Modification of coevolved insect–plant interactions by an exotic plant pathogen

New Perspectives is intended to allow the communication of comments, viewpoints, and speculative interpretation of issues in ecology pertinent to entomology. Comments, viewpoints, or suggestions arising from published papers intended to fuel discussion and debate are also welcome. Contributions should be as concise as possible, normally not exceeding two thousand words. Formal research reports will not be acceptable, but summarised novel data, suitably supported by statistics, may be allowed.     

Mixed infections and insect–pathogen interactions

Abstract Most studies of insect–pathogen interactions consider the direct interaction between one disease agent and one species of host. However, given that hosts are subject to challenge from many pathogen/parasite species, mixed infections are probably common. In this study, using the desert locust and two species of fungal entomopathogen, we show how mixed infection with a largely avirulent pathogen can alter the virulence and reproduction of a second, highly virulent pathogen. We find that two strains of the avirulent pathogen vary in their interaction with the virulent pathogen, depending on the order of infection and environmental conditions. We propose that avirulent pathogens, which have largely been overlooked to date, could play a significant role in host–pathogen dynamics, with implications for biological control and evolution of virulence.     

Nitrogen fertilization affects interactions between the components of an insect–fungus–plant tripartite system

1. The chrysomelid beetle, Gastrophysa viridula and the rust fungus, Uromyces rumicis both occur on leaves of Rumex obtusifolius growing in a wide range of soil nutrient conditions. We investigated the effect of fertilizing plants with eight nitrate and four ammonium concentrations on the components of this tripartite interaction in a controlled environment.
2. Leaf weight, area and total plant weight increased as both nitrate and ammonium concentrations increased up to 15mmol l^–1. Between 15 and 50mmol l^–1 added nitrate, leaf and total plant weight decreased. Total plant weight was unaffected by increasing ammonium fertilization from 15 to 25mmol l^–1.
3. The density and percentage of U. rumicis pustules sporulating 8 days after infection decreased with increasing nitrate but were unaffected by increasing the concentration of ammonium fertilization.
4. Leaf area consumed and number of eggs laid by G. viridula decreased as the concentration of nitrate fertilization increased. Increasing the concentration of ammonium decreased leaf area eaten.
5. First instar mortality of G. viridula was increased and gregariousness and adult fecundity was decreased additively by the combination of U. rumicis infection and decreasing the nitrate concentration fed to plants from 10 to 1mmol l^–1.     

Nutritional ecology beyond the individual: a conceptual framework for integrating nutrition and social interactions

Over recent years, modelling approaches from nutritional ecology (known as Nutritional Geometry) have been increasingly used to describe how animals and some other organisms select foods and eat them in appropriate amounts in order to maintain a balanced nutritional state maximising fitness. These nutritional strategies profoundly affect the physiology, behaviour and performance of individuals, which in turn impact their social interactions within groups and societies. Here, we present a conceptual framework to study the role of nutrition as a major ecological factor influencing the development and maintenance of social life. We first illustrate some of the mechanisms by which nutritional differences among individuals mediate social interactions in a broad range of species and ecological contexts. We then explain how studying individual‐ and collective‐level nutrition in a common conceptual framework derived from Nutritional Geometry can bring new fundamental insights into the mechanisms and evolution of social interactions, using a combination of simulation models and manipulative experiments.     

Plant polyploidy and the evolutionary ecology of plant/animal interactions

Until recently almost nothing was known about the effects of plant polyploidy on interactions with herbivores and pollinators. Studies of the saxifrage Heuchera grossulariifolia throughout its geographical range in the US northern Rockies have shown that autopolyploidy has probably arisen multiple times within this species since the end of the Pleistocene. Tetraploids from those different origins experience higher levels of attack by the moth Greya politella (Prodoxidae) than sympatric or parapatric diploids. In addition, within one intensively studied region, the plants are also attacked by two other lepidopteran species: G. piperella , which preferentially attack diploids, and Eupithecia misturata (Geometridae), which preferentially attacks tetraploids. Sympatric diploid and tetraploid plants also differ in the overall suites of pollinators they attract. Hence, the evolution of polyploid populations has the potential to change significantly the evolutionary ecology of interactions with herbivores and pollinators. Because a large number of plant lineages include polyploid species, the evolution of plant polyploidy may have had major effects on the interaction structure of terrestrial communities.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 82 , 511–519.     

Effect of soil-applied complex fertiliser on an insect–host plant relationship: Liriomyza trifolii on Solanum tuberosum

Insects respond to very low levels of nutritional and non‐nutritional compounds in plants, which influence their acceptance and colonisation of the plant or plant part, and thereby their growth and development. Plant nutrient levels can vary within and between plants, and are influenced by external factors such as fertiliser treatments, irrigation regime, and light. Soil levels of nitrogen, potassium, phosphorus, calcium, and magnesium can have significant effects on the amounts of these nutrients in the plant, and thereby on pest infestation. This study reports on the influence of seven different NPK fertiliser rates in potted potato (Solanum tuberosum cv. Mondial) plants on the nitrogen, phosphorus, potassium, calcium, and magnesium levels in the leaves, and the concomitant influence on infestation by, and development of, the serpentine leafminer, Liriomyza trifolii Burgess (Diptera: Agromyzidae). Results showed that increases in nitrogen in the potato leaves increased larval and pupal survival, and pupal and adult body weight and length. Potassium and phosphorus, on the other hand, decreased the host suitability of potato plants to L. trifolii, and were detrimental to the pest.     

Chloroplast genome phylogenetics: why we need independent approaches to plant molecular evolution

The traditional approach to plant molecular phylogenetics involves amplifying, sequencing and analyzing one or a few genes from many species and is conducive to broad taxon sampling. An independent approach involves chloroplast genome sequencing, providing much larger amounts of data per taxon but for a smaller number of species. In principle, the two strategies can inform each other but in practice their results sometimes conflict for reasons that are currently debated. An Opinion article published in the October 2004 issue of Trends in Plant Science cautioned against the pursuit of genome-based phylogenies. Here, we provide a different perspective on issues at the heart of the current debate and defend the use of chloroplast genome phylogenetics for crucial species because it provides an independent test of hypotheses generated by the traditional approach.     

Review: Nutritional ecology of heavy metals

The aim of this review is to focus the attention on the nutrition ecology of the heavy metals and on the major criticisms related to the heavy metals content in animal feeds, manure, soil and animal-origin products. Heavy metals are metallic elements that have a high density that have progressively accumulated in the food chain with negative effects for human health. Some metals are essential (Fe, I, Co, Zn, Cu, Mn, Mo, Se) to maintain various physiological functions and are usually added as nutritional additives in animal feed. Other metals (As, Cd, F, Pb, Hg) have no established biological functions and are considered as contaminants/undesirable substances. The European Union adopted several measures in order to control their presence in the environment, as a result of human activities such as: farming, industry or food processing and storage contamination. The control of the animal input could be an effective strategy to reduce human health risks related to the consumption of animal-origin products and the environmental pollution by manure. Different management of raw materials and feed, animal species as well as different legal limits can influence the spread of heavy metals. To set up effective strategies against heavy metals the complex interrelationships in rural processes, the widely variability of farming practices, the soil and climatic conditions must be considered. Innovative and sustainable approaches have discussed for the heavy metal nutrition ecology to control the environmental pollution from livestock-related activities.     

Evolutionary ecology of plant-microbe interactions: soil microbial structure alters selection on plant traits

? Below-ground microbial communities influence plant diversity, plant productivity, and plant community composition. Given these strong ecological effects, are interactions with below-ground microbes also important for understanding natural selection on plant traits? ? Here, we manipulated below-ground microbial communities and the soil moisture environment on replicated populations of Brassica rapa to examine how microbial community structure influences selection on plant traits and mediates plant responses to abiotic environmental stress. ? In soils with experimentally simplified microbial communities, plants were smaller, had reduced chlorophyll content, produced fewer flowers, and were less fecund when compared with plant populations grown in association with more complex soil microbial communities. Selection on plant growth and phenological traits also was stronger when plants were grown in simplified, less diverse soil microbial communities, and these effects typically were consistent across soil moisture treatments. ? Our results suggest that microbial community structure affects patterns of natural selection on plant traits. Thus, the below-ground microbial community can influence evolutionary processes, just as recent studies have demonstrated that microbial diversity can influence plant community and ecosystem processes.     

Marine eutrophication and benthos: the need for new approaches and concepts

In this review, using examples drawn from field observations or experimental studies, our goals are (i) to briefly summarize the major changes, in terms of species composition and functional structure, occurring in phyto and zoobenthic communities in relation to nutrient enrichment of the ecosystems; particular interest is given to the major abiotic and biotic factors occurring during the eutrophication process, (ii) to discuss the direct and indirect influences of benthic organisms on eutrophication and whether the latter can be controlled or favoured by benthos; most benthic species play a major role in the process of benthic nutrient regeneration, affecting primary production by supplying nutrients directly and enhancing rates of pelagic recycling; experimental studies have shown that the impact of benthic fauna on benthic–pelagic coupling and nutrient release is considerable. Thus, once the eutrophication process is engaged—that is, high organic matter sedimentation—it may be indirectly favoured by benthic organisms; benthos should always be considered in eutrophication studies, (iii) to evaluate the limits of our observations and data, highlighting the strong need for integrated studies leading to new concepts. Coastal ecosystems and benthic communities are potentially impacted by numerous human activities (demersal fishing, toxic contaminants, aquaculture…); in order to design strategies of ecosystem restoration or rehabilitation, we have to better understand coastal eutrophication and develop tools for quantifying the impacts; in order to achieve this goal, some possible directions proposed are: integrated studies leading to new concepts, model development based on these concepts and finally comparison of various ecosystems on a global scale.     

Seed mass and light-demand: the need to control for soil–type and plant stature

Studies on whether or not species which need more light for establishment have smaller seeds should be made between plants of similar mature height living in the same soil and macroclimate. Salisbury's classic comparisons confused differences in light-requirement during establishment with differences in mature height and in the supply of soil resources.     

Molecular approaches for AM fungal community ecology: A primer

Molecular techniques are no longer optional for ecologists interested in arbuscular mycorrhizal (AM) communities. Understanding the role of these soil fungi in natural systems requires knowledge of their abundance and identity but this is impossible to achieve without a molecular approach. Adapting molecular tools to AM fungi can be challenging because of the unique biology of the fungi. Moreover, many recruits in the field of mycorrhizal ecology have little or no experience with molecular biology. Here, we outline a conceptual framework for designing robust ecological experiments with AM fungi using molecular approaches.     

Conservation planning beyond giant pandas: the need for an innovative telecoupling framework

正Meeting human needs while sustaining ecosystems and the benefits they provide is a global challenge.A major barrier to achieve sustainable development goals is the lack of sufficient knowledge on the complex relationships between humans and nature(Loucks et al.,2001;Liu et al.,2007).Different parts of the world have never been as closely connected through all means of flows(e.g.information,labor,     

Plant hormone interactions: innovative targets for crop breeding and management

Here we highlight how both the root and shoot environment impact on whole plant hormone balance, particularly under stresses such as soil drying, and relate hormone ratios and relative abundances to processes influencing plant performance and yield under both mild and more severe stress. We discuss evidence (i) that abscisic acid (ABA) and ethylene act antagonistically on grain-filling rate amongst other yield-impacting processes; (ii) that ABA's effectiveness as an agent of stomatal closure can be modulated by coincident ethylene or cytokinin accumulation; and (iii) that enhanced cytokinin production can increase growth and yield by improving foliar stay-green indices under stress, and by improving processes that impact grain-filling and number, and that this can be the result of altered relative abundances of cytokinin and ABA (and other hormones). We describe evidence and novel processes whereby these phenomena are/could be amenable to manipulation through genetic and management routes, such that plant performance and yield can be improved. We explore the possibility that a range of ABA-ethylene and ABA-cytokinin relative abundances could represent targets for breeding/managing for yield resilience under a spectrum of stress levels between severe and mild, and could circumvent some of the pitfalls so far encountered in the massive research effort towards breeding for increases in the complex trait of yield.     

Collaboration in scientific research: a critical need for freshwater ecology

1. Collaboration means actively working together to achieve things which could not be done alone. This article attempts to provide an overall, unified, guiding framework for collaboration in freshwater ecology by discussing aspects of collaboration at individual and organizational levels, and addressing international linkages.
2. The essential elements of collaboration are communication and trust, and effective project management. Barriers to effective collaboration include competition, organizational cultures and organizational instabilities.
3. The success of collaboration can be measured by tangible benefits such as increased numbers of peer-reviewed publications, the production of working models and a number of intangible benefits.
4. Interactions between individuals lie at the heart of an effective collaboration; organizational arrangements should facilitate this interaction. Some governments are encouraging collaboration to increase cost efficiency and allocate accountability. This trend should continue on an international level.
5. Collaboration is a key to future research in freshwater ecology.