Ecological Complexity最新文献

Numerous studies have demonstrated the significance of climatic and edaphic conditions in regulating the species composition and forest structure. However, there is still a lack of knowledge regarding the ecological processes that are brought about by phenological expression and regeneration. This study postulates that phenology, regeneration, and species dominance are a sequence of intermediary processes through which environmental conditions affect forest structure. In a dry deciduous forest of Similipal Biosphere Reserve (SBR), India, we analysed the relationships between various environmental characteristics, phenological parameters, seedling density, sapling density, and tree density using Structural Equation Modelling (SEM). The study revealed an immediate association between climate and leafing (Path Coefficient: -0.67; T: 9.374; p < 0.01), flowering (Path Coefficient: -0.61; T: 2.981; p < 0.01), and fruiting (Path Coefficient: -0.67; T: 3.51; p < 0.01). The sequential association between seedling and sapling density and forest structure was also significant (p < 0.5). However, these were found to have no direct link with phenology (T < 1; p > 0.05) which has been assumed to be the outcome of anthropogenic activities in the forest having an impact on the system. Comparatively, synchrony of fruit senescence and synchrony of flowering were the principal events that supported regeneration more than others, each accounting for 79 % and 74 % of their data, respectively. On the other hand, the monthly minimum temperature (contributing 97 % of data) was a key contribution to the principal component (PC1) and was primarily responsible for triggering the phenological cycle. Most of the important phenophases were seasonal (Rayleigh's Z varied from 10.93 to 50.01; p < 0.01) except the fruit initiation (Rayleigh's Z = 0.48; p = 0.2). Most of the species (72 % of all species) had regeneration densities that were corresponding to their competitive scores. Similarly, density of adult tree species proportionated with their density in regeneration stage (sapling and seedling), supporting the research hypothesis. However, several deviant species suggested that the system was affected by a wide range of other factors. This is the first study of its kind to evaluate the critical ecological processes together, and recommends further investigation across different woodland ecosystems to deepen understanding of forest functioning.

The analysis of keystone species based on network structure has increasingly emphasized the significance of quantitative food webs. In this study, Zhangze Lake was chosen as the research subject, and assigned a weighted index to each index by creatively combined isotope techniques with topological important and uniqueness theories, then united centrality theory. Next, various scales of indices were used to examine the importance of each nutrient in the food web, the correlation between the ordering and distribution across indices, and the difference in time. This study revealed that the centrality of phytoplankton was significantly higher in April compared to July. Both of the monthly unique species in this ecosystem were planktivorous feeders, while the keystone species serving as higher consumers were identified to be Exopalaemon modestus. The ranking results of the indices other than the weighted closeness centrality and weighted betweenness centrality showed consistency. Additionally, the distributions of the weighted indices differed significantly from their corresponding unweighted indices, with the weighted centrality indices being more similar to the out-degree ordering and more strongly correlated in April. When only strong interactions between species were considered, there was a negative correlation found between species centrality and uniqueness. Through the quantitative construction of a diet proportion food web model, combined with multiple indices, we have provided a practical solution for holistically and quantitatively identifying key species, thus aiding in the accurate and effective protection of biodiversity.

Exploring how food webs are assembled from basic modules is charming and crucial for understanding how communities are self-organized. As one of the basic modules, intraguild predation (IGP) consists of a prey being consumed by both an intermediate and a top predator, with the former also being consumed by the latter (thus encompassing both predation and competition). This interaction has been shown to govern food web stability, and therefore underpin the organization of network structures. While some studies have been made in understanding the factors and mechanisms behind the prevalence of IGP modules in food webs, the specific role of food web topological structures in relation to these modules remains largely unexplored and is not well understood. Here, 103 food webs were analyzed, and we found that the number of modules in each food web was largely determined by taxon richness and connectance. After controlling richness and connectance, the specific scale-free pattern and core-periphery structure of empirical food webs explains the higher prevalence of IGP modules in empirical food webs better than by chance. Lastly, the loss of taxa which supported large number of IGP modules would lead to serious damage to food web robustness, indicating the keystone role of these taxa in maintaining food web structure and stability. Our results provide new insight into the assembly of empirical food webs from the perspective of IGP modules.

Many authors have reported the risk of habitat fragmentation and the importance of connecting corridors between subpopulations (patches). However, we report that the connection of corridors may be harmful to species conservation. The paper deals with the birth and death processes of a single species living in a network composed of three patches. The disturbance due to a changing environment is assumed to affect only one patch. Two types of metapopulation models are applied. One is the lattice simulation model where we set a lattice as a patch. The other is based on metapopulation theory, which utilizes reaction-migration equations. The lattice simulation reveals that the connecting corridor between patches may be disadvantageous; the complete graph or a network with fully connected corridors is found not to be optimal for species conservation. Similar results are indicated by the application of metapopulation theory. We discuss the relationship between the risk of corridor construction and the effect of the hub patch.

Contacts between individuals are key for the spread of infectious disease. Although essential to understanding disease spread, contact rates are difficult to predict, based simply on population demographics in wildlife populations, because contact rates depend upon environmental features as well as the nature of social interactions within and between groups of individuals. We developed a detailed, behaviorally structured, individual-based model (IBM) in Netlogo to simulate contacts between- and within-groups of individual mule deer (Odocoileus hemionus), a species particularly susceptible to chronic wasting disease. The model tracks contacts (defined as two individuals coming within five meters of one another), recorded as between- or within-group depending on the social group membership of the two individuals (dyad). We parameterized the model with data from mule deer with global positioning systems (GPS) collars in east-central Alberta, Canada. Individuals move according to habitat preferences, home range attraction, and grouping behaviours. Animals were tracked at two-hour time steps and were modelled as selecting locations relative to preferred resources based on sex-specific integrated step-selection functions (iSSFs) with steps biased toward a home range centroid. Total within-group contacts increased with group size and were sensitive to changes in movement cohesion of the group and movement persistence, particularly movement cohesion. Total between-group contacts were sensitive only to the number of groups. We compared model predictions for where the locations of deer contacts occurred against an existing statistical model for the relative contact probabilities (RCP) on the same landscape (Dobbin et al. 2023). Predicted locations of deer contacts generally were consistent with higher predicted RCP values. When disease transmission is a function of contact rate, the model can be used to assess the interaction between model components (e.g., movement rates, grouping rules, home ranges, animal densities) and the spatial distribution of key natural and artificial resources that may attract deer and potentially increase disease spread.

The response threshold model explains the emergence of division of labor (i.e., task specialization) in an unstructured population by assuming that the individuals have different propensities to work on different tasks. The incentive to attend to a particular task increases when the task is left unattended and decreases when individuals work on it. Here we derive mean-field equations for the stimulus dynamics and show that they exhibit complex attractors through period-doubling bifurcation cascades when the noise disrupting the thresholds is small. In addition, we show how the fixed threshold can be set to ensure specialization in both the transient and equilibrium regimes of the stimulus dynamics. However, a complete explanation of the emergence of division of labor requires that we address the question of where the threshold variation comes from, starting from a homogeneous population. We then study a structured population scenario, where the population is divided into a large number of independent groups of equal size, and the fitness of a group is proportional to the weighted mean work performed on the tasks during a fixed period of time. Using a winner-take-all strategy to model group competition and assuming an initial homogeneous metapopulation, we find that a substantial fraction of workers specialize in each task, without the need to penalize task switching.

Dispersal is an ecological process central to population dynamics, describing one of the most important movement behaviours between populations and across landscapes. In spatial population models for terrestrial vertebrates, capturing and portraying plausible dispersal behaviour is of particular importance when considering the spread of disease or invasive species. The distribution of distances travelled by dispersers, or the dispersal kernel, is typically highly skewed, with most individuals remaining close to their origin but some travelling substantially further. Using mechanistic models to simulate individual dispersal behaviour, the dispersal kernel can be generated as an emergent property. Through stepwise simulation of the entire movement path, models can also account for the influence of the local environment, and contacts during the dispersal event which may spread disease. In this study, we explore a range of simple rules to emulate individual dispersal behaviour within a mosaic model generated using irregular geometry. Movement rules illustrate a limited range of behavioural assumptions and when applied across these simple synthetic landscapes generated a wide range of emergent kernels. We establish that naturalistic kernels can emerge when simulating dispersal across irregular mosaic landscapes. Given the variability in dispersal distances observed within species, our results highlight the importance of considering landscape heterogeneity and individual-level variation in movement, with simpler rules approximating random walks providing less plausible emergent kernels. As a case study, we demonstrate how rule sets can be selected by comparison to an empirical kernel for a study species (red fox; Vulpes vulpes). These results provide a foundation for the selection of movement rules to represent dispersal in spatial agent-based models, however, we also emphasise the need to corroborate rules against the behaviour of specific species and within chosen landscapes to avoid the potential for these rules to bias predictions.

Gymnophiona (caecilians) are inconspicuous, wormlike amphibians that are often hidden from human sight due to their aquatic or fossorial lifestyles. While Google Trends data have been widely used within conservation biology to provide information about the relative interest in species, and therefore of their flagship-making potential, as well as to identify current taxonomic biases. This study aimed to evaluate public interest in amphibians, with a particular focus on caecilians, and possible taxonomic biases of and within the class Amphibia. Google Trends data from amphibians, reptiles (sauropsids, excluding aves), and fishes (chondrichthyans + osteichthyans, excluding tetrapods) were analyzed and compared. In addition, a framework for a representation index and web representation index is presented. The introduced relative representation index was able to confirm taxonomic bias concerning Amphibia. Differences in worldwide public interest could also be evaluated within amphibians, indicating severe underrepresentation in public interest for caecilians.

Avoiding the ‘tragedy of the commons’ remains a challenge in many natural resource systems, and open-access fisheries are well-studied in this context. Here, an agent-based model is used to investigate how variation in fisher goals change what policies best solve the tragedy. When fishers’ goals are easily satisfied, commons problems are avoided without management interventions, but the imposition of quota limits triggers the tragedy. Thus, commons problems are not necessarily inevitable and sophisticated governance institutions or regulations are not always required to manage them; the same policy may prevent the tragedy or trigger it, depending on the fisher's goals. Given that it is difficult to ascertain them, by using a simulation model we can find patterns that help us identify fishers' goals and incorporate these patterns within our management procedure. This can assist adaptive management to better incorporate behaviour into policy evaluation.