Influence Of Biotic Interactions Research Articles

Can we manage microbial systems to enhance carbon storage?

Climate change is an urgent environmental issue with wide-ranging impacts on ecosystems and society. Microbes are instrumental in maintaining the balance between carbon (C) accumulation and loss in the biosphere, actively regulating greenhouse gas fluxes from vast reservoirs of organic C stored in soils, sediments and oceans. Heterotrophic microbes exhibit varying capacities to access, degrade and metabolise organic C-leading to variations in remineralisation and turnover rates. The present challenge lies in effectively translating this accumulated knowledge into strategies that effectively steer the fate of organic C towards prolonged sequestration. In this article, we discuss three ecological scenarios that offer potential avenues for shaping C turnover rates in the environment. Specifically, we explore the promotion of slow-cycling microbial byproducts, the facilitation of higher carbon use efficiency, and the influence of biotic interactions. The ability to harness and control these processes relies on the integration of ecological principles and management practices, combined with advances in economically viable technologies to effectively manage microbial systems in the environment.

Environmental filtering, spatial processes and biotic interactions jointly shape different traits communities of stream macroinvertebrates

The metacommunity concept has been widely used to explain the biodiversity patterns at various scales. It considers the influences of both local (e.g., environmental filtering and biotic interactions) and regional processes (e.g., dispersal limitation) in shaping community structures. Compared to environmental filtering and spatial processes, the influence of biotic interactions on biodiversity patterns in streams has received limited attention. We investigated the relative importance of three ecological processes, namely environmental filtering (including local environmental and geo-climatic factors), spatial processes and biotic interactions (represented by interactions of macroinvertebrates and diatom), in shaping different traits of macroinvertebrate communities in subtropical streams, Eastern China. We applied variance partitioning to uncover the pure and shared effects of different ecological processes in explaining community variation. The results showed that environmental filtering, spatial processes, and biotic interactions jointly determined taxonomic and trait compositions of stream macroinvertebrates. Spatial processes showed a stronger influence in shaping stream macroinvertebrate communities than environmental filtering. The contribution of biotic interactions to explain variables was, albeit significant, rather small, which was likely a result of insufficient representation (by diatom traits) of trophic interactions associated with macroinvertebrates. Moreover, the impact of three ecological processes on macroinvertebrate communities depends on different traits, especially in terms of environmental filtering and spatial processes. For example, spatial processes and environmental filtering have the strongest effect on strong dispersal ability groups; spatial processes have a greater effect on scrapers than other functional feeding groups. Overall, our results showed that the integration of metacommunity theory and functional traits provides a valuable framework for understanding the drivers of community structuring in streams, which will facilitate the development of effective bioassessment and management strategies.

Pathogen infection influences the relationship between spring and autumn phenology at the seedling and leaf level.

Seasonal life history events are often interdependent, but we know relatively little about how the relationship between different events is influenced by the abiotic and biotic environment. Such knowledge is important for predicting the immediate and evolutionary phenological response of populations to changing conditions. We manipulated germination timing and shade in a multi-factorial experiment to investigate the relationship between spring and autumn phenology in seedlings of the pedunculate oak, Quercus robur, and whether this relationship was mediated by natural colonization of leaves by specialist fungal pathogens (i.e., the oak powdery mildew complex). Each week delay in germination corresponded to about 2days delay in autumn leaf senescence, and heavily shaded seedlings senesced 5-8days later than seedlings in light shade or full sun. Within seedlings, leaves on primary-growth shoots senesced later than those on secondary-growth shoots in some treatments. Path analyses demonstrated that germination timing and shade affected autumn phenology both directly and indirectly via pathogen load, though the specific pattern differed among and within seedlings. Pathogen load increased with later germination and greater shade. Greater pathogen load was in turn associated with later senescence for seedlings, but with earlier senescence for individual leaves. Our findings show that relationships between seasonal events can be partly mediated by the biotic environment and suggest that these relationships may differ between the plant and leaf level. The influence of biotic interactions on phenological correlations across scales has implications for understanding phenotypic variation in phenology and for predicting how populations will respond to climatic perturbation.

Effects of asymmetrical biotic interactions on multispecies dynamics

One of the key challenges in ecology is to predict multispecies spatial distributions in the future. The influence of biotic interactions in the form of competition and environmental change such as climate are thought to have significant impacts on the distribution of species. To ascertain this, we study a multispecies community assembly with asymmetrical competition across heterogeneous environments using mathematical modelling. With the aid of analytical and simulation analyses, we achieved the predictions of the species range margins (comprising the geographic boundary beyond which a species is not present). We also perform bifurcation analysis in order to understand the competitive dynamics across location. Our results show that the combined influence of the biotic and abiotic factors lead to coexistence of species when competition is relatively weak and existence of single dominant species territory during aggressive competitions. Also, the threshold values observed in the bifurcation analysis correspond to transcritical bifurcation points.

Keystone taxa predict compositional change in microbial communities.

The influence of biotic interactions on microbial community assembly is intensely debated. We hypothesized that keystone taxa, which influence community assembly through strong biotic interactions, are important for regulating microbial community composition. While highly connected microbes have been identified, evidence that these taxa act as keystones is lacking, because keystone status requires influence on whole-community dynamics. We address this gap, showing that small subsets of highly connected keystone taxa (generally 1%-5% of richness) can be optimal predictors of whole-community compositional change. In three long-term data sets, greater connectivity due to the presence of keystone taxa corresponded to lower compositional turnover. We further hypothesized that the influence of keystone taxa would be diminished when environmental disturbance was a strong driver of compositional change. We used two case studies of reference and disturbed communities to investigate how biotic and abiotic forces interact to shape community composition. Most of the same taxa were present in both the reference and disturbed communities, but keystone taxa had much greater explanatory power in the reference communities. Our results suggest that greater biotic connectivity arising from the presence of keystone taxa is stabilizing to community composition, and that keystone taxa can be good indicators of pending community shifts.

Influence of biotic interactions on the distribution of Canada lynx (Lynx canadensis) at the southern edge of their range

The persistence of cold-adapted species along their equatorial range edge (i.e., southern range edge for species in the Northern Hemisphere and northern range edge for species in the Southern Hemisphere) is threatened by climate change. These species will be challenged not just by unfavorable climatic regimes, but also by changing biotic interactions, which may be more intense along equatorial edges. However, we currently have a poor understanding of the nature of biotic interactions at range edges and how climate may mediate those interactions, particularly for cold-adapted mammals. We studied the distribution of threatened Canada lynx (Lynx canadensis) at their southern range edge in northern Washington, United States from 2014 to 2016. Using data collected from 397 camera-trap stations in snow-on and snow-off seasons, and single- and 2-species occupancy models, we investigated seasonal patterns of habitat selection and spatial association of lynx with their primary prey (snowshoe hares, Lepus americanus) and potential competitors (bobcats, Lynx rufus; cougars, Puma concolor). Single-species occupancy models revealed lynx distribution was strongly associated with snowshoe hare abundance and topographic variables related to lower temperatures and increased moisture. In contrast, bobcats and cougars were more generalized in their habitat associations or displayed the reverse response to environmental variables. Spatial overlap of the 3 felid species increased during snow-off seasons. Two-species occupancy models showed a decrease in use of camera sites by lynx when bobcats were present, suggesting lynx were avoiding their warm-adapted competitor. Taken together, these results suggest that biotic interactions are partly shaping large-scale lynx distribution patterns along their southern range edge. Increasing temperatures and loss of snow may result in a combination of habitat isolation and potential for increased competitive interactions for lynx at the margins of their range.

The unity, diversity and conformity of bugs (Hemiptera) through time

ABSTRACTThis paper outlines and discusses the fossil record of the Hemiptera – the fifth most diverse insect order. The diversity of these insects in comparison with the “Big Four” group is given, together with a short history of its classification. Updated information is presented about the fossil record of particular families, with a brief analysis. The main evolutionary traits of the major Hemiptera lineages are briefly described. The influence of biotic interactions with endosymbionts, shaping the evolution of the hemipterans as well as abiotic events and major global changes, is disputed. The innovations and perils of the evolutionary history of the Hemiptera are presented.

Contrasting effects of biotic interactions on richness and distribution of vascular plants, bryophytes and lichens in an arctic–alpine landscape

Biotic interactions may strongly affect the distribution of individual species and the resulting patterns of species richness. However, the impacts can vary depending on the species or taxa examined, suggesting that the influences of interactions on species distributions and diversity are not always straightforward and can be taxon-contingent. The aim of this study was therefore to examine how the importance of biotic interactions varies within a community. We incorporated three biotic predictors (cover of the dominant vascular species) into two correlative species richness modelling frameworks to predict spatial variation in the number of vascular plants, bryophytes and lichens in arctic–alpine Fennoscandia, in N Europe. In addition, predictions based on single-species distribution models were used to determine the nature of the impact (negative vs. positive outcome) of the three dominant species on individual vascular plant, bryophyte and lichen species. Our results suggest that biotic variables can be as important as abiotic variables, but their relative contributions in explaining the richness of sub-dominant species vary among dominant species, species group and the modelling framework implemented. Similarly, the impacts of biotic interactions on individual species varied among the three species groups and dominant species, with the observed patterns partly reflecting species’ biogeographic range. Our study provides additional support for the importance of biotic interactions in modifying arctic–alpine biodiversity patterns and highlights that the impacts of interactions are not constant across taxa or biotic drivers. The influence of biotic interactions, including the taxon contingency and range-based impacts, should therefore be accounted for when developing biodiversity forecasts.

Functional and phylogenetic assembly in a Chinese tropical tree community across size classes, spatial scales and habitats

Summary Increasingly, ecologists are using functional and phylogenetic approaches to quantify the relative importance of stochastic, abiotic filtering and biotic filtering processes shaping the pattern of species co‐occurrence. A remaining challenge in functional and phylogenetic analyses of tropical tree communities is to successfully integrate the functional and phylogenetic structure of tree communities across spatial and size scales and habitats in a single analysis. We analysed the functional and phylogenetic structure of tree assemblages in a 20‐ha tropical forest dynamics plot in south‐west China. Because the influence of biotic interactions may become more apparent as cohorts age, on local scales, and in resource‐rich environments, we perform our analyses across three size classes, six spatial scales and six distinct habitat types, using 10 plant functional traits and a molecular phylogeny for the >400 tree taxa found in the plot. All traits, except leaf area and stem‐specific resistance, had significant, albeit weak phylogenetic signal. For canopy species, phylogenetic clustering in small and medium size classes turned to phylogenetic overdispersion in the largest size class and this change in dispersion with size was found in each habitat type and across all spatial scales. On fine spatial scales, functional dispersion changed from clustering to overdispersion with increasing size classes. However, on larger spatial scales assemblages were functionally clustered for all size classes and habitats. Phylogenetic and functional structure across spatial and size scales and habitats gave strong support for a deterministic model of species co‐occurrence rather than for a neutral model. The results also support the hypothesis that abiotic determinism is more important at larger scales, while biotic determinism is more important on smaller scales within habitats.

Shifting Species Interaction in Soil Microbial Community and Its Influence on Ecosystem Functions Modulating

The supportive and negative evidence for the stress gradient hypothesis (SGH) led to an ongoing debate among ecologists and called for new empirical and theoretical work. In this study, we took various biological soil crust (BSCs) samples along a spatial gradient with four environmental stress levels to examine the fitness of SGH in microbial interactions and evaluate its influence on biodiversity-function relationships in BSCs. A new assessment method of species interactions within hard-cultured invisible soil community was employed, directly based on denaturing gradient gel electrophoresis fingerprint images. The results showed that biotic interactions in soil phototroph community dramatically shifted from facilitation to dominant competition with the improvement of microhabitats. It offered new evidence, which presented a different perspective on the hypothesis that the relative importance of facilitation and competition varies inversely along the gradient of abiotic stress. The path analysis indicated that influence of biotic interactions (r = 0.19, p < 0.05) on ecosystem functions is lower than other community properties (r = 0.62, p < 0.001), including soil moisture, crust coverage, and biodiversity. Furthermore, the correlation between species interactions and community properties was non-significant with low negative influence (r = -0.27, p > 0.05). We demonstrate that the inversion of biotic interaction as a response to the gradient of abiotic stresses existed not only in the visible plant community but also in the soil microbial community.

Can we disentangle predator–prey interactions from species distributions at a macro‐scale? A case study with a raptor species

There is a debate on whether an influence of biotic interactions on species distributions can be reflected at macro‐scale levels. Whereas the influence of biotic interactions on spatial arrangements is beginning to be studied at local scales, similar studies at macro‐scale levels are scarce. There is no example disentangling, from other similarities with related species, the influence of predator–prey interactions on species distributions at macro‐scale levels. In this study we aimed to disentangle predator–prey interactions from species distribution data following an experimental approach including a factorial design. As a case of study we selected the short‐toed eagle because of its known specialization on certain prey reptiles. We used presence–absence data at a 100 km2 spatial resolution to extract the explanatory capacity of different environmental predictors (five abiotic and two biotic predictors) on the short‐toed eagle species distribution in peninsular Spain. Abiotic predictors were relevant climatic and topographic variables, and relevant biotic predictors were prey richness and forest density. In addition to the short‐toed eagle, we also obtained the predictor's explanatory capacities for 1) species of the same family Accipitridae (as a reference), 2) for other birds of different families (as controls) and 3) artificial species with randomly selected presences (as null models). We run 650 models to test for similarities of the short‐toed eagle, controls and null models with reference species, assessed by regressions of explanatory capacities. We found higher similarities between the short‐toed eagle and other species of the family Accipitridae than for the other two groups. Once corrected by the family effect, our analyses revealed a signal of predator–prey interaction embedded in species distribution data. This result was corroborated with additional analyses testing for differences in the concordance between the distributions of different bird categories and the distributions of either prey or non‐prey species of the short‐toed eagle. Our analyses were useful to disentangle a signal of predator–prey interactions from species distribution data at a macro‐scale. This study highlights the importance of disentangling specific features from the variation shared with a given taxonomic level.

Plant–Mycorrhizal Fungus Interactions Affect the Expression of Inbreeding Depression in Wild Strawberry

The influence of biotic interactions on the expression of inbreeding depression has received only modest investigation; however, these interactions may be important in determining the magnitude and/or variation of inbreeding depression seen in the wild and invoked in models of mating and sexual system evolution. We present the first experimental test of the effects of plant–mycorrhizal fungus interactions on the expression of inbreeding depression. We inoculated selfed and outcrossed seedlings from eight hermaphrodite genotypes of wild strawberry (Fragaria virginiana) with mycorrhizal fungal spores and determined the effect on vegetative growth and sexual and asexual reproduction. We found that inoculated plants grew at rates similar to those of control plants but produced fewer flowers and more plantlets than controls. However, some of these effects varied with maternal genotype and cross type. As a consequence, mycorrhizal fungal inoculation had variable and trait‐dependent effects on the expression of ...

The influence of biotic interactions on soil biodiversity

Belowground communities usually support a much greater diversity of organisms than do corresponding aboveground ones, and while the factors that regulate their diversity are far less well understood, a growing number of recent studies have presented data relevant to understanding how these factors operate. This review considers how biotic factors influence community diversity within major groups of soil organisms across a broad spectrum of spatial scales, and addresses the mechanisms involved. At the most local scale, soil biodiversity may potentially be affected by interactions within trophic levels or by direct trophic interactions. Within the soil, larger bodied invertebrates can also influence diversity of smaller sized organisms by promoting dispersal and through modification of the soil habitat. At larger scales, individual plant species effects, vegetation composition, plant species diversity, mixing of plant litter types, and aboveground trophic interactions, all impact on soil biodiversity. Further, at the landscape scale, soil diversity also responds to vegetation change and succession. This review also considers how a conceptual understanding of the biotic drivers of soil biodiversity may assist our knowledge of key topics in community and ecosystem ecology, such as aboveground-belowground interactions, and the relationship between biodiversity and ecosystem functioning. It is concluded that an improved understanding of what drives the diversity of life in the soil, incorporated within appropriate conceptual frameworks, should significantly aid our understanding of the structure and functioning of terrestrial communities.

Evaluation of Xanthomonas campestris survival in a soil microcosm system.

Xanthomonas campestris pv. campestris is a pathogen of cruciferous plants. We studied the survival of the wild type strain and mutant derivatives which are deficient in exopolysaccharide (EPS) or in extracellular protease synthesis in soil microcosms in order to test the hypothesis that, in this environment, adherence to soil particles and scavenging of nutrients are very important strategies for bacterial survival. In sterile soil microcosms, differences in survival were only observed between the EPS producer and its mutant. In non-sterile soil experiments, survival of Prt- mutant was similar to EPS- mutant, suggesting that both characteristics have a strong influence in survival in the presence of the natural bacterial community. Bacterial decrease represented by the slope of regression lines was higher in non-sterile soil microcosms due to the influence of biotic interactions.

The Distribution of Polychaetes Along Environmental Gradients: An Example from the Or betel I o Lagoon, Italy

Abstract. Biological zonation in brackish habitats is usually related to the gradients of several factors, of which salinity is often taken as the most important. In contrast, recent papers, mainly on Mediterranean lagoons, have emphasized the role of other factors such as water movement and trophic status. In this paper, the distribution of polychaetes in the Orbetello lagoon (a poly‐hyperhaline pond on the northern Tyrrhenian coast) is compared with the gradients of a number of environmental parameters. Polychaete distribution turned out to be under the control of a variety of highly interrelated factors. The study of biotic zonation as a function of a single driving factor is thus overly simplistic even when dealing with ‘simple’ environments, as lagoons are often defined. Several factors and their synergistic effects must always be taken into account.SummaryA total of 79 species was collected from 13 sites in the Orbetello lagoon, comprising both brackish‐water and marine species as well as a large number of species typical of organically enriched habitats. Through correspondence analysis, three major polychaete assemblages were recognized, linked to three different zones of the lagoon: 1) the channels connecting the lagoon to the sea; 2) the western lagoon; 3) the eastern lagoon (including a small part of the western lagoon situated near the town of Orbetello). Such a zonation was shown ‐ by Trend Surface and linear correlation analyses ‐ to be consistent with the spatial trends of a number of environmental parameters such as vivification/confinement, water movement, dissolved oxygen, poikilohalinity, and poikilothermy (in the order of importance); in contrast, salinity (minimal values), sediment grain size, and primary productivity showed little or no relation to polychaete distribution. However, almost all environmental parameters were significantly correlated with each other, thus making it impossible to identify the principal factor. This demonstrates that biotic zonation cannot be explained as the resultant of the action of a single driving factor (e. g., salinity or confinement), even in environments which are usually considered to be relatively simple from a synecological point of view, such as brackish habitats. Both the synergism among the various abiotic factors and the influence of biotic interactions must always be taken into account.