Players In Ecosystem Research Articles

Composition of Bacterial Communities Associated with Aurelia aurita Changes with Compartment, Life Stage, and Population.

The scyphozoan Aurelia aurita is recognized as a key player in marine ecosystems and a driver of ecosystem change. It is thus intensely studied to address ecological questions, although its associations with microorganisms remain so far undescribed. In the present study, the microbiota associated with A. aurita was visualized with fluorescence in situ hybridization (FISH) analysis, and community structure was analyzed with respect to different life stages, compartments, and populations of A. aurita by 16S rRNA gene amplicon sequencing. We demonstrate that the composition of the A. aurita microbiota is generally highly distinct from the composition of communities present in ambient water. Comparison of microbial communities from different developmental stages reveals evidence for life stage-specific community patterns. Significant restructuring of the microbiota during strobilation from benthic polyp to planktonic life stages is present, arguing for a restructuring during the course of metamorphosis. Furthermore, the microbiota present in different compartments of the adult medusa (exumbrella mucus and gastric cavity) display significant differences, indicating body part-specific colonization. A novel Mycoplasma strain was identified in both compartment-specific microbiota and is most likely present inside the epithelium as indicated by FISH analysis of polyps, indicating potential endosymbiosis. Finally, comparison of polyps of different populations kept under the same controlled laboratory conditions in the same ambient water showed population-specific community patterns, most likely due the genetic background of the host. In conclusion, the presented data indicate that the associated microbiota of A. aurita may play important functional roles, e.g., during the life cycle.

Born globals and international business: Evolution of a field of research

Knight and Cavusgil’s award-winning article has played an important role in the development of the growing body of research on companies that internationalize early and rapidly. These “born global” firms represent important contributors to many economies, often as key players in ecosystems that support large multinational enterprises. Despite their growing importance, our understanding of how and why these firms develop and implement their internationalization strategies, and what makes them successful, remains incomplete. Addressing such questions has contributed substantially to the development of the research domain of international entrepreneurship (IE), which focuses on entrepreneurial aspects of doing business across borders, in the context of both small and large firms. While IE is much broader than born globals, these firms are central to the IE domain and the impact of the Knight and Cavusgil paper has helped to develop a stronger awareness of the important linkages and intersections between IE and the wider international business research community. We reflect on the important contribution of this paper, and suggest some directions for the future development of research into firms that choose to operate internationally practically from the start of their operations.

Influence of environmental variables on the structure and composition of soil bacterial communities in natural and constructed wetlands

Bacteria are key players in wetland ecosystems, however many essential aspects regarding the ecology of wetland bacterial communities remain unknown. The present study characterizes soil bacterial communities from natural and constructed wetlands through the pyrosequencing of 16S rDNA genes in order to evaluate the influence of wetland variables on bacterial community composition and structure.The results show that the composition of soil bacterial communities was significantly associated with the wetland type (natural or constructed wetland), the type of environment (lagoon, Typha or Salix) and three continuous parameters (SOM, COD and TKN). However, no clear associations were observed with soil pH. Bacterial diversity values were significantly lower in the constructed wetland with the highest inlet nutrient concentrations. The abundances of particular metabolic groups were also related to wetland characteristics.

Phylogenetic placement of Symplocastrum (Phormidiaceae, Cyanophyceae) with a new combination S. californicum and two new species: S. flechtnerae and S. torsivum

:Filamentous nonheterocytous cyanobacteria have been recognized as key ecosystem players in terms of soil stabilization, carbon sequestration, and water retention. Although the ecological importance of this group is well understood, its taxonomy is understudied. Microcoleus, Schizothrix, and Leptolyngbya, the most common cyanobacterial genera reported from soils, have all been found to be polyphyletic and in need of revision. In this study, strains morphologically corresponding to M. steenstrupii were isolated from North American desert soils. This species has been found to be polyphyletic, forming several distinct clades in numerous analyses. Three desert soil strains were analysed using ecological and geographical information, detailed morphological investigations, and DNA sequence data of the 16S rRNA gene and associated 16S–23S internal transcribed spacer. On the basis of this polyphasic characterization, we concluded that they represented the genus Symplocastrum. Until now, this cyanobacterial genus was poorly understood and lacked molecular definition. A more precise description of Symplocastrum is provided, including its phylogenetic position based on 16S rRNA gene sequence. Two new species are described (S. flechtnerae, S. torsivum) and Schizothrix californica is transferred to Symplocastrum. Phylogenetic placement of Symplocastrum is a critical component of the revisionary work underway in the nonheterocytous filamentous cyanobacteria and will lead to further revisionary work in this problematic group. Furthermore, with increasing taxonomic clarification of these filamentous taxa, ecological studies will have greater resolution and accuracy.

The genome-scale metabolic network of Ectocarpus siliculosus (EctoGEM): a resource to study brown algal physiology and beyond.

Brown algae (stramenopiles) are key players in intertidal ecosystems, and represent a source of biomass with several industrial applications. Ectocarpus siliculosus is a model to study the biology of these organisms. Its genome has been sequenced and a number of post-genomic tools have been implemented. Based on this knowledge, we report the reconstruction and analysis of a genome-scale metabolic network for E.siliculosus, EctoGEM (http://ectogem.irisa.fr). This atlas of metabolic pathways consists of 1866 reactions and 2020 metabolites, and its construction was performed by means of an integrative computational approach for identifying metabolic pathways, gap filling and manual refinement. The capability of the network to produce biomass was validated by flux balance analysis. EctoGEM enabled the reannotation of 56 genes within the E.siliculosus genome, and shed light on the evolution of metabolic processes. For example, E.siliculosus has the potential to produce phenylalanine and tyrosine from prephenate and arogenate, but does not possess a phenylalanine hydroxylase, as is found in other stramenopiles. It also possesses the complete eukaryote molybdenum co-factor biosynthesis pathway, as well as a second molybdopterin synthase that was most likely acquired via horizontal gene transfer from cyanobacteria by a common ancestor of stramenopiles. EctoGEM represents an evolving community resource to gain deeper understanding of the biology of brown algae and the diversification of physiological processes. The integrative computational method applied for its reconstruction will be valuable to set up similar approaches for other organisms distant from biological benchmark models.

Factors affecting application developers’ loyalty to mobile platforms

Mobile platform providers, including Apple and Google, have grown quickly to become central players in the mobile ecosystem. They now act as gatekeepers of information among multiple niche players in the mobile ecosystem. Many players from different industry sectors have tried to build their ecosystem centered on their own mobile platform, but only a few have succeeded so far. In the so called ‘ecosystem war’, one of the key issues for platform providers is how to retain a sustainable relationship with other niche players in the ecosystem. This paper investigates the factors influencing application developers’ loyalty to mobile platforms. To do this, this paper develops a model with key variables based on loyalty theory and adds variables that reflect the specific context of mobile platforms. The empirical analysis that was conducted in South Korea shows that satisfaction is a direct antecedent of application developers’ loyalty to a mobile platform. The results also show that the quality of a mobile platform’s software development kit (SDK) is one of the important determinants of application developers’ satisfaction with a particular mobile platform and also of the platform’s credibility. However, there is no significant relationship between the credibility and loyalty, which is not consistent with previous studies in different research settings. This provides us a clue to understand how the mobile platform market works and that mobile platform providers have less incentive to create a fair relationship with developers when they have a large customer base.

Changes in the quantitative distribution of Caspian Sea polychaetes: Prolific fauna formed by non-indigenous species

Although considered major players in many ecosystems around the world, the ecology of Caspian Sea polychaetes is currently understudied. This study describes the species composition and quantitative distribution of polychaetes in the southern Caspian Sea and relates the distribution to seasonal changes in environmental parameters of water (temperature, salinity, and surface current speed) and sediments (organic matter and grain size composition) at four depths (2, 5, 9 and 14m) on the Noshahr coast in the southern Caspian Sea in 2010. Four species were found: Alitta succinea, Hediste diversicolor, Hypania invalida, and Streblospio gynobranchiata. Among them, the non-indigenous S. gynobranchiata was the dominant species, accounting for 87% of the total abundance. Significant differences in abundance across the four species were observed among depths and seasons. Additionally, significant correlations between species abundances and the tested environmental factors were evident. This study highlights the potential consequences of established non-indigenous species in the southern Caspian Sea.

A Secure Cloud-Based NFC Mobile Payment Protocol

Near Field Communication (NFC) is one the most recent technologies in the area of application development and service delivery via mobile phone. NFC enables the mobile phone to act as identification and a credit card for customers. Dynamic relationships of NFC ecosystem players in an NFC transaction process make them partners in a way that sometimes they should share their access permissions on the applications that are running in the service environment. One of the technologies that can be used to ensure secure NFC transactions is cloud computing which offers wide range advantages compare to the use of a Secure Element (SE) as a single entity in an NFC enabled mobile phone. In this paper, we propose a protocol based on the concept of NFC mobile payments. Accordingly, we present an extended version of the NFC cloud Wallet model [14], in which, the Secure Element in the mobile device is used for customer authentication whereas the customer's banking credentials are stored in a cloud under the control of the Mobile Network Operator (MNO). In this circumstance, Mobile Network Operator plays the role of network carrier which is responsible for controlling all the credentials transferred to the end user. The proposed protocol eliminates the requirement of a shared secret between the Point-of-Sale (POS) and the Mobile Network Operator before execution of the protocol, a mandatory requirement in the earlier version of this protocol [16]. This makes it more practicable and user friendly. At the end, we provide a detailed analysis of the protocol where we discuss multiple attack scenarios.

The Coevolution of Sustainable Strategic Management in the Global Marketplace

Sustainable strategic management emerged from the coevolution of strategic thinking in today’s sustainability challenging business environment. Business ecosystems, designed to create socially and ecologically responsible economic opportunities for their members, have emerged as excellent structures for implementing sustainable strategic management strategies along the whole pyramid of coevolving developed, developing, and undeveloped markets. Both the business ecosystem leaders and niche players in these whole pyramid business ecosystems have critical roles to play in formulating and implementing potentially profitable strategies that help reduce the human footprint and improve the quality of human life. Ecosystem leaders need to be responsible for creating and shepherding their business ecosystems’ visions of a sustainable future, and niche players need to be responsible for providing the ecosystem with an innovation trajectory designed to make those visions a reality.

Effects of Disturbance Intensity and Frequency on Bacterial Community Composition and Function

Disturbances influence community structure and ecosystem functioning. Bacteria are key players in ecosystems and it is therefore crucial to understand the effect of disturbances on bacterial communities and how they respond to them, both compositionally and functionally. The main aim of this study was to test the effect of differences in disturbance strength on bacterial communities. For this, we implemented two independent short-term experiments with dialysis bags containing natural bacterial communities, which were transplanted between ambient and ‘disturbed’ incubation tanks, manipulating either the intensity or the frequency of a salinity disturbance. We followed changes in community composition by terminal restriction fragment analysis (T-RFLP) and measured various community functions (bacterial production, carbon substrate utilization profiles and rates) directly after and after a short period of recovery under ambient conditions. Increases in disturbance strength resulted in gradually stronger changes in bacterial community composition and functions. In the disturbance intensity experiment, the sensitivity to the disturbance and the ability of recovery differed between different functions. In the disturbance frequency experiment, effects on the different functions were more consistent and recovery was not observed. Moreover, in case of the intensity experiment, there was also a time lag in the responses of community composition and functions, with functional responses being faster than compositional ones. To summarize, our study shows that disturbance strength has the potential to change the functional performance and composition of bacterial communities. It further highlights that the overall effects, rates of recovery and the degree of congruence in the response patterns of community composition and functioning along disturbance gradients depend on the type of function and the character of the disturbance.

Identifying key species in ecosystems with stochastic sensitivity analysis

The development of approaches to estimate the vulnerability of biological communities and ecosystems to extirpations and reductions of species is a central challenge of conservation biology. One key aim of this challenge is to develop quantitative approaches to estimate and rank interaction strengths and keystoneness of species and functional groups, i.e. to quantify the relative importance of species. Network analysis can be a powerful tool for this because certain structural aspects of ecological networks are good indicators of the mechanisms that maintain co-evolved, biotic interactions. A static view of ecological networks would lead us to focus research on highly-central species in food webs (topological key players in ecosystems). There are a variety of centrality indices, developed for several types of ecological networks (e.g. for weighted and un-weighted webs). However, truly understanding extinction and its community-wide effects requires the use of dynamic models. Deterministic dynamic models are feasible when population sizes are sufficiently large to minimize noise in the overall system. In models with small population sizes, stochasticity can be modelled explicitly. We present a stochastic simulation-based ecosystem model for identification of “dynamic key species” in situations where stochastic models are appropriate. To demonstrate this approach, we simulated ecosystem dynamics and performed sensitivity analysis using data from the Prince William Sound, Alaska ecosystem model. We then compare these results to those of purely topological analyses and deterministic dynamic (Ecosim) studies. We present the relationships between various topological and dynamic indices and discuss their biological relevance. The trophic group with the largest effect on others is nearshore demersals, the species mostly sensitive to others is halibut, and the group of both considerable effect on and sensitivity to others is juvenile herring. The most important trophic groups in our dynamical simulations appear to have intermediate trophic levels.

Hydroperiod, predators and the distribution of physid snails across the freshwater habitat gradient

Summary1. Studies of species distributions across environmental gradients further our understanding of mechanisms regulating species diversity at the landscape scale. For some freshwater taxa the habitat gradient from small, shallow and temporary ponds to large, deep and permanent lakes has been shown to be an important environmental axis. Freshwater snails are key players in freshwater ecosystems, but there are no comprehensive studies of their distributions across the entire freshwater habitat gradient. Here we test the hypothesis that snail species in the family Physidae are distributed in a non‐random manner across the habitat gradient. We sampled the snails, their predators and the abiotic environment of 61 ponds and lakes, spanning a wide range in depth and hydroperiod.2. Temporary habitats had the lowest biomass of predators. Shallow permanent ponds had the highest biomass of invertebrate predators but an intermediate fish biomass. Deep ponds and lakes had the highest fish biomass and intermediate invertebrate biomass. Five species of physids occurred in the regional species pool and 60 of the 61 ponds and lakes surveyed contained physid snails. Each pond and lake contained an average of just 1.2 physid species, illustrating limited membership in local communities and substantial among‐site heterogeneity in species composition.3. Physids showed strong sorting along the habitat gradient, with Physa vernalis found in the shortest hydroperiod ponds and Aplexa elongata, P. gyrina, P. acuta and P. ancillaria found in habitats of successively greater permanence. When organised into a site‐by‐species incidence matrix with sites ordered according to their hydroperiods, we found the pattern of incidence to be highly coherent, showing that much of the heterogeneity in species composition from one pond to another is explained by hydroperiod. We also found that the number of species replacements along this gradient was higher than random, showing that replacement is more important than nesting in describing species composition in ponds of different hydroperiod.4. Discriminant analysis showed that pond depth, invertebrate biomass and fish biomass were the best predictors of species composition. Analysis of these niche dimensions showed that P. vernalis and A. elongata were most successful in shallow, temporary ponds with few predators. P. gyrina and P. acuta were typically found in ponds of intermediate depth and high predator abundance. P. ancillaria was found in the deepest lakes, which had abundant fish predators but few invertebrate predators. Of the five species considered, P. ancillaria, P. vernalis and A. elongata were relatively specialised with regard to key habitat characteristics, P. gyrina was moderately generalised and P. acuta was remarkably generalised, since it alone occurred across the entire freshwater habitat gradient. The exceptional habitat breadth of P. acuta stands in contrast to distributional studies of other freshwater taxa and deserves further attention.

Majority rule: adaptation and the long-term dynamics of species

Where do species that become important players in ecosystems evolve? This simple yet crucial question must be answered if we want to understand how the biosphere is rejuvenated following a crisis. We cannot simply assume that the environments in which we find fossil remains of a given species, or living populations of a species, are the environments in which that species evolved. Take the most obvious example: Fossil human skeletons have been unearthed by the hundreds in North America, but all available evidence points to a human origin in Africa. We can often identify the general geographic origins of species and clades thanks to fossil occurrences and the application of phylogenetic techniques; but can we do likewise for more ecological aspects of the environment? Advances in population biology and in paleobiology now permit us to outline a hypothesis of the circumstances most favorable to the evolution of abundant, widespread, or ecologically powerful species, those with adaptations that are selectively advantageous across many environments, and large short-term and long-term effects in ecosystems. We can rephrase the problem and the question. Of the very large number of populations of a species inhabiting Earth at any given time, not all will contribute to the population composition of the species in the future. How does the environment in which a population is embedded affect the contribution that it will make over evolutionary time? The importance of this issue is underscored by the finding that the type and expression of selective regime varies greatly from place to place and over time within most species (Thompson 1994, 1998, 1999a,b; Benkman et al. 2001, 2003; Thompson and Cunningham 2002; Forde et al. 2004). Some populations of pollinating moths and figwasps, for instance, may have a mutualistic relationship with their …