1,720,986 research outputs found
Bryophytes are predicted to lag behind future climate change despite their high dispersal capacities
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Vulnerability of cloud forests to climate change: what can we learn from high-resolution climatologies in a topographically complex oceanic archipelago?
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Predicting the dynamics of range shifts under climate change: assumptions and applications to the European bryophyte flora
Full text linkClimate change has and will have a dramatic impact on species ranges. Terrestrial species have accordingly already migrated poleward at a median speed of 16.9km per decade since the beginning of the industrial era. However, many species are not equipped to efficiently track the geographic changes of the conditions matching their climatic niche, and are consequently prone to extinction. No less than about 20% of land plant species are hence threatened with extinction in the future, with major consequences on human food resources and health. In this context, Species distribution models (SDMs) offer an appealing framework to test the potential effects of climate change on species ranges. Like many biodiversity analyses, SDMs have traditionally been conducted at the species level. Cryptic speciation, which results in taxa that cannot rapidly be distinguished morphologically, but underwent divergent evolutionary histories, has been, however, increasingly reported, raising the question of whether SDMs should be fitted at the level of species (clade models), cryptic species or intraspecific lineages (subclade models). Projecting models through time further raises several questions and relies on several assumptions. In particular, projecting species potential ranges in the future based on their niche inferred from extant climate conditions onto future climatic layers involves that (I) species climatic niches are conserved through time (niche conservatism hypothesis) and that (ii) species are at equilibrium with their environment (i.e. their entire niche is filed), implying that they are not limited by their dispersal capacities, and are immediately able to colonize any newly suitable area.
Focusing on bryophytes, whose ecophysiological characteristics, such as poikilohydry and reliance on rainfall for water uptake, make them excellent candidates to study the impact of climate change, but which exhibit reduced morphologies, raising concerns about broadly defined morphological species concepts, we address here the following questions:
1 At which taxonomic level should SDMs be computed? We compare the extent to which model projections generated at the level of species differ from those obtained for intraspecific lineages. Modelling at the level of infraspecific lineages raises a second issue, which is associated with the very small sample sizes that typically characterize molecularly defined lineages, that is: how can ensemble of small models calibrated from very small datasets be evaluated? In the light of analyses of niche overlap, we finally determine whether models should be calibrated at the level of the species or intraspecific lineages.
2 Is there climatic niche conservatism in bryophytes, and how does the tendency for closely related taxa to share the same climatic niche vary at increasing taxonomic depth?
3 To what extent will such efficient dispersers as bryophytes successfully track the shift of their suitable areas during the next decades?
To address Q1, Ensembles of Small Models were evaluated by null models calibrated from randomly sampled presence points. We compared the extent of suitable area predicted by the projections of clade and subclade models. Niche overlaps were quantified using Schoener's D and Hellinger's I metrics, and the significance of these metrics in terms of niche conservatism or divergence was assessed by niche similarity tests. Combined predictions from subclade models contributed, on average, five times more than clade models to the total suitable area predicted by the combination of both subclade and clade models. Niche overlap was 0.71 on average, with evidence for niche conservatism in half of the species and no signal for niche divergence. Given the poor performance of models based on small datasets, we pragmatically suggest that, in the absence of evidence for niche divergence during diversification of closely related intraspecific lineages, SDMs should be based on all available occurrence data at the species level.
The hypothesis of climatic niche conservatism and its evolutionary ‘labillity’ was further tested at the level of an entire phylum of land plants, the Marchantiophyta, through analyses of the relationship between the spatial turnover of floras and macroclimatic variation. Phylogenetic turnover among floras was quantified through πst statistics. πst-through-time profiles were generated at 1 myr intervals along the phylogenetic time-scale and were correlated with current geographic distance and macroclimatic variation with Mantel tests based on Moran spectral randomization to control for spatial autocorrelation. The contribution of macroclimatic variation to phylogenetic turnover was about four-times higher than that of geographic distance. The correlation between phylogenetic turnover and geographic distance rapidly decayed at increasing phylogenetic depth, whereas the relationship with macroclimatic variation remained constant until 100 myrs. Our analyses reveal that changes in the phylogenetic composition among liverwort floras across the globe are primarily shaped by macroclimatic variation. They demonstrate the relevance of macroclimatic niche conservatism for the assembly of liverwort floras over very large spatial and evolutionary time scales, which may explain why such a pervasive biodiversity pattern as the increase of species richness towards the tropics also applies to organisms with high dispersal capacities.
Finally, we developed a newly designed spatially-explicit model of dispersal by wind in the context of changing climate and presented an example of application in the case of the European flora. A grid of pixel-specific environmental conditions and dispersal kernels, combining information on species dispersal traits, local wind conditions, as well as landscape features affecting dispersal by wind, was generated and used as input in simulations of species dispersal in the landscape under changing climate conditions. In European bryophytes, the median ratios between predicted range loss vs expansion by 2050 across species and climate change scenarios ranged from 1.6 to 3.3 when only shifts in climatic suitability were considered, but increased to 34.7–96.8 when species dispersal abilities were added to our models. This highlights the importance of accounting for dispersal restrictions when projecting future distribution ranges and suggests that even highly dispersive organisms like bryophytes are not equipped to fully track the rates of ongoing climate change in the course of the next decades
Ecological and biological indicators of the accuracy of species distribution models: lessons from European bryophytes
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Spatial resolution impacts projected plant responses to climate change on topographically complex islands
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Can we accurately predict the distribution of soil microorganism presence and relative abundance?
Full text linkpeer reviewedSoil microbes play a key role in shaping terrestrial ecosystems. It is therefore essential to understand what drives their distribution. While multivariate analyses have been used to characterise microbial communities and drivers of their spatial patterns, few studies have focused on predicting the distribution of amplicon sequence variants (ASVs). Here, we evaluate the potential of species distribution models (SDMs) to predict the presence–absence and relative abundance distribution of bacteria, archaea, fungi, and protist ASVs in the western Swiss Alps. Advanced automated selection of abiotic covariates was used to circumvent the lack of knowledge on the ecology of each ASV. Presence–absence SDMs could be fitted for most ASVs, yielding better predictions than null models. Relative abundance SDMs performed less well, with low fit and predictive power overall, but displayed a good capacity to differentiate between sites with high and low relative abundance of the modelled ASV. SDMs for bacteria and archaea displayed better predictive power than for fungi and protists, suggesting a closer link of the former with the abiotic covariates used. Microorganism distributions were mostly related to edaphic covariates. In particular, pH was the most selected covariate across models. The study shows the potential of using SDM frameworks to predict the distribution of ASVs obtained from topsoil DNA. It also highlights the need for further development of precise edaphic mapping and scenario modelling to enhances prediction of microorganism distributions in the future
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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