scholarly journals The compound topology of a continent-wide interaction network explained by an integrative hypothesis of specialization

2017 ◽  
Author(s):  
Gabriel Moreira Felix ◽  
Rafael Barros Pereira Pinheiro ◽  
Robert Poulin ◽  
Boris R. Krasnov ◽  
Marco Aurelio Ribeiro de Mello
Keyword(s):  
Interaction Network ◽  
Interaction Networks ◽  
Resource Exploitation ◽  
Ecological Specialization ◽  
Large Dataset ◽  
Host Parasite Interactions ◽  
And Performance ◽  
Host Parasite ◽  
The Relationship ◽  
Shed Light

ABSTRACTIs there a prevalent pattern among interaction networks: nestedness or modularity? Must consumers always trade-off generalism for average performance in resource exploitation? These two questions have been addressed in various systems, with contradictory results. A recent integrative hypothesis combines both questions within a common theoretical framework, proposing that ecological specialization is structured by different prevailing processes in smaller and larger network units. This should produce both a compound interaction network, formed by internally nested modules, and a scale-dependence on the relationship between consumer performance and generalism. Here, we confirm both predictions in a large dataset on host-parasite interactions. We show that modules indeed constrain nestedness at the whole network level, and that the relationship between parasite generalism and performance on their hosts changed from negative at large to positive at small scales. Our results shed light on both debates, and provide some clues to their integration and solution.

The risk of use small matrices to measure specialization in host–parasite interaction networks: a comment to Rivera-García et al. (2016)

Parasitology ◽  
2017 ◽  
Vol 144 (8) ◽  
pp. 1102-1106 ◽  
Author(s):  
PEDRO LUNA ◽  
ERICK J. CORRO ◽  
DIANA A. AHUATZIN-FLORES ◽  
REUBER L. ANTONIAZZI ◽  
NATHALIA BARROZO ◽  
...  
Keyword(s):  
Species Richness ◽  
Species Interactions ◽  
Simulated Data ◽  
Interaction Networks ◽  
Host Parasite Interactions ◽  
The Matrix ◽  
Bat Fly ◽  
Host Parasite

SUMMARYIn the last years, there were a growing number of studies using the metric H2′ to calculate complementary specialization in host–parasite interaction networks. However, only a few studies have explored the sensitivity of H2′ to network dimensions (i.e. species richness and number of interactions), which consequently could generate studies that are not comparable among them or lead to biased conclusions. In this study, we used the recent published study conducted by Rivera-García et al. in 2016 involving host–bat fly networks as an example to call attention to the risk of using H2′ to calculate specialization for small matrices. After conducting analyses based on both empirical and simulated data, we show that H2′ values are strongly affected by randomly allocation of species interactions to another cell in the matrix for small networks and that therefore the results and conclusions presented in Rivera-García et al. in 2016 are only an artefact of the dataset used. Therefore, we fully recommended taking into account the careful use of small networks to measuring specialization in host–parasite interactions.

scholarly journals Deconstructing AMO framework: a systematic review

2016 ◽  
Vol 12 (4) ◽  
pp. 1040 ◽  
Author(s):  
Juan A. Marin-Garcia ◽  
Juan Martinez Tomas
Keyword(s):  
Social Sciences ◽  
Systematic Review ◽  
Web Of Science ◽  
Social Sciences And Humanities ◽  
Positive Effects ◽  
Scientific Papers ◽  
And Performance ◽  
The Relationship ◽  
Measures Of Performance ◽  
Shed Light

Purpose: The AMO framework has been widely accepted in HRM literature for explaining the linkage between human resources practices and performance. However, it remains unclear whether this model has been fully demonstrated or not. Hence, we propose a systematic review that aims at identifying those investigations that have thoroughly tested the model, as well as the approaches used by them.Design/methodology/approach: Systematic literature review, filtering scientific papers published in journals indexed in Scopus, Web of Science or Google Scholar, from the year 1993 to 2016, in the field of Social Sciences and Humanities with research that indirectly apply the AMO model in their analysis.Findings: AMO model is an excellent and structured framework that provides a better understanding of the relationship between HRM and performance. Moreover, the effectiveness of the model's proposal appears to be beyond doubt. In fact, a well trained and skilled employee will perform better, and a motivated worker will be ready to "go the extra mile". Likewise, if the work environment does not provide adequate opportunities, both abilities and motivation might become meaningless. However, we consider that many other factors could influence the positive effects of HPWS. As a matter of fact, not only contextual factors, but also individual beliefs, personal affinities, or personal circumstances (among others) might affect the implementation of these practices and the subsequent outcomes. For this reason, we consider that developing an HRM model that perfectly fit any situation is a very complicated, if not impossible, task.Research limitations/implications: The results show a significant variability in both research approaches and variables taken into consideration. In addition, it seems that little research has been conducted to verify the AMO model directly. Therefore, we consider that there is a great need to study the model from a more systematic perspective. A thorough understanding of the model could lead to a better understanding of the problems that organizations face when implementing human resource practices.Originality/value: Our study shed light on some aspects of the AMO framework within the HRM context. Specifically, we aimed to identify whether or not it is possible to confirm the model as it was originally proposed. We also find out which HR practices and measures of performance were considered across investigations, to define a standard approach.

The people versus science: can passively crowdsourced internet data shed light on host-parasite interactions?

Parasitology ◽  
2021 ◽  
pp. 1-24
Author(s):  
Jean-François Doherty ◽  
Antoine Filion ◽  
Jerusha Bennett ◽  
Upendra Raj Bhattarai ◽  
Xuhong Chai ◽  
...  
Keyword(s):  
Host Parasite Interactions ◽  
The People ◽  
Host Parasite ◽  
Shed Light

scholarly journals The Effect of Communicative Activities on EFL Learners’ Motivation: A Case of Students in the Amazon Region of Ecuador

2016 ◽  
Vol 18 (2) ◽  
pp. 39 ◽  
Author(s):  
César Ochoa ◽  
Paola Cabrera ◽  
Ana Quiñónez ◽  
Luz Castillo ◽  
Paúl González
Keyword(s):  
Amazon Region ◽  
Efl Learners ◽  
Face To Face ◽  
Efl Teachers ◽  
Communicative Activities ◽  
And Performance ◽  
The Relationship ◽  
Quantitative And Qualitative Methods ◽  
Method Approach ◽  
Shed Light

This study sought to shed light on the relationship between communicative activities and their impact on students’ motivation to learn English as a Foreign Language (EFL). A total of 180 senior high school learners (86 male and 94 female) and 8 EFL teachers in a town of the Amazon region of Ecuador completed a questionnaire. A sample of these students and all of the teachers participated in a face-to-face interview. Both instruments were applied to obtain data concerned with use of communicative activities in the classroom and their relation with motivation. The data gathered was analyzed using a mixed-method approach, which comprised quantitative and qualitative methods. The results showed that students and teachers believe that communicative activities are motivating. Furthermore, students feel highly motivated when participating in interactive activities because these enhance their fluency, pronunciation and performance in the use of English in a realistic and enjoyable way. 

scholarly journals Effect of Localization on the Stability of Mutualistic Ecological Networks

2015 ◽  
Author(s):  
Samir Suweis ◽  
Jacopo Grilli ◽  
Jayanth Banavar ◽  
Stefano Allesina ◽  
Amos Maritan
Keyword(s):  
Species Abundance ◽  
Interaction Network ◽  
Species Interaction ◽  
Interaction Networks ◽  
Ecological Communities ◽  
Weighted Degree ◽  
Perturbation Propagation ◽  
The Stability ◽  
The Impact ◽  
The Relationship

The relationships between the core-periphery architecture of the species interaction network and the mechanisms ensuring the stability in mutualistic ecological communities are still unclear. In particular, most studies have focused their attention on asymptotic resilience or persistence, neglecting how perturbations propagate through the system. Here we develop a theoretical framework to evaluate the relationship between architecture of the interaction networks and the impact of perturbations by studying localization, a measure describing the ability of the perturbation to propagate through the network. We show that mutualistic ecological communities are localized, and localization reduces perturbation propagation and attenuates its impact on species abundance. Localization depends on the topology of the interaction networks, and it positively correlates with the variance of the weighted degree distribution, a signature of the network topological hetereogenity. Our results provide a different perspective on the interplay between the architecture of interaction networks in mutualistic communities and their stability.

scholarly journals Molecular Evidence that Lysiphlebia japonica Regulates the Development and Physiological Metabolism of Aphis gossypii

2020 ◽  
Vol 21 (13) ◽  
pp. 4610
Author(s):  
Xueke Gao ◽  
Hui Xue ◽  
Junyu Luo ◽  
Jichao Ji ◽  
Lijuan Zhang ◽  
...  
Keyword(s):  
Aphis Gossypii ◽  
The Body ◽  
Molecular Evidence ◽  
Functional Categories ◽  
Host Parasite Interactions ◽  
Physiological Metabolism ◽  
Major Pest ◽  
Host Parasite ◽  
The Relationship ◽  
Insight Into

Lysiphlebia japonica Ashmead (Hymenoptera, Braconidae) is an endophagous parasitoid and Aphis gossypii Glover (Hemiptera, Aphididae) is a major pest in cotton. The relationship between insect host-parasitoids and their hosts involves complex physiological, biochemical and genetic interactions. This study examines changes in the development and physiological metabolism of A. gossypii regulated by L. japonica. Our results demonstrated that both the body length and width increased compared to non-parasitized aphids. We detected significantly increases in the developmental period as well as severe reproductive castration following parasitization by L. japonica. We then used proteomics to characterize these biological changes, and when combined with transcriptomes, this analysis demonstrated that the differential expression of mRNA (up or downregulation) captured a maximum of 48.7% of the variations of protein expression. We assigned these proteins to functional categories that included immunity, energy metabolism and transport, lipid metabolism, and reproduction. We then verified the contents of glycogen and 6-phosphate glucose, which demonstrated that these important energy sources were significantly altered following parasitization. These results uncover the effects on A. gossypii following parasitization by L. japonica, additional insight into the mechanisms behind insect-insect parasitism, and a better understanding of host-parasite interactions.

EFFECTS OF CROWDING ON SUPLHURETYLENCHUS SPP. (NEMATODA: ALLANTONEMATIDAE) IN THE HAEMOCOEL OF THEIR BARK BEETLE HOSTS (COLEOPTERA: SCOLYTIDAE)

1989 ◽  
Vol 121 (9) ◽  
pp. 821-822
Author(s):  
Marek Tomalak ◽  
Harold E. Welch ◽  
Terry D. Galloway
Keyword(s):  
Bark Beetle ◽  
Bark Beetles ◽  
Biological Control Agents ◽  
Infection Rates ◽  
Intensity Of Infection ◽  
Nematode Parasites ◽  
Host Parasite Interactions ◽  
Host Parasite ◽  
The Relationship ◽  
Growth And Reproduction

Nematode parasites of bark beetles are taxonomically diverse, and may, in some cases, cause serious pathological and behavioural changes in their hosts (Kaya 1984). Their potential as biological control agents has long been recognized, but to date there is a shortage of elementary information on host-parasite interactions. Though the effects of superparasitism and subsequent crowding on the parasite have been studied for some mermithids (Petersen 1972) and steinernematids (Sandner and Stanuszek 1971), no such observations have been reported for bark beetle parasites. During a survey of nematode parasites of bark beetles in Manitoba, we encountered two examples where nematodes were detrimentally affected at the higher infection rates observed. It was our objective, therefore, to examine the relationship between intensity of infection, and impact on growth and reproduction of the parasites.

Election Cycles and Organizations: How Politics Shapes the Performance of State-owned Enterprises over Time

2019 ◽  
Vol 65 (3) ◽  
pp. 677-709 ◽  
Author(s):  
Carlos Inoue
Keyword(s):  
Disadvantaged Communities ◽  
Political Incentives ◽  
Dynamic Perspective ◽  
And Performance ◽  
Private Investors ◽  
Resource Support ◽  
The Relationship ◽  
Shed Light ◽  
Over Time ◽  
Election Cycles

This study develops a dynamic perspective on how elected state officials’ political incentives shape the behavior and performance of organizations, particularly state-owned enterprises (SOEs). Drawing on theoretical views about the relationship between politicians and firms, I argue that state officials seeking votes manipulate SOEs to boost employment before elections. As a result, SOEs exhibit both higher employment levels and lower financial performance in election years. The positive relationship between elections and SOE employment, however, is not uniform across firms and geographic communities: it is likely to be stronger in economically disadvantaged communities and weaker for SOEs with private investors. Data from Brazil’s water sector—an industry managing a crucial societal resource—support these predictions. These results shed light on the mechanisms linking officials’ political incentives and SOE behavior and show that SOE performance is politically contingent and thus varies systematically over time. More broadly, this study reveals how firms’ responses to political pressures depend on both organizational and community attributes and highlights how the interplay of election cycles, organizations, and communities shapes the performance of organizations in state capitalism.

scholarly journals Management entrenchment and performance: case of Tunisian firms

2008 ◽  
Vol 5 (3) ◽  
pp. 418-427
Author(s):  
Rym Hachana ◽  
Jamila Hajri
Keyword(s):  
Ownership Structure ◽  
Service Sector ◽  
Cross Section Data ◽  
Section Data ◽  
Management Entrenchment ◽  
The Board Of Directors ◽  
And Performance ◽  
The Relationship ◽  
Debt Policy ◽  
Shed Light

Since entrenchment strategy has a real impact on performance, we examine in this paper the relationship between entrenchment and performance. This study is based on cross-section data of 21 quoted Tunisian companies (from both manufacturing and service sector) over the period 2000 to 2006. Our evidence contributes to understanding the role played by several entrenchment pathways, such as the ownership structure, the debt policy and the structure of the board of directors. In this paper, we aim to shed light on these governance’s features by indicating by which channel entrenchment strategy is carried out in Tunisian companies

Corporate and product brands: do they improve SMEs' performance?

2014 ◽  
Vol 18 (1) ◽  
pp. 78-91 ◽  
Author(s):  
Lara Agostini ◽  
Roberto Filippini ◽  
Anna Nosella
Keyword(s):  
Positive Impact ◽  
Sampling Technique ◽  
Fashion Industry ◽  
Time Series Regression ◽  
Cross Sectional ◽  
Content Type ◽  
And Performance ◽  
The Impact ◽  
The Relationship ◽  
Shed Light

Purpose – The aim of this paper is to investigate the impact of brands on small to medium-sized enterprise (SME) performance in the fashion industry, trying also to shed light on the different effect that corporate and product brands may produce. Design/methodology/approach – The approach uses cross-sectional time series regression to investigate the relationship between trademarks and sales, controlling for firm size. A purposive sampling technique is adopted, focusing on a sample of Italian SMEs in the fashion industry. Findings – Results indicate that trademarks do have a positive impact on SMEs' performance in the fashion industry, and in particular corporate trademarks seem to be effective in producing a sales increase, while product trademarks do not. Research limitations/implications – The main limit of this research is that no variable mediating the relationship between trademarks and performance was considered. Furthermore, the number of trademarks may not capture all the dimensions of brand. Practical implications – The most important aspect is that SME managers in the fashion industry could benefit from a trademarking strategy; in particular, investments in building a strong corporate brand, thus concentrating SMEs' effort, instead of having many different product brands, seems to create greater effect in the minds of consumers, and thus result in sales increases. Originality/value – This paper is one of first attempts to shed light on the issue regarding the association between SMEs' branding strategy and performance. Moreover, the distinction between corporate and product brands represents an innovative element in this type of study.

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