Species turnover is ubiquitous. However, it remains unknown whether certain types of species are consistently gained or lost across different habitats. Here, we analysed the trajectories of 1827 plant species over time intervals of up to 78 years at 141 sites across mountain summits, forests, and lowland grasslands in Europe. We found, albeit with relatively small effect sizes, displacements of smaller‐ by larger‐ranged species across habitats. Communities shifted in parallel towards more nutrient‐demanding species, with species from nutrient‐rich habitats having larger ranges. Because these species are typically strong competitors, declines of smaller‐ranged species could reflect not only abiotic drivers of global change, but also biotic pressure from increased competition. The ubiquitous component of turnover based on species range size we found here may partially reconcile findings of no net loss in local diversity with global species loss, and link community‐scale turnover to macroecological processes such as biotic homogenisation.
Background
The intracellular accommodation of arbuscular mycorrhizal (AM) fungi involves a profound molecular reprogramming of the host cell architecture and metabolism, based on the activation of a symbiotic signaling pathway. In analogy with other plant biotrophs, AM fungi are reported to trigger cell cycle reactivation in their host tissues, possibly in support of the enhanced metabolic demand required for the symbiosis.
Results
We here compare the efficiency of three Fiji/ImageJ image analysis plugins in localizing and quantifying the increase in nuclear size - a hallmark of recursive events of endoreduplication - in
M. truncatula
roots colonized by the AM fungus
Gigaspora margarita
.
All three approaches proved to be versatile and upgradeable, allowing the investigation of nuclear changes in a complex tissue; 3D Object Counter provided more detailed information than both TrackMate and Round Surface Detector plugins.
On this base we challenged 3D Object Counter with two case studies: verifying the lack of endoreduplication-triggering responses in
Medicago truncatula
mutants with a known non-symbiotic phenotype; and analysing the correlation in space and time between the induction of cortical cell division and endoreduplication upon AM colonization.
Both case studies revealed important biological aspects. Mutant phenotype analyses have demonstrated that the knock-out mutation of different key genes in the symbiotic signaling pathway block AM-associated endoreduplication. Furthermore, our data show that cell divisions occur during initial stages of root colonization and are followed by recursive activation of the endocycle in preparation for arbuscule accommodation.
Conclusions
In conclusion, our results indicate 3D Object Counter as the best performing Fiji/ImageJ image analysis script in plant root thick sections and its application highlighted endoreduplication as a major feature of the AM pre-penetration response in root cortical cells.
Electronic supplementary material
The online version of this article (10.1186/s12870-019-1791-1) contains supplementary material, which is available to authorized users.
According to projects and practices that the Italian botanists and ecologists are carrying out for bringing "more nature in the city", new insights for a factual integration between ecological perspectives and more consolidated aesthetic and agronomic approaches to the sustainable planning and management of urban green areas are provided.Keywords Ecosystem services, Human well-being, Green infrastructure, Urban green areas, Urban biodiversity.
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