Miranda M. Hart

Bio: Miranda M. Hart is an academic researcher from University of British Columbia. The author has contributed to research in topics: Microbial inoculant & Soil biology. The author has an hindex of 44, co-authored 117 publications receiving 8195 citations. Previous affiliations of Miranda M. Hart include University of Guelph.

Reciprocal Rewards Stabilize Cooperation in the Mycorrhizal Symbiosis

Abstract: Plants and their arbuscular mycorrhizal fungal symbionts interact in complex underground networks involving multiple partners. This increases the potential for exploitation and defection by individuals, raising the question of how partners maintain a fair, two-way transfer of resources. We manipulated cooperation in plants and fungal partners to show that plants can detect, discriminate, and reward the best fungal partners with more carbohydrates. In turn, their fungal partners enforce cooperation by increasing nutrient transfer only to those roots providing more carbohydrates. On the basis of these observations we conclude that, unlike many other mutualisms, the symbiont cannot be "enslaved." Rather, the mutualism is evolutionarily stable because control is bidirectional, and partners offering the best rate of exchange are rewarded.

Taxonomic basis for variation in the colonization strategy of arbuscular mycorrhizal fungi

Abstract: Summary • Arbuscular mycorrhizal fungi (AMF) are important components of terrestrial communities but the basic ecology of individual AMF, including their colonization strategy, remains unclear. The colonizing behaviours of 21 AMF isolates from three families (Acaulosporaceae, Gigasporaceae and Glomaceae) were compared to test for a relationship between AMF taxonomy and colonization strategy. • Both the rate and extent of colonization were considered by measuring percentage root colonization, root fungal biomass, soil hyphal length and soil fungal biomass over 12 wk. • Most Glomaceae isolates colonized roots before Acaulosporaceae and Gigasporaceae isolates. The fastest colonizers were also often the most extensive. Taxonomic differences were apparent in the amount and proportion of fungal biomass found in roots vs in soil. Glomaceae isolates had high root colonization but low soil colonization, Gigasporaceae isolates showed the opposite trend whereas Acaulosporaceae isolates had low root and soil colonization. These results were similar for four different host plants. • The results indicate that the colonizing strategies of AM fungi differ considerably and that this variation is taxonomically based at the family level. Arbuscular mycorrhizal fungal taxonomy therefore has a functional basis.

Plant-soil feedbacks and mycorrhizal type influence temperate forest population dynamics

Abstract: Feedback with soil biota is an important determinant of terrestrial plant diversity. However, the factors regulating plant-soil feedback, which varies from positive to negative among plant species, remain uncertain. In a large-scale study involving 55 species and 550 populations of North American trees, the type of mycorrhizal association explained much of the variation in plant-soil feedbacks. In soil collected beneath conspecifics, arbuscular mycorrhizal trees experienced negative feedback, whereas ectomycorrhizal trees displayed positive feedback. Additionally, arbuscular mycorrhizal trees exhibited strong conspecific inhibition at multiple spatial scales, whereas ectomycorrhizal trees exhibited conspecific facilitation locally and less severe conspecific inhibition regionally. These results suggest that mycorrhizal type, through effects on plant-soil feedbacks, could be an important contributor to population regulation and community structure in temperate forests.

The influence of arbuscular mycorrhizae on the relationship between plant diversity and productivity

Abstract: Ecological theory predicts a positive and asymptotic relationship between plant diversity and ecosystem productivity based on the ability of more diverse plant communities to use limiting resources more fully. This is supported by recent empirical evidence. Additionally, in natural ecosystems, plant productivity is often a function of the presence and composition of mycorrhizal associations. Yet, the effect of mycorrhizal fungi on the relationship between plant diversity and productivity has not been investigated. We predict that in the presence of AMF, productivity will saturate at lower levels of species richness because AMF increase the ability of plant species to utilize nutrient resources. In this study we manipulated old-field plant species richness in the presence and absence of two species of AMF. We found that in the absence of AMF, the relationship between plant species richness and productivity is positive and linear. However, in the presence of AMF, the relationship is positive but asymptotic, even though the maximum plant biomass was significantly different between the two AMF treatments. This is consistent with the hypothesis that AMF increase the redundancy of plant species in the productivity of plant communities, and indicates that these symbionts must be considered in future investigations of plant biodiversity and ecosystem function.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

Effects of biodiversity on ecosystem functioning: a consensus of current knowledge

Abstract: Humans are altering the composition of biological communities through a variety of activities that increase rates of species invasions and species extinctions, at all scales, from local to global. These changes in components of the Earth's biodiversity cause concern for ethical and aesthetic reasons, but they also have a strong potential to alter ecosystem properties and the goods and services they provide to humanity. Ecological experiments, observations, and theoretical developments show that ecosystem properties depend greatly on biodiversity in terms of the functional characteristics of organisms present in the ecosystem and the distribution and abundance of those organisms over space and time. Species effects act in concert with the effects of climate, resource availability, and disturbance regimes in influencing ecosystem properties. Human activities can modify all of the above factors; here we focus on modification of these biotic controls. The scientific community has come to a broad consensus on many aspects of the re- lationship between biodiversity and ecosystem functioning, including many points relevant to management of ecosystems. Further progress will require integration of knowledge about biotic and abiotic controls on ecosystem properties, how ecological communities are struc- tured, and the forces driving species extinctions and invasions. To strengthen links to policy and management, we also need to integrate our ecological knowledge with understanding of the social and economic constraints of potential management practices. Understanding this complexity, while taking strong steps to minimize current losses of species, is necessary for responsible management of Earth's ecosystems and the diverse biota they contain.

Modern Applied Statistics With S

Abstract: Thank you very much for downloading modern applied statistics with s. As you may know, people have search hundreds times for their favorite readings like this modern applied statistics with s, but end up in harmful downloads. Rather than reading a good book with a cup of coffee in the afternoon, instead they cope with some harmful virus inside their laptop. modern applied statistics with s is available in our digital library an online access to it is set as public so you can download it instantly. Our digital library saves in multiple countries, allowing you to get the most less latency time to download any of our books like this one. Kindly say, the modern applied statistics with s is universally compatible with any devices to read.

The Role of Root Exudates in Rhizosphere Interactions with Plants and Other Organisms

Abstract: The rhizosphere encompasses the millimeters of soil surrounding a plant root where complex biological and ecological processes occur. This review describes recent advances in elucidating the role of root exudates in interactions between plant roots and other plants, microbes, and nematodes present in the rhizosphere. Evidence indicating that root exudates may take part in the signaling events that initiate the execution of these interactions is also presented. Various positive and negative plant-plant and plant-microbe interactions are highlighted and described from the molecular to the ecosystem scale. Furthermore, methodologies to address these interactions under laboratory conditions are presented.