1,721,028 research outputs found
Thermal limits to the geographic distributions of shallow-water marine species
No full textTemperature profoundly affects species’ geographic ranges, but the extent to which it limits contemporary range edges has been difficult to assess from laboratory experiments of thermal tolerance. The persistence of populations depends on temperature-mediated outcomes of ecological and demographic processes across all stages of a species’ life history, as well as any adaptation to local temperature regimes. We assessed the relationships between sea temperature and observed distributional ranges for 1,790 shallow-water marine species from 10 animal classes and found remarkable consistencies in trends in realized thermal limits among taxa and ocean basins, as well as general agreement with previous laboratory findings. Realized thermal niches increase from the Equator towards cold–temperate locations, despite an opposite trend in geographic range size. Species’ cool distribution limits are best predicted by the magnitude of seasonality within their range, while a relatively firm thermal barrier exists on the equatorward range edge for temperate species. Our findings of consistencies in realized thermal limits indicate potential limits to adaptation among common marine species and highlight the value of realized thermal niches for predicting species’ distributional dynamics in warming seas
Biological interactions both facilitate and resist climate-related functional change in temperate reef communities
No full textShifts in the abundance and location of species are restructuring life on the Earth, presenting the need to build resilience into our natural systems. Here, we tested if protection from fishing promotes community resilience in temperate reef communities undergoing rapid warming in Tasmania. Regardless of protection status, we detected a signature of warming in the brown macroalgae, invertebrates and fishes, through increases in the local richness and abundance of warm-affinity species. Even so, responses in protected communities diverged from exploited communities. At the local scale, the number of cool-affinity fishes and canopy-forming algal species increased following protection, even though the observation window fell within a period of warming. At the same time, exploited communities gained turf algal and sessile invertebrate species. We further found that the recovery of predator populations following protection leads to marked declines in mobile invertebrates—this trend could be incorrectly attributed to warming without contextual data quantifying community change across trophic levels. By comparing long-term change in exploited and protected reefs, we empirically demonstrate the role of biological interactions in both facilitating and resisting climate-related biodiversity change. We further highlight the potential for trophic interactions to alter the progression of both range expansions and contractions
Thermal biases and vulnerability to warming in the world’s marine fauna
No full textA critical assumption underlying projections of biodiversity change associated with global warming is that ecological communities comprise balanced mixes of warm-affinity and cool-affinity species which, on average, approximate local environmental temperatures. Nevertheless, here we find that most shallow water marine species occupy broad thermal distributions that are aggregated in either temperate or tropical realms. These distributional trends result in ocean-scale spatial thermal biases, where communities are dominated by species with warmer or cooler affinity than local environmental temperatures. We use community-level thermal deviations from local temperatures as a form of sensitivity to warming, and combine these with projected ocean warming data to predict warming-related loss of species from present-day communities over the next century. Large changes in local species composition appear likely, and proximity to thermal limits, as inferred from present-day species’ distributional ranges, outweighs spatial variation in warming rates in contributing to predicted rates of local species loss
Fishing-gear restrictions and biomass gains for coral reef fishes in marine protected areas
No full textConsiderable empirical evidence supports recovery of reef fish populations with fishery closures. In countries where full exclusion of people from fishing may be perceived as inequitable, fishing-gear restrictions on nonselective and destructive gears may offer socially relevant management alternatives to build recovery of fish biomass. Even so, few researchers have statistically compared the responses of tropical reef fisheries to alternative management strategies. We tested for the effects of fishery closures and fishing gear restrictions on tropical reef fish biomass at the community and family level. We conducted 1,396 underwater surveys at 617 unique sites across a spatial hierarchy within 22 global marine ecoregions that represented 5 realms. We compared total biomass across local fish assemblages and among 20 families of reef fishes inside marine protected areas (MPAs) with different fishing restrictions: no-take, hook-and-line fishing only, several fishing gears allowed, and sites open to all fishing gears. We included a further category representing remote sites, where fishing pressure is low. As expected, full fishery closures, (i.e., no-take zones) most benefited community- and family-level fish biomass in comparison with restrictions on fishing gears and openly fished sites. Although biomass responses to fishery closures were highly variable across families, some fishery targets (e.g., Carcharhinidae and Lutjanidae) responded positively to multiple restrictions on fishing gears (i.e., where gears other than hook and line were not permitted). Remoteness also positively affected the response of community-level fish biomass and many fish families. Our findings provide strong support for the role of fishing restrictions in building recovery of fish biomass and indicate important interactions among fishing-gear types that affect biomass of a diverse set of reef fish families.</p
Resilience and signatures of tropicalization in protected reef fish communities
No full textHabitat reserves can promote ecological resilience to climate variability by supporting intact trophic webs and large-bodied individuals1, 2, 3. Protection may also alter community responses to long-term climate change by offering habitat for range-shifting species4. Here we analyse the species richness, diversity and functional traits of temperate reef fish communities over 20 years in a global warming hotspot and compare patterns in a marine reserve with nearby sites open to fishing. Species richness and diversity oscillated strongly on the decadal scale. Long-term warming signatures were also present as increasing functional trait richness and functional diversity, driven in part by a general increase in herbivores. Nevertheless, reserve sites were distinguished from fished sites by displaying: greater stability in some aspects of biodiversity; recovery of large-bodied temperate species; resistance to colonization by subtropical vagrants; and less pronounced increases in the community-averaged temperature affinity. We empirically demonstrate that protection from fishing has buffered fluctuations in biodiversity and provided resistance to the initial stages of tropicalization
New approaches to marine conservation through scaling up of ecological data
Full text linkIn an era of rapid global change, conservation managers urgently need improved tools to track and counter declining ecosystem conditions. This need is particularly acute in the marine realm, where threats are out of sight, inadequately mapped, cumulative, and often poorly understood, thereby generating impacts that are inefficiently managed. Recent advances in macroecology, statistical analysis, and the compilation of global data will play a central role in improving conservation outcomes, provided that global, regional, and local data streams can be integrated to produce locally relevant and interpretable outputs. Progress will be assisted by (a) expanded rollout of systematic surveys that quantify species patterns, including some carried out with help from citizen scientists; (b) coordinated experimental research networks that utilize large-scale manipulations to identify mechanisms underlying these patterns; (c) improved understanding of consequences of threats through the application of recently developed statistical techniques to analyze global species’ distributional data and associated environmental and socioeconomic factors; (d) development of reliable ecological indicators for accurate and comprehensible tracking of threats; and (e) improved data-handling and communication tools.<br/
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
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