Current unprecedented declines in biodiversity reduce the ability of ecological communities to provide many fundamental ecosystem services. Here we evaluate evidence that reduced biodiversity affects ...the transmission of infectious diseases of humans, other animals and plants. In principle, loss of biodiversity could either increase or decrease disease transmission. However, mounting evidence indicates that biodiversity loss frequently increases disease transmission. In contrast, areas of naturally high biodiversity may serve as a source pool for new pathogens. Overall, despite many remaining questions, current evidence indicates that preserving intact ecosystems and their endemic biodiversity should generally reduce the prevalence of infectious diseases.
Predator-prey interactions are ubiquitous and powerful forces that structure ecological communities.1–3 Habitat complexity has been shown to be particularly important in regulating the strength of ...predator-prey interactions.4–6 While it is well established that changes in habitat structure can alter the efficacy of predatory and anti-predatory behaviors,7–9 little is known about the consequences of engineering activity by prey species who modify the external environment to reduce their own predation risk. Using field surveys and manipulative experiments, we evaluated how habitat modification by Brandt’s voles (Lasiopodomys brandtii) influences predation risk from a principal avian predator (shrike; Lanius spp.) in a steppe grassland, located in Inner Mongolia, China. We found that voles actively modify habitat structure by cutting down a large, unpalatable bunchgrass species (Achnatherum splendens) in the presence of shrikes, a behavior that disappeared when these avian predators were excluded experimentally. The damage activities of these voless dramatically decreased the volume of unpalatable grasses, which in turn reduced visitations by shrikes and thus mortality rates. Our study shows that herbivorous prey that act as ecosystem engineers can directly reduce their own predation risk by modifying habitat structure. Given the ubiquity of predation risks faced by consumers, and the likely ability of many consumers to alter the habitat structure in which they live, the interplay between predation risk and ecosystem engineering may be an important but unappreciated mechanism at play in natural communities.
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•Voles modified habitat structure by destroying a large, unpalatable bunchgrass•Damage activities of voles decreased the plant volume of the bunchgrasses•Vole damage activities were enhanced at the presence of the predatory birds•Habitat modifications by voles reduced predation risk and increased vole survival
Zhong et al. show that by damaging a large, unpalatable bunch grass, Brandt’s voles in steppe grasslands in China can reduce the predation risk from avian predators (Lanius spp.) probably due to improved vision. Habitat modifications by voles can reduce the visiting frequency of avian predators and thus increase the survival of voles.
Explaining the maintenance of tropical forest diversity under the countervailing forces of drift and competition poses a major challenge to ecological theory. Janzen–Connell effects, in which ...host-specific natural enemies restrict the recruitment of juveniles near conspecific adults, provide a potential mechanism. Janzen–Connell is strongly supported empirically, but existing theory does not address the stable coexistence of hundreds of species. Here we use high-performance computing and analytical models to demonstrate that tropical forest diversity can be maintained nearly indefinitely in a prolonged state of transient dynamics due to distance-responsive natural enemies. Further, we show that Janzen–Connell effects lead to community regulation of diversity by imposing a diversity-dependent cost to commonness and benefit to rarity. The resulting species–area and rank–abundance relationships are consistent with empirical results. Diversity maintenance over long time spans does not require dispersal from an external metacommunity, speciation, or resource niche partitioning, only a small zone around conspecific adults in which saplings fail to recruit. We conclude that the Janzen–Connell mechanism can explain the maintenance of tropical tree diversity while not precluding the operation of other niche-based mechanisms such as resource partitioning.
Thyroid eye disease (TED) results in varying degrees of proptosis and diplopia negatively affecting quality of life (QoL), producing possibly substantial visual changes, disfigurement, and ...disability.
To determine the association of varying TED severities with QoL in a non-TED population by assessing health state utility scores.
This qualitative study, conducted from April 20, 2020, to April 29, 2021, assessed health states for active, moderate-severe TED, and values were elicited using time trade-off methods. Six health states of varying severity were determined from 2 placebo-controlled clinical trials (171 patients with TED and clinical activity score ≥4, ±diplopia/proptosis) and refined using interviews with US patients with TED (n = 6). Each health state description was validated by interviews with additional TED patient advocates (n = 3) and physician experts (n = 3). Health state descriptions and a QOL questionnaire were piloted and administered to a general population. Visual analog scales (VASs) were also administered to detect concurrence of the findings.
TED health state utility scores and whether they differ from one another were assessed using Shapiro-Wilk, Kruskal-Wallis, pairwise Wilcoxon rank sum, and paired t tests.
A total of 111 participants completed time trade-off interviews. The mean (SD) utility value was 0.44 (0.34). The lowest (worse) mean utility value was observed in the most severe disease state (constant diplopia/large proptosis) with 0.30 (95% CI, 0.24-0.36), followed by constant diplopia/small proptosis (0.34; 95% CI, 0.29-0.40), intermittent or inconstant diplopia/large proptosis (0.43; 95% CI, 0.36-0.49), no diplopia/large proptosis (0.46; 95% CI, 0.40-0.52), and intermittent or inconstant diplopia/small proptosis (0.52; 95% CI, 0.45-0.58). The highest (best) mean value, 0.60 (95% CI, 0.54-0.67), was observed for the least severe disease state (no diplopia/small proptosis).
These findings suggest that patients with active, moderate-severe TED may have substantial disutility, with increasing severity of proptosis/diplopia more likely to have detrimental associations with QoL. These health state scores may provide a baseline for determining QoL improvement in these TED health states (utility gains) treated with new therapies.
Habitat loss and fragmentation has long been considered the primary cause for biodiversity loss and ecosystem degradation worldwide, and is a key research topic in landscape ecology.
Numerous cancers have been linked to microorganisms. Given that colorectal cancer is a leading cause of cancer deaths and the colon is continuously exposed to a high diversity of microbes, the ...relationship between gut mucosal microbiome and colorectal cancer needs to be explored. Metagenomic studies have shown an association between Fusobacterium species and colorectal carcinoma. Here, we have extended these studies with deeper sequencing of a much larger number (n = 130) of colorectal carcinoma and matched normal control tissues. We analyzed these data using co-occurrence networks in order to identify microbe-microbe and host-microbe associations specific to tumors.
We confirmed tumor over-representation of Fusobacterium species and observed significant co-occurrence within individual tumors of Fusobacterium, Leptotrichia and Campylobacter species. This polymicrobial signature was associated with over-expression of numerous host genes, including the gene encoding the pro-inflammatory chemokine Interleukin-8. The tumor-associated bacteria we have identified are all Gram-negative anaerobes, recognized previously as constituents of the oral microbiome, which are capable of causing infection. We isolated a novel strain of Campylobacter showae from a colorectal tumor specimen. This strain is substantially diverged from a previously sequenced oral Campylobacter showae isolate, carries potential virulence genes, and aggregates with a previously isolated tumor strain of Fusobacterium nucleatum.
A polymicrobial signature of Gram-negative anaerobic bacteria is associated with colorectal carcinoma tissue.
The world is changing at a rapid rate, threatening extinction for a large part of the world's biota. One potential response to those altered conditions is to evolve so as to be able to persist in ...place. Such evolution includes not just traits themselves, but also the phenotypic plasticity of those traits. We used individual‐based simulations to explore the potential of an evolving phenotypic plasticity to increase the probability of persistence in the response to either a step change or continual, directional change in the environment accompanied by within‐generation random environmental fluctuations. Populations could evolve by altering both their nonplastic and plastic genetic components. We found that phenotypic plasticity enhanced survival and adaptation if that plasticity was not costly. If plasticity was costly, for it to be beneficial the phenotypic magnitude of plasticity had to be great enough in the initial generations to overcome those costs. These results were not sensitive to either the magnitude of the within‐generation correlation between the environment of development and the environment of selection or the magnitude of the environmental fluctuations, except for very small phenotypic magnitudes of plasticity. So, phenotypic plasticity has the potential to enhance survival; however, more data are needed on the ubiquity of trait plasticity, the extent of costs of plasticity, and the rate of mutational input of genetic variation for plasticity.
Environmental fluctuations are pervasive in nature, but the influence of non-directional temporal variation on range limits has received scant attention. We synthesize insights from the literature ...and use simple models to make conceptual points about the potentially wide range of ecological and evolutionary effects of temporal variation on range limits. Because organisms respond nonlinearly to environmental conditions, temporal variation can directionally alter long-term growth rates, either to shrink or to expand ranges. We illustrate this diversity of outcomes with a model of competition along a mortality gradient. Temporal variation can permit transitions between alternative states, potentially facilitating range expansion. We show this for variation in dispersal, using simple source-sink population models (with strong Allee effects, or with gene flow hampering local adaptation). Temporal variation enhances extinction risk owing to demographic stochasticity, rare events, and loss of genetic variation, all tending to shrink ranges. However, specific adaptations to exploit variation (including dispersal) may permit larger ranges than in similar but constant environments. Grappling with temporal variation is essential both to understand eco-evolutionary dynamics at range limits and to guide conservation and management strategies. This article is part of the theme issue 'Species' ranges in the face of changing environments (Part II)'.
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