1,720,990 research outputs found
Ecological Assemblages in a Warming Climate: Addressing Knowledge Gaps in the Role of Thermal Heterogeneity and Realised Niches at a Global Scale
No full textEcological responses to Anthropogenic climate warming are occurring across the globe. The aim of this thesis is to critically examine knowledge gaps in: i) how assemblages respond to multidimensional temperature change; ii) patterns of realised niches across species’ assemblages. I investigate these gaps to build the requisite knowledge to describe and predict assemblage scale responses to climatic warming.Chapter 2 develops a conceptual framework relating the processes of individual movements and population dynamics to the spatial and temporal dimensions of temperature change. I find that most studies do not consider the dimensionality of temperature change when quantifying assemblage dynamics.Chapter 3 finds that, on average, the abundance of reef fish species across their thermal ranges supports the ‘abundant-niche centre’ hypothesis. I also find a systematic pattern in the skew of realised thermal niches amongst species, which relates to latitude and biogeographic habitat variation.Chapter 4 quantifies spatial patterns in the diversity of species’ responses to heatwave events in five functional groups of reef fishes on the Great Barrier Reef and western Coral Sea. Browsing herbivores, scraping herbivores and corallivores have spatially homogenous patterns of response diversity indicating resilience at a regional scale. Further, all functional groups positively respond to temperature warming but only corallivores and excavators negatively respond to coral loss, and no functional groups strongly respond to algae loss.Chapter 5 critically examines the ‘wide-ranged winners’ paradigm for terrestrial ectotherms (insects) across land-use types that represent a microclimatic gradient. I find that species’ niche metrics consistently outperform geographic range size in predicting species occurrence. Species with warmer and drier affinities increased in occupancy in agricultural land uses which matched the expected warmer and dryer conditions.Overall, realised niches are structured by abundance, exhibit diversity within local assemblages and regional species pools, and can predict occupancy at local scales even in thermally heterogeneous terrestrial systems. This thesis therefore further establishes the thermal niche as a core concept to quantify the dynamics of assemblages in a warming world. Chapter 6 critically evaluates the benefits and limitations of this niche perspective for quantifying biodiversity change and suggests future research avenues.<br/
The shape of abundance distributions across temperature gradients in reef fishes
No full textImproving predictions of ecological responses to climate change requires understanding how local abundance relates to temperature gradients, yet many factors influence local abundance in wild populations. We evaluated the shape of thermal‐abundance distributions using 98 422 abundance estimates of 702 reef fish species worldwide. We found that curved ceilings in local abundance related to sea temperatures for most species, where local abundance declined from realised thermal ‘optima’ towards warmer and cooler environments. Although generally supporting the abundant‐centre hypothesis, many species also displayed asymmetrical thermal‐abundance distributions. For many tropical species, abundances did not decline at warm distribution edges due to an unavailability of warmer environments at the equator. Habitat transitions from coral to macroalgal dominance in subtropical zones also influenced abundance distribution shapes. By quantifying the factors constraining species’ abundance, we provide an important empirical basis for improving predictions of community re‐structuring in a warmer world
Insect occurrence in agricultural land‐uses depends on realized niche and geographic range properties
Full text linkGeographic range size predicts species’ responses to land‐use change and intensification, but the reason why is not well established because many correlates of larger geographic ranges, such as realized niche breadth, may mediate species’ responses to environmental change. Agricultural land uses (hereafter ‘agroecosystems’) have warm, dry and more variable microclimates than do cooler and wetter mature forests, so are predicted to filter for species that have warmer, drier and broader fundamental and realized niches. To test these predictions, we estimated species’ realized niches, for temperature and precipitation, and geographic range sizes of 764 insect species by matching GBIF occurrence records to global climate layers, and modelled how species presence/absence in mature forest and nearby agroecosystems depend on species’ realized niches or geographic ranges. The predicted species niche effects consistently matched the expected direction of microclimatic transition from mature forest to agroecosystems. We found a clear signal that species with preference for warmer and drier climates were more likely to be present in agroecosystems. In addition, the probability that species occurred in different land‐use types was predicted better by species’ realized niche than their geographic range size. However, niche effects are often context‐dependent and varied amongst studies, taxonomic groups and regions used in this analysis: predicting which particular aspects of species’ realized niche cause sensitivity to land‐use change, and the underpinning mechanisms, remains a major challenge for future research and multiple components of species’ realized niches may be important to consider. Using realized niches derived from open‐source occurrence records can be a simple and widely applicable tool to help identify when biodiversity responds to the microclimate component of land‐use change
Temperature-driven biodiversity change : disentangling space and time
Full text linkCW was supported by the Natural Environmental Research Council (grant no. NE/L002531/1). AEB is supported by the Canada Research Chairs program. MD is grateful for support through Scottish Funding Council's (Marine Alliance for Science and Technology for Scotland grant no. HR09011), the European Research Council grant nos. AdG-250189 (BioTIME) and PoC-727440 (BioCHANGE).Temperature regimes have multiple spatial and temporal dimensions that have different impacts on biodiversity. Signatures of warming across these dimensions may contribute uniquely to the large-scale species redistributions and abundance changes that underpin community dynamics. A comprehensive review of the literature reveals that 86% of studies were focused on community responses to temperature aggregated over spatial or temporal dimensions (e.g., mean, median, or extremes). Therefore, the effects of temperature variation in space and time on biodiversity remain generally unquantified. In the present article, we argue that this focus on aggregated temperature measures may limit advancing our understanding of how communities are being altered by climate change. In light of this, we map the cause-and-effect pathways between the different dimensions of temperature change and communities in space and time. A broadened focus, shifted toward a multidimensional perspective of temperature, will allow better interpretation and prediction of biodiversity change and more robust management and conservation strategies.Peer reviewe
Temperature-related biodiversity change across temperate marine and terrestrial systems
No full textClimate change is reshaping global biodiversity as species respond to changing temperatures. However, the net effects of climate-driven species redistribution on local assemblage diversity remain unknown. Here, we relate trends in species richness and abundance from 21,500 terrestrial and marine assemblage time series across temperate regions (23.5–60.0° latitude) to changes in air or sea surface temperature. We find a strong coupling between biodiversity and temperature changes in the marine realm, where species richness mostly increases with warming. However, biodiversity responses are conditional on the baseline climate, such that in initially warmer locations richness increase is more pronounced while abundance declines with warming. In contrast, we do not detect systematic temperature-related richness or abundance trends on land, despite a greater magnitude of warming. As the world is committed to further warming, substantial challenges remain in maintaining local biodiversity amongst the non-uniform inflow and outflow of ‘climate migrants’. Temperature-driven community restructuring is especially evident in the ocean, whereas climatic debt may be accumulating on land.</p
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
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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Neglecting biodiversity baselines in longitudinal river connectivity restoration impacts priority setting.
No full textRiver habitats are fragmented by barriers which impede the movement and dispersal of aquatic organisms. Restoring habitat connectivity is a primary objective of nature conservation plans with multiple efforts to strategically restore connectivity at local, regional, and global scales. However, current approaches to prioritize connectivity restoration do not typically consider how barriers spatially fragment species' populations. Additionally, we lack knowledge on biodiversity baselines to predict which species would find suitable habitat after restoring connectivity. In this paper, we asked how neglecting these biodiversity baselines in river barrier removals impacts priority setting for conservation planning. We applied a novel modelling approach combining predictions of species distributions with network connectivity models to prioritize conservation actions in rivers of the Rhine-Aare system in Switzerland. Our results show that the high number and density of barriers has reduced structural and functional connectivity across representative catchments within the system. We show that fragmentation decreases habitat suitability for species and that using expected distributions as biodiversity baselines significantly affects priority settings for connectivity restorations compared to species-agnostic metrics based on river length. This indicates that priorities for barrier removals are ranked higher within the expected distributions of species to maximize functional connectivity while barriers in unsuitable regions are given lower importance scores. Our work highlights that the joint consideration of existing barriers and species past and current distributions are critical for restoration plans to ensure the recovery and persistence of riverine fish diversity
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