Resource rivalry between brood mates of a facultative gregarious parasitoid Dendrocerus carpenteri

Larvae of Dendrocerus carpenteri Curtis (Hymenoptera: Megaspilidae) develop as solitary ectoparasitoids on the prepupae and pupae of primary aphid parasitoids inside the aphid mummy. First instars are aggressive and kill potential competitors; however, facultative gregarious development of two, and occasionally three, larvae may occur under superparasitism. To test the hypothesis that gregarious larvae share host resources equally, adult dry mass is compared between three brood types: ‘double’ mummies containing (i) two males; (ii) two females; or (iii) one male plus one female, respectively. Resource rivalry varies with the sex of the competing larvae. Surviving adults differ significantly in size if both wasps are of the same sex, male or female. A minimum amount of resources is required for a larva to be viable; this threshold does not differ between sexes and is independent of the sex of a competing larva. The outcome of competition between a male larva and a female larva varies with the amount of the available resources, with neither sex being inherently dominant over the other. Females are eight times more likely to be larger than a male competitor if the amount of host resources is ≥0.116 mg, whereas males can win over a female competitor in terms of adult size if the available resources are <0.116 mg. It is suggested that rivalry between larvae for limiting host resources constrains the transition from solitary to gregarious development and should be considered in studies of parasitoid life‐history evolution.     

On the relationship between a resource based measure of geodiversity and broad scale biodiversity patterns

Geodiversity, (diversity of the geosphere) incorporates many of the environmental patterns and processes that are considered drivers of biodiversity. Components of geodiversity (climate, topography, geology and hydrology) can be considered in terms of their resource giving potential, where resources are taken as energy, water, space and nutrients. The total amount of these resources, along with their spatial and temporal variation, is herein proposed as a compound index of geodiversity that has the potential to model broad scale biodiversity patterns. This paper outlines potential datasets that could be used to represent geodiversity, and then reviews the theoretical links between each element of the proposed compound index of geodiversity (overall resource availability, temporal variation and spatial variation in those resources) and broad-scale patterns of biodiversity. Support for the influence of each of the elements of geodiversity on overall biodiversity patterns was found in the literature, although the majority of relevant research focuses on resource availability, particularly available energy. The links between temporal and spatial variation in resources and biodiversity have been less thoroughly investigated in the literature. For the most part, it was reported that overall resource availability, temporal variation and spatial variation in those resources do not act in isolation in terms of controlling biodiversity. Overall there are sufficient datasets to calculate the proposed compound index of geodiversity, and evidence in the literature for links between the geographical distribution of biodiversity and each of the elements of the compound index defined. Since data for measuring geodiversity is more spatially consistent and widely available (thanks to satellite remote sensing) geodiversity has potential as a conservation planning tool, especially where biological data are not available or sparsely distributed.     

Mahogany as a genetic resource

The development of a strategy for the sustainable management and conservation of mahogany is an urgent priority. Such a strategy should be based upon clear information about the extent of genetic differentiation within and between populations, and on an understanding of the processes maintaining this variation. At present, such information is very limited for mahogany. Preliminary data are presented from two genetic tests of Swietenia macrophylla King (Meliaceae), indicating significant differences between provenances and half-sib progenies in both growth and form characteristics. In addition, the use of molecular markers for the characterization of genetic resources of mahogany is discussed. On the basis of the results available, the impacts of deforestation and logging activities on genetic resources are evaluated. Although both deforestation and selective logging may deplete genetic resources, no quantitative information on the extent of such depletion in mahogany is currently available. Additional research is therefore required before clear guidelines can be provided for the sustainable management of mahogany.     

江苏省南通市农村生物质能资源潜力估算及地区分布

摸清农村生物质能资源潜力对南通市农村能源建设具有重大意义。以南通市为实证区域,利用草谷比、收集系数、折标系数、副产物系数并根据南通市可能源化利用的实际情况,从县域层面较为全面地估算了包括秸秆、农业加工副产品、人畜粪便等可能源化利用的生物质能资源总量。估算结果表明:(1)南通市每年提供的可能源化利用秸秆资源量约为105万t标煤,以稻秸、麦秸和油菜秸为主;农业加工副产品资源量约为20万t标煤,以稻壳、玉米芯、棉籽等为主;人禽粪便资源量为108万t标煤,以猪粪和禽粪为主,约占到资源总量的1/2。(2)南通市拥有较为丰富的生物质能资源,其中可能源化利用的生物质资源总量为年均233万t标煤,并且其资源总量呈增长趋势;预计在短期内其资源总量将增加到240万t标煤。(3)南通市生物质资源的地区分布极不均匀,从生物质能资源总量、单位国土面积生物质能资源量、人均生物质能资源量看,海安县、如东县和如皋市等经济比较薄弱的县市均具有明显优势,其中海安县在南通各县市中凭借其规模渐增的养殖业、种植业产生的生物质资源而遥遥领先;此外如东县的秸秆资源也具有重要地位。(4)南通市生物质资源的季节分布也不均匀,这种季节分布不均主要是由秸秆资源引起的,因为秸秆资源主要集中在秋季和春季,约占到60%—75%;而夏季和冬季则很少。这就给农村能源的持续开发利用带来一定难度。建议:需要针对各县市的生物质能开发利用的实际情况因地制宜合理开发生物质资源,科学布局避免恶性竞争,并及时做好秸秆资源的收集、转运与储存工作以避免资源的浪费和严重的环境污染,从而促进南通农村能源建设的健康发展。     

Effects of resource availability on the trade-off between seed and vegetative reproduction

Aims To explore whether the trade-off between seed and vegetative reproductive modes is flexible in environments with different amounts of available resources to maintain optimal behaviors.Methods A transition matrix model was established to determine the optimal trade-off between seed and vegetative reproduction in resources–variable habitats.Important findings The model predicts that plants allocate more resources to seed reproduction when available resources are scarce. With increasing resources, more vegetative propagules are produced. However, if resources keep increasing to a harmful level, plants would switch to seeds again.     

The chromosome 4 workshop report

In the concluding session the compilation and availability of available resources on chromosome 4 were discussed. A listing of these resources is available from Jeff Murray at the University of Iowa for anyone with an interest in human chromosome 4. Rick Myers stressed the commitment of the UCSF Genome Center to make resources available to the mapping community as a whole as soon as they have been identified and characterized. There was general agreement that such a philosophy will facilitate the rapid generation and integration of the maps from several groups currently working in this area. The chromosome 4 committee for the Human Gene Mapping workshops was scheduled to meet in August of 1991, and a second chromosome 4-specific meeting is to be held in Leiden on June 13 and 14, 1992 (contact Gert-Jan van Ommen for information). Future venues for the meeting are planned to alternate between countries with groups participating in mapping projects on this chromosome and initially will focus particularly on groups with chromosome wide mapping interests such as EUROGEM and the Human Genome Center.     

The Economics of Epidemic Diseases

Epidemic, infectious, diseases affect a large number of individuals across developing as well as developed countries. With reference to some very simple diffusion models, in this paper we consider how available economic resources could be optimally allocated by health authorities to mitigate, possibly eradicate, the disease. Optimality was defined as the minimization of the long run number of infected people. The main goal of the work has been to introduce a methodology for deciding if it would be best to concentrate resources to prevent contact between individuals and with an external source, or to develop a new treatment for curing the disease, or both. The analysis suggests that this depends on the cost functions, that is the available technology, for controlling the relevant parameters underlying the epidemics as well as on the available financial resources. In the case of the recent Ebola outbreak, the suggestions of the model have been consistent with the policies adopted.     

Refining the conditions for sympatric ecological speciation

Can speciation occur in a single population when different types of resources are available, in the absence of any geographical isolation, or any spatial or temporal variation in selection? The controversial topics of sympatric speciation and ecological speciation have already stimulated many theoretical studies, most of them agreeing on the fact that mechanisms generating disruptive selection, some level of assortment, and enough heterogeneity in the available resources, are critical for sympatric speciation to occur. Few studies, however, have combined the three factors and investigated their interactions. In this article, I analytically derive conditions for sympatric speciation in a general model where the distribution of resources can be uni‐ or bimodal, and where a parameter controls the range of resources that an individual can exploit. This approach bridges the gap between models of a unimodal continuum of resources and Levene‐type models with discrete resources. I then test these conditions against simulation results from a recently published article (Thibert‐Plante & Hendry, 2011, J. Evol. Biol. 24 : 2186–2196) and confirm that sympatric ecological speciation is favoured when (i) selection is disruptive (i.e. individuals with an intermediate trait are at a local fitness minimum), (ii) resources are differentiated enough and (iii) mating is assortative. I also discuss the role of mating preference functions and the need (or lack thereof) for bimodality in resource distributions for diversification.     

Resource limitation in natural populations of phytophagous insects. A long-term study case with the chestnut weevil

The chestnut weevil, Curculio elephas (Gyll.), is a non-outbreaking species whose populations and food resources, the European chestnut, Castanea sativa, can be precisely defined. Thirteen and 17 generations of this insect were studied in two isolated sites. Field observations and experiments allowed us to estimate the absolute abundance, availability and use of chestnuts for weevil oviposition, and the number of weevil females emerging per site. Unavailable chestnuts were defined as the fruits either infested first by the chestnut moth (Cydia splendana) larvae (because of competition between the two species) or those avoided by chestnut weevil females when selecting their egg-laying sites, independently of chestnut moth presence. From a third to a half of the chestnuts were not available on the average for weevil infestation. Only one-fourth, on the average, of those available for oviposition were actually used by chestnut weevil females. Regardless of year and site, the number of available chestnuts per weevil female was higher than that of weevil-infested fruits per female, considering global food resources independently of their temporal variation in quality. However, realized fecundity of weevil females was positively correlated with the mean number of available chestnuts per female. We concluded that food resources can be limiting without being fully exploited by females because of temporal variation in chestnut quality.     

Partitioning of Stored Resources Between Shoots in a Clone, and its Effects on Shoot Size Hierarchy

A theoretical study is described of the effects of the patternof partitioning of stored resources between the shoots of aclone on the development of shoot size hierarchy. When thereis an increasing convex relationship between the amount of resourcesavailable to a shoot at the start of growth and its biomassat maturity, the mode of competition between the shoots is asymmetricand the sharing of stored resources between shoots will notmaximize above-ground biomass of the clone at maturity. Underthis condition, the plant is predicted to allocate a smalleramount of its resources to storage, producing a lower below/above-groundbiomass ratio. Clonal species in which shoots compete asymmetricallyare known to have smaller below/above-ground biomass ratios.When there is an increasing concave relationship between theamount of resources available to a shoot at the start of growthand shoot biomass at maturity, the mode of competition willbe symmetric, and equal sharing of stored resources betweenall shoots at the start of growth will maximize the above-groundbiomass of the clone at maturity. If sharing of resources isthe optimal pattern of partitioning, all shoots of the cloneare predicted to be equal in size at maturity and, therefore,a size hierarchy will not develop within a clone. Copyright2001 Annals of Botany Company Clonal plants, pattern of partitioning, stored resources, shoot competition, size hierarchy, sharing of resources, symmetric competition     

Understanding Acceptable Level of Risk: Incorporating the Economic Cost of Under-Managing Invasive Species

Management of nonindigenous species includes prevention, early detection and rapid response and control. Early detection and rapid response depend on prioritizing and monitoring sites at risk for arrival or secondary spread of nonindigenous species. Such monitoring efforts require sufficient biosecurity budgets to be effective and meet management or policy directives for reduced risk of introduction. Such consideration of risk reduction is rarely considered, however. Here, we review the concepts of acceptable level of risk (ALOR) and associated costs with respect to nonindigenous species and present a framework for aligning risk reduction priorities with available biosecurity resources. We conclude that available biosecurity resources may be insufficient to attain stated and desired risk reduction. This outcome highlights the need to consider policy and management directives when beginning a biosecurity program to determine the feasibility of risk reduction goals, given available resources.     

Characterised and Projected Costs of Nonindigenous Species in Canada

Biological invasions by nonindigenous species (NIS) can have adverse effects on economically important goods and services, and sometimes result in an ‘invisible tax’ on natural resources (e.g. reduced yield). The combined economic costs of NIS may be significant, with implications for environmental policy and resource management; yet economic impact assessments are rare at a national scale. Impacts of nuisance NIS may be direct (e.g. loss of hardwood trees) or indirect (e.g. alteration of ecosystem services provided by growing hardwoods). Moreover, costs associated with these effects may be accrued to resources and services with clear ‘market’ values (e.g. crop production) and to those with more ambiguous, ‘non-market’ values (e.g. aesthetic value of intact forest). We characterised and projected economic costs associated with nuisance NIS in Canada, through a combination of case-studies and an empirical model derived from 21 identified effects of 16 NIS. Despite a severe dearth of available data, characterised costs associated with ten NIS in Canadian fisheries, agriculture and forestry totalled $187 million Canadian (CDN) per year. These costs were dwarfed by the ‘invisible tax’ projected for sixteen nuisance NIS found in Canada, which was estimated at between $13.3 and $34.5 billion CDN per year. Canada remains highly vulnerable to new nuisance NIS, but available manpower and financial resources appear insufficient to deal with this problem. An erratum to this article is available at .     

THE EFFECT OF INVESTMENT IN ATTRACTIVE STRUCTURES ON ALLOCATION TO MALE AND FEMALE FUNCTIONS IN PLANTS

Expressions for male and female fitnesses of partially self-fertilizing cosexual plants are derived, assuming that allocation to pollinator attraction at the time of flowering may decrease resources available for male and female primary structures. The total female fertility is assumed to be controlled by factors at two stages, flowering-time and fruiting-time, with resources for fruit maturation being limited so that maximum seed production may be limited by the availability of these resources. The fitness formulas are used to calculate ESS (evolutionarily stable strategy) allocations at flowering time to primary male and female sex functions and to attractive structures. These are compared with some data that are available for dry weights of different flower parts. The fitnesses of unisexual mutant forms are calculated, assuming that they are introduced into a population consisting mostly of the initial cosexual form and that they obey the same gain curves as that form. When compared with the fitness of the ESS cosexual form, this enables one to ask whether unisexual forms will be favored. We show that the spread of females is unlikely, unless there is high inbreeding depression and a rather high selfing rate, and that in some circumstances a linear relation between number of fertilized ovules and number of seeds matured can be less favorable for the invasion of females than is a highly concave relation. With a nearly linear relation between numbers of fertilized ovules and mature seeds, invasion by females is more likely when investment in attraction is low than when it is high. These effects are discussed in relation to the distribution of dioecy. The spread of male mutants is never likely in these models.     

Balancing exploitation of renewable resources by a robot swarm

Renewable resources like fish stock or forests should be exploited at a rate that supports regeneration and sustainability—a complex problem that requires adaptive approaches to maintain a sufficiently high exploitation while avoiding depletion. In the presence of oblivious agents that cannot keep track of all available resources—a frequent condition in swarm robotics—ensuring that the exploitation effort is correctly balanced is particularly challenging. Additionally, the possibility to exploit resources by multiple robots opens the way to focusing the effort either on a single or on multiple resources in parallel. This means that the swarm needs to collectively decide whether to remain cohesive or split among multiple resources, as a function of the ability of the available resources to replenish after exploitation. In this paper, we propose a decentralised strategy for a swarm of robots that adapts to the available resources and balances the effort among them, hence allowing to maximise the exploitation rate while avoiding to completely deplete the resources. A detailed analysis of the strategy parameters provides insights into the working principles and expected performance of the robot swarm.     

CoMent: Relationships Between Biomedical Concepts Inferred From the Scientific Literature

The mining of the massive amounts of biomedical information is hindered by the still scarce representation of these data using formal vocabularies and ontologies, which is necessary for cross-linking conceptual entities between different resources and, in general, representing the information in a computer-tractable way. Basic things such as retrieving a comprehensive list of associations between complex diseases and their reported symptoms or underlying biological processes, given in terms of formal identifiers, are not trivial and, in many cases, these have to be generated by manual curation or inferred/predicted from indirect evidences. In this work, using a text-mining approach based on detecting significant co-mentions in the scientific literature, we generated a resource with millions of relationships between thousands of terms representing diseases, symptoms, biological processes, molecular functions and cellular compartments, all given in terms of formal identifiers of these terms in the main resources dealing with them. We show some examples that highlight the differences between these relationships and those that are available in other resources. These relationships can be queried and inspected in an interactive web interface freely available at: https://sysbiol.cnb.csic.es/CoMent.     

Arabidopsis genomic information for interpreting wheat EST sequences

The resources available from Arabidopsis thaliana for interpreting functional attributes of wheat EST are reviewed. A focus for the review is a comparison between wheat EST sequences, generated from developing endosperm tissue, and the complete genomic sequence from Arabidopsis. The available information indicates that not only can tentative annotations be assigned to many wheat genes but also putative or unknown Arabidopsis gene annotations can be improved by comparative genomics. Electronic Publication     

Aggregations from using inadvertent social information: a form of ideal habitat selection

Social information in breeding site selection has received extensive study; however, few attempts have been made to link this process to pre‐existing models. We examine the importance of social information to three pertinent models of habitat selection that describe breeding aggregations and spatial patterns: 1) the ideal despotic distribution (IDD) which considers conspecific competition and habitat availability, 2) the perceptual constraints model which accounts for patch selection when animals experience a threshold of undetectable difference in quality, and 3) the “neighbourhood model” which predicts concordance between resources and settlers can be disrupted by conspecific attraction when resources are patchy. These models all predict initial settlers will select a high quality patch first. However, their predictions of subsequent settlement behaviour in remaining patches differ: the IDD predicts subsequent settlers will be distributed regularly, the perceptual constraints model predicts a random distribution, and the neighbourhood model predicts clustering from conspecific attraction. We examined which model best described settlement patterns of bobolink Dolichonyx oryzivorus and savannah sparrow Passerculus sandwichensis, in the context of social information. We observed settlement timing, quantified available resources, and determined where they occurred in the highest (local population “core”) and lowest densities (local population “periphery”). We then assessed whether individuals in the periphery settled in greater concordance with resources or conspecific presence. Core territories were clustered strongly on relevant resources, and these territory holders were older than in the periphery. Peripheral territories were likewise clustered but did not always co‐occur with the best available resources, matching the neighbourhood model prediction that social information may not always direct them to the best sites available. This suggests older individuals used their own experience to locate ideal habitat, whereas younger individuals attempted to aggregate on seemingly ideal habitat by using conspecific location; such information asymmetry due to age can be viewed as an “ideal aggregative distribution”.