Topic
Species richness
About: Species richness is a research topic. Over the lifetime, 61672 publications have been published within this topic receiving 2183796 citations.
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TL;DR: Higher foraging activity in bats suggests that habitat quality in terms of prey availability is greater on organic farms, and as the number of organic enterprises increases it may help to reverse declines in bat populations.
Abstract: Summary 1. Agricultural intensification is perceived to be a major cause of the decline in many European bat populations. Because organic farming prohibits the use of agrochemicals, we compared organic vs. conventional farm types to test the hypothesis that agricultural intensification based on high levels of agrochemical use has been a factor in bat population declines. Bat activity and species richness were compared on matched pairs of organic and conventional farms. 2. Bat activity was quantified using acoustic surveys within specific habitats on farms in southern England and Wales. Eighty-nine per cent of bat passes were identified to species level using artificial neural networks (ANN). A further 9% were identified to genus. 3. Total bat activity was significantly higher on organic farms than on conventional farms. Significantly more bat passes were recorded over water on organic farms than on conventional farms. Foraging activity (quantified in two ways: total feedings buzzes and feeding buzzes per pass) was significantly higher on organic farms than on conventional farms. 4. The dominant species on both farm types were Pipistrellus pipistrellus and Pipistrellus pygmaeus . Significantly more passes of Myotis species were recorded on organic farms than on conventional farms. This difference was also significant when water habitats were considered alone. 5. The activity of both Myotis daubentonii and Myotis brandtii was significantly higher on organic farms than on conventional farms. The activity of Myotis bechsteinii and Myotis brandtii was significantly higher over organic water habitats than over conventional water habitats. Rhinolophus hipposideros and Rhinolophus ferrumequinum were only recorded on organic farms in wooded, arable and pasture habitats. 6. Synthesis and applications. This study highlights the position of bats as bioindicators and victims of agricultural change. The differences in bat activity between farm types may reflect features such as taller hedgerows and better water quality on organic farms. Higher foraging activity also suggests that habitat quality in terms of prey availability is greater on organic farms. Less intensive farming benefits bats, and as the number of organic enterprises increases it may help to reverse declines in bat populations.
298 citations
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TL;DR: The survival of approximately 235 000 individual tropical trees and saplings in the 50 ha permanent plot on Barro Colorado Island, Panama was analyzed over a 13-year interval as a function of four biotic neighborhood variables: total stem density; conspecific density; relative plant size; and relative species richness.
Abstract: The survival of approximately 235 000 individual tropical trees and saplings in the 50 ha permanent plot on Barro Colorado Island (BCI), Panama was analyzed over a 13-year interval (1982–1995) as a function of four biotic neighborhood variables: (i) total stem density; (ii) conspecific density; (iii) relative plant size; and (iv) relative species richness. These neighborhood variables were measured in annular rings of width 2.5 m, extending 30 m from a given focal plant, and in one more distant annulus at 47.5–50 m. Because survival was spatially autocorrelated, a Gibbs sampler and a Monte Carlo Markov chain method were used for fitting an autologistic regression model to obtain unbiased estimates of parameter variances for hypothesis testing. After pooling all species at the community level, results showed that all four variables had significant and often strong effects on focal plant survival. Three of the four variables had negative effects on focal plant survival; relative plant size was the only variable with a positive effect (18% increase in the survival odds ratio). The variables with a negative effect on the survival odds ratio, in order of their effect strength in the nearest annulus, were: stem density (a 70% reduction in the survival odds ratio), conspecific density (50% reduction) and species richness (13% reduction). A guild-level analysis revealed considerable heterogeneity among guilds in their responses to these variables. For example, survival of gap species showed a much larger positive response to relative plant size than did survival of shade-tolerant species. Survival of shrub species was positively affected by conspecific density, but canopy tree survival was negatively affected. Conspecific density negatively affected survival of rare species much more strongly than survival of common species. The neighborhood effects of conspecific density disappear within approximately 12–15 m of the focal plant. Although locally strong, the rapid spatial decay of these effects raises unanswered questions about their quantitative contribution to the maintenance of tree diversity on landscape scales in the BCI forest.
298 citations
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TL;DR: It is found that mammal communities from highly fragmented sites have lower species richness, species diversity, functional diversity and higher dominance when compared with sites in partially fragmented and continuous forest.
Abstract: Terrestrial mammals are a key component of tropical forest communities as indicators of ecosystem health and providers of important ecosystem services. However, there is little quantitative information about how they change with local, regional and global threats. In this paper, the first standardized pantropical forest terrestrial mammal community study, we examine several aspects of terrestrial mammal species and community diversity (species richness, species diversity, evenness, dominance, functional diversity and community structure) at seven sites around the globe using a single standardized camera trapping methodology approach. The sites—located in Uganda, Tanzania, Indonesia, Lao PDR, Suriname, Brazil and Costa Rica—are surrounded by different landscape configurations, from continuous forests to highly fragmented forests. We obtained more than 51 000 images and detected 105 species of mammals with a total sampling effort of 12 687 camera trap days. We find that mammal communities from highly fragmented sites have lower species richness, species diversity, functional diversity and higher dominance when compared with sites in partially fragmented and continuous forest. We emphasize the importance of standardized camera trapping approaches for obtaining baselines for monitoring forest mammal communities so as to adequately understand the effect of global, regional and local threats and appropriately inform conservation actions.
297 citations
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National Museum of Natural History1, Smithsonian Conservation Biology Institute2, United States Geological Survey3, University of Aberdeen4, Chinese Academy of Sciences5, United States Department of Agriculture6, National University of Colombia7, University of Hong Kong8, National Taiwan University9, University of Montana10, University of Oxford11, Smithsonian Institution12, Centre national de la recherche scientifique13, Sewanee: The University of the South14, Far Eastern University15, Harvard University16, National Ecological Observatory Network17, Royal Society18, Council of Agriculture19
TL;DR: Because large-diameter trees constitute roughly half of the mature forest biomass worldwide, their dynamics and sensitivities to environmental change represent potentially large controls on global forest carbon cycling.
Abstract: Aim: To examine the contribution of large-diameter trees to biomass, stand structure, and species richness across forest biomes. Location: Global. Time period: Early 21st century. Major taxa studied: Woody plants. Methods: We examined the contribution of large trees to forest density, richness and biomass using a global network of 48 large (from 2 to 60 ha) forest plots representing 5,601,473 stems across 9,298 species and 210 plant families. This contribution was assessed using three metrics: the largest 1% of trees >= 1 cm diameter at breast height (DBH), all trees >= 60 cm DBH, and those rank-ordered largest trees that cumulatively comprise 50% of forest biomass. Results: Averaged across these 48 forest plots, the largest 1% of trees >= 1 cm DBH comprised 50% of aboveground live biomass, with hectare-scale standard deviation of 26%. Trees >= 60 cm DBH comprised 41% of aboveground live tree biomass. The size of the largest trees correlated with total forest biomass (r(2) 5.62, p < .001). Large-diameter trees in high biomass forests represented far fewer species relative to overall forest richness (r(2) = 5.45, p < .001). Forests with more diverse large-diameter tree communities were comprised of smaller trees (r(2) = 5.33, p < .001). Lower large-diameter richness was associated with large-diameter trees being individuals of more common species (r(2) =5.17, p=5.002). The concentration of biomass in the largest 1% of trees declined with increasing absolute latitude (r(2) = 5.46, p < .001), as did forest density (r(2) = 5.31, p < .001). Forest structural complexity increased with increasing absolute latitude (r(2) = 5.26, p < .001). Main conclusions: Because large-diameter trees constitute roughly half of the mature forest biomass worldwide, their dynamics and sensitivities to environmental change represent potentially large controls on global forest carbon cycling. We recommend managing forests for conservation of existing large-diameter trees or those that can soon reach large diameters as a simple way to conserve and potentially enhance ecosystem services.
297 citations
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TL;DR: It is shown that host diversity inhibits transmission of the virulent pathogen Ribeiroia ondatrae and reduces amphibian disease as a result of consistent linkages among species richness, host composition and community competence.
Abstract: A combination of extensive field surveys and realistic experiments involving an amphibian disease system reveals that biodiversity reduces pathogen transmission due to a predictable link between species richness and the ability of communities to support infection. Several lines of evidence have suggested that biodiversity loss in an ecosystem can affect pathogen transmission and host disease, with the pathogens gaining the upper hand. Pathogens tend to infect multiple host species, which can vary in their ability to maintain and transmit infections, and for biodiversity to protect against disease risk, resistant hosts would need to be the last to be added to an ecosystem and the first to be lost. Species-poor communities would then dominated by highly susceptible hosts. This study combines wetland field surveys with experimental mesocosms to show that, in an amphibian community experiencing infection with the parasitic flatworm Ribeiroia ondatrae, the negative correlation between disease and diversity is the result of this 'dilution effect'. These findings highlight the value of biodiversity as a cost-effective approach to minimizing the spread of infectious disease. Accelerating rates of species extinctions and disease emergence underscore the importance of understanding how changes in biodiversity affect disease outcomes1,2,3. Over the past decade, a growing number of studies have reported negative correlations between host biodiversity and disease risk4,5,6,7,8, prompting suggestions that biodiversity conservation could promote human and wildlife health9,10. Yet the generality of the diversity–disease linkage remains conjectural11,12,13, in part because empirical evidence of a relationship between host competence (the ability to maintain and transmit infections) and the order in which communities assemble has proven elusive. Here we integrate high-resolution field data with multi-scale experiments to show that host diversity inhibits transmission of the virulent pathogen Ribeiroia ondatrae and reduces amphibian disease as a result of consistent linkages among species richness, host composition and community competence. Surveys of 345 wetlands indicated that community composition changed nonrandomly with species richness, such that highly competent hosts dominated in species-poor assemblages whereas more resistant species became progressively more common in diverse assemblages. As a result, amphibian species richness strongly moderated pathogen transmission and disease pathology among 24,215 examined hosts, with a 78.4% decline in realized transmission in richer assemblages. Laboratory and mesocosm manipulations revealed an approximately 50% decrease in pathogen transmission and host pathology across a realistic diversity gradient while controlling for host density, helping to establish mechanisms underlying the diversity–disease relationship and their consequences for host fitness. By revealing a consistent link between species richness and community competence, these findings highlight the influence of biodiversity on infection risk and emphasize the benefit of a community-based approach to understanding infectious diseases.
297 citations