Ecological Complexity最新文献

In ecological systems, multiple interactions connect various kinds of components. Strong and weak as well as positive and negative effects cause complex dynamics and often quite unpredictable processes. Human impact is added to this complexity, with all of its diverse effects. In this paper, we present a case study on the Kelian river ecosystem (Borneo), connecting pristine habitats upstream, a gold mine close to the middle section and human settlements downstream. For six locations, separate food web models had been developed earlier. Here we first analyze the ecological system by loop analysis and compare its outcome for different sites. Second, we identify the most crucial human impacts and implement these in modified loop analysis models. We determine the sign of various effects and study the consistency of human impact on different sites and various organisms. Adding human impact to the models (1) increased the ratio of clear predictions, (2) caused the appearance of “zero” predictions in three sites and (3) reduced the variability of predictability along the river.

Abies religiosa's forests are severely endangered as a result of climate change; to save this species and its biological interactions, population assisted migration is discussed in forest management, but not in the microbial ecology field. Our objectives were to analyze its mycorrhizal networks; and, with this data, to identify potential facilitator plants and it's most important mycorrhizal fungal links. This information could be used together in assisted migration programs to connect Abies religiosa saplings to their mycorrhizal network and improve their field establishment. We collected 47 rhizosphere samples from 19 plant species and sequenced their fungal ITS2 region by Illumina. In the whole fungal community, 464 species were mycorrhizal fungi with assigned guild (32%). In this subset, 85 fungi are arbuscular, 365 ectomycorrhizal and 14 from orchid-mycorriza. The Abies religiosa bipartite network is low nested and highly modular, and has a scale-free architecture. Besides Abies religiosa, the plants with the largest degree and the lowest average shortest path were Salix paradoxa, Muhlenbergia spp., and Baccharis conferta. The most important fungal nodes are species of Cortinarius, Genea, Rhodoscypha, Russula, and Tomentella. We suggest to evaluate the Abies' future establishment in the following scheme: in the first year reintroduce Muhlenbergia spp., and Baccharis conferta, in the second year Salix paradoxa, and in the third year–once the mycorrhizal network is reestablished– Abies religiosa' saplings in close proximity of these plants. This scheme is proposed using the data and network analyses of the present study.

Anti-predator behavior in the form of vigilance greatly influences the dynamics of a predator-prey system. In the present work, we investigate the impact of prey vigilance in a three-species food chain model where both prey and middle predator use vigilance as a survival strategy in the presence of their respective predators. We present basic mathematical results such as local and global stability, bifurcation behavior of the system. We explore the variation of the densities of the populations in different bi-parameter spaces and observe that vigilance plays a crucial role in the survival and extinction of the populations.

Climate change is a grave danger for humans and a looming threat to Earth's biodiversity in the twenty-first century. Assessing the vulnerability of species to climate change is critical for practical conservation efforts. Due to their limited dispersal ability, amphibians are one of the most vulnerable groups of vertebrates to climate change. Among them, the species that inhabit mountains suffer a tremendous amount of climate change-induced pressures. We, therefore, adopted the Azerbaijan Mountain Newt (Neurergus crocatus), which currently inhabits Northwest Iran, North Iraq, and Southeast Turkey, as a case study for assessing the effects of climate change on the distribution patterns of mountain amphibians. By applying the species distribution models (SDMs) in this study, we tried to hindcast the species distribution area in the past and illustrate the impacts of climate change on its distribution in the present and future (the 2050s and 2070s) climate conditions. Also, the patch metrics have been deployed for identifying habitat fragmentation. Our results indicate a more than 50% rise in the species’ current suitable habitats compared to its glacial refugia. The suitable habitat is expected to gradually decrease in RCP 2.6 and RCP 8.5. Among the three countries in which the species occurs, its distribution overlaps with protected areas only in Iraq. The number of habitat patches will grow and reach approximately 20 to 60 patches by 2070 and the average area of the patches will decrease throughout this time. Aside from the numerous threats that endanger the species, climate change puts the long-term existence of Azerbaijan Newt in jeopardy. The results of this study stress the urgent need for taking extreme measures on the species management and conserving its remnant habitat patches.

Allelopathy plays a crucial role in providing competitive advantage to several alien invasive species, and assists in their establishment beyond native boundaries. Role of allelopathy in the invasion success of the alien weed, Parthenium hysterophorus is well established; however, the ecological and evolutionary factors that could affect its allelopathic interactions are relatively unexplored. In our earlier findings, we suggested the presence of two morphotypes (P_A and P_B) in the population of P. hysterophorus, with variable morphology, physiology, and level of ecological impacts. Here, we hypothesize that phenotypically distinct morphotypes of P. hysterophorus may vary in their phytotoxicity and allelochemistry, thereby producing differential ecological impact. To test this hypothesis, effects of rhizospheric soil (RS) and plant amended soils (PAS) of the two morphotypes of P. hysterophorus (P_A and P_B) were studied on selected dicot (Bidens pilosa and Senna occidentalis) and monocot species (Phalaris minor and Avena fatua). Also, the composition of allelochemicals in P_A and P_B was assessed using Liquid Chromatography and Mass Spectrometry (LC-MS). The study revealed that the phytotoxic effect of P_B was greater than P_A in all the parameters measured for dicot species and in most of the parameters studied in monocot species. A generalized dose-dependent response was observed in the test species (PAS0 < PAS10 < PAS20 < PAS40) and the effect of RS was comparable to PAS20 and PAS40. A greater number of allelochemicals were reported from P_B, which is in accordance with the growth studies. The study concludes that intraspecific variations account for differential phytotoxicity and allelochemistry in P. hysterophorus.

The interest in understanding the climate-life system that has fostered the Gaia hypothesis (GH) has resulted in multiple explanatory theories, making its status unclear and controversial. This work seeks to bring some clarity to the debates surrounding the GH with the aim to make it amenable to scientific scrutiny. We discuss what it means to take the GH at face value and its implications for a potential research programme we call ‘functional climatology’.

Plant diseases are among the major causes of the low productivity of crops, causing yield losses of up to 30%, heralding an enormous threat to global food security. Indiscriminate use of chemical-based fungicides for controlling fungal diseases has raised severe concerns about ecosystem health. Moreover, pathogens have become insensitive against these chemicals necessitating excessive use of chemicals for adequate control. The resulting accumulation of these chemicals in the food chain has provoked numerous health complications. For combating the adversaries of chemical-based fungicides, biological control of fungal pathogens is proposed as an eco-friendly alternative. Among various biological controls, Trichoderma-based biological control agents (BCAs) are widely used in agriculture for controlling soil-borne pathogens. These BCAs are commercialized and known as; stimulators of resistance in plants, growth enhancers, bio-fertilizers, and bio-pesticides. Biological management of plant pathogens has yielded valuable results in the sustainability of ecosystems and compelling improvements in the quality and quantity of agricultural produce. These BCAs exhibit potential against pathogens, remarkably improve photosynthesis, plant growth, and nutrient use efficiency for impressive crop yields. Despite these peculiarities, Trichoderma's mechanisms against pathogens and their growth promotional effects are not thoroughly investigated, hence formulating the prime objective of the current review. Along with these, Trichoderma-based fungicides marketed in different geographical locations are encompassed in this review. Finally, the knowledge gaps and future research directions for improving the efficacy of Trichoderma-based BCAs are discussed.

The Rosenzweig-MacArthur predator-prey model is the building block in modeling food chain, food webs and ecosystems. There are a number of hidden assumptions involved in the derivation. For instance the prey population growth is logistic without predation but also with predation. In order to reveal these we will start with modelling a resource-predator-prey system in a closed spatially homogeneous environment. This allows us to keep track of the nutrient flow. With an instantaneous remineralisation of the products excreted in the environment by the populations and dead body mass there is conservation of mass. This allows for a model dimension reduction and yields the mass balance predator-prey model. When furthermore the searching and handling processes are much faster that the population changing rates, the trophic interaction is described by a Holling type II functional response, also assumed in the Rosenzweig-MacArthur model. The derivation uses an extended deterministic model with number of searching and handling predators as model variables where the ratio of the predator/prey body masses is used as a mechanistic time-scale parameter. This extended model is also used as a starting point for the derivation of a stochastic model. We will investigate the stochastic effects of random switching between searching and handling of the predators and predator dying. Prey growth by consumption of ambient resources is still deterministic and therefore the stochastic model is hybrid. The transient dynamics is studied by numerical Monte Carlo simulations and also the quasi-equilibrium distribution for the population quantities is calculated. The body mass of the prey individual is the scaling parameter in the stochastic model formulation. This allows for a quantification of the mean-field approximation criterion for the justification of replacement of the stochastic by a deterministic model.

Environmental interactions and the effects of such interactions on the evolution of genome attributes is an intriguing area of ongoing research. Several earlier studies have delved into how the genome size (GS) and the guanine-cytosine content (GC) of genomes are shaped by species’ ecology while largely disregarding other genome attributes, such as number of chromosomes (CR), number of genes (GE), and protein count (PC) from such comparisons. The present study was designed at understanding the influence of ecology––climate, habitat, and depth––on genome attributes by using the most current data on 579 whole fish genomes available at NCBI. Given the diverse and intricate roles of GS and GC in species adaptations to temperature, salinity, and hydrostatic pressure, the focus was on finding if and how the genomes responded to these stressors and if any common patterns existed in the genome-level responses. Our analyses exhibited some significant and intriguing trends for fishes as a whole while indicating strong effects of ecology on GS, GC, CR, and PC. Also, some very unique trends were observed on regressing GS and GC values across temperature, salinity, and depth clines. Accordingly, a very strong decline in the GS and a concomitant increase in GC were observed in species through the tropics/sub tropics to the temperate/poles, from freshwater to the marine habitats, and from the pelagic to bathydemersal depths. Observed patterns strongly support the notion that smaller GS and larger GC are associated with species inhabiting more stable environments and vice versa. The results also signify the effect of these patterns on protein flexibility and its role in tolerating stressful conditions. Observed patterns are discussed in the light of latitudinal biodiversity gradient, habitat complexity, and energy and metabolic expenditure hypothesis.