Role Of Biotic Factors Research Articles

Strong cooperations among diazotroph and arbuscular mycorrhizal fungi taxa promote free-living nitrogen fixation at soil-rock mixing layer

Soil nitrogen (N) is a renewable resource of N fixed by free-living N fixation (FLNF) diazotrophs. Thus, understanding the microbial driving mechanism of FLNF activity can aid in the optimization of N input. However, the role of co-symbiosis between diazotrophs and arbuscular mycorrhizal fungi (AMF) in the FLNF activity at different soil depths has been largely overlooked, particularly in karst ecosystems. Thus, we investigated soil properties and the characteristics of diazotroph and AMF across soil depths, from topsoil to soil-rock mixing layer, based on the soil profile. Soil properties such as soil organic matter and ammonium N decreased with increasing soil depth, whereas pH showed the opposite trend. Similarly, diazotroph abundance and diversity and AMF abundance were higher by 8–73% in 0–20 cm soil than in 20–40 cm and soil-rock mixing layer. Despite high diazotroph abundance in the topsoil, the FLNF activity was higher by 30% at soil-rock mixing layer than in 0–20 cm. The co-occurrence network analysis revealed a strengthening of the cooperative relationship between the diazotroph and AMF taxa at the soil-rock mixing layer via an increase in the number of unique AMF taxa. A structural equation model indicated that increasing soil depth improves the FLNF activity due to increasing soil pH and mutualistic cooperations between diazotrophs and AMF taxa, such as Bradyrhizobium to AMF unclassified taxa and Bradyrhizobium to Racocetra. This study provides novel insights into the interspecific interactions between diazotrophs and AMF, rather than their abundance and diversity, which were found to be the most important driving factors of FLNF activity at the soil-rock mixing layer. Consequently, the roles of biotic factors in influencing mutually beneficial microbial taxa regulating FLNF activity should be considered during vegetation recovery in the fragile karst region.

The forgotten ones of ports: The filter feeders at the heart of siltation processes

Siltation is a major concern in dynamic and complex ecosystems, such as ports. The mud must be regularly dredged to avoid disturbing the navigation channels. Sediments are carried by the waters entering the port and are partially trapped by harbour structures. Numerous studies have been conducted on the physical factors influencing siltation in port areas, whereas, few have focused on the role of biotic factors in mud formation. However, research in other contexts has shown that organisms that are abundant in pontoons, such as bivalves and tunicates, play an important role in this siltation process. All of these organisms belong to the filter feeder group. The sediments sucked in by the filter feeders are excreted in the form of faeces or mucus-bound pseudo-faeces. These waste materials, called bioproducts, settle efficiently and are involved in the composition of the mud. This study aimed to highlight the role of filter feeders in the siltation process in port areas and to determine the factors that influence the production of bioproducts by filter feeders. To investigate the role of filter feeders in the siltation processes, an experimental analysis was conducted in the largest marina in Europe (La Rochelle, France). It is divided into four basins with distinct filter feeder communities and environmental conditions, allowing for a detailed study of the environmental factors that influence the production of bioproducts. This analysis consisted of recovering and studying the bioproducts generated by the filter feeders using sediment traps fixed under pontoons. To explore the evolution of this biological production, 16 campaigns were conducted from January to March 2020 and May to July 2020. The total amount of dry matter produced was constant between seasons at approximately 130 g/m2/d; marina-wide, this amount represents a total daily production of 3.2 tons. However, the production amount varies spatially and temporally in relation to marine hydrodynamics and the organisms involved. Bioproduction was taxon-dependent: areas abundant in oysters and mussels were the areas with the most pronounced bioproduction, whereas there was no significant relationship between bioproduction and the presence of tunicates or scallops. If we consider bioproduction on a seasonal scale, we can see that the campaigns with the greatest production correspond to the periods when the sediment supply was the highest, i.e. when the tidal range was the highest. The quality of the bioproducts (organic matter content) differed between seasons, which can be explained by both environmental and metabolic changes. Understanding the role of filter feeders in siltation processes appears to be essential in port environments that need to be regularly dredged to ensure safe navigation.

Spatial models can improve the experimental design of field-based transplant gardens by preventing bias due to neighborhood crowding.

Field-based transplant gardens, including common and reciprocal garden experiments, are a powerful tool for studying genetic variation and gene-by-environment interactions. These experiments assume that individuals within the garden represent independent replicates growing in a homogenous environment. Plant neighborhood interactions are pervasive across plant populations and could violate assumptions of transplant garden experiments. We demonstrate how spatially explicit models for plant-plant interactions can provide novel insights on genotypes' performance in field-transplant garden designs. We used individual-based models, based on data from a sagebrush (Artemisia spp.) common garden, to simulate the impact of spatial plant-plant interactions on between-group differences in plant growth. We found that planting densities within the range of those used in many common gardens can bias experimental outcomes. Our results demonstrate that higher planting densities can lead to inflated group differences and may confound genotypes' competitive ability and genetically underpinned variation. Synthesis. We propose that spatially explicit models can help avoid biased results by informing the design and analysis of field-based transplant garden experiments. Alternately, including neighborhood effects in post hoc analyses of transplant garden experiments is likely to provide novel insights into the roles of biotic factors and density dependence in genetic differentiation.

Species Diversity Regulates Ecological Strategy Spectra of Forest Vegetation Across Different Climatic Zones.

Ecological strategy is the tactics employed by species in adapting to abiotic and biotic conditions. The ecological strategy spectrum is defined as the relative proportion of species in different ecological strategy types within a community. Determinants of ecological strategy spectrum of plant community explored by most previous studies are about abiotic factors. Yet, the roles of biotic factors in driving variations of ecological strategy spectra of forest communities across different geographic regions remains unknown. In this study, we established 200 0.04-ha forest dynamics plots (FDPs) and measured three-leaf functional traits of tree and shrub species in four forest vegetation types across four climatic zones. Based on Grime’s competitor, stress-tolerator, ruderal (CSR) triangular framework, and the StrateFy method, we categorized species into four ecological strategy groups (i.e., C-, S-, Int-, and R-groups) and related the ecological spectra of the forests to three species diversity indices [i.e., species richness, Shannon-Wiener index, and stem density (stem abundance)]. Linear regression, redundancy analysis, and variance partition analysis were utilized for assessing the roles of species diversity in regulating ecological strategy spectra of forest communities across different climatic zones. We found that the proportion of species in the C- and Int-groups increased, while the proportion of species in the S-group decreased, with the increase of three indices of species diversity. Among the three species diversity indices, stem abundance played the most important role in driving variations in ecological strategy spectra of forests across different climatic zones. Our finding highlights the necessity of accounting for biotic factors, especially stem abundance, in modeling or predicting the geographical distributions of plant species with varied ecological adaptation strategies to future environmental changes.

State of dark coniferous plantations in the southern part of the Yenisei Siberia: the role of biotic factors

The article assumes that, the areas of dark coniferous forests with disturbed and lost stability are catastrophically expanding in Siberian regions in the modern period. This fully applies to the plantations with a prevalence of Abies sibirica Ledeb., located in the southern part of the Yenisei Siberia (territory of the Krasnoyarsk Region). The research was carried out in the spruce and fir plantations of the Biryusinsky district forestry of the KGU “Emelyanovskoye lesnichestvo” in order to clarify the role of the main biotic factors of the sanitary state violation and drying out of dark coniferous plantations. The method of research is route and detailed forest pathological inspection with the subsequent integral evaluation of the sanitary and forest pathological state of forest plantations. On the basis of all indicators of the state and tree falling parameters, a slight disturbance of the stability of the forest plantations Picea obovata Ledeb. was established; weak-strong disturbance until the loss of stability of A. sibirica plantation with their progressive drying out. The main biotic factors in the accumulation of pathological tree fallings and degradation of fir stands are the root pathogen Armillaria mellea s. l. and the invasive xylophage Polygraphus proximus Blandford in association with the micromycete Grosmannia aoshimae, that have a concomitant negative effect on trees. Additional factors of weakening, less often drying of fir trees are necrotic rust diseases; they are bacterial dropsy (pathogen is an association of phytopathogenic bacteria) and blister rust (pathogen is Melampsorella caryophyllacearum G. Schrot.), genus Monochamus.

The role of biotic factors during plant establishment in novel communities assessed with an agent-based simulation model.

BackgroundEstablishment success of non-native species is not only influenced by environmental conditions, but also by interactions with local competitors and enemies. The magnitude of these biotic interactions is mediated by species traits that reflect competitive strength or defence mechanisms. Our aim was to investigate the importance of species traits for successful establishment of non-native species in a native community exhibiting biotic resistance in the form of competition and herbivory.MethodsWe developed a trait-based, individual-based simulation model tracking the survival of non-native plants in a native community. In the model, non-native plants are characterized by high or low values of competition and defence traits. Model scenarios included variation of initial number of non-natives, intensity of competitive interaction, density of herbivores and density as well as mixture of the native community.ResultsTraits related to competition had a much greater impact on survival of non-native species than traits related to defence. Survival rates of strong competitors never fell below 50% while survival of weak competitors averaged at about 10%. Weak competitors were also much more susceptible to competitive pressures such as community density, composition and competition intensity. Strong competitors responded negatively to changes in competition intensity, but hardly to composition or density of the native community. High initial numbers of non-native individuals decreased survival rate of strong competitors, but increased the survival rate of weak competitors. Survival under herbivore attack was only slightly higher for plants with high defensive ability than for those with low defensive ability. Surprisingly, though, herbivory increased survival of species classified as weak competitors.DiscussionHigh survival rates of strong non-native competitors relate to a higher probability of successful establishment than for weak competitors. However, the reduced survival of strong competitors at high initial numbers indicates a self-thinning effect, probably mediated by a strongly competitive milieu. For weak competitors, our model emphasizes positive effects of high propagule pressure known from field studies. General effects of herbivory or defence abilities on survival were not supported by our model. However, the positive effect of herbivory on survival of weak competitors indicated side effects of herbivory, such as weakening resident competitors. This might play an important role for establishment of non-natives in a new community.

Biotic drivers of river and floodplain geomorphology – New molecular methods for assessing present‐day and past biota

AbstractGeomorphology has increasingly considered the role of biotic factors as controls upon geomorphic processes across a wide range of spatial and temporal scales. Where timescales are long (centennial and longer), it has been possible to quantify relationships between geomorphic processes and vegetation using, for example, the pollen record. However, where the biotic agents are fauna, longer term reconstruction of the impacts of biological activity upon geomorphic processes is more challenging. Here, we review the prospect of using environmental DNA as a molecular proxy to decipher the presence and nature of faunal influences on geomorphic processes in both present and ancient deposits. When used appropriately, this method has the potential to improve our understanding of biotic drivers of geomorphic processes, notably fauna, over long timescales and so to reconstruct how such drivers might explain the landscape as we see it today. Copyright © 2017 John Wiley & Sons, Ltd.

ТРЕНДЫ В ЭВОЛЮЦИОННОЙ СИСТЕМЕ БИОСФЕРЫ

Предлагается рассматривать эволюцию биосферы как процесс, поддерживаемый совокупностью взаимосвязанных трендов, образующих ее эволюционную систему. Под трендом эволюции биосферы понимается преемственное развитие системы структур и связей, имеющее определенную направленность в эволюционном пространстве-времени. Введение понятия трендов обусловлено неоднородностью и разнообразием процесса эволюции биосферы. Эта неоднородность существовала и существует в эволюционном времени, поскольку в истории биосферы ее эволюционная система не была постоянной по структуре трендов, изменялись и механизмы эволюционных процессов. По мере развития биосферы возрастала роль кооперативных, симбиотических взаимосвязей и биотических факторов в общебиосферных процессах. Разнообразие свойственно не только эволюционирующим системам, но и самому процессу эволюции. Эволюция жизни в биосфере, биологическая эволюция, которая обычно рассматривается как «происхождение видов» и крупных таксонов, есть только часть эволюции биосферы, которая эволюционирует как единая биокосная система. Концепция эволюционной системы и трендов как ее элементов представляет собой попытку упорядочения этого разнообразия на основе системного подхода.

Papel de los factores bióticos y las sequías en el decaimiento del bosque: aportaciones desde la dendroecología

Sanguesa-Barreda, G., Camarero, J.J., Linares, J.C., Hernandez, R., Oliva, J., Gazol, A., et al. 2015. Role of biotic factors and droughts in the forest decline: contributions from dendroecology. Ecosistemas 24(2): 15-23. Doi.: 10.7818/ECOS.2015.24-2.03. Increasing mortality and decline of forests are affecting several tree species and biomes. These events of forest decline have been related to the interaction of several global change elements, like the increase in drought stress or a higher incidence of biotic stress factors. However, the roles played by biotic stressors have been scarcely explored as related to drought stress. In this paper we retrospectively characterize the effects of these organisms on radial growth of trees already stressed by drought using dendrochronology. The combined effect of mistletoe and droughts reduce tree growth in Scots pine and increase defoliation, being these effects more noticeable in the apex. The pine processionary moth induces growth losses in the affected stands of black pine, but they usually recover two years after the outbreak. We did not find a determinate role of root pathogens on silver fir dieback. Finally, dead Aleppo pine trees infested by bark beetles showed similar growth patterns than living pine trees. This study allows characterizing some of the complex and multiple effects of different biotic stressors on growth and vulnerability of forests subjected to the negative effects exerted by droughts.

Recent advances in knowledge of BTV‑host‑vector interaction.

Bluetongue virus (BTV) has since 1998 extended its distribution further North than where it has previously been encountered. Changes in the epidemiology of Bluetongue (BT), as well as novel features of recent outbreaks of BTV in Europe, have stimulated research on BTV‑vector‑host interaction. The outbreak of BTV‑8 in Northern Europe from 2006‑2008 is particular noteworthy in this regard, as the European strain of BTV‑8 demonstrated novel properties, including high virulence - especially for cattle - and the capability to cross the ruminant placenta. The virus was in addition transmitted by indigenous European Culicoides species that had not previously been implicated in the widespread transmission of BTV. Recent advances in the scientific understanding of BTV‑vector‑host interaction include increased knowledge of the virus' replication cycle, the role of biotic factors in influencing viral infection of the insect vector, increased knowledge of BTV immunology and pathogenesis in the mammalian host, and increased knowledge of virulence and pathogenicity features of newly discovered serotypes/strains of the virus. New research on aspects of BTV‑vector‑host interaction has been driven in part by developments in molecular biology and experimental infection biology, of which next generation sequencing, the expression of individual viral proteins in cell culture, the establishment of a reverse genetics system for the virus, the development of novel in vitro and in vivo infection models, and refinement of existing BTV experimental infection methodologies have proven instrumental. Moreover, these developments have also provided the opportunity for the development of novel vaccine strategies. This article provides a synopsis of selected recent advances that have been made in the understanding of BTV‑vector‑host interaction, with a particular focus on research that has been conducted in Europe over the last 5 years.

Crab regulation of cross-ecosystem resource transfer by marine foraging fire ants

Permeability of boundaries in biological systems is regulated by biotic and/or abiotic factors. Despite this knowledge, the role of biotic factors in regulating resource transfer across ecosystem boundaries has received little study. Additionally, little is known about how cross-ecosystem resource transfer affects source populations. We used experiments, observations and stable isotopes, to evaluate: (1) the proportion of intertidal-foraging black fire ant (Solenopsis richteri) diet derived from marine sources, (2) how black fire ant cross-ecosystem resource transfer is altered by the dominant bioengineer in the intertidal, a burrowing crab (Neohelice granulata), (3) the top-down impact of these terrestrial ants on a marine resource, and (4) the effect of marine resources on recipient black fire ants. We found that more than 85% of the black fire ant diet is derived from marine sources, the number of intertidal foraging ants doubles in the absence of crab burrows, and that ants cause a 50% reduction in intertidal polychaetes. Also, ant mound density is three times greater adjacent to marine systems. This study reveals that cross-ecosystem foraging terrestrial ants can clearly have strong impacts on marine resources. Furthermore, ecosystem engineers that modify and occupy habitat in these ecosystem boundaries can strongly regulate the degree of cross-ecosystem resource transfer and resultant top down impacts.

The role of biotic factors in the transmission of free-living endohelminth stages

The transmission success of free-living larval stages of endohelminths is generally modulated by a variety of abiotic and biotic environmental factors. Whereas the role of abiotic factors (including anthropogenic pollutants) has been in focus in numerous studies and summarized in reviews, the role of biotic factors has received much less attention. Here, we review the existing body of literature from the fields of parasitology and ecology and recognize 6 different types of biotic factors with the potential to alter larval transmission processes. We found that experimental studies generally indicate strong effects of biotic factors, and the latter emerge as potentially important, underestimated determinants in the transmission ecology of free-living endohelminth stages. This implies that biodiversity, in general, should have significant effects on parasite transmission and population dynamics. These effects are likely to interact with natural abiotic factors and anthropogenic pollutants. Investigating the interplay of abiotic and biotic factors will not only be crucial for a thorough understanding of parasite transmission processes, but will also be a prerequisite to anticipate the effects of climate and other global changes on helminth parasites and their host communities.

MOVEMENT IN CORRIDORS: ENHANCEMENT BY PREDATION THREAT, DISTURBANCE, AND HABITAT STRUCTURE

Movement by stream fish is known to be strongly influenced by abiotic factors such as floods and temperature, but roles of biotic factors, such as predation threat, and interactions of abiotic and biotic factors are less clear. Predation threat is known to fragment populations of killifish, Rivulus hartii, in Trinidad rivers by rendering habitat inhospitable. We asked whether such spatial fragmentation was accompanied by reduced movement by fish in the predator-occupied zone of a river, relative to a zone free of the strong piscivore, Hoplias malabaricus, that causes the fragmentation. We used a 19-mo marking study in a river with a predator barrier, field experiments in the river, and mesocosms to evaluate four hypotheses: (1) the predator reduces prey movement in the river; (2) for the special case of prey leaving refugia, the predator increases movement; (3) movement positively cor- relates with water level in the predator's presence; and (4) complex physical structure in hazardous habitat promotes prey movement. We marked 1467 Rivulus in the natural study areas and had 1015 recaptures. Contrary to Hypothesis 1 but in support of Hypothesis 2, prey showed greater movement along the river in the presence of the predator, regardless of whether the fish resided in a refuge at its previous capture. An experiment with introduced fish confirmed the findings that move- ment was elevated in the predator's presence. Effects of an abiotic factor (water level, Hypothesis 3) and a phenotypic trait (body size) depended upon whether the predator was present: movement was independent of water level and body size in the absence of the predator, but positively related to both variables in the predator's presence. Emigration from the river to tributaries was also independent of body size in the predator's absence, but positively size-dependent in the predator's presence. Complex physical structure (Hy- pothesis 4), in the form of cobble added to experimental pools, enhanced the transit of fish through hazardous pools. This study shows that spatial fragmentation does not necessarily imply that movement between fragments will be impeded (dynamical fragmentation). Rather, it is possible that movement among spatial fragments may be enhanced by the same factor, predation threat, that produced the spatial fragmentation in the first place. Because of the context-dependent effects of an abiotic factor (water level) and a phenotypic variable (body size) on movement, the study also emphasizes the need to clarify the exact role of predation as an agent promoting or retarding movement, and it suggests a need for incorporating such parameters into models of movement and metapopulation dynamics.

Role of biotic factors in the control of soil-borne fungi by fluorescent pseudomonads

Several biological agents isolated from the rhizosphere of cabbage plants were shown to be able to attack antagonistic strains of Pseudomonas fluorescens. Bdellovibrio sp. formed plaques on layers of Ps. fluorescens cultivated on a yeast extract-peptone medium; on the other hand, addition of fluorescent pseudomonads increased the population of Bdellovibrio sp. in rhizosphere soil. Non-identified protozoa and nematode species were shown to feed on Ps. fluorescens grown on artificial media.

THE SEDIMENT BUDGET OF THE LILLOOET RIVER BASIN, BRITISH COLUMBIA

The sediment and solute budget of the Lillooet River basin in British Columbia (3,150 km2) is developed to exemplify a methodology that has the potential to unify geomorphological research. Sediment and solute transport processes in Holocene time are identified and quantified. The budget is demonstrated to be severely unbalanced. Historical events and transient response to those events are implicated. A minimum of four time scales of integration—geological, Pleistocene, Holocene and contemporary—are proposed, and the role and status of the components of the sediment budget are examined. Storage sites and solute sinks, linkages among sediment and solute transport processes, the role of biotic factors, weathering, stratigraphic evidence, and the hydrologic balance are individually reviewed. Spatial scale considerations provide a way of interpreting and aggregating the above complex factors. In general, there appears to be no spatial scale at which sediment and solute supply from the slopes is in balance wit...

Abiotic and biotic factors influencing the winter distribution of predatory insects.

Various environmental factors were investigated to analyse those involved in successful overwintering and possibly overwintering site selection for Tachyporus hypnorum and Demetrias atricapillus, both important coleopteran predators of cereal aphids. The results of the study indicated food supply to be important for both predator species during the winter period, although the role of biotic factors in site selection in the autumn could not be clearly demonstrated. The winter distribution of the two species could, however, be explained well in terms of abiotic factors. It is suggested that these and other similar predator species have well-defined overwintering requirements and that these can be exploited in the management of field boundary habitats.

Observations of the biotic factors affecting the populations of Epicerura pulverulenta Hampson (Lepidoptera: Notodontidae)

Field and laboratory observations of Epicerura pulverulenta Hampson (Lepidoptera:Notodontidae) elucidated the role of biotic factors in the moth’s populations. Natural enemies recorded included Gryon and Telenomus spp (Hymenoptera:Scelionidae) which parasitized 33% of eggs studied. Also, about 4% of the larvae were parasitized by the dipterous tachinids Zygobothria atropivora Robineau-Desvoidy, Exorista xanthaspis Wiedeman, Blepharella sp., and P. quadrizonula (Thompson); and the perilampid Perilampus dubius (Walker), all solitary endoparasitoids. The predators included Belanogaster dubius Kohl. (Vespidae), Glypsus erubescens Dist. (Pentatomidae), Camponotus macuiatus F. (Formicidae) and a kite (bird). They accounted for 12% of larval mortality. In addition, 27% of the 4346 larvae studied developed mycosis caused by Paecilomyces farinosus (Dickson ex Fries) Browne and Smith. A nematode, Hexamermis sp. was also associated with the larvae killing 1.5% of them. High pupal mortality was observed, but the cause was unknown.