Comprehensive Analysis of 11 Species of Euodia (Rutaceae) by Untargeted LC-IT-TOF/MS Metabolomics and In Vitro Functional Methods.

The Euodia genus comprises numerous untapped medicinal plants that warrant thorough evaluation for their potential as valuable natural sources of herbal medicine or food flavorings. In this study, untargeted metabolomics and in vitro functional methods were employed to analyze fruit extracts from 11 significant species of the Euodia genus. An investigation of the distribution of metabolites (quinolone and indole quinazoline alkaloids) in these species indicated that E. rutaecarpa (Euodia rutaecarpa) was the most widely distributed species, followed by E. compacta (Euodia compacta), E. glabrifolia (Euodia glabrifolia), E. austrosinensis (Euodia austrosinensis), and E. fargesii (Euodia fargesii). There have been reports on the close correlation between indole quinazoline alkaloids and their anti-tumor activity, especially in E. rutaecarpa fruits which exhibit effectiveness against various types of cancer, such as SGC-7901, Hela, A549, and other cancer cell lines. Additionally, the E. rutaecarpa plant contains indole quinazoline alkaloids, which possess remarkable antibacterial properties. Our results offer novel insights into the utilization of Euodia resources in the pharmaceutical industry.

Among-individual differences in foraging modulate resource exploitation under perceived predation risk.

Foraging is risky and involves balancing the benefits of resource acquisition with costs of predation. Optimal foraging theory predicts where, when and how long to forage in a given spatiotemporal distribution of risks and resources. However, significant variation in foraging behaviour and resource exploitation remain unexplained. Using single foragers in artificial landscapes of perceived risks and resources with diminishing returns, we aimed to test whether foraging behaviour and resource exploitation are adjusted to risk level, vary with risk during different components of foraging, and (co)vary among individuals. We quantified foraging behaviour and resource exploitation for 21 common voles (Microtus arvalis). By manipulating ground cover, we created simple landscapes of two food patches varying in perceived risk during feeding in a patch and/or while travelling between patches. Foraging of individuals was variable and adjusted to risk level and type. High risk during feeding reduced feeding duration and food consumption more strongly than risk while travelling. Risk during travelling modified the risk effects of feeding for changes between patches and resulting evenness of resource exploitation. Across risk conditions individuals differed consistently in when and how long they exploited resources and exposed themselves to risk. These among-individual differences in foraging behaviour were associated with consistent patterns of resource exploitation. Thus, different strategies in foraging-under-risk ultimately lead to unequal payoffs and might affect lower trophic levels in food webs. Inter-individual differences in foraging behaviour, i.e. foraging personalities, are an integral part of foraging behaviour and need to be fully integrated into optimal foraging theory.

An empirically based simulation of group foraging in the harvesting ant, Messor pergandei.

We present an empirically based group model of foraging interactions in Messor pergandei, the Sonoran desert harvesting ant. M. pergandei colonies send out daily foraging columns consisting of tens of thousands of individual ants. Each day, the directions of the columns may change depending on the resource availability and the neighbor interactions. If neighboring columns meet, ants fight, and subsequent foraging is suppressed. M. pergandei colonies face a general problem which is present in many systems: dynamic spatial partitioning in a constantly changing environment, while simultaneously minimizing negative competitive interactions with multiple neighbors. Our simulation model of a population of column foragers is spatially explicit and includes neighbor interactions. We study how different behavioral strategies influence resource exploitation and space use for different nest distributions and densities. Column foraging in M. pergandei is adapted to the spatial and temporal properties of their natural habitat. Resource and space use is maximized both at the colony and the population level by a model with a behavioral strategy including learning and fast forgetting rates.

Generic catastrophic poverty when selfish investors exploit a degradable common resource.

The productivity of a common pool of resources may degrade when overly exploited by a number of selfish investors, a situation known as the tragedy of the commons. Without regulations, agents optimize the size of their individual investments into the commons by balancing incurring costs with the returns received. The resulting Nash equilibrium involves a self-consistency loop between individual investment decisions and the state of the commons. As a consequence, several non-trivial properties emerge. For N investing actors we prove rigorously that typical payoffs do not scale as 1/N, the expected result for cooperating agents, but as (1/N)2. Payoffs are hence reduced with regard to the functional dependence on N, a situation denoted catastrophic poverty. We show that catastrophic poverty results from a fine-tuned balance between returns and costs. Additionally, a finite number of oligarchs may be present. Oligarchs are characterized by payoffs that are finite and not decreasing when N increases. Our results hold for generic classes of models, including convex and moderately concave cost functions. For strongly concave cost functions the Nash equilibrium undergoes a collective reorganization, being characterized instead by entry barriers and sudden death forced market exits.

Resource exploitation efficiency collapses the home range of an apex predator.

Optimizing energy acquisition and expenditure is a fundamental trade-off for consumers, strikingly reflected in how mobile organisms use space. Several studies have established that home range size decreases as resource density increases, but the balance of costs and benefits associated with exploiting a given resource density is unclear. We evaluate how the ability of consumers to exploit their resources through movement (termed "resource exploitation") interacts with resource density to influence home range size. We then contrast two hypotheses to evaluate how resource exploitation influences home range size across a vast gradient of productivity and density of human-created linear features (roads and seismic lines) that are known to facilitate animal movements. Under the Diffusion Facilitation Hypothesis, linear features are predicted to lead to more diffuse space use and larger home ranges. Under the Exploitation Efficiency Hypothesis, linear features are predicted to increase foraging efficiency, resulting in less space being required to meet energetic demands and therefore smaller home ranges. Using GPS telemetry data from 142 wolves (Canis lupus) distributed over more than 500,000 km2 , we found that wolf home range size was influenced by the interaction between resource density and exploitation efficiency. Home range size decreased as linear feature density increased, supporting the Exploitation Efficiency Hypothesis. However, the effect of linear features on home range size diminished in more productive areas, suggesting that exploitation efficiency is of greater importance when resource density is low. These results suggest that smaller home ranges will occur where both linear feature density and primary productivity are higher, thereby increasing regional wolf density.

The Native Ant Lasius niger Can Limit the Access to Resources of the Invasive Argentine Ant.

Within ant communities, the biotic resistance of native species against invasive ones is expected to be rare, because invasive species are often highly dominant competitors. The invasive Argentine ant (Linepithema humile (Mayr)) often demonstrated numerical dominance against its opponents, increased aggressiveness, and ability to quickly recruit to food. The present study aimed to assess the behavioral mechanisms involved in the interspecific competition between L. humile, facing either an invasive species (Lasius neglectus Van Loon, Boomsma and Andrásfalvy) or a native dominant species (Lasius niger (Linnaeus)). The resource exploitation by the Argentine ant was investigated during one-hour competitive interactions using 10 dead Drosophila flies as prey. When facing La. niger, L. humile exploratory behavior was strongly inhibited, it brought very few prey resources, and killed few opponents. Conversely, La. neglectus had a low impact on L. humile. Contrarily to expectations, the invasive La. neglectus lacked the ability to hinder L. humile resource exploitation, whereas the native La. niger did. These results suggest that La. niger could impact invasive populations of L. humile by interference competition, perhaps better so than some invasive species. While L. humile has become invasive in Southern Europe, the invasion process could be slowed down in the northern latitudes by such native dominant species.

Joint effects of weather and interspecific competition on foraging behavior and survival of a mountain herbivore.

Weather variations have the potential to influence species interactions, although effects on competitive interactions between species are poorly known. Both weather and competition can influence foraging behavior and survival of herbivores during nursing/weaning, a critical period in the herbivore life cycle. We evaluated the joint effects of weather and competition with red deer Cervus elaphus on the foraging behavior of adult female Apennine chamois Rupicapra pyrenaica ornata in summer, and on winter survival of chamois kids. High temperature and low rainfall during the growing season of vegetation had negative effects on bite rate. Effects of weather were greater in forb patches, including cold-adapted, nutritious plants of key importance to chamois, than in graminoid ones. Our results confirm previous indications of a negative effect of competition on bite rate of female chamois and on kid survival. Furthermore, harsh weather conditions and competition with deer had additive, negative roles on foraging behavior and survival of chamois. Growing temperatures are expected to influence distribution, growth, and/or nutritional quality of plants; competition would reduce pasture quality and food availability through resource depletion. Both factors would limit food/energy intake rates during summer, reducing survival of the youngest cohorts in winter. We suggest that interspecific competition can be an important additive factor to the effects of weather changes on behavior and demography.

Virulence evolution of a sterilizing plant virus: Tuning multiplication and resource exploitation.

Virulence evolution may have far-reaching consequences for virus epidemiology and emergence, and virologists have devoted increasing effort to understand the modulators of this process. However, still little is known on the mechanisms and determinants of virulence evolution in sterilizing viruses that, as they prevent host reproduction, may have devastating effects on host populations. Theory predicts that sterilizing parasites, including viruses, would evolve towards lower virulence and absolute host sterilization to optimize the exploitation of host resources and maximize fitness. However, this hypothesis has seldom been analyzed experimentally. We investigated the evolution of virulence of the sterilizing plant virus Turnip mosaic virus (TuMV) in its natural host Arabidopsis thaliana by serial passage experiments. After passaging, we quantified virus accumulation and infectivity, the effect of infection on plant growth and development, and virulence of the ancestral and passaged viral genotypes in A. thaliana. Results indicated that serial passaging increased the proportion of infected plants showing absolute sterility, reduced TuMV virulence, and increased virus multiplication and infectivity. Genomic comparison of the ancestral and passaged TuMV genotypes identified significant mutation clustering in the P1, P3, and 6K2 proteins, suggesting a role of these viral proteins in the observed phenotypic changes. Our results support theoretical predictions on the evolution of virulence of sterilizing parasites and contribute to better understand the phenotypic and genetic changes associated with this process.

Extravagance in the commons: Resource exploitation and the frontiers of ecosystem service depletion in the Amazon estuary.

Estuaries hold major economic potential due their strategic location, close to seas and inland waterways, thereby supporting intense economic activity. The increasing pace of human development in coastal deltas over the past five decades has also strained local resources and produced extensive changes across both social and ecological systems. The Amazon estuary is located in the Amazon Basin, North Brazil, the largest river basin on Earth and also one of the least understood. A considerable segment of the population living in the estuary is directly dependent on the local extraction of natural resources for their livelihood. Areas sparsely inhabited may be exploited with few negative consequences for the environment. However, recent and increasing pressure on ecosystem services is maximised by a combination of factors such as governance, currency exchange rates, exports of beef and forest products. Here we present a cross methodological approach in identifying the political frontiers of forest cover change in the estuary with consequences for ecosystem services loss. We used a combination of data from earth observation satellites, ecosystem service literature, and official government statistics to produce spatially-explicit relationships linking the Green Vegetation Cover to the availability of ecosystems provided by forests in the estuary. Our results show that the continuous changes in land use/cover and in the economic state have contributed significantly to changes in key ecosystem services, such as carbon sequestration, climate regulation, and the availability of timber over the last thirty years.

Competition and the Effect of Spatial Resource Heterogeneity on Evolutionary Diversification.

A model is presented to explore how the form of selection arising from competition for resources is affected by spatial resource heterogeneity. The model consists of a single species occupying two patches connected by migration, where the two patches can differ in the type of resources that they contain. The main goal is to determine the conditions under which competition for resources results in disruptive selection (i.e., selection favoring a polymorphism) since it is this form of selection that will give rise to the evolutionary diversification of resource exploitation strategies. In particular, comparing the conditions giving rise to disruptive selection when the two patches are identical to the conditions when they contain different resources reveals the effect of spatial resource heterogeneity. Results show that when the patches are identical, the conditions giving rise to disruptive selection are identical to those that give rise to character displacement in previous models. When the patches are different, the conditions giving rise to disruptive selection can be either more or less stringent depending upon demographic parameters such as the intrinsic rate of increase and the migration rate. Surprisingly, spatial resource heterogeneity can actually make forms of evolutionary diversification such as character displacement less likely. It is also found that results are dependent on how the resource exploitation strategies and the spatial resource heterogeneity affect the population dynamics. One robust conclusion however, is that spatial resource heterogeneity always has a disruptive effect when the migration rate between patches is low.

Attractiveness and exploitation of decaying herbage by Drosophila in temperate woodland : An experimental analysis.

The Drosophila fauna of a deciduous flood plain forest rich in undergrowth near the river Isar, close to Munich, Germany, was surveyed in summer 1990. Decaying herbage baits (decay artificially induced) were set out to study the exploitation of that resource by Drosophila. Sixteen plant species belonging to several families dominant in the collecting area were tested. All attracted and produced drosophilid flies. Ten Drosophila species utilized decaying plant material as breeding sites; at least eight of the ten are polyphagous. Decaying stalks and leaves of Angelica sylvestris (Apiaceae) were examined in detail. In the case of the most frequent species of Drosophila attracted to A. sylvestris, the number of adults collected did not correlate with the number of flies emerging from the substrate. This was particularly true of D. limbata and D. phalerata. When oviposition and larval development of D. limbata and D. phalerata on A. sylvestris was tested in the laboratory, the number of offspring per female was the same in both species. The difference between these two species of the quinaria group in the exploitation of A. sylvestris in the field is therefore not due to differential suitability of the substrate.

Small-scale resource tracking in a population of a long-lived insect.

How plant-feeding insects distribute themselves and utilize their host plant resources is still poorly understood. Several processes may be involved, and their relative roles may vary with the spatial scale considered. Herein, we investigate small-scale patterns, namely how population density of a gall midge is affected by individual growth form, phenology, and microsite characteristics of its herb host. The long-lived plant individuals vary much with regard to number of shoots, flower abundance, and flowering phenology. This variation is connected to site characteristics, primarily the degree of sun exposure. The monophagous insect galls the flowers of the host plant - an easily defined food resource. It is a poor disperser, but very long-lived; diapausing larvae can stay in the soil for many years. Galls were censused on individual plants during 5 years; from a peak to a low in gall population density. Only a very small fraction of the flowers produced (<0.5%) were galled even in the peak year. Nevertheless, most plant individuals had galls at least 1 year. In a stepwise multiple regression, plant size (number of shoots) was found to be the most important predictor of gall density (galls/flower). However, gall density decreased more than one order of magnitude over the plant size range observed. There was also a weak effect of plant phenology. Early flowering plants had lower gall densities than those starting later. Sun exposure had no direct effect on gall density, but a path analysis revealed indirect effects via the timing of flowering. Gall population change was highly synchronous in different parts of the study area with no significant decrease in synchrony with distance.