The Physics of Foraging Viswanathan, Gandhimohan. M.; da Luz, Marcos G. E.; Raposo, Ernesto P. ...
06/2011
eBook, Book
Do the movements of animals, including humans, follow patterns that can be described quantitatively by simple laws of motion? If so, then why? These questions have attracted the attention of ...scientists in many disciplines, and stimulated debates ranging from ecological matters to queries such as 'how can there be free will if one follows a law of motion?' This is the first book on this rapidly evolving subject, introducing random searches and foraging in a way that can be understood by readers without a previous background on the subject. It reviews theory as well as experiment, addresses open problems and perspectives, and discusses applications ranging from the colonization of Madagascar by Austronesians to the diffusion of genetically modified crops. The book will interest physicists working in the field of anomalous diffusion and movement ecology as well as ecologists already familiar with the concepts and methods of statistical physics.
A predictive understanding of the ecological impacts of nonnative species has been slow to develop, owing largely to an apparent dearth of clearly defined hypotheses and the lack of a broad ...theoretical framework. The context dependency of impact has fueled the perception that meaningful generalizations are nonexistent. Here, we identified and reviewed 19 testable hypotheses that explain temporal and spatial variation in impact. Despite poor validation of most hypotheses to date, evidence suggests that each can explain at least some impacts in some situations. Several hypotheses are broad in scope (applying to plants and animals in virtually all contexts) and some of them, intriguingly, link processes of colonization and impact. Collectively, these hypotheses highlight the importance of the functional ecology of the nonnative species and the structure, diversity, and evolutionary experience of the recipient community as general determinants of impact; thus, they could provide the foundation for a theoretical framework for understanding and predicting impact. Further substantive progress toward this goal requires explicit consideration of within-taxon and across-taxa variation in the per capita effect of invaders, and analyses of complex interactions between invaders and their biotic and abiotic environments.
Biological invasions present a global problem underlain by an ecological paradox that thwarts explanation: how do some exotic species, evolutionarily naïve to their new environments, outperform ...locally adapted natives? We propose that community assembly theory provides a framework for addressing this question. Local community assembly rules can be defined by evaluating how native species’ traits interact with community filters to affect species abundance. Evaluation of exotic species against this benchmark indicates that exotics that follow assembly rules behave like natives, while those exhibiting novel interactions with community filters can greatly underperform or outperform natives. Additionally, advantages gained by exotics over natives following disturbance can be explained by accounting for extrinsic assembly processes that bias exotic traits toward ruderal strategies.
We build on recent studies to demonstrate how community assembly theory can provide a framework for advancing invasion ecology.
In this framework, the success of exotic species in recipient communities is determined by how their traits interact with local ecological filters.
This approach illustrates that most exotics follow community rules to become naturalized species that behave like the natives; that is, traits predict their abundance according to local rules as they do for natives. However, some exotics can underperform or outperform relative to the natives when they exhibit novel interactions with local filters due to their unique ecological–evolutionary histories.
This approach also illustrates that the widely noted advantage of exotics over natives following disturbances can arise when extrinsic filters bias local exotic species pools toward traits that facilitate invasiveness.
The roles of species richness, resource use, and resource availability are central to many hypotheses explaining the diversity-invasion phenomenon but are generally not investigated together. Here, ...we created a large diversity gradient of soil microbial communities by either assembling communities of pure bacterial strains or removing the diversity of a natural soil. Using data on the resource-use capacities of the soil communities and an invader that were gathered from 71 carbon sources, we quantified the niches available to both constituents by using the metrics community niche and remaining niche available to the invader. A strong positive relationship between species richness and community niche across both experiments indicated the presence of resource complementarity. Moreover, community niche and the remaining niche available to the invader predicted invader abundance well. This suggested that increased competition in communities of higher diversity limits community invasibility and underscored the importance of resource availability as a key mechanism through which diversity hinders invasions. As a proof of principle, we subjected selected invaded communities to a resource pulse, which progressively uncoupled the link between soil microbial diversity and invasion and allowed the invader to rebound after nearly being eliminated in some communities. Our results thus show that (1) resource competition suppresses invasion, (2) biodiversity increases resource competition and decreases invasion through niche preemption, and (3) resource pulses that cannot be fully used, even by diverse communities, are favorable to invasion.
Human activities such as the transport of species to new regions and modifications of the environment are increasingly reshaping the distribution of biota. Accordingly, developing robust, repeatable, ...and consistent definitions of alien species that serve scientific and policy purposes has become of prime importance. We provide a set of classification criteria that are widely applicable across taxa and realms and offer guidance on their use in practice. The criteria focus on (a) acknowledging the role of assessment uncertainty, (b) incorporating time since introduction, (c) considering infraspecific taxonomic ranks, and (d) differentiating between alien species whose survival depends on explicit human assistance from those that survive without such assistance. Furthermore, we make recommendations for reducing assessment uncertainty, suggest thresholds for species assessment, and develop an assessment scheme. We illustrate the application of the assessment criteria with case studies. Finally, the implications for alien species management, policy, and research are discussed.
Biological invasions have steadily increased over recent centuries. However, we still lack a clear expectation about future trends in alien species numbers. In particular, we do not know whether ...alien species will continue to accumulate in regional floras and faunas, or whether the pace of accumulation will decrease due to the depletion of native source pools. Here, we apply a new model to simulate future numbers of alien species based on estimated sizes of source pools and dynamics of historical invasions, assuming a continuation of processes in the future as observed in the past (a business‐as‐usual scenario). We first validated performance of different model versions by conducting a back‐casting approach, therefore fitting the model to alien species numbers until 1950 and validating predictions on trends from 1950 to 2005. In a second step, we selected the best performing model that provided the most robust predictions to project trajectories of alien species numbers until 2050. Altogether, this resulted in 3,790 stochastic simulation runs for 38 taxon–continent combinations. We provide the first quantitative projections of future trajectories of alien species numbers for seven major taxonomic groups in eight continents, accounting for variation in sampling intensity and uncertainty in projections. Overall, established alien species numbers per continent were predicted to increase from 2005 to 2050 by 36%. Particularly, strong increases were projected for Europe in absolute (+2,543 ± 237 alien species) and relative terms, followed by Temperate Asia (+1,597 ± 197), Northern America (1,484 ± 74) and Southern America (1,391 ± 258). Among individual taxonomic groups, especially strong increases were projected for invertebrates globally. Declining (but still positive) rates were projected only for Australasia. Our projections provide a first baseline for the assessment of future developments of biological invasions, which will help to inform policies to contain the spread of alien species.
The number of alien species has been increasing worldwide, but we still lack clear expectations about future developments of biological invasions. Using a model predicting alien species numbers based on observed developments and species pools, we here provide the first quantitative projections of alien species numbers until 2050 worldwide for a range of taxonomic groups and regions. Our projections show that the rise in alien species numbers will persist to grow with little signs of slowdowns. Overall, the number of alien species is predicted to increase by 36% with particularly steep increases expected for Europe and invertebrates.
We present an updated list of introduced ants to continental Ecuador, and compile records of occurrence, as well as map the distribution of 15 exotic species. We analyzed specimens in entomological ...collections and data from AntWeb, GBIF and iNaturalist. Among these, we add two new records for the country: Cardiocondyla mauritanica Forel, 1980 and Pheidole megacephala (Fabricius, 1793). The former is also the first record for South America, while the finding of the latter shows how little we know about introduced tramp ants. In addition, we add site records for nine species: Cardiocondyla emeryi Forel, 1881, Cardiocondyla minutior Forel, 1899, Cardiocon­dyla wroughtonii (Forel, 1890), Linepithema humile (Mayr, 1868), Monomorium floricola (Jerdon, 1851), Monomo­rium pharaonis (Linnaeus, 1758), Paratrechina longicornis (Latreille, 1802), Tapinoma melanocephalum (Fabricius, 1793), and Tetramorium bicarinatum (Nylander, 1846). Based on our previous fieldwork observations, it appears that our understanding of exotic species richness is still in its early stages.
Biological invasions are responsible for substantial biodiversity declines as well as high economic losses to society and monetary expenditures associated with the management of these invasions
. The ...InvaCost database has enabled the generation of a reliable, comprehensive, standardized and easily updatable synthesis of the monetary costs of biological invasions worldwide
. Here we found that the total reported costs of invasions reached a minimum of US$1.288 trillion (2017 US dollars) over the past few decades (1970-2017), with an annual mean cost of US$26.8 billion. Moreover, we estimate that the annual mean cost could reach US$162.7 billion in 2017. These costs remain strongly underestimated and do not show any sign of slowing down, exhibiting a consistent threefold increase per decade. We show that the documented costs are widely distributed and have strong gaps at regional and taxonomic scales, with damage costs being an order of magnitude higher than management expenditures. Research approaches that document the costs of biological invasions need to be further improved. Nonetheless, our findings call for the implementation of consistent management actions and international policy agreements that aim to reduce the burden of invasive alien species.
Indirect effects of parasites in invasions Dunn, Alison M.; Torchin, Mark E.; Hatcher, Melanie J. ...
Functional ecology,
December 2012, Letnik:
26, Številka:
6
Journal Article
Recenzirano
Odprti dostop
1. Introduced species disrupt native communities and biodiversity worldwide. Parasitic infections (and at times, their absence) are thought to be a key component in the success and impact of ...biological invasions by plants and animals. They can facilitate or limit invasions, and positively or negatively impact native species. 2. Parasites have not only direct effects on their hosts, but also indirect effects on the species with which their hosts interact. Indirect effects include density-mediated effects (resulting from parasite-induced reduction in host reproduction and survival) as well as trait-mediated indirect effects (resulting from parasite-induced changes in host phenotype, behaviour or life history). These effects are not mutually exclusive but often interact. 3. The importance of these indirect interactions for invasion success, and the extent to which these effects ramify throughout communities and influence ecosystems undergoing biological invasion provide the focus of our review. Examples from the animal and plant literature illustrate the importance of parasites in mediating both competitive and consumer—resource interactions between native and invasive species. 4. Parasites are involved in indirect interactions at all trophic levels. Furthermore, the indirect effects of parasitic infection are important at a range of biological scales from within a host to the whole ecosystem in determining invasion success and impact. 5. To understand the importance of parasitic infection in invasion success and in the outcomes for invaded communities requires an interdisciplinary approach by ecologists and parasitologists, across animal and plant systems. Future research should develop a framework integrating community ecology, evolution and immunology to better understand and manage the spread of invasive species and their diseases.
PDF
