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Workshop: Designing NEON initiatives for invasive species
Synthesis of Submitted Research Questions

I. Biology of Invasion

Including the natural history, genetics, characteristics of specific invasive species, or suites of species, and their interactions with the surrounding community

  • Do invasive species or native species relationships across the country share similar characteristics? For example, do the invasives typically have longer germination period than the natives?

  • What are the traits that make some species invasive and others not? Are there general principles so that successful invasions are predictable a priori? This can be separated into (a) probability of arrival at new region from native region, (b) success in local invasions (once arrived at a site, does it become dominant?) and (c) rate and extent of spread into new sites (how fast and how broadly does an invasive spread once arrived in a new region?)

  • Are traits that lead to success of a recent invader in a community the same as those that lead to dominance of native species in a community? Alternatively, is success of invaders due to qualitatively different processes that are due to the lack of common evolutionary history of the invader and the rest of the community? For example, the predator escape hypothesis is clearly an example of the latter. The answer to this question bears on how much we can learn about the broader questions of community ecology from studying invasive species and vice versa.

  • What is the evolutionary history of invasive species and populations?

  • Can we develop accurate ecological classifications for types of invasive species?

  • How do traits of potential invaders and characteristics of communities interact? That is, do the traits that make good invaders depend on the characteristics of the community that is being invaded? If so, are there general principles that underlie the interactions so that they are predictable? Similarly, do the consequences depend on particular combinations of the traits of invaders and community characteristics?

  • There are a number of cases in which particular species may become naturalized without showing any tendency to spread. Then all of a sudden they take off. Does this reflect some change in the environment, the coinciding of several favorable ecological conditions at one time, changes in the genetics of the populations, etc?

II. Ecology of Invasion

The ecological aspects of invasion, including, the characteristics of ecosystems that make them resilient or vulnerable to invasion, and responses to disturbance

Characteristics of ecosystems

  • What are the attributes of ecosystems that are less vulnerable to invasion or the consequences of invasion? Are there general principles so that easily invadible communities are predictable a priori?

  • In diverse communities, can redundancy of functional types buffer process rates in response to species loss or gain?

  • In what conditions are invasive species able to out-compete natives?

  • What role does environmental stochasticity play in the establishment, naturalization and spread of invasives?

  • Are there links between native diversity, productivity and invasion?

  • What role do invasive mutualisms (bird-plant) have in invasion success (e.g. starlings and oriental bittersweet)?

Effects of disturbance

  • In diverse landscapes with multiple types of land use, do invasion and extinction processes accelerate?

  • Are there relationships among invasive species, habitat alteration, and the dynamics of disease vectors?

  • How may land-use history influence invasive species occurrences? Very little work has been done to understand the extent to which past land-use practices influence patterns of occurrence and abundance of invasive species vis-a-vis ecological or environmental variables. In the Northeast understanding the linkage between land-use and invasive species distribution patterns seems to be particularly important. For example large, old intact forest stands in the Northeast appear to resist the establishments of invasive species. This contrasts with agricultural lands that have reverted to forests, even decades ago, or smaller forest patches with many edges.

  • What ecosystems are most vulnerable, what is the role of disturbance and does this change with the species that is introduced?

  • What are the factors explaining the invasibility of ecosystems? This question has received substantial attention in the last decade, and reasonable and general explanations have been offered. (e.g., Davis et al. 2000; Davis 2003). However, within this framework, the relative significance of other components of global environmental change (e.g., climate, atmospheric chemistry, historical range of variability issues, fragmentation, etc) needs to be established.

III. Distribution

The current and future distribution of one or several invasive species

Current Distribution

  • How can we detect rare populations of invasives before they become explosive? We need to develop new and innovative methods for the early detection of invasive, or potentially invasive, species in the landscape. The most effective methods for the eradication of invasive species is to find the small populations of establishing invasives in the landscape, and then respond rapidly to eradicate them.

  • Document and map the historical and current spread of all invasive species in the U.S.. Each species should have an on-line map that traces its spread from introduction to current distribution. These maps should be linked to climatic/habitat data.

  • We should have on-line bibliographies for each invasive species.

  • During what period of time have invasive species spread most rapidly?

Future Distribution

  • We need more and better predictive modeling of invasive species spread. The objective of this research is to allow one to predict where and how fast invasive species will spread across the landscape, and which localities are most vulnerable. These models need to be calibrated and tested to evaluate their predictions. The joint modeling of suites of invasive species will allow the identification of invasive "hotspots" as well as the site attributes associated with such hotspots or vulnerable regions.

  • What are the variances associated with predicted invasive species occurrences and abundances-since modeling needs to include uncertainty?

  • Characterize the tails of species dispersal functions in order to predict future spread.

  • Do biomes vary in the type, spread, or consequences of invasive species?

  • How frequently do invasive species spread by wavefronts or by leap-frogging and back-fill, and are these predictable based upon taxonomy or functional groups?

  • What controls the rate of spread of invasions?

IV. Impacts of Invasion

The ecological and economic impacts of invasion

  • How may invasive species change ecosystem functions and services? How do invasive species alter ecosystems processes (e.g. soil nutrient status and dynamics, carbon storage, hydrology, etc.). Reversal of the drivers that facilitated invasion will not exclude the invasive species because the invader changes biogeochemical/structural of the system. More effort should be focused on soil-plant interactions as well as feedbacks on native and invasive plant species performance.

  • How does the abundance of invasive species alter the water cycle and the carbon cycle? Is evapotranspiration increased/decreased and does this feedback to the atmosphere increase/decrease precipitation?

  • What are the relationships among invasive species, changes in biodiversity, and changes in ecosystem function?

  • What the impacts of invasive species and how can these impacts be mitigated?

  • At present, invasive species appear to have idiosyncratic impacts on biodiversity and ecosystem services. A much more thorough analysis of impacts and analysis of the mitigation of impacts is warranted.

  • Do the invasives replace and provide suitable habitat for endangered species?

  • What are the consequences of invasion for community structure and ecosystem processes of the invaded community? Are there general principles so that consequences (e.g., for diversity or productivity) are predictable a priori?

  • What are the widespread impacts of invasion throughout the food chain. Comparing baseline data before an invasion with information on changes to ecosystems after an invasion will be valuable for making predictions that policy makers will take notice of.

  • In the figure below, the relationship between "invasion" and each of the other components, alone and in combination, forms a research, education, and management question.

    biodiversity, invasion, and ecosystem functioning
  • At what point is the damage caused by invasive species irreversible? Therefore, how much perturbation can a community withstand and recover from?

  • What are the consequences of invasion by the full range of exotic species - in terms that can be understood by policymakers (usually, that means money/costs/losses!)?

  • What is the economic impact of invasive species? There are a number of estimates on the economic impact invasive species, but very little of this is based on reliable data or economic models. One option is to develop standard economic models to compare with published economic costs to landowners, conservationists, and other stakeholders of invasive species in the US or regionally. An alternative approach using ecological economic models would provide costs in terms of ecosystems services valuation, system sustainability, etc. A third phase could focus on the impact on the Green Industry of state and federal regulations. It is this later unknown that has many in the Green Industry fighting regulation.

V. Responses to Invasion

  • Measures that can be taken to limit the effects of invasive species, and what are the consequences of those actions

  • How can we define success for projects: What are the consequences and efficacy of prevention programs?

  • Can current biotechnology be used to neutralize alien species? Non-reverting horticultural cultivars may be developed that lack pollen or seed production, even though fruits may formed.

  • What are the ecological responses to various mitigation activities, such as herbicide response, response to biological control agents, and controls. At present, no agency or group has the mandate to organize these activities at scales appropriate for analysis and management

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