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Seleção de habitats, comportamentos dominantes e modelação dos ritmos circadianos de um núcleo populacional de Bico-de-lacre (Estrilda astrild)
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The study of invasion ecology usually focuses on the negative impacts of alien species, while potential positive impacts are often overlooked. Understanding of biotic interactions may thus be skewed towards the negative, which could have important implications for ecological management and conservation. This article provides a comprehensive review of all types of impacts, both beneficial and detrimental, that can result from species translocation. An extensive review of literature on species introductions to terrestrial, freshwater and marine ecosystems and involving a wide range of taxa (including microorganisms, parasites, plants, insects, amphibians, reptiles, birds, mammals, fish and Crustacea) showed that, despite limited research into facilitative alien-native interactions, such interactions occur surprisingly frequently. Examples were found of introduced species acting as hosts, food sources, pollinators or seed dispersers for native species, as well as providing herbivory, predatory or parasite release. However, research showed that numerous negative interactions also occurred and combination impacts (when an alien benefits some natives but disadvantages others) were common. In many cases, the traditional view that biological invasions constitute a significant threat to native biota is both accurate and appropriate. Efforts to prevent translocation and control non-native species can be vital. However, the "native good, alien bad" maxim does not convey the complexity of invasion ecology: alien species do not axiomatically pose a threat to native biota. In order to move understanding of invasion ecology forward and to develop maximally-effective management strategies, facilitative alien-native interactions need to be added into the alien species debate.
Behavioral differences among individuals are common and are organized into personalities in a wide variety of species. Hypotheses for the coexistence of behavioral differences fall into 3 categories: variation in selection, frequency-dependent selection, and behavioral plasticity. We tested predictions of those hypotheses regarding geographic covariation of behavior with ecology, using a recent (≈40 years) biological invasion of common waxbills (Estrilda astrild). Behavior in tests for exploration and social interaction covaried among individuals, suggesting a behavioral syndrome, although we could only demonstrate within-individual repeatability in the test for social interaction. These 2 behaviors changed geographically with the ecology of sites (degree of climate variation) in an apparently adaptive way, rather than with the direction of invasion. We found behavioral plasticity but showed that short-term plastic effects do not explain geographic divergence. Differential dispersal does not explain geographic divergence either, which is orthogonal to the direction of invasion. Results are best interpreted either as evolved divergences, although a candidate-gene approach could not identify genetic correlates of behavior, or as long-term behavioral plasticity (e.g., effects of rearing environment). In this recent invasion, geographic differences in ecology and behavior equate to repeated and fast changes over time. Thus, fluctuations in ecological conditions, which are common in nature, may have a widespread role maintaining behavioral and personality differences via selection and/or long-term behavioral plasticity.
The common waxbill Estrilda astrild was first introduced to Portugal from Africa in 1964, and has spread across much of the country and into Spain. We modelled the expansion of the common waxbill on a 20 × 20 km UTM grid in 4-year periods from 1964 to 1999. The time variation of the square root of the occupied area shows that this expansion process is stabilizing in Portugal, and reasons for this are discussed. Several methods used to model biological expansions are not appropriate for the present case, because little quantitative data are available on the species ecology and because this expansion has been spatially heterogeneous. Instead, colonization on a grid was modelled as a function of several biophysical and spatio-temporal variables through the fitting of a multivariate autologistic equation. This approach allows examination of the underlying factors affecting the colonization process. In the case of the common waxbill it was associated positively with its occurrence in adjacent cells, and affected negatively by altitude and higher levels of solar radiation.
Natural freshwater wetlands are among the most threatened habitats on Earth. Effective wetland biodiversity conservation can not, however, be evaluated without fully understanding the roles of artificial waterbodies as refuges for water-dependent plants and animals. Waterbird assemblages were examined on 59 farm ponds in the Elgin and Caledon districts of the Western Cape, South Africa. This study examines the relationship between waterbird use and habitat characteristics of farm ponds. Patterns of temporal and spatial variation of waterbird species richness and abundance were quantified in relation to the habitat characteristics of each pond. Cluster analysis and multiple regression analyses identified surface area of the farm ponds as an important variable determining the presence and abundance of many waterbird species. Structural diversity in terms of vegetation in and around the ponds was especially important in determining their usage by waterbirds. These variables were evaluated in terms of creating a mosaic of habitat types (by varying vegetation structure and pond topography), which may be a useful way to enhance waterbird diversity at farm ponds. This study concludes that the high number of farm ponds in the transformed habitat matrix of the Western Cape plays an important role in conserving waterbirds.
The common waxbill Estrilda astrild was first introduced to Portugal, from Africa, in 1964, from where it has spread to much of the country and to Spain. We
modelled the expansion of this species on a 20×20-km UTM grid in 4-year periods from 1964 to 1999. Colonisation process on
a grid was modelled as a function of several biophysical and spatio-temporal variables through the fitting of several multiple
logistic equations. Variation partitioning confirmed the importance of the spatial-temporal component, explaining 33% of the
total variation, followed by the combined effects of both environmental and spatial-temporal variables (around 25%). Only
11% of the total variation can be attributed strictly to the considered environmental factors.
Species invasions provide numerous unplanned and frequently, but imperfectly, replicated experiments that can be used to better understand the natural world. Classic studies by Darwin, Grinnell, Elton and others on these species-invasion experiments provided invaluable insights for ecology and evolutionary biology. Recent studies of invasions have resulted in additional insights, six of which we discuss here; these insights highlight the utility of using exotic species as ‘model organisms’. We also discuss a nascent hypothesis that might provide a more general, predictive understanding of invasions and community assembly. Finally, we emphasize how the study of invasions can help to inform our understanding of applied problems, such as extinction, ecosystem function and the response of species to climate change.
Species-typical patterns of grouping have profound impacts on many aspects of physiology and behavior. However, prior to our recent studies in estrildid finches, neural mechanisms that titrate species-typical group-size preferences, independent of other aspects of social organization (e.g., mating system and parental care), have been wholly unexplored, likely because species-typical group size is typically confounded with other aspects of behavior and biology. An additional complication is that components of social organization are evolutionarily labile and prone to repeated divergence and convergence. Hence, we cannot assume that convergence in social structure has been produced by convergent modifications to the same neural characters, and thus any comparative approach to grouping must include not only species that differ in their species-typical group sizes, but also species that exhibit convergent evolution in this aspect of social organization. Using five estrildid finch species that differ selectively in grouping (all biparental and monogamous) we have demonstrated that neural motivational systems evolve in predictable ways in relation to species-typical group sizes, including convergence in two highly gregarious species and convergence in two relatively asocial, territorial species. These systems include nonapeptide (vasotocin and mesotocin) circuits that encode the valence of social stimuli (positive-negative), titrate group-size preferences, and modulate anxiety-like behaviors. Nonapeptide systems exhibit functional and anatomical properties that are biased toward gregarious species, and experimental reductions of nonapeptide signaling by receptor antagonism and antisense oligonucleotides significantly decrease preferred group sizes in the gregarious zebra finch. Combined, these findings suggest that selection on species-typical group size may reliably target the same neural motivation systems when a given social structure evolves independently.
Since the Age of Exploration began, there has been a drastic breaching of biogeographic barriers that previously had isolated the continental biotas for millions of years. We explore the nature of these recent biotic exchanges and their consequences on evolutionary processes. The direct evidence of evolutionary consequences of the biotic rearrangements is of variable quality, but the results of trajectories are becoming clear as the number of studies increases. There are examples of invasive species altering the evolutionary pathway of native species by competitive exclusion, niche displacement, hybridization, introgression, predation, and ultimately extinction. Invaders themselves evolve in response to their interactions with natives, as well as in response to the new abiotic environment. Flexibility in behavior, and mutualistic interactions, can aid in the success of invaders in their new environment.
Agent-based simulation models can reproduce the interactions between members of an organization or between different organizations in an artificial environment where "agents" make decisions and communicate with one another. This article discusses possible applications to core issues in organization science and provides an introductory guide to simulation platforms. Agent-based modeling requires writing computer code, a skill that, if properly mastered, may turn into a career opportunity.
1. Non-native species can be major drivers of biodiversity loss and cause economic damage. Predicting the potential distribution of a non-native species, and understanding the environmental factors that limit this distribution, is useful for informing their potential management. This is often carried out using species distribution models (SDMs) that attempt to classify grid cells as suitable or unsuitable for a species based on a set of environmental covariates.
2. A key assumption of SDMs is that a species is in equilibrium with its environment. Spreading non-native species often violate this assumption due to dispersal limitation.
3. We present a simple method for dealing with this problem: dispersal weighting (DW). This uses the probability that a species can disperse to a grid cell to weight a SDM. We use simulations to compare the ability of DW and unweighted models at parameterising the true species–environment relationship (SER) of a simulated species, and to test their ability at predicting the future distribution of this species. We investigate how varying the degree of spatial autocorrelation in explanatory variables affects the performance of the methods.
4. Dispersal weighting models outperformed unweighted models at parameterising the SER, and at predicting the future distribution of the species when dispersal probabilities were incorporated into the model predictions. Unweighted models had a stronger tendency than DW models to overestimate the magnitude of relationships with spatially autocorrelated explanatory variables, but underestimate the magnitude of relationships with randomly distributed variables.
5. We then applied our method to a real case study, using it to model the distribution of the non-native common waxbill Estrilda astrild in the Iberian Peninsula as a function of climate and land-use variables. The relative performance of DW and unweighted models reflected the results of the simulation.
6. We conclude that DW models perform better than unweighted models at modelling the true SER of non-native species, and recommend using DW whenever enough data exist to create a dispersal model.
Biological invasions often threaten biodiversity, yet their ecological effects are unpredictable and in some cases may be neutral. Assessing potential interactions between invasive and native species is thus important to understand community functioning and prioritize conservation efforts. With this purpose, we compared the ecological niche and occurrence of a successful avian invader in SW Europe, the common waxbill (Estrildidae: Estrilda astrild), with those of co-occurring native passerine species. We found that common waxbills occupy a marginal niche relative to the community of native passerines, with a larger average ecological distance to the remaining species in the community compared to the native species amongst themselves, and a nearest-neighbour ecological distance identical to those of native species. Furthermore, ecological similarity did not predict co-occurrence of waxbills with other bird species. This is consistent with the invasion using a vacant niche in unsaturated communities, which is likely related to invading waxbills occupying partly human-modified habitats. Similar explanations may apply to other biological invasions of human-modified environments. Results also suggest that detrimental ecological effects due to interspecific competition with native passerines are unlikely. Notwithstanding, the ecological nearest-neighbour of common waxbills was the reed bunting (Emberiza schoeniclus), whose SW European subspecies are endangered, and may justify conservation attention regarding possible interactions between these two species.
Concern over the impact of invaders on biodiversity and on the functioning of ecosystems has generated a rising tide of comparative analyses aiming to unveil the factors that shape the success of introduced species across different regions. One limitation of these studies is that they often compare geographically rather than ecologically defined regions. We propose an approach that can help address this limitation: comparison of invasions across convergent ecosystems that share similar climates. We compared avian invasions in five convergent mediterranean climate systems around the globe. Based on a database of 180 introductions representing 121 avian species, we found that the proportion of bird species successfully established was high in all mediterranean systems (more than 40% for all five regions). Species differed in their likelihood to become established, although success was not higher for those originating from mediterranean systems than for those from nonmediterranean regions. Controlling for this taxonomic effect with generalized linear mixed models, species introduced into mediterranean islands did not show higher establishment success than those introduced to the mainland. Susceptibility to avian invaders, however, differed substantially among the different mediterranean regions. The probability that a species will become established was highest in the Mediterranean Basin and lowest in mediterranean Australia and the South African Cape. Our results suggest that many of the birds recently introduced into mediterranean systems, and especially into the Mediterranean Basin, have a high potential to establish self-sustaining populations. This finding has important implications for conservation in these biologically diverse hotspots.
The relationships between seed characteristics (size and nutrient contents) and bird morphology were investigated in ten species belonging to three specialized families of granivorous passerines. Wild-caught birds were exposed in captivity to a fixed mixture of thirteen seed types before measuring their consumption rates and seed preferences. A multivariate analysis of seed characteristics showed two principal and independent gradients of covariation, namely seed nutritive value and seed size. The smaller the birds, the more nutritive the seeds they selected, this result being largely independent of the family the bird belonged to. The selected seed size was directly related to both the body and bill sizes of the birds, hut these relationships varied between families, most probably as a consequence of interfamilial differences in the structure of the ramphotheca and the associated seed handling method.
Different approaches can be used to model the spread of invasive species. Here we demonstrate the use of survival regression, an approach that can be used to study a variety of events, not just death, to model the time to colonization. The advantage of survival regression to study colonisation of new areas is that information on those areas that have not been invaded by the end of a study can be included in the analysis, thus potentially increasing the accuracy of parameter estimation. We use proportional hazards regression (PHR; a type of survival regression) to model the spread of the common waxbill Estrilda astrild in Portugal. The species invaded Portugal in two peaks of invasion between 1964 and 1999. We built a PHR model with the information available up to the first invasion peak, then used this model to predict the pattern of invasion in the second peak. PHR had useful forecasting capabilities: areas that were actually colonised by 1999 had significantly higher hazards of colonization based on information from the first wave of invasion than areas that were not colonised. We then built a final model of expansion of the common waxbill that combined all available data up to 1999. Among climate variables, the most important predictor of colonization was temperature, followed by relative humidity. We used this model to estimate the invasion potential of the species under climate change scenarios, observing that an increase of 1°C in mean annual temperature increased the risk of a new invasion by 47%. Our analyses suggest that survival regression may be a useful tool for studying the geographical spread of invasive species. However, PHR was conceived as a descriptive technique rather than as a predictive tool, and thus further research is needed to empirically test the predictive capabilities of PHR.
Feeding, flighting and clumping are all synchronized in captive flocks of Amandava subflava and Uraeginthus bengalus. Feeding and flighting A. subflava, and flighting in U. bengalus, are synchronized by both visual releasers and calls, whereas clumping in both species and feeding in U. bengalus are synchronized by birds reacting to the sight of others performing these activities. In captive mixed flocks, birds react to the sight of one another, so that there is interspecific synchronization, but not to calls of the other species. Calls and visual releasers are also important in synchronizing behaviour in the wild. Mixed flocks sometimes occur and one species, the firefinch, Lagonosticta senegala, has a well developed tendency to flock with other species.
Each modeller who builds and analyses an individual-based model learns of course a great deal, but what has ecology as a whole learned from the individual-based models published during the last decade? Answering this question proves extremely difficult as there is no common motivation behind individual-based models. The distinction is introduced between ‘pragmatic’ motivation, which uses the individual-based approach as a tool without any reference to the theoretical issues which have emerged from the classical state variable approach and ‘paradigmatic’ motivation, which explicitly refers to theoretical ecology. A mini-review of 50 individual-based animal population models shows that the majority are driven by pragmatic motivation. Most models are very complex and special techniques to cope with this complexity during their analysis are only occasionally applied. It is suggested that in order to orient individual-based modelling more towards general theoretical issues, we need increased explicit reference to theoretical ecology and an advanced strategy for building and analysing individual-based models. To this end, a heuristic list of rules is presented which may help us to advance the practice of individual-based modelling and to learn more general lessons from individual-based modelling in the future than we have during the last decade. The main ideas behind these rules are as follows: (1) Individual-based models usually make more realistic assumptions than state variable models, but it should not be forgotten that the aim of individual-based modelling is not ‘realism’ but modelling. (2) The individual-based approach is a bottom-up approach which starts with the ‘parts’ (i.e. individuals) of a system (i.e. population) and then tries to understand how the system’s properties emerge from the interaction among these parts. However, bottom-up approaches alone will never lead to theories at the systems level. State variable or top-down approaches are needed to provide an appropriate integrated view, i.e. the relevant questions at the population level.
Human management activities have altered the frequency and intensity of ecosystem disturbance often with enormous impacts on landscape structure and composition. One additional and under-appreciated way in which humans have altered disturbance regimes is through the introduction of invasive non-native species, themselves capable of modifying existing disturbance regimes or introducing entirely new disturbances. In many cases, modifications of disturbance regimes results in maintenance of ecosystems in a new or transitional state. There is now evidence that alteration of disturbance regime may be the most profound effect that a species or functional group can have on ecosystem structure and function.
Five software platforms for scientific agent-based models (ABMs) were reviewed by implementing example models in each. NetLogo is the highest-level platform, providing a simple yet powerful programming language, built-in graphical interfaces, and comprehensive documentation. It is designed primarily for ABMs of mobile individuals with local interactions in a grid space, but not necessarily clumsy for others. NetLogo is highly recommended, even for prototyping complex models. MASON, Repast, and Swarm are "framework and library" platforms, providing a conceptual framework for organizing and designing ABMs and corresponding software libraries. MASON is least mature and designed with execution speed a high priority. The Objective-C version of Swarm is the most mature library platform and is stable and well organized. Objective-C seems more natural than Java for ABMs but weak error-handling and the lack of developer tools are drawbacks. Java Swarm allows Swarm's Objective-C libraries to be called from Java; it does not seem to combine the advantages of the two languages well. Repast provides Swarm-like functions in a Java library and is a good choice for many, but parts of its organization and design could be improved. A rough comparison of execution speed found MASON and Repast usually fastest (MASON 1-35% faster than Repast), Swarm (including Objective-C) fastest for simple models but slowest for complex ones, and NetLogo intermediate. Recommendations include completing the documentation (for all platforms except NetLogo), strengthening conceptual frameworks, providing better tools for statistical output and automating simulation experiments, simplifying common tasks, and researching technologies for understanding how simulation results arise. 10.1177/0037549706073695
Behavioural flexibility has long been thought to provide advantages for animals when they invade novel environments. This hypothesis has recently received empirical support in a study of avian species introduced to New Zealand, but it remains to be determined whether behavioural flexibility is a general mechanism influencing invasion success. In this study, we examined introduction success of 69 bird species in different regions of the world as a function of their degree of behavioural flexibility. Specifically, we predicted that species with relatively large brains and a high frequency of foraging innovations in their area of origin should show a higher probability of establishing themselves where they were introduced than species with small brains and low innovation frequencies. An analysis with general linear modelling (GLM) supported the prediction for relative brain size, even when controlling for phylogenetic biases and potential confounding variables. The only covariates that remained with relative brain size were plumage dimorphism, human commensalism and nest site. A pairwise comparison of closely related species also revealed that successful invaders showed a higher frequency of foraging innovations in their region of origin. This result held even when differences in research effort between species were considered. Overall, the results confirm and generalize the hypothesis that behavioural flexibility is a major determinant of invasion success in birds.
There has been a dramatic growth in research on biological invasions over the past 20 years, but a mature understanding of the field has been hampered because invasion biologists concerned with different taxa and different environments have largely adopted different model frameworks for the invasion process, resulting in a confusing range of concepts, terms and definitions. In this review, we propose a unified framework for biological invasions that reconciles and integrates the key features of the most commonly used invasion frameworks into a single conceptual model that can be applied to all human-mediated invasions. The unified framework combines previous stage-based and barrier models, and provides a terminology and categorisation for populations at different points in the invasion process.
Anthropogenic introduction of species is homogenizing the earth's biota. Consequences of introductions are sometimes great, and are directly related to global climate change, biodiversity AND release of genetically engineered organisms. Progress in invasion studies hinges on the following research trends: realization that species' ranges are naturally dynamic; recognition that colonist species and target communities cannot be studied independently, but that species-community interactions determine invasion success; increasingly quantitative tests of how species and habitat characteristics relate to invasibility and impact; recognition from paleobiological, experimental and modeling studies that history, chance and determinism together shape community invasibility.
For many animals, nest construction is a prerequisite for successful breeding. The choice of nesting materials is an important component of nest construction, because material properties can influence nest design and, potentially, reproductive success. Common waxbills are small African finches that select carnivore scat as a material to include in, on, and around their nests. I investigated the hypothesis that scat functions to reduce predation risk by documenting its use in a wild population of common waxbills and by conducting an artificial nest experiment. Among natural nests, scat was present in every nest that hatched young, and parents continued to add scat to nests throughout the nestling period. Among artificial nests, those that received experimental additions of carnivore scat survived at a significantly higher rate than did untreated nests, suggesting that scat functions to reduce predation risk. The mechanism by which nests are protected remains unclear, although it is likely that scat acts as an olfactory deterrent and/or camouflage. Researchers have long focused on the implications of nest site characteristics for avian life-history evolution. Results of the present study suggest that nest materials, similar to nest sites, may influence life histories of nest-building animals by affecting predation risk. Copyright 2005.
This report reviews both general agent based modelling (ABM) and battlefield-specific ABM toolkits against established criteria, namely flexibility, documentation, speed, and facilities. The other main focus of this report is to consider which ABM toolkits are best suited to studying self-organisation, adaptation, and causality in networks, since these are all essential parts of complex adaptive systems of interest to defence. The ABM toolkits evaluated against these requirements were BactoWars, EINSTein, MANA, MASON, NetLogo, Repast, Swarm and WISDOM-II. Many complex systems are amenable to study through the use of agent based models. Agent based models provide useful insights into how individual interactions give rise to emergent properties. Of these, structures and causality are of great interest. The focus of this report is firstly to evaluate both general agent based modelling (ABM) and battlefield-specific agent based modelling (BSABM) toolkits against established criteria: speed, flexibility, documentation provided, and general facilities (for example graphing facilities) provided. The toolkits are also assessed for statistical capabilities in order to highlight this area as needing (generally) better support from ABM toolkits. The other main focus of this report is to consider which ABM toolkits are best suited to studying structure formation and causality in networks. Two processes that generate and/or preserve structure—adaptation and self-organisation—are considered and the toolkits are evaluated as to how well they support these two processes. The toolkits are also evaluated as to what facilities (if any) they have for supporting causal decision making in networks of agents. These three criteria together are critical for modelling complex adaptive systems, of which battlefield scenarios are one example of importance to defence. A simple ABM was developed to conduct the evaluation of the ABM platforms for their support of adaptation, self-organisation, and networked causality, along with more general criteria established in previous ABM platform reviews. MASON is the overall best choice, and fit for the purpose of exploring complex adaptive systems, but requires a high level of programming experience. For simple models, and for people with little programming experience, NetLogo is highly recommended. EINSTein is recommended as a BSABM platform requiring no programming experience.
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