No full-text available
To read the full-text of this research,
you can request a copy directly from the author.
Fluctuations of Animal Populations and a Measure of Community Stability
... That is, if the index used to study the correlation between SDi and trophic production changes from one author to another, then it is practically impossible to find a relevant and non-contingent pattern. Amidst this controversy, a fact solidly contrasted with empirical evidence (see Fig. 2 in Rodríguez et al., 2013) is that, assuming those steady conditions early defined by MacArthur (1955; i.e., that the amount of energy going out of the food web is equal to the amount coming in) the relationship between total eco-kinetic energy per plot (Eq. (7) in section 3) and the value of H (Eq. (1)) follows an inverted Upattern. ...
... Given the difficulties in developing an ecosystem theory fully homomorphic with statistical mechanics (Svirezhev, 2000;Ulanowicz, 2004;Nielsen et al., 2020), mainstream ecology assumed that k = 1 in Eq. (1). However, according to Margalef (1972;, the increase of H has an anti-kinetic effect on the 'oscillation' of organisms ('talandic temperature'; Goodwin, 1963;Margalef, 2021), by reducing their dispersal activity around a given reference functional position to perform their ecological niche in an equivalent manner either across space or over time (ergodicity; Hopf, 1932;Tolman, 1938;MacArthur, 1955;Kerner, 1957;Kikuzawa et al., 2009;Gould and Tobochnik, 2021). Therefore, since T increases with kinetic energy (see above), then H has an anti-thermic effect on flora and fauna. ...
The spectrum of species diversity (SDi) can be broken down into αSDi (taxocene level), βSDi (community level), and γSDi (metacommunity level). Species richness (S) and Shannon's index (H) are well-known SDi measures. The use of S as a surrogate for SDi often neglects evenness (J). Additionally, there is a wide variety of indicators of SDi. However, there are no reliable theoretical criteria for selecting the most appropriate SDi index despite the undeniable empirical usefulness of this parameter. This situation is probably due to the analytical gap still existing between SDi and trophodynamics. This article contributes to closing that gap by analyzing why S as a single surrogate for SDi is inconsistent from the trophodynamic point of view, so that an index combining S and J, such as H or H B (Brillouin's index), are the most appropriate choices in the context of a new theoretical framework (organic biophysics of ecosystems, OBEC) based on the well-known classical links between ecosystem ecology and thermodynamics. Exploration of data from reef fish surveys under stationary and non-stationary conditions corroborated the existence of the ecological equivalent of Boltzmann's constant (k eτ(e)) at the worldwide scale. This result substantiates the usefulness of the ecological equivalent of the compressibility factor as an indicator of environmental impact. k eτ(e) stablishes an analytical linkage between ecology, information theory, and statistical mechanics that allowed us to propose a new measure of total negative entropy (a.k.a. syntropy) per survey (S eτT) that is easy to calculate and displayed a highly significant correlation with total standing biomass per survey (m eTs). According to the slope of the regression equation S eτT , m eTs there is a large portion of S eτT that leaks into the environment and/or is captured by numerous ecological degrees of freedom independent of standing biomass. According to the changing value of the exponent of k eτ(e) , even among coex-isting taxocenes, it would have been impossible to obtain the results discussed in this article if the analysis had been carried out at the βSDi or γSDi level. This establishes αSDi as the most appropriate level of analysis to obtain empirically useful results about the key functional connections on which trophodynamic stability depends in dynamic multispaces. The results summarized here are based on the careful selection and intertwining of a few key variables, which indicates the importance of developing models as simple as possible in order to achieve the reliability necessary for successful biological conservation.
... That is, if the index used to study the correlation between SDi and trophic production changes from one author to another, then it is practically impossible to find a relevant and non-contingent pattern. Amidst this controversy, a fact solidly contrasted with empirical evidence (see Fig. 2 in Rodríguez et al., 2013) is that, assuming those steady conditions early defined by MacArthur (1955; i.e., that the amount of energy going out of the food web is equal to the amount coming in) the relationship between total eco-kinetic energy per plot (Eq. (7) in section 3) and the value of H (Eq. (1)) follows an inverted Upattern. ...
... Given the difficulties in developing an ecosystem theory fully homomorphic with statistical mechanics (Svirezhev, 2000;Ulanowicz, 2004;Nielsen et al., 2020), mainstream ecology assumed that k = 1 in Eq. (1). However, according to Margalef (1972;, the increase of H has an anti-kinetic effect on the 'oscillation' of organisms ('talandic temperature'; Goodwin, 1963;Margalef, 2021), by reducing their dispersal activity around a given reference functional position to perform their ecological niche in an equivalent manner either across space or over time (ergodicity; Hopf, 1932;Tolman, 1938;MacArthur, 1955;Kerner, 1957;Kikuzawa et al., 2009;Gould and Tobochnik, 2021). Therefore, since T increases with kinetic energy (see above), then H has an anti-thermic effect on flora and fauna. ...
The spectrum of species diversity (SDi) can be broken down into αSDi (taxocene level), βSDi (community level), and γSDi (metacommunity level). Species richness (S) and Shannon's index (H) are well-known SDi measures. The use of S as a surrogate for SDi often neglects evenness (J). Additionally, there is a wide variety of indicators of SDi. However, there are no reliable theoretical criteria for selecting the most appropriate SDi index despite the undeniable empirical usefulness of this parameter. This situation is probably due to the analytical gap still existing between SDi and trophodynamics. This article contributes to closing that gap by analyzing why S as a single surrogate for SDi is inconsistent from the trophodynamic point of view, so that an index combining S and J, such as H or H B (Brillouin's index), are the most appropriate choices in the context of a new theoretical framework (organic biophysics of ecosystems, OBEC) based on the well-known classical links between ecosystem ecology and thermodynamics. Exploration of data from reef fish surveys under stationary and non-stationary conditions corroborated the existence of the ecological equivalent of Boltzmann's constant (k eτ(e)) at the worldwide scale. This result substantiates the usefulness of the ecological equivalent of the compressibility factor as an indicator of environmental impact. k eτ(e) stablishes an analytical linkage between ecology, information theory, and statistical mechanics that allowed us to propose a new measure of total negative entropy (a.k.a. syntropy) per survey (S eτT) that is easy to calculate and displayed a highly significant correlation with total standing biomass per survey (m eTs). According to the slope of the regression equation S eτT , m eTs there is a large portion of S eτT that leaks into the environment and/or is captured by numerous ecological degrees of freedom independent of standing biomass. According to the changing value of the exponent of k eτ(e) , even among coex-isting taxocenes, it would have been impossible to obtain the results discussed in this article if the analysis had been carried out at the βSDi or γSDi level. This establishes αSDi as the most appropriate level of analysis to obtain empirically useful results about the key functional connections on which trophodynamic stability depends in dynamic multispaces. The results summarized here are based on the careful selection and intertwining of a few key variables, which indicates the importance of developing models as simple as possible in order to achieve the reliability necessary for successful biological conservation.
... In ecological studies, stability is a multifaceted concept that characterizes the ability of an ecosystem to minimize fluctuations in its properties against perturbations and variations in environmental conditions 4 . Traditionally, ecosystem stability has been assessed through temporal invariability, which involves calculating the mean of an ecosystem property divided by its standard deviation [4][5][6] . ...
... In ecological studies, stability is a multifaceted concept that characterizes the ability of an ecosystem to minimize fluctuations in its properties against perturbations and variations in environmental conditions 4 . Traditionally, ecosystem stability has been assessed through temporal invariability, which involves calculating the mean of an ecosystem property divided by its standard deviation [4][5][6] . As a result, temporal invariability has been commonly referred to as temporal stability. ...
Eutrophication usually impacts grassland biodiversity, community composition, and biomass production, but its impact on the stability of these community aspects is unclear. One challenge is that stability has many facets that can be tightly correlated (low dimensionality) or highly disparate (high dimensionality). Using standardized experiments in 55 grassland sites from a globally distributed experiment (NutNet), we quantify the effects of nutrient addition on five facets of stability (temporal invariability, resistance during dry and wet growing seasons, recovery after dry and wet growing seasons), measured on three community aspects (aboveground biomass, community composition, and species richness). Nutrient addition reduces the temporal invariability and resistance of species richness and community composition during dry and wet growing seasons, but does not affect those of biomass. Different stability measures are largely uncorrelated under both ambient and eutrophic conditions, indicating consistently high dimensionality. Harnessing the dimensionality of ecological stability provides insights for predicting grassland responses to global environmental change.
... The biodiversity index is an important indicator for evaluating and judging the diversity of biological community structure or ecosystem stability (MacArthur, 1955).To analyze the diversity level of MZP and their major group communities, we used the following biodiversity indices. ...
Microzooplankton (MZP) are an important part of the microbial food web and play a pivotal role in connecting the classic food chain with the microbial loop in the marine ecosystem. They may play a more important role than mesozooplankton in the lower latitudes and oligotrophic oceans. In this article, we studied the species composition, dominant species, abundance, and carbon biomass of MZP, including the relationship between biological variables and environmental factors in the eastern equatorial Indian Ocean during the spring intermonsoon. We found that the MZP community in this ocean showed a high species diversity, with a total of 340 species. Among these, the heterotrophic dinoflagellates (HDS) (205 species) and ciliates (CTS) (126 species) were found to occupy the most significant advantageous position. In addition, CTS (45.3%) and HDS (39.7%) accounted for a larger proportion of the population abundance, while HDS (47.1%) and copepod nauplii (CNP) (46.4%) made a larger contribution to the carbon biomass. There are significant differences in the ability of different groups of MZP to assimilate organic carbon. In this sea area, MZP are affected by periodic currents, and temperature is the main factor affecting the distribution of the community. The MZP community is dominated by eurytopic species and CNP. CTS are more sensitive to environmental changes than HDS, among which Ascampbelliella armilla may be a better habitat indicator species. In low-latitude and oligotrophic ocean areas, phytoplankton with smaller cell diameters were found to occupy a higher proportion, while there was no significant correlation between the total concentration of integrated chlorophyll a and the biological variables of MZP. Therefore, we propose that the relationship between size-fractionated phytoplankton and MZP deserves further study. In addition, the estimation of the carbon biomass of MZP requires the establishment of more detailed experimental methods to reflect the real situation of organisms. This study provides more comprehensive data for understanding the diversity and community structure of MZP in the eastern equatorial Indian Ocean, which is also of good value for studying the adaptation mechanism and ecological functions of MZP in low-latitude and oligotrophic ocean ecosystems.
... The vascular-species dominance structure in different EC zones was estimated using Pielou's evenness index, which takes values from 0 to 1, where 1 means that all species are represented in equal numbers. Pielou's index is a variant of the Shannon index [18]: H/logN, where H is the Shannon index and N is the number of species. ...
The logging of mature tree stands, where part of the forest is clear-cut, results in the formation of an ecotone complex (EC) consisting of the forest (F), a transition from forest to a clear-cut site under canopy cover (forest edge—FE), a transition from forest to a clear-cut site outside of canopy cover (clear-cutting edge—CE), and the clear-cut site per se (C). Ground vegetation descriptions (percentage cover of dominants and height of subshrubs) were carried out on the sampling subplots along the transects running from spruce forest into the clear-cut site. We studied the effects of the time since logging and some microhabitat factors (aspect, coniferous and deciduous regeneration, downed deadwood, microrelief, and the abundance of subshrubs, grasses, and forbs) on the abundance of the main ground vegetation dominants of the bilberry-type spruce stands and the clear-cut sites: Vaccinium myrtillus, V. vitis-idaea, Deschampsia flexuosa, and Epilobium angustifolium, in different EC zones. The factor found to have the greatest modifying effect on the abundance of all the species in the CE and C zones was the time since clear-cutting. The clear-cutting pioneer species Deschampsia flexuosa and Epilobium angustifolium preferred open areas in the clear-cut site, whereas the abundance of V. myrtillus and V. vitis-idaea positively correlated with the amount of coniferous and deciduous regeneration. Some factors (downed deadwood, microrelief, coniferous regeneration) were found to act similarly on subshrubs both under the tree canopy (F and FE) and in clear-cut microhabitats (CE and C). The shoot height of subshrubs as well as its percentage cover varied depending on the time since clear-cutting and the microhabitat conditions.
... A recent study in a semi-arid grassland found that 13 years of grazing by sheep indirectly increased the community pathogen load, by increasing the abundances of grazing-tolerant hosts [13]. Compared with semi-arid grasslands, alpine grasslands generally have higher vegetation cover and plant species diversity, and their plant community structures are more resistant to grazing disturbances [51,52]. In our study system (an alpine grassland), we found that 8 years of grazing by either yak or sheep did not significantly alter the plant species richness and Shannon diversity. ...
In grassland ecosystems, the occurrence and transmission of foliar fungal diseases are largely dependent on grazing by large herbivores. However, whether herbivores that have different body sizes differentially impact foliar fungal diseases remains largely unexplored. Thus, we conducted an 8-year grazing experiment in an alpine grassland on the Qinghai-Tibet Plateau in China and tested how different types of livestock (sheep (Ovis aries), yak (Bos grunniens), or both)) affected foliar fungal diseases at the levels of both plant population and community. At the population level, grazing by a single species (yak or sheep) or mixed species (sheep and yak) significantly decreased the severity of eight leaf spot diseases. Similarly, at the community level, both single species (yak or sheep) and mixed grazing by both sheep and yak significantly decreased the community pathogen load. However, we did not find a significant difference in the community pathogen load among different types of livestock. These results suggest that grazing by large herbivores, independently of livestock type, consistently decreased the prevalence of foliar fungal diseases at both the plant population and community levels. We suggest that moderate grazing by sheep or yak is effective to control the occurrence of foliar fungal diseases in alpine grasslands. This study advances our knowledge of the interface between disease ecology, large herbivores, and grassland science.
... The relationship between species diversity and stability is controversial. MacArthur and Elton developed the diversity-stability hypothesis, which holds that species diversity and community stability have a positive effect-the more resistant to external disturbance, the better for community and ecosystem stability [32,33]. Species diversity can contribute to the stability of ecosystem functions [34], and species diversity is the key to the ecosystem stability [35]. ...
Plant diversity plays an important role in maintaining the stability of ecosystem functioning. Based on field surveys and indoor analyses, this study investigated the relationship between species diversity and community stability at different stages of bare patch succession in degraded alpine meadow ecosystems. Results show that: (1) Using the ICV (the Inverse of the Coefficient of Variation) method to analyze changes in plant community stability, community stability was generally ranked as follows: Long-term recovered patches > Healthy alpine meadow > Degraded alpine meadow > Short-term recovered patch > Bare Patches. (2) Using factor analysis to construct an evaluation system, the stability ranking based on species diversity was as follows: Healthy alpine meadow > Long-term recovered patches > Degraded alpine meadow > Short-term recovered patches > Bare Patches. (3) The community stability index was significantly positively correlated with vegetation coverage, height, biomass, species richness, Shannon–Wiener diversity index, species evenness, and Simpson’s diversity index (p < 0.05). Therefore, a positive correlation exists between plant diversity and community stability, such that plant communities with a higher species diversity tend to be more stable. To maintain the plant diversity and community stability of alpine meadow ecosystems, it is necessary to consider the characteristics of grassland plant composition and community structure, as well as their influencing factors, and promote the positive succession process of grasslands.
... In general, native TGP land use conversion for CT wheat cropland enhanced the relationship between network stability and complexity. For an ecological system, relationships between complexity and stability often have important functional implications [54,55]. Greater complexity could produce differential effects on stability creating a more resistant [56,57] but less resilient system [58]. ...
Soils harbor highly diverse microbial communities that are critical to soil health, but agriculture has caused extensive land use conversion resulting in negative effects on critical ecosystem processes. However, the responses and adaptations of microbial communities to land use conversion have not yet been understood. Here, we examined the effects of land conversion for long-term crop use on the network complexity and stability of soil microbial communities over 19 months. Despite reduced microbial biodiversity in comparison with native tallgrass prairie, conventionally tilled (CT) cropland significantly increased network complexity such as connectivity, connectance, average clustering coefficient, relative modularity, and the number of species acting at network hubs and connectors as well as resulted in greater temporal variation of complexity indices. Molecular ecological networks under CT cropland became significantly more robust and less vulnerable, overall increasing network stability. The relationship between network complexity and stability was also substantially strengthened due to land use conversion. Lastly, CT cropland decreased the number of relationships between network structure and environmental properties instead being strongly correlated to management disturbances. These results indicate that agricultural disturbance generally increases the complexity and stability of species "interactions", possibly as a trade-off for biodiversity loss to support ecosystem function when faced with frequent agricultural disturbance. The ISME Journal; https://doi.
... Broadly speaking, the interaction between two species will be more competitive the more traits they share (i.e., the more similar the two species are). This type of interaction structure has also been studied in models combining resources and consumers, both in economics and in ecology [12,13,[23][24][25]. A particularly notable model is that by MacArthur and collaborators [26][27][28]. ...
We study communities emerging from generalized random Lotka-Volterra dynamics with a large number of species with interactions determined by the degree of niche overlap. Each species is endowed with a number of traits, and competition between pairs of species increases with their similarity in trait space. This leads to a model with random Hopfield-like interactions. We use tools from the theory of disordered systems, notably dynamic mean-field theory, to characterize the statistics of the resulting communities at stable fixed points and determine analytically when stability breaks down. Two distinct types of transition are identified in this way, both marked by diverging abundances but differing in the behavior of the integrated response function. At fixed points only a fraction of the initial pool of species survives. We numerically study the eigenvalue spectra of the interaction matrix between extant species. We find evidence that the two types of dynamical transition are, respectively, associated with the bulk spectrum or an outlier eigenvalue crossing into the right half of the complex plane.
... The concept of stability encapsulates the holistic capacity of an ecosystem to endure both natural environmental fluctuations and human-induced disturbances. This resilience reflects the ecosystem's ability to sustain its original state and recover from such perturbations [1,2]. Since the introduction of the stability concept, scholars have embarked on a series of theoretical inquiries and empirical investigations into the intricate interplay between diversity and stability [3,4]. ...
In contrast to intensive management practices focused on wood production, plantations designed to safeguard fragile environments prioritize the sustainable fulfillment of ecological functions. To assess the potential for Chinese pine (Pinus tabuliformis Carr.) plantations in the Loess Hilly Region to effectively serve their ecological protection role over the long term, we selected nine indices representing biological stability, resistance stability, and functional stability. Employing a novel unit circle method, we evaluated the total stability (sum of the three stability components) of 44 plantation plots in Huanglong Mountain. We also explored the connections between total stability and standing spatial structure parameters to offer insights for promptly enhancing stability through thinning. The findings revealed that 79.5% of Chinese pine plantations exhibited moderate total stability, with 20.5% demonstrating good stability. Most plots displayed a random distribution pattern, moderate size differentiation, low species spatial mixing, and high stand crowding. Among the correlations analyzed, mingling exhibited the highest coefficient, followed by differentiation, while the uniform angle index showed the weakest correlation, and crowding displayed an insignificant correlation. While the presence of good functional stability contributed to the moderate total stability, addressing inadequate biological and resistance stability necessitates thinning measures. This study identifies spatial structure types negatively linked to total stability, offering targeted management insights for enhancing the stability of Chinese pine plantations. The stability assessment methodology and indicators presented in this study can serve as a valuable reference for similar plantations with comparable functions and planting conditions.
... Current multiple anthropologic stresses on ecosystems have heightened the need to understand the mechanism underlying food web stability. The relation between the structure and stability of food webs has been widely studied (MacArthur 1955;Paine 1966), since key features to stability provide necessary information for both ecological theorists and operators for the restoration and management of ecosystems. ...
A central and fundamental issue in ecology is to understand the relationship between complexity and stability. Increased empirical evidences demonstrated no clear relationships between complexity metrics and stability, and recent food web loop analyses suggested that maximum loop weight as well as the summation ratio between 3- and 2-link feedback loop weights could be better estimators of system stability. However, the importance of longer loops than 3-link on the stability remains unclear. Here, we use 127 marine food webs and the matrix product and trace method to investigate the relationship between loops with maximum of 7 links and food web stability. We found that feedback metrics |a2n+1/a2n|\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$| a_{2n+1}/a_{2n} |$$\end{document}, i.e., the ratio of the sums of (2n + 1)-link and 2n-link loop weights, are strongly related with stability. These sum weight ratios can be regarded as the coupling strength between omnivory loops and their one-species-delete subloops, including the smallest three species and high-level omnivory ones. Further theoretical simulations of bioenergetic consumer-resource models with allometric constraints strengthen this finding. These results suggest that both longer loops and omnivory are important drivers of the food web stability.
... Many authors note the discrepancy of data; however, in general, the functional complexity of an ecosystem increases its stability (Odum, 1986). According to the hypothesis proposed by MacArthur, sustainability can be achieved either by a larger number of species each of which has a rather limited diet or by a smaller number of species each of which has a wide range of diets (MacArthur, 1955). However, it is well known that species diversity decreases from low latitudes to high latitudes, and although the main causes of this phenomenon are still the subject of discussion, many authors name the climatic factor as the key factor (Pianka, 1966;Odum, 1986;Andrews and O'Brien, 2000;Willig et al., 2003;Qian et al., 2009;Brodie, 2019), with this phenomenon being more pronounced for extratropical latitudes (Qian et al., 2009). ...
... Thus, ecological theory can be used to interpret the internal workings of the complex [58]. For an ecological system, ecologists, before the 1970s, believed that system stability increases as the numbers of links (connectance) and species increase [59][60][61]. This belief was challenged by May [62,63] who used mathematics to investigate the complexity-stability relationship [64]. ...
The recent years have witnessed the explosive application of sequencing technologies to study tumor–microenvironment interactions and their role in shaping intratumoral heterogeneity, neoplastic progression and tumor resistance to anticancer drugs. Statistical modeling is an essential tool to decipher the function of cellular interactions from massive amounts of transcriptomic data. However, most available approaches can only capture the existence of cell interconnections, failing to reveal how cells communicate with each other in (bi)directional, signed, and weighted manners. Widely used ligand–receptor signaling analysis can discern pairwise or dyadic cell–cell interactions, but it has little power to characterize the rock–paper–scissors cycle of interdependence among a large number of interacting cells. Here, we introduce an emerging statistical physics theory, derived from the interdisciplinary cross-pollination of ecosystem theory, allometric scaling law, evolutionary game theory, predator–prey theory, and graph theory. This new theory, coined quasi-dynamic game-graph theory (qdGGT), is formulated as generalized Lotka–Volterra predator–prey equations, allowing cell–cell crosstalk networks across any level of organizational space to be inferred from any type of genomic data with any dimension. qdGGT can visualize and interrogate how genes reciprocally telegraph signals among cells from different biogeographical locations and how this process orchestrates tumor processes. We demonstrate the application of qdGGT to identify genes that drive intercellular cooperation or competition and chart mechanistic cell–cell interaction networks that mediate the tumor–microenvironment crosstalk.
... The biodiversity-stability relationship has been the subject of a long debate [25,37,41,[79][80][81]125,140,141,[144][145][146][147][148][149][150][151][152]. Although the biodiversity-stability relationship is not yet fully resolved, experimental and theoretical advances have indicated that biodiversity may promote the stability of aggregate ecosystem functioning, and concomitantly destabilize species abundances, which increases robustness [5,25,31,42,79,81,[151][152][153][154]]. ...
Understanding the relationship between biodiversity and ecosystem functioning (BEF) is essential to comprehend the impacts of biodiversity changes on ecosystem functioning. This knowledge helps to detect and anticipate significant trends in global biodiversity loss and the homogenization of biota worldwide to prevent them. Species act together with climate, resource availability, and disturbance regimes to modulate ecological processes defining ecosystems’ complexity and their dynamic adaptation to variability. In this article, we revisit the BEF paradigm by addressing current knowledge of how biodiversity connects to ecosystem functioning across scales in the context of complex adaptive systems (CAS). We focus on ecosystem processes that lead to the emergence of the BEF relationship, considering ecosystem functioning as a macroscopic emergent property. Specifically, this work integrates the knowledge of the processes that connect biodiversity to ecosystem functioning. It addresses how biodiversity supports ecosystem multifunctionality across scales, resulting in the persistence of CAS in a rapidly changing world. We present a framework for ecological management considering the BEF relationship within the scope of CAS. The CAS standpoint brings new insights into the BEF field and its relevance for future ecological conservation of the Earth’s life support.
... However, diversity can increase uncertainty and randomness in a complex network because a large number of uncontrollable and sensitive parameters surge, which introduces instability into the whole system (May, 1973). However, many case-based studies indicate that diversity is ubiquitous in the natural world, which provides a multitransformation pathway of energy and information (MacArthur, 1955). Thus, even though the internal mechanism of diversity and system evolution is still controversial in science, for human society, increasing biodiversity will at least overweigh the disadvantages in the short term (Smith et al., 2019;Suski et al., 2018). ...
Aquatic ecosystem restoration is a crucial aspect of ecological management. However, current research tends to concentrate on single factors, such as water quality or biodiversity, rather than ecological restoration strategies based on the characteristics of an ecological network system. Due to the large number of parameters to be considered, the latter approach presents still full of challenges in practical implementation. This study introduces a food web dynamic model that can guide and facilitate aquatic ecological network restoration. The model calculates the network-based interaction relationships of species in the food web, predicting the changes in ecosystem structure and function. We test our food web model by conducting a case study. The food web considered 9 kinds of species nodes, 12 links, and 1 uncertain predator-prey interaction. Our model simulations presented a strong correlation with the measured data (R 2 = 0.837). We performed sensitivity analysis on 12 parameters and also conducted link prediction analysis, which revealed that there was no predator-prey relationship between species A and N (A + N = 0). By comparing population dynamics under 3 conditions, we determined that the mass reproduction of nonnative species and the population decline of native species were both related to indirect food web interactions. Finally, we comprised 27 scenarios, including fishing and stock enhancement approaches, to predict the potential restoration effects. The results showed that the fishing approach was more effective in removing alien species when the fishing frequency was shorter. It was also found that selecting catches and releasing native or endangered species back into the environment (F4, F5, F6, and F12) was necessary. On the other hand, the stock enhancement approach was concluded to be effective in increasing the number of native species as long as the frequency of enhancement was high (per 1 year, S1, S2, and S3). However, it was found to be challenging to rely on this approach to reduce the population of nonnative species. This research will enhance the previous studies in terms of (a) including whole species interactions in the ecological network; (b) considering the influence of abiotic factors, such as water quality, terrigenous carrying capacity, shoreline substrate, and hydrological connection in our model; and (c) coupling significant parameters in ecological restoration practices. This research will provide a valuable tool for managing aquatic ecological networks and decision-making suggestions for determining restoration schemes in complex aquatic food webs.
... However, there is no doubt that the symbiotic relationship between fungi and their environment could enhance the stability of the ecosystem (Averill et al., 2014;Treseder et al., 2018;Aqeel et al., 2023). The relationship between biodiversity and ecosystem stability is one of the key theoretical issues in ecology and was proposed by MacArthur (1955) and Elton (1958) in the 1950s. Some studies have concluded that there is no clear positive correlation between fungal alpha diversity and the stability of soil systems or stand health (Deng, 2012;Guo et al., 2020). ...
Soil fungi in forest ecosystems have great potential to enhance host plant growth and systemic ecological functions and services. Reforestation at Saihanba Mechanized Forest Farm, the world's largest artificial plantation, has been integral to global forest ecosystem preservation since the 1950s. To better assess the ecological effects of soil microbiology after afforestation, fungal diversity and community structure (using Illumina sequencing) from forests dominated by Larix gmelinii var. principis-rupprechtii, Pinus sylvestris var. mongolica and Picea asperata, and from grassland were surveyed. In total, 4,540 operational taxonomic units (OTUs) were identified, with Mortierella and Solicoccozyma being the dominant genera of grassland soil and Inocybe, Cortinarius, Piloderma, Tomentella, Sebacina, Hygrophorus and Saitozyma dominating the plantation soil. Principle coordinate analysis (PCoA) and co-occurrence networks revealed differences in fungal structure after afforestation. Significantly, more symbiotroph guilds were dominated by ectomycorrhizal fungi in plantations under the prediction of FUNGuild. The community composition and diversity of soil fungi were significantly influenced by pH via redundancy analysis (RDA) and the Mantel test (p
... The ecological relevance of specialization arises from a better performance of specialist organisms in their optimal habitats, at the expense of their performance in other habitats (Futuyma & Moreno, 1988). In addition, specialists could be negatively affected by disturbance, which may increase their probability of extinction (MacArthur, 1955). For this reason, understanding how specialization is driven and determining which species show a specialist pattern can help to find vulnerable species and to develop conservation strategies (Devictor et al., 2010). ...
Specialization, contextualized in a resource axis of an organism niche, is a core concept in ecology. In biotic interactions, specialization can be determined by the range of interacting partners. Evolutionary and ecological factors, in combination with the surveyed scale (spatial, temporal, biological, and/or taxonomic), influence the conception of specialization. This study aimed to assess the specialization patterns and drivers in the lichen symbiosis, considering the interaction between the principal fungus (mycobiont) and the associated Nostoc (cyanobiont), from a community perspective considering different spatial scales. Thus, we determined Nostoc phylogroup richness and composition of lichen communities in 11 Nothofagus pumilio forests across a wide latitudinal gradient in Chile. To measure specialization, cyanobiont richness, Simpson's and d' indices were estimated for 37 mycobiont species in these communities. Potential drivers that might shape Nostoc composition and specialization measures along the environmental gradient were analysed. Limitations in lichen distributional ranges due to the availability of their cyanobionts were studied. Turnover patterns of cyanobionts were identified at multiple spatial scales. The results showed that environmental factors shaped the Nostoc composition of these communities, thus limiting cyanobiont availability to establish the symbiotic association. Besides, specialization changed with the spatial scale and with the metric considered. Cyanolichens were more specialized than cephalolichens when considering partner richness and Simpson's index, whereas the d' index was mostly explained by mycobiont identity. Little evidence of lichen distributional ranges due to the distribution of their cyanobionts was found. Thus, lichens with broad distributional ranges either associated with several cyanobionts or with widely distributed cyanobionts. Comparisons between local and regional scales showed a decreasing degree of specialization at larger scales due to an increase in cyanobiont richness. The results support the context dependency of specialization and how its consideration changes with the metric and the spatial scale considered. Subsequently, we suggest considering the entire community and widening the spatial scale studied as it is crucial to understand factors determining specialization.
... What is then the simplest quantitative description that displays all the salient dynamical features of evolution? This question has a long list of partial answers (Nowak 2006;Tikhonov 2016;Posfai et al. 2017), although much work in the field concerns equilibria (MacArthur and Wilson 1963;MacArthur 1955;Chesson 1990;Hubbell 2001). Here, we show that the already successful variants of MacArthur models can be amended with a simple stochastic mechanism that introduces new species, which allows us to show many of the biologically relevant dynamical features of evolution even when the starting point for the dynamics is a single primordial ancestor. ...
Ecosystem dynamics is often considered driven by a coupling of species’ resource consumption and its population size dynamics. Such resource-population dynamics is captured by MacArthur-type models. One biologically relevant feature that would also need to be captured by such models is the introduction of new and different species. Speciation introduces a stochastic component in the otherwise deterministic MacArthur theory. We describe here how speciation can be implemented to yield a model that is consistent with current theory on equilibrium resource-consumer models, but also displays readily observable rank diversity metric changes. The model also reproduces a priority effect. Adding speciation to a MacArthur-style model provides an attractively simple extension to explore the rich dynamics in evolving ecosystems.
... Regarding the trophic network structure, highly connected taxa control the dispersion of community energy flow and provide multiple energy pathways to compensate for the loss of one taxon (MacArthur 1955;Dunne et al. 2002), despite its low occurrence probability (see Pimm 2002 for more information about it). Ecological effects on a community after disturbance should not be inferred solely from the number of taxa affected but also from the taxa role in the community, which can promote significantly faster side effects in the community structure than random taxa loss (Dunne et al. 2002;Srinivasan et al. 2007). ...
To investigate the influence of non-native aquatic invertebrate species on food web structure, we selected two reservoirs located in the Grande River (upper Paraná River basin, Brazil) with similar fish communities, different age and different taxa introductions history. We quarterly collected fish and benthonic macroinvertebrates samples in the Volta Grande and Funil reservoirs between October 2015 and August 2016. We used conventional methods of diet evaluation to assess the sampled fish and measured the availability of invertebrates (i.e. composition and density) present in the sediment samples from each reservoir. In addition, we performed a structural analysis of trophic interaction networks. Based on the data obtained, it was possible to identify that in Volta Grande most of the energy flow, between benthonic invertebrates (prey) and the fish community (predators), occurred through non-native prey species, especially Limnoperna fortunei and Macrobrachium amazonicum, while in Funil it was shared between non-native and native prey.
Species loss simulations indicated that the networks did not differ substantially between random losses and losses between groups. In general, there was a decrease in the probability of occurrence of highly connected species in both reservoirs and between non-native and native species. Results showed that the new interactions among species influenced the importance of the available energy sources for the fish in the Volta Grande reservoir. The presence of non-native prey, especially M. amazonicum, may influence the interaction network structure, promoting community dependence on non-native species to ensure robustness to environmental disturbances. In the absence of pre-invasion data, the comparative study between systems with similar fish communities may provide a better understanding of the impacts caused by the introduction of non-native invertebrate prey.
... One of the most well-known scientific debates occurs at the interface of Biology, Mathematics, and Physics, and relates to determining the patterns and processes that govern the stability of ecological networks. This debate originates from the middle of the last century when Robert MacArthur argued that speciesrich, biodiverse communities are more likely to be stable than species-poor, less diverse communities [17]. The argument's foundation is that diverse communities are more robust to environmental disturbances because the more complex network of ecological interactions will act as a buffer against the disturbances. ...
From 08-12 August, 2022, 32 individuals participated in a workshop, Stability and Fluctuations in Complex Ecological Systems, at the Lorentz Center, located in Leiden, The Netherlands. An interdisciplinary dialogue between ecologists, mathematicians, and physicists provided a foundation of important problems to consider over the next 5-10 years. This paper outlines eight areas including (1) improving our understanding of the effect of scale, both temporal and spatial, for both deterministic and stochastic problems; (2) clarifying the different terminologies and definitions used in different scientific fields; (3) developing a comprehensive set of data analysis techniques arising from different fields but which can be used together to improve our understanding of existing data sets; (4) having theoreticians/computational scientists collaborate closely with empirical ecologists to determine what new data should be collected; (5) improving our knowledge of how to protect and/or restore ecosystems; (6) incorporating socio-economic effects into models of ecosystems; (7) improving our understanding of the role of deterministic and stochastic fluctuations; (8) studying the current state of biodiversity at the functional level, taxa level and genome level.
... In addition, the higher robustness of salt lakes (Fig. 5b) further confirmed that the stability of microeukaryotic communities improved with increasing salinity (49). Our results provide explicit evidence that network stability decreased with network complexity, which was consistent with the theoretical analysis showing that higher complexity destabilizes ecological systems (50). ...
Our findings have important implications for understanding the distribution patterns and the driving mechanisms of microeukaryotic communities among the lakes of the Inner Mongolia-Xinjiang Plateau and whether and how climate change directly or indirectly affects microeukaryotic communities. Our study also establishes the groundwork to use the lake microbiome for the assessment of aquatic ecological health and climate change, which is critical for ecosystem management and for projecting the ecological consequences of future climate warming.
... Understanding the relationship between food web complexity and ecosystem functioning has been a long-standing theme in ecology. A first intuitive hypothesis was that more complex ecosystems are more stable (Elton, 1958;MacArthur, 1955). This was later challenged by May (1972) who used a random matrix approach to demonstrate that complexity generally impairs stability. ...
While the relationship between food web complexity and stability has been well documented, how complexity affects productivity remains elusive. In this study, we combine food web theory and a data set of 149 aquatic food webs to investigate the effect of complexity (i.e. species richness, connectance, and average interaction strength) on ecosystem productivity. We find that more complex ecosystems tend to be more productive, although different facets of complexity have contrasting effects. A higher species richness and/or average interaction strength increases productivity, whereas a higher connectance often decreases it. These patterns hold not only between realized complexity and productivity, but also characterize responses of productivity to simulated declines of complexity. Our model also predicts a negative association between productivity and stability along gradients of complexity. Empirical analyses support our predictions on positive complexity‐productivity relationships and negative productivity‐stability relationships. Our study provides a step forward towards reconciling ecosystem complexity, productivity and stability.
... Because of its relic origin, small and discontinuous habitat, and declining population number, the Olkhon mountain vole can be classified as an endangered species (Gerrie & Kennerley, 2016). The loss of any biological species threatens human civilization by disrupting the biological balance (MacArthur, 1955). As recently reported, the largest habitat patches of the Olkhon mountain vole are located on Lake Baikal islands, which have been isolated for an appreciably long time, are characterized by a set of different conditions and limited migration, and can be viewed as biological systems that can be used to analyze and simulate the eco-evolutionary processes occurring in contemporary animal populations and communities (Litvinov et.al., 2000;Abramov et.al., 2017). ...
... This results in higher network complexity, measured by e.g., modularity and nestedness (Bascompte et al. 2003;Olesen et al. 2007). The complexity of flower visitor networks reflects the diversity and interdependence of species within the ecosystem and has important implications for ecosystem functioning and stability (see e.g., the diversity-stability debate; (MacArthur 1955;Bersier and Banasek-Richter 2009;Dunne et al. 2002)). Because larger habitats can support more species (species-area relationship, Schoener 1976), and, thus, support more interactions between species, the complexity and stability of networks is expected to increase with habitat area (Galiana et al. 2018). ...
Pollinating insects are essential for food production. Both bee and non-bee pollinators are undergoing dramatic declines due to land use intensification and its consequences on native ecosystems. While interactions between crops and bee pollinators are well studied, our understanding of the pollination service provided by non-bee flower visitors including flies, ants, beetles and others is still limited. Moreover, the effects of landscape urbanization and changes in floral and nesting resource availability on the network structure of pollinators with both cultivated and wild plants have been poorly studied. We assessed which common bee and non-bee flower visitor groups dominate the interactions with both wild (e.g. Trifolium pratense, Taraxacum officinales) and cultivated plants (e.g. Fragaria ananassa, Cucurbita pepo) in urban community gardens in Berlin and Munich and explored how these interactions between flower visitor groups and plants change over the growing season. We further investigated the effect of changes in urbanization surrounding community gardens, and the availability of floral and nesting resources within gardens on the complexity (i.e. nestedness, linkage density, connectance) of interaction networks. We observed 20 focal plant species and 13 common bee and non-bee flower visitor groups in 30 urban community gardens. We found that dominant plant visitors changed over the growing season, with non-bee flower visitors including ants and flies as dominant early season visitors, and bee pollinators as important visitors later in the season. Nestedness of the flower visitor network increased with increases in floral richness in community gardens, while neither floral abundance nor the impervious surface surrounding the community gardens, garden size or the availability of nesting resources in gardens strongly influenced the flower visitor networks. Our findings suggest that high floral richness in community gardens may ensure the complexity and, thus, the stability of flower visitor networks. Findings further suggest that the role of non-bee flower visitors should be considered for pollination service provision especially in the shoulder seasons. Finally, our results emphasize that urban gardeners play a key role in mediating flower visitor interactions through their gardening practices.
Biodiversity was first proposed by Fisher et al. (1943) in the study of insect species abundance, and its concept and connotation have been continuously developed since then. Biodiversity refers to the sum of all living things in nature, such as animals, plants, and microorganisms, as well as the ecological complex formed between them and the environment and all related ecological processes. Biodiversity includes that of genes, cells, tissues, organs, populations, communities, and ecosystems. They are interconnected and inseparable, among which, genetic diversity is considered the basis of species diversity and ecosystem diversity. Species diversity is not only the expression of genetic diversity but also the basic unit that constitutes the diversity of biological communities and ecosystems. Ecosystem diversity is inseparable from species diversity and the genetic diversity of different species. Plant diversity is an important part of biodiversity, which refers to the exploration of diverse plant species between species and ecosystems, with plants as the main body of biodiversity. Forests are one of the main habitats maintaining biodiversity. Therefore, a comprehensive understanding of the connotations and components of biodiversity is helpful to better understand the plant diversity of forest communities.
Background: The Anna Karenina Principle predicts that stability in host-associated microbiomes correlates with health in the host. Microbiomes are ecosystems, and classical ecological theory suggests that predators impact ecosystem stability. Phages can act as predators on bacterial species in microbiomes. However, our ability to extrapolate results from existing ecological theory to phages and microbiomes is limited because some phages can stage lysogenic infections, a process with no precise analog in classical ecology. In lysogenic infections, so-called "temperate" phages integrate into the cells of their hosts where they can remain dormant as prophages for many generations. Prophages can later be induced by environmental conditions, whereupon they lyse their host cells and phage progeny are released. It has been suggested that prophages can act as biological timebombs that destabilize microbial ecosystems, but formal theory to support this hypothesis is lacking.
Results: We studied the effects of temperate and virulent phages on diversity and stability in computationally simulated microbiomes. The presence of either phage type in a microbiome increased bacterial diversity. Bacterial populations were more likely to fluctuate over time when there were more temperate phages in the system. When microbiomes were disturbed from their steady states, both phage types affected return times, but in different ways. Bacterial species returned to their pre-disturbance densities more slowly when there were more temperate phage species, but cycles engendered by disturbances dampened more slowly when there were more virulent phage species.
Conclusions: Phages shape the diversity and stability of microbiomes, and temperate and virulent phages impact microbiomes in different ways. A clear understanding of the effects of phage life cycles on microbiome dynamics is needed to predict the role of microbiome composition in host health, and for applications including phage therapy and microbiome transplants. The results we present here provide a theoretical foundation for this body of work.
Extreme drought events are expected to increase in frequency and severity, posing significant threats to ecosystems worldwide. While considerable research has been concentrated on the effects of climate extremes on the stability of grasslands, the process by which grassland productivity may recover after extreme drought events are still not well understood. Here, we conducted a four-year (2019–2022) recovery investigation after four-year's (2015–2018) extreme drought treatments of different intensities (control, press and pulse) to explore the vegetation recovery of desert-grassland ecosystems Inner Mongolia, China. Press drought involved a 66 % reduction in natural precipitation from May to August, while pulse drought reduced it by 100 % during June and July. We found that both press and pulse droughts led to a sharp decrease in aboveground net primary productivity (ANPP) after four years, primarily due to reduced growth, density, and productivity of annual and perennial plants. However, ANPP under pulse drought could recover fully after four years of stopping of drought treatment, and it could not under press drought. Additionally, community structure (i.e., species richness, plant density, and height) fully recovered within 1 year after the end of the two extreme drought treatments. Both plant density and height contributed to the ANPP recovery after press and pulse droughts. Structural equation modeling (SEM) results further revealed that the reduction in ANPP during the extreme drought was primarily due to a decrease in plant density caused by reduced soil water content. The recovery of ANPP in pulse drought was directly caused by increased soil water content in the post-extreme drought. These results suggest that drought intensity and precipitation determine ANPP recovery in a degraded desert steppe. Our findings are crucial for deepening understanding of the processes and mechanisms of ecosystem recovery after extreme drought, as well as for the successful management and protection of grassland ecosystems.
The human gut microbiota is a complex community comprised of hundreds of species, with a few present in high abundance and the vast majority in low abundance. The biological functions and effects of these low-abundant species on the host are not yet fully understood. In this study, we assembled a bacterial consortium (SC-4) consisting of B. paravirosa, C. comes, M. indica , and A. butyriciproducens , which are low-abundant, short-chain fatty acid (SCFA) producing bacteria isolated from healthy human gut and tested its effect on host health using germfree and human microbiota associated mice models of colitis. Our findings demonstrate that SC-4 can colonize in Germ-free (GF) mice, increasing mucin thickness by activating the MUC-1 and MUC-2 genes, thereby protecting GF mice from Dextran Sodium Sulfate (DSS)-induced colitis. Moreover, SC-4 aided in the recovery of human microbiota-associated mice from DSS-induced colitis, and intriguingly, its administration enhanced the alpha diversity of the gut microbiome, shifting the community composition closer to control levels. We also show a functional redundancy existing in the gut microbiome, resulting in the low abundant SCFA producers acting as a form of insurance, which in turn accelerates recovery from dysbiotic state upon the administration of SC-4. SC-4 colonization also upregulated iNOS gene expression, further supporting its ability to enhance mucin thickness upon colonization. A metagenomic analysis of Inflammatory Bowel Disease (IBD) patient samples revealed a decrease in the abundance of SC-4 bacteria in both Ulcerative Colitis (UC) and Crohn’s Disease (CD), highlighting the potential importance of these species in the human gut. Collectively, our results provide evidence that low-abundant SCFA-producing species in the gut may offer a novel therapeutic approach for IBD.
Phytoplankton are the base of the food web, and their efficiency to capture carbon in the organic form via the process of photosynthesis determines the rate of primary productivity. Similar to many other species in the higher trophic levels, fish stocks are inherently dependent on primary productivity. This could be in the form of larval survival that determines the success of recruitment or in the form of providing food for adult fishes that takes up long migration to the breeding ground. The dynamics of phytoplankton distribution itself is connected to the met-ocean processes, including teleconnection to the processes far in the Indian Ocean or even in the Pacific Ocean. In this chapter, these linkages are described by using the fish catch landings as well as satellite remote sensing data to provide a holistic view of how fish catch may vary because of the combination of factors, including anthropogenic and natural.
Coastal ecosystems provide a wide range of valuable ecosystem services (ES) for human wellbeing. Such services depend on the functioning and structure of ecosystems. Unfortunately, these ecosystems are threatened by humans, directly impairing their ability to provide these services. In order to predict such changes, we used a food web model to forecast potential spatial changes in ES supply in the Seine Bay (English Channel), due to climate change effects (CC) and the setup of an offshore wind farm (OWF). Three ES were studied, food production from fishing, top predator production for cultural purposes and the potential resistance of the ecosystem inferred from its organization. The ability of the Seine Bay ecosystem to produce food appears to be negatively impacted by the effect of climate change. Because of the important economic role of fishing in Normandy, such changes could percolate on the entire social and economic system of the bay. The Courseulles-sur-Mer offshore wind farm appears to increase the supply of services and limit the impact of climate change at the local spatial scale, which could give stakeholders insights into mitigating the effects of climate change. Such ecosystem approach enables for a more integrative view of ES supply, through the characterization of the entire system functioning.
Eutrophic lakes often exhibit two alternative types: macrophytes-dominated (MD) and phytoplankton-dominated (PD) types. However, the nature of bacterial community types that whether the transition from the MD to PD types occurs in a gradual or abrupt manner remains hotly debated. Further, the theoretical recognition that stability regulates the transition of bacterial community types remains qualitative. To address these issues, we divided the transition of bacterial communities along a trophic gradient into 12 successional stages, ranging from the MD to PD types. Results showed that 12 states were clustered into 3 distinct regimes: MD type, intermediate transitional type, and PD type. Bacterial communities were not different between consecutive stages, suggesting that the transition of alternative types occurs in a continuous gradient. At the same time, the stability of bacterial communities was significantly lower in the intermediate type than in the MD or PD types, highlighting that the collapse and re-establishment of community stability regulate the transition. Further, our results showed that high complexity of taxon interactions and strong stochastic processes disrupt the stability. Ultimately, this study enables us deeper insights into the understanding the alternative types of microbial communities in the view of community stability.
Der vorliegende Band versammelt die umgearbeiteten Beiträge einer Tagung, die im März 2002 im Warburg-Haus in Hamburg stattfand. Sie wurde im Rahmen des Forschungsprojekts „Natur im Konflikt“ veranstaltet, das von der Volkswagenstiftung innerhalb des Förderprogramms „Schlüsselthemen der Geisteswissenschaften“ finanziert wird. Dieses interdisziplinäre Vorhaben widmet sich der Untersuchung von mentalen Konzepten, Bildern, Modellen und Wertzuschreibungen, die zum kollektiven Fundus unserer Vorstellungen von Natur gehören. Dabei richten sich die Untersuchungen aus der Perspektive verschiedener Fachrichtungen – Ethnologie bzw. Sozialanthropologie, Geschichtswissenschaft, naturwissenschaftliche Küstenforschung, Literatur-, Sprach- und Medienwissenschaft – insbesondere auf die diejenigen Naturbilder und Modellierungen, die zu den oft nicht thematisierten Argumentationen und Überzeugungen gehören.
In addition to the fate of individual species, the considerable concerns over the declines of moths apply to the three main parameters of richness, abundance and distribution, for all of which evidence has its foundations in the extensive documentation and historical record of larger moths in the northern temperate regions, most notably in the United Kingdom flowing from surveys initiated in 1933 as the Rothamsted Insect Survey. These extensive long-term light-trap samples that cover the entire flight periods of most species have enabled sound interpretation of trends in diversity and the fate of numerous individual species. Without such long-term monitoring data, trends in insect population sizes (which may vary greatly, irregularly and rapidly about a long-term mean abundance) are highly uncertain. Concerns have arisen also from collector experiences—for the north-eastern United States, moth declines have been a concern for well over half a century, and Wagner (2012) cited the observations of enthusiasts who had observed larger moths over several decades, during which a number of Saturniidae and Sphingidae had declined or been extirpated. Thus, of Connecticut’s 35 resident or previously resident hawk moth species, two have been extirpated, a third are considered likely to have gone and 14 others have declined—some of them are apparently close to being lost. Several previously abundant species had become ‘noticeably less abundant’.
Restoration of riverine ecosystems is a key aspect of river management, driven by concerns over water sustainability and declining biodiversity caused by anthropogenic and environmental perturbations. Anthropogenic perturbations include agricultural sedimentation and nutrient input, deforestation, and river regulation including damming, which disturbs longitudinal, lateral and vertical connectivity. Restoring perturbed riverine systems is costly, and many such restorations are ineffective, with restored systems continuing to degrade. Gravel augmentation, the adding of in-stream gravels, focusses mainly on improving habitat for salmonids, and is one method frequently used to mitigate the impacts of damming. The impact of these augmentations on riverine macroinvertebrates and ecosystem functioning in catchments with altered riparian inputs of leaf litter is, however, still unclear, given the lack of work to date investigating leaf litter combined with macroinvertebrate assemblage structure.
This thesis investigates, for the first time, macroinvertebrate assemblage composition, functional diversity and leaf litter breakdown at macro and meso-scales across two low-order, sediment-starved streams on Dartmoor, UK, subject to gravel augmentation. Investigations used macroinvertebrate survey techniques, leaf litter breakdown experiments and univariate and multivariate analyses to explore potential shifts in ecosystem functioning and impacts to the food web related to augmentation. In total, 5641 individuals from 44 taxa were recorded across both catchments. Evidence was found that augmentation led to small and large-scale differences in assemblage structure and functioning, which has the potential to influence both higher and lower trophic levels. Leaf litter breakdown was found to be higher in augmented reaches, although whether associated differences in macroinvertebrate assemblage, diversity, functionality and leaf pack mass loss were due solely to augmentation or a combination of augmentation and other biological and environmental factors remains unclear and merits further study.
The two invasive blue crabs, Callinectes sapidus and Portunus segnis have spread rapidly in the Mediterranean and no data exists on the connectivity of populations. Determining the source and recruitment areas is crucial to prioritize where population control measures should be put into immediate action. We simulated the dispersal of blue crab larvae using a Lagrangian model coupled at high resolution to estimate the potential connectivity of blue crab populations over a 3-year period. Our results reveal that the main areas at risk are the Spanish, French, Italian Tyrrhenian and Sardinian coasts for Callinectes sapidus with high populations connectivity. Tunisia and Egypt represent high auto recruitment zones for Portunus segnis restricted to the central and western basins. This study provides an overview of the connectivity between populations and will help define priority areas that require the urgent implementation of management measures.
Ocean acidification (OA) has considerably changed the metabolism and structure of plankton communities in the ocean. Evaluation of the response of the marine bacterioplankton community to OA is critical for understanding the future direction of bacterioplankton‐mediated biogeochemical processes in the ocean. Understanding the diversity of functional genes is important for linking the microbial community to ecological and biogeochemical processes. However, the influence of OA on the functional diversity of bacterioplankton remains unclear. Using high‐throughput functional gene microarray technology (GeoChip 4), we investigated the functional gene structure and diversity of bacterioplankton under three different p CO 2 levels (control: 175 μ atm, medium: 675 μ atm, and high: 1085 μ atm) in a large Arctic Ocean mesocosm experiment. We observed a higher evenness of microbial functional genes under elevated p CO 2 compared with under low p CO 2 . OA induced a more stable community as evaluated by decreased dissimilarity of functional gene structure with increased p CO 2 . Molecular ecological networks under elevated p CO 2 became more complex and stable, supporting the central ecological tenet that complexity begets stability. In particular, increased average abundances were found under elevated p CO 2 for many genes involved in key metabolic processes, including carbon degradation, methane oxidization, nitrogen fixation, dissimilatory nitrite/nitrate reduction, and sulfide reduction processes. Altogether, these results indicate a significant influence of OA on the metabolism potential of bacterioplankton in the Arctic Ocean. Consequently, our study suggests that biogeochemical cycling mediated by these microbes may be altered by the OA in the future.
The ongoing biodiversity crisis has urged the scientific community to concentrate more research efforts on the mechanisms underlying the mass extinctions that have repeatedly affected our planet in deep time. This work implements a novel combination of palaeoecological and statistical routines to assess disruptions in the trophic architecture of non-avian dinosaur communities across the latest Cretaceous (83.6–66.0 Mya) of North America. Using these extinct beasts as model organisms, this work aims at increasing our ability to predict the susceptibility of ecological communities to extinction events under different levels of environmental disturbance. There was a trophic shift in the large, bulk-feeding herbivorous ornithischians and theropod carnivores during the Campanian–Maastrichtian transition that led to a simplification of North American terrestrial food webs several million years before the asteroid impact. Their disappearance during the Maastrichtian (72.0–66.0 Mya) made terrestrial communities more prone to extinction in the aftermath of the Chicxulub impact, which suggests that conservation schemes should pay special attention to keystone species in present-day food webs. In conclusion, palaeoecological transitions in the fossil record provide a valuable source of information for predicting the potential consequences of large-scale disturbances on contemporary biodiversity.KeywordsDisturbanceLate cretaceousMass extinction
Urban metabolism uses the idea that cities are resource consuming systems that are supported by flows of energy and materials, and they produce goods and wastes, which generate greenhouse gas emissions both directly and indirectly. This research builds on other recent applications of input-output and ecological network analyses to urban metabolism with added value of comparing in one study both approaches across Europe and China specifically at the city scale. We use input-output (IO) and ecological network analyses (ENA) in a study of the urban metabolism of four cities, Vienna, Austria, Malmö, Sweden, Beijing and Shanghai, China. Based on economic input-output tables and environmental weighting coefficients, we create a connected network of flows between 17 economic sectors that captures the carbon emissions from transactions in a producer orientation. Ecological network analysis is conducted to identify the main sectors contributing to the direct and indirect carbon emissions in the four cities. Our results reveal these to be Transportation, Manufacturing, and Electricity production. Furthermore, we show that final demand in terms of domestic export is the highest contributor in each city, indicating that each city is a producer overall in the countries’ economies generating carbon flows that are consumed elsewhere.
In food web models that include more than one prey type for a single predator, it is common for the predator's functional response to include some form of switching-preferential consumption of more abundant prey types. Predator switching promotes coexistence among competing prey types and increases diversity in the prey community. Here, we show how the dynamics of a diamond-shaped food web model of a marine plankton community are sensitive to a parameter that sets the strength of predator switching. Stronger switching destabilizes the model's coexistence equilibrium and leads to the appearance of limit cycles. Stronger switching also increases the evenness of the asymptotic prey community and promotes synchrony in the dynamics of disparate prey types. Given the dependence of model behavior on the strength of predator switching, it is important that modelers carefully consider the parameterization of functional responses that include switching.
It was established that the water does not meet the upper limit of the 1st quality class according to DSTU 4808:2007 by all indicators except for chloride ions, SPAR and suspended substances. There is a decrease in the level of BSK5 at the monitoring post in the lower part of the reservoir, which indicates the entry of substances into the watercourse that inhibit biochemical processes. There is also an increasing trend in the content of sulfates, phosphates, nitrogen compounds and HSC in water for control points located within the influence of industrial cities, along the reservoir. The highest values of the entropy index of water quality are characteristic of points p2, p. Adamivka, Chygyryn district (0.59015) and p3, village. Pronozivka Globyn district, (0.63092). These control points are located at a considerable distance from industrial centers, so pollution caused by agricultural production (application of phosphate and nitrogen fertilizers) probably plays a decisive role in the formation of water quality. The smallest value of the index (0.39397) is characteristic of item p1 – c. Sokirne, drinking water intake in the city of Cherkasy. The value of the non-torsion water quality index is in the range from 0.39397 (point p1) to 0.63092 (point p3).
The distribution and abundance of animals Toward a general theory of growth
- H G Andrewartha
- L C Birch
- K E Boulding
Andrewartha, H. G., and L. C. Birch. 1954. The distribution and abundance of animals. Chicago: University of Chicago Press, 782 pp. Boulding, K. E. 1953. Toward a general theory of growth. Canadian J. of Econ. and Poli. Sci., 19: 326-340.
An outline of the dynamics of animal populations REFERENCES Feller, W. 1950. An introduction to probability theory and its applications
- A J Nicholson
Nicholson, A. J. 1954. An outline of the dynamics of animal populations. Australian J. Zool., 2: 9-65. REFERENCES Feller, W. 1950. An introduction to probability theory and its applications. New York: Wiley.
The structure of physical chemistry. London: Oxford. This content downloaded from 128.223.86.31 on Fri
- C H Hinshelwood
Hinshelwood, C. H. 1951. The structure of physical chemistry. London: Oxford. This content downloaded from 128.223.86.31 on Fri, 12 Dec 2014 11:20:54 AM All use subject to JSTOR Terms and Conditions