Effects Of Invasive Species Research Articles

Does fire and herbicide benefit cattle production in invaded grassland landscapes?

Invasive species management is promoted as a general practice to maintain rangeland biodiversity and mitigate livestock performance losses (e.g., weight gain) stemming from invasive-species effects (e.g., competitive exclusion of palatable forages). It is hypothesized that altering fire-timing (e.g., moving from early to late-growing season burning) or integrating herbicide application into fire management regimes may lead to more successful reduction of certain invasive species without negatively affecting livestock weight gains. However, large-scale, replicated experimental evidence linking invasive species abundance or management practices to cattle weight gain is mostly lacking across grasslands. We manipulated eight large (333 – 766 ha) pastures managed with fire and grazing (i.e., pyric herbivory) to test how growing (i.e., August-September) and dormant (i.e., March-April) season fires, herbicide application, or invasive species abundance (namely Lespedeza cuneata) affected yearling stocker cattle weight gain – i.e., per head weight gain – from 2018 to 2020. We found that yearling stocker cattle gained significantly less weight in pastures burned during the growing season, and herbicide application did not increase weight gains overall. Moreover, we did not find a significant relationship between L. cuneata abundance and per head yearling stocker cattle weight gain. Our results add to a growing line of evidence that invasive species management does not always benefit livestock producers. The hypothesized negative relationship between invasive species abundance and cattle weight gain may be minimal (or neutral) across large grassland landscapes, particularly those managed with pyric herbivory. To date, pyric herbivory is the only management regime known to simultaneously promote biodiversity, and restrict some invasive plant species like L. cuneata.

Combination Synchronization of Three Nonidentical Ecological Systems with Species Invasion

The research investigates synchronizing dynamics of three nonidentical ecological systems, one of which is invaded by an exterior top predator. For studying the effects of species invasion in the synchronizing dynamics, combination synchronization of one drive system and two response systems is designed: the ecological system with species invasion taken as drive system, and the other ecological systems as response systems. Using active backstepping design, the conditions for achievement of combination synchronization are derived. Under the conditions, numerical simulations are performed to demonstrate the synchronizing dynamics of ecological systems under species invasion. The results suggest that mechanism of synchronization plays an important role in determining chaos when ecological systems are interacting with each other.

Effects of species invasion on population dynamics, vital rates and life histories of the native species

Effects of species invasion on population dynamics, vital rates and life histories of the native species

Effects of species invasion on population dynamics, vital rates and life histories of the native species

Effects of species invasion on population dynamics, vital rates and life histories of the native species

Unsuccessful invaders structure a natural freshwater phytoplankton community

AbstractSpecies invasion dynamics are a core topic in ecology and the effects of species invasions on ecosystems are well described. However, the knowledge about the mechanisms during the invasion process itself is limited. Many interactions between invaders and resident species occur during the invasion process. These interactions influence individual species abundance and subsequently community composition. Even though invaders are often unsuccessful, the very short interactions with the resident species can influence species abundances and therefore community composition. The prominent effects of unsuccessful invaders on community composition were already predicted in a theoretical model. To empirically test the effect of such unsuccessful invaders on a resident phytoplankton community, we conducted a mesocosm experiment in a mesotrophic freshwater pond. Six freshwater algae belonging to three taxonomic groups (chlorophyta, cyanobacteria, and bacillariophyta) were added as potential invader species to the natural phytoplankton community of the pond (as single species or as combination of two species of the same taxonomic group). After nine days, the invasion success and the impact on the natural phytoplankton community were estimated. Results show that although all invaders were unsuccessful, they had lasting effects on the resident community. In all communities exposed to invasion, biodiversity (H′) was maintained. In contrast, in control communities, the diversity at the end of the experiment was lower compared to the initial community. Furthermore, communities exposed to invasion were less similar to control communities without invasion than to the other invaded communities. Differences were found in taxonomic group composition as well as in species composition. Additionally, we found evidence for synergistic effects between the combined added species. Our results give clear evidence of strong transient effects of unsuccessful invaders on freshwater phytoplankton community composition.

Potential of remote sensing to predict species invasions

Understanding the causes and effects of species invasions is a priority in ecology and conservation biology. One of the crucial steps in evaluating the impact of invasive species is to map changes in their actual and potential distribution and relative abundance across a wide region over an appropriate time span. While direct and indirect remote sensing approaches have long been used to assess the invasion of plant species, the distribution of invasive animals is mainly based on indirect methods that rely on environmental proxies of conditions suitable for colonization by a particular species. The aim of this article is to review recent efforts in the predictive modelling of the spread of both plant and animal invasive species using remote sensing, and to stimulate debate on the potential use of remote sensing in biological invasion monitoring and forecasting. Specifically, the challenges and drawbacks of remote sensing techniques are discussed in relation to: i) developing species distribution models, and ii) studying life cycle changes and phenological variations. Finally, the paper addresses the open challenges and pitfalls of remote sensing for biological invasion studies including sensor characteristics, upscaling and downscaling in species distribution models, and uncertainty of results.

Clarifying debates in invasion biology: A survey of invasion biologists

Invasion biology is a relatively new field, so there are ongoing debates about foundational issues regarding terminology and assessment of the causes and consequences of invasive species. These debates largely reflect differing views about the extent to which invasion biologists should advocate on behalf of native species. We surveyed reviewers of the journal Biological Invasions to obtain a better sense of how invasion biologists evaluate several foundational issues. We received 422 replies, which represented a very good response rate for an online survey of 42.5% of those contacted. Responses to several debates in the field were distributed bimodally, but respondents consistently indicated that contemporary biological invasions are unprecedented. Even still, this was not seen as justification for exaggerated language (hyperbole). In contrast to prevalent claims in the literature, only 27.3% of respondents ranked invasive species as the first or second greatest threat to biodiversity. The responses also highlighted the interaction of invasive species with other threats and the role of human activity in their spread. Finally, the respondents agreed that they need to be both more objective and better at communicating their results so that those results can be effectively integrated into management.

How might science misdirect policy? Insights into the threats and consequences of invasive species

Humans frequently introduce novel organisms (e.g., non-native species and, more recently, genetically modified organisms) into ecosystems for economic or biological purposes. However, prior to this, risk analysis is an inherent part of the decision about which species to release. In this contribution we draw upon our experience with non-native species to illustrate two ways in which science can potentially misdirect policy and management of novel organisms. The first involves scientific error, and the challenges in evaluating risk in complex systems. For example, predicting the ecological impact of an evolutionary novel organism on its proposed new ecosystem carries substantial uncertainty, which, depending on how it is explained or framed, can result in different policy outcomes. The second category involves potential biases amongst scientists. As a result of their training scientists may be inclined towards particular opinions that are not necessarily shared by the larger public. Moreover, differences in values also exist among scientists due to different cultures. Examples include a predisposition among scientists against non-native species which can result in an overstatement of perceived risks, as well as an under-appreciation of potential benefits. We illustrate how both scientific and epistemological error can result in sub-optimal policy. Scientists as experts can, and should, express their personal positions, but these should be clearly distinguished from scientific analyses.

Effects of invasive seaweeds on feeding preference and performance of a keystone Mediterranean herbivore

The consequences of invasive species on ecosystem processes and ecological interactions remain poorly understood. Predator–prey interactions are fundamental in shaping species evolution and community structure and can be strongly modified by species introductions. To fully understand the ecological effects of invasive species on trophic linkages it is important to characterize novel interactions between native predators and exotic prey and to identify the impacts of invasive species on the performance of native predators. Although seaweed invasions are a growing global concern, our understanding of invasive algae—herbivore interactions is still very limited. We used a series of feeding experiments between a native herbivore and four invasive algae in the Mediterranean Sea to examine the potential of native sea urchins to consume invasive seaweeds and the impacts of invasive seaweed on herbivore performance. We found that three of the four invasive species examined are avoided by native herbivores, and that feeding behaviour in sea urchins is not driven by plant nutritional quality. On the other hand, Caulerpa racemosa is readily consumed by sea urchins, but may escape enemy control by reducing their performance. Recognizing the negative impacts of C. racemosa on herbivore performance has highlighted an enemy escape mechanism that contributes to explaining how this widespread invasive alga, which is preferred and consumed by herbivores, is not eradicated by grazing in the field. Furthermore, given the ecological and economic importance of sea urchins, negative impacts of invasive seaweeds on their performance could have dramatic effects on ecosystem function and services, and should be accounted for in sea urchin population management strategies.

Using local–regional richness plots to test for species saturation: pitfalls and potentials

1. Plots of local versus regional species richness are an exciting new tool for testing for species saturation in ecological communities. In this method, the local richness of a community is plotted as a function of its regional richness for different biogeographical regions. A proportional relationship between local and regional richness is interpreted as evidence for an unsaturated community, that is, a community with strong evolutionary limits to local richness. There will be no correlation between local and regional richness in a saturated community, that is, a community whose local species richness is limited largely by ecological processes. 2. Although at least 36 data sets have now been analysed using local–regional richness plots, there has not been much critical evaluation of the method. This paper provides such a critique, focusing on the selection of communities for comparison, the prevalence of pseudoreplication and multiple null models, and the effects of differing region size. 3. Local–regional richness plots are best suited for comparing similar habitats between different regions, not different habitats in a single region. In the latter, taxa effects and species pool effects are confounded. 4. Four very different types of local–regional richness plots have been published. Each type of plot has important underlying assumptions which are often not addressed by ecologists. 5. Of the 36 data sets reviewed in this paper, 13 were spatially pseudoreplicated, and 2 were temporally pseudoreplicated. Furthermore, ecologists differ in their choice of null model, with the result that the same local–regional plot could be interpreted as evidence for saturation by one ecologist, and for lack of saturation by another. 6. Differences in region size can result in pseudosaturation, the appearance of saturation by an unsaturated community. A simple model demonstrates this phenomenon. Other sources of error in estimating the regional species pool are also of concern. 7. In conclusion, local–regional richness plots are a potentially useful tool for distinguishing saturated from unsaturated communities, but should be used cautiously, and in conjunction with other supporting evidence (such as the presence or absence of competitive exclusion, resource limitation, density compensation and the effects of species invasions).