SPRINGER. - 1385-0237 .- 1573-5052. ; 218:5, s. 595-607
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the factors limiting population growth is crucial for species management and conservation. We assessed the effects of seed and microsite limitation, along with climate variables, on Helianthemum squamatum, a gypsum soil specialist, in two sites in central Spain. We evaluated the effects of experimental seed addition and soil crust disturbance on H. squamatum vital rates (survival, growth and reproduction) across four years. We used this information to build integral projection models (IPMs) for each combination of management (seed addition or soil disturbance), site and year. We examined differences in population growth rate (lambda) due to management using life table response experiments. Soil crust disturbance increased survival of mid to large size individuals and germination. Contributions to lambda of positive individual growth (progression) and negative individual growth (retrogression) due to managements varied among years and sites. Soil crust disturbance increased lambda in the site with the highest plant density, and seed addition had a moderate positive effect on lambda in the site with lowest plant density. Population growth rate (lambda) decreased by half in the driest year. Differences in management effects between sites may represent a shift from seed to microsite limitation at increasing densities. This shift underscores the importance of considering what factors limit population growth when selecting a management strategy.
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