Invasive species impacts on ecosystem structure and function: A comparison of the Bay of Quinte, Canada, and Oneida Lake, USA, before and after zebra mussel invasion

As invasion rates of exotic species increase, an ecosystem level understanding of their impacts is imperative for predicting future spread and consequences. We have previously shown that network analyses are powerful tools for understanding the effects of exotic species perturbation on ecosystems. We now use the network analysis approach to compare how the same perturbation affects another ecosystem of similar trophic status. We compared food web characteristics of the Bay of Quinte, Lake Ontario (Canada), to previous research on Oneida Lake, New York (USA) before and after zebra mussel (Dreissena polymorpha) invasion. We used ecological network analysis (ENA) to rigorously quantify ecosystem function through an analysis of direct and indirect food web transfers. We used a social network analysis method, cohesion analysis (CA), to assess ecosystem structure by organizing food web members into subgroups of strongly interacting predators and prey. Together, ENA and CA allowed us to understand how food web structure and function respond simultaneously to perturbation. In general, zebra mussel effects on the Bay of Quinte, when compared to Oneida Lake, were similar in direction, but greater in magnitude. Both systems underwent functional changes involving focused flow through a small number of taxa and increased use of benthic sources of production; additionally, both systems structurally changed with subgroup membership changing considerably (33% in Oneida Lake) or being disrupted entirely (in the Bay of Quinte). However, the response of total ecosystem activity (as measured by carbon flow) differed between both systems, with increasing activity in the Bay of Quinte, and decreasing activity in Oneida Lake. Thus, these analyses revealed parallel effects of zebra mussel invasion in ecosystems of similar trophic status, yet they also suggested that important differences may exist. As exotic species continue to disrupt the structure and function of our native ecosystems, food web network analyses will be useful for understanding their far-reaching effects.     

Adaptations in a hierarchical food web of southeastern Lake Michigan

Two issues in ecological network theory are: (1) how to construct an ecological network model and (2) how do entire networks (as opposed to individual species) adapt to changing conditions? We present a novel method for constructing an ecological network model for the food web of southeastern Lake Michigan (USA) and we identify changes in key system properties that are large relative to their uncertainty as this ecological network adapts from one time point to a second time point in response to multiple perturbations. To construct our food web for southeastern Lake Michigan, we followed the list of seven recommendations outlined in Cohen et al. [Cohen, J.E., et al., 1993. Improving food webs. Ecology 74, 252–258] for improving food webs. We explored two inter-related extensions of hierarchical system theory with our food web; the first one was that subsystems react to perturbations independently in the short-term and the second one was that a system's properties change at a slower rate than its subsystems’ properties. We used Shannon's equations to provide quantitative versions of the basic food web properties: number of prey, number of predators, number of feeding links, and connectance (or density). We then compared these properties between the two time-periods by developing distributions of each property for each time period that took uncertainty about the property into account. We compared these distributions, and concluded that non-overlapping distributions indicated changes in these properties that were large relative to their uncertainty. Two subsystems were identified within our food web system structure (p < 0.001). One subsystem had more non-overlapping distributions in food web properties between Time 1 and Time 2 than the other subsystem. The overall system had all overlapping distributions in food web properties between Time 1 and Time 2. These results supported both extensions of hierarchical systems theory. Interestingly, the subsystem with more non-overlapping distributions in food web properties was the subsystem that contained primarily benthic taxa, contrary to expectations that the identified major perturbations (lower phosphorous inputs and invasive species) would more greatly affect the subsystem containing primarily pelagic taxa. Future food-web research should employ rigorous statistical analysis and incorporate uncertainty in food web properties for a better understanding of how ecological networks adapt.     

Trophic specialisation of metazoan meiofauna at the Håkon Mosby Mud Volcano: fatty acid biomarker isotope evidence

We report the results of a detailed investigation on the trophoecology of two dominant meiofaunal species at the Håkon Mosby Mud Volcano (HMMV), a deep-sea cold methane-venting seep. Analyses of fatty acids (FAs) and their stable carbon isotopes were used to determine the importance of chemosynthetic nutritional pathways for the dominant copepod species (morphologically very similar to Tisbe wilsoni) inhabiting the volcano’s centre and the abundant nematode Halomonhystera disjuncta from the surrounding microbial mats. The strong dominance of bacterial biomarkers (16:1ω7c, 18:1ω7c and 16:1ω8c) coupled with their individual light carbon isotopes signatures (δ¹³C ranging from ?52 to ?81‰) and the lack of symbiotic relationships with prokaryotes (as revealed by molecular analyses and fluorescent in situ hybridisation) indicated that chemosynthetically derived carbon constitutes the main diet of both species. However, the copepod showed a stronger reliance on the utilisation of methanotrophic bacteria and contained polyunsaturated FAs of bacterial origin (20:5ω3 and 22:6ω3 with isotope signatures δ¹³C < ?80‰). Instead, the FA profiles of H. disjuncta suggested that sulphide-oxidising bacteria constituted the main diet of this nematode. Therefore, HMMV can be regarded as a persistent deep-sea cold seep, allowing a chemosynthesis-based trophic specialisation by the dominant meiofaunal species inhabiting its sediments. The present investigation, through the determination of the fatty acid profiles, provides the first evidence for trophic specialisation of meiofauna associated with sub-habitats within a cold seep.     

How does spouse career support relate to employee turnover? Work interfering with family and job satisfaction as mediators

Employee turnover is a major concern because of its cost to organizations. Although theory supports the influence of nonwork factors on turnover, our understanding of the degree to which nonwork factors relate to actual turnover behavior is not well developed. Using a sample of 5505 U.S. Army officers, we assessed the extent to which spouse career support related to reduced turnover four years later through work interfering with family (WIF) and job satisfaction as mechanisms. Results revealed that spouse career support decreased the odds of turnover, and WIF and job satisfaction sequentially mediated this relationship, with lower WIF and higher job satisfaction reducing the odds of turnover. Practical implications of using family support systems as retention interventions are discussed. Copyright © 2013 John Wiley & Sons, Ltd.     

Relationship of firm attributes,ownership structure and business network on climate change efforts: evidence from Malaysia

This paper presents a case study of land-use/land-cover (LULC) changes from 1975 to 2014 in the central highlands of Ethiopia and traces out its impact on socioeconomic conditions of the local community in the study area. We used four time series Landsat satellite images, that is, Landsat MSS (1975), Landsat Thematic Mapper (1986), Enhanced Thematic Mapper (2000), and Landsat 8 OLI scenes (2014), to investigate the changes in LULC. In addition, individual interviews with 51 randomly selected households, discussions with focus group and key informants, and field observations were also incorporated for the study. The image classification indicated four categories of LULC classes: Natural forest, eucalyptus plantations, cropland/settlements, and grasslands. Between 1975 and 2014, cropland/settlements and eucalyptus plantations considerably increased, whereas grassland cover drastically decreased. According to the results, the area under cropland/settlements and eucalyptus plantations increased by 62 and 335%, respectively, with 74% concomitant decrease in the area of grasslands in the same period. Survey results showed that deterioration of soil fertility (41.2%) followed by shortage of land (35.3%) is the major constraint for crop production for poor farmers in the study area. However, better-off farmers ranked deterioration of soil fertility (64.7%) followed by lack of credit (17.6%) as priority constraints for crop production. Interviews mainly focused on selected women group revealed that the expansion of eucalyptus in the area greatly curbed the burdens of collecting fuel woods from long distances in the past. The availability of too many religious holidays (on average 16 days/month) directly or indirectly contributes to the current seasonal food shortages of the community. Generally, our results show that the community in the study area is beset with a host of social, economic, and institutional challenges. As a result, majority of the farming households are destitute, unable to make a livelihood from their small plot of land and live in absolute poverty. Therefore, in light of these finding, it is imperative that timely interventions by government and other development stakeholders are needed to come to grips with problems of soil fertility, land-use change, and food insecurity in the study area.     

Multiple categorization in resume screening: Examining effects on hiring discrimination against Arab applicants in field and lab settings

Debate exists as to what the more appropriate prediction is regarding the effects of multiple stigmatized group memberships on employment discrimination. The ethnic prominence (EP), multiple minority status (MMS), and subordinate male target hypotheses were assessed for the combined effects of ethnic group membership (Arabic), sex, social status, and job type on hiring evaluations. Two correspondence tests in the field (Study 1) and two experimental studies in the lab (Study 2) and in the field (Study 3) were conducted. Studies 1 and 2 showed evidence for the EP hypothesis when low‐status jobs were tested. The odds for rejection were four times higher for Arab than for Dutch applicants. Applicants' sex, socio‐economic status, and external client contact did not moderate findings (Study 1). The effect of applicants' ethnic group membership was further moderated by raters' motivation to control prejudice (Study 2). Study 3 showed evidence for the MMS hypothesis. We found double jeopardy against Arab women who applied for high‐status jobs when recruiters' prejudice was controlled. Study findings show that discrimination in resume screening may depend upon the particular intersection of applicant, job, and recruiter characteristics. We discussed implications for anonymous resume screening and research on evaluation of applicants possessing multiple stigmatizing characteristics. Copyright © 2011 John Wiley & Sons, Ltd.     

Minimising waste in the food and drink sector: using the business club approach to facilitate training and organisational development

The aim of the East Anglian Waste Minimisation in the Food And Drink Industry Project was to develop waste minimisation capability in food and drink sector companies by providing a structured training programme and consultancy support to participating members of a business club. The business club forum provided the structure within which interactive training and development sessions were delivered. Expertise and assistance in implementing waste minimisation and waste management programmes was given to member companies at their sites.The project resulted in pound 1,800,000 per annum of identified savings with pound 1,100,000 of verified savings already achieved. Training and development contributed fundamentally to these project outcomes and achievements.The structured training package used three different approaches or methods. Teaching and workshop sessions were used to present interactive training on waste minimisation practice. These were supplemented by interactive 'report-back' sessions where the 'project champions' presented progress reports to the club on waste minimisation at their sites.An overview of the business club approach is described, together with an account of the successes and challenges of applying a structured training and development programme and the barriers to waste minimisation that were overcome. Training effectiveness was measured according to reaction, learning, application and impact.     

Estimation Using Contingent Valuation Data from a "Dichotomous Choice with Follow-Up" Questionnaire

Dichotomous-choice (referendum) contingent-valuation questions are inefficient in that a very large number of observations is required to identify a distribution of resource values with any degree of accuracy. An alternative questioning strategy introduces a follow-up dichotomous-choice question. We generalize upon previous analyses of this type of data by relaxing the assumption that the identical unobserved resource value motivates both responses. While values implied by the first and second responses are highly correlated and may be drawn from the same distribution, they are definitely not identical. Furthermore, assuming that they are can severely distort the estimated valuation distribution.     

Female preferences for male calling bout duration in a field cricket

Summary The calls of male field crickets attract sexually receptive females. In Gryllus integer, males differ from one another in their durations of uninterrupted calling (calling bout lengths). Tape recordings of the calls of 50 wild-caught males revealed that 14 males spent most of their calling time in short bouts (Fig. 1A), 18 in both short and long bouts (Fig. 1B), and 18 in long bouts (Fig. 1C). Re-recordings of 32 males after 3 weeks showed that calling bout lengths of individual males are stable with time (age) (Fig. 2). Three phonotaxis experiments investigated whether calling bout lengths of males affect female preferences. They demonstrated that (1) females can discriminate among conspecific males on the basis of calls alone; (2) females are preferentially attracted to males with long calling bout lengths; and (3) calling bout length is the specific factor responsible for preferential attraction. These results precisely identify a criterion that females use to discriminate among potential mates of their own species.