Importance of Engaging Stakeholders in the Genetic Modification Process

by Morgan Beltz

Genetic biocontrol technology is one way of controlling invasive fish species. However, like genetically modified organisms, it is controversial in the eyes of the public. Sharpe (2013) studied the public perceptions of genetic biocontrol of invasive fish by conducting eight focus groups in the Great Lakes and Lake Champlain regions. The focus groups were asked the same set of questions and allowed to voice opinions to discuss as a whole group. The discussions of the focus groups were then analyzed in three phases; sorting individual transcripts into reaction categories, coding the text to see emerging themes, and coding the written responses. The author found three central themes in the focus group discussions: issues of uncertainty, acting cautiously, and the question of balance. Most participants thought research for biocontrol was good, but the actual implementation should be analyzed with very high standards. The participants came up with a wide scope of concerns which the author believes is important for developers and researchers to take into consideration.

Sharpe conducted the focus groups in the Great Lakes and Lake Champlain region because they are both facing invasive species problems. The focus groups ranged from 4 to 16 participants with a total of 61. The participants were all people that would potentially have a stake in genetic biocontrol, such as employees of management agencies, therefore not the general public. However, the author noted that not including the general public was of little concern because no participant had a position of authority, no one has vested interests in the approval or disapproval of technology, and all the discussions were confidential. To begin the discussion all participants were provided with the same background information packet that also included the discussion questions. The packet reviewed the genetic manipulation techniques that could be used and the purpose of each one. After the discussions each participant wrote down three benefits of, and concerns about, using biocontrol techniques. These responses were categorized and used as part of the results. The results were arrived at by transcribing the discussion of each focus group and sorting the reactions into categories, coding the categories to find overlapping themes, coding the participants’ written responses, and adding them to the different categories.

The author found that the participants generally had four major categories of initial reactions; science fiction, food and agriculture, concerns about the uncertainty and danger associated with the technology, and public perception of the technology. These categories addressed initial fears and controversies regarding genetic biocontrol, such as problems with consumption of GMOs, costs and consequences, and overcoming the negative public perceptions of GMOs. The participants next discussed potential benefits of genetic biocontrol and those responses landed in three broad categories; development of a potential control of invasive aquatic species, other benefits related to the technology, and concerns about benefits. Overall the participants were able to come up with 156 different benefits of genetic biocontrol. These benefits included being able to control species, having more tools to control species, increased knowledge of the technology that could lead to more innovations, and possible creation of an industry. Lastly the participants listed their concerns with this technology, coming up with 300 concerns that fit into five categories: ecological, related to uncertainty, financial, technological, and regulatory. These concerns covered all fears of transgenes being transferred to non-targeted organisms, negative outcomes and impacts, financial costs, success of the technology, and overlapping regulations.

The author concluded from the group discussions that participants feel that the concerns outweigh the benefits with genetic biocontrol. Concerns were much broader than benefits, falling into 11 categories and 22 subcategories, whereas benefits only had eight categories and three subcategories. Although several issues could be cross referenced as both benefits and concerns, there was too much uncertainty surrounding the issue for it to be seen as an overall benefit. In conclusion, the participants made recommendations for the producers of genetic biocontrol organisms. The recommendations included doing no harm, engaging many different viewpoints, requiring thorough unbiased testing, have a case-by-case approach, clear reasoning for stopping or going forward, an effective regulatory framework, and transparency at all steps.

From leading these focus groups the author found that stakeholders felt that developers do not necessarily consider the viewpoints of others and want to be included in the process. In general, stakeholders want a more determined path of action that includes knowledge of known benefits and harms. These stakeholders are affected directly by genetic biocontrol so they could potentially contribute valid information and knowledge of the implications of this technology to the scientists. Although this was a small sample, the focus groups came up with a wide variety of concerns that could be legitimate issues to solve in the production of aquatic species for genetic biocontrol.

Sharpe, L., 2013. Public perspectives on genetic biocontrol technologies for controlling invasive fish. Biological Invasions, doi: 10.1007/s10530-013-0545-5.

Invasive Forb Benefits From Water Savings by Native Plants and Carbon Fertilization Under Elevated CO2 and Warming

by Makari Krause

As global warming proceeds there will be numerous shifts in plant communities around the world. Blumenthal et al. (2013), realizing that the implications of these shifts are not well known, set about testing how reorganization of plant communities may affect invasive plants. They hypothesize that elevated CO2 levels and warming might strongly influence the success of invasive species in semi-arid grasslands. In order to test their hypothesis they placed Linaria dalmatica, an invasive forb, into grass prairie that was treated with free-air CO2 enrichment and infrared warming. They then measured survival, growth, and reproduction of the forb over a four-year period. The CO2 enrichment had huge effects on the growth and survival rates of L. dalmatica; biomass increased 13 fold, seed production increased 32 fold, and expansion increased seven fold. Warming had little effect. Blumenthal et al. then compared the leaf gas exchange and carbon isotopic composition between L. dalmatica and the native C3 grass, Pascopyrum smithii. The elevated CO2 decreased stomatal conductance in the grass but not in he forb and didn’t increase the photosynthesis rate in the grass nearly as much as it did in the forb. The invasive species benefited hugely from CO2 enrichment, which could have far reaching implications for future colonization. Continue reading

Asian Tiger Mosquitoes Expanding in Northeastern US

by Sarah King

Mosquitoes are known for dispersing many different kinds of diseases that affect human health. Asian tiger mosquitoes (Aedes albopictus), originating in Southeast Asia, are among the most invasive and widespread species of mosquitoes in the world. This species has been the cause of the reemergence of several mosquito-borne diseases such as chikungunya and dengue, and in the United States it is largely responsible for the reemergence of West Nile Virus. Using census information, temperature data, precipitation data, CO2 emissions forecasts, and generated maps of Ae. albopictus population distributions, Rochlin and his collgues (2013) statistically modeled projections of Ae. albopictus expansion through the next seventy years (2020s, 2050s, and 2080s). Their modeling shows that the range of Ae. albopictus will grow over the next seventy years to Continue reading

Potential Changes in Mammal Fauna in Denmark in the 21st Century

The initial rise in global temperatures has already caused the altitudinal range limit of many mammals to have shifted upwards. Given the expected temperature increase due to global warming we can expect further dramatic spatial changes in species composition (Flojgaard et al. 2009). Evidence from the Last Ice Age has shown that European mammals have the capacity to respond to climate change, however, when taking anthropogenic threats into account, such as habitat loss, disturbance, pollution, overexploitation, and invasive species, these mammals may not be able to adapt to shifting temperatures. This paper discusses possible consequences of climate change and the effects it might have on Danish mammal fauna. Climate models for Europe at the end of the 21st century generally show a climatic shift in a north-eastern direction, with Denmark displaying a relatively stable climate over the next 100 years. Denmark currently has a highly fragmented landscape of natural habitats and intensely managed agricultural land and urban areas. Over the last thousand years, this has led to the extinction of many mammals, most notably moose, aurochs, lynx, wildcat brown bear, wolf. More recently, in the last 100 years, species such as the bank vole, European polecat, pine marten, and badger have all experienced population declines due to habitat loss and fragmentation. Estimations based on models and literature reviews show that climate change will cause a general enrichment of mammal fauna in Denmark. Only one species was found to be highly threatened with extinction. — Patricio Ku
Flojgaard, C., Holme, N., Skov, F., Madsen, A., Svenning, J, 2009. Potential 21st century changes to the mammal fauna of Denmark —implications of climate change, land use, and invasive species. IOP Conf Series: Earth and Environmental Science 8, doi:10.1088/1755‑1315/8/1/012016

The scientists focused on terrestrial non-volant mammals in this paper, and got their distribution data from the Atlas of European Mammals and the Danish Mammal Atlas. Climate scenarios were drawn using the A2 future climate scenario as modeled in the TYN_SC 1.0 data set, which is commonly used in the prediction of species potential future distribution. The migration rate for mammals across modern European landscapes was modeled after two studies that observed the spread of introduced mammals in Europe. Finally, to select the most relevant species that were judged most at risk of extinction, scientists used species distribution modeling to quantify their potential distributions under present and future climatic conditions.
The results showed that many species are within migration distance of the Danish border and could potentially migrate to Denmark during the 21st century and change the species distribution. Only one mammal, the northern birch mouse, was found to be at serious risk of extinction. Predictions of the species’ future distribution indicate that climate change might be one of the biggest threats to this species’ survival in Denmark. A few other species were considered to be at risk due to competition with introduced species. Recently there has been competition between the introduced American mink and native European polecat, but this has not been considered a serious threat to the polecat. However, the American mink has caused a decline in the water vole population in the British Isles due to predation. Since there are so many species within migration distance it is very likely that they will immigrate over the Danish border. These species include: Millet’s shrew, Miller’s water shrew, bi-colored shrew, lesser shrew, common hamster, common pine vole, southern water vole, fat dormouse, and garden dormouse. The species just mentioned are all native to Europe and it is considered unlikely that they will cause problems to competing native Danish species. Most of the changes in species distribution will occur because of climate change and other anthropogenic factors. As a result, the future abundance of the species discussed will depend on factors like habitat restoration. Introduced species in Denmark will become an increasing problem, but will not have an extremely large impact on native species since many of them already coexist in other areas of Europe. In conclusion, habitats throughout Denmark are not in critical danger, but should be monitored closely in order to ensure that any negative impacts are met with management and conservation plans. 

Can Native Plant Diversity Limit the Survival of Invasive Species?

Phragmites australis, the common reed, is a perennial grass that can be found on most continents except Antarctica. During the last century Phragmites has rapidly expanded its habitat, invading many salt marsh communities along the Atlantic coast in North America. This degrades healthy ecosystems by replacing short stalk native grasses with long stands of reed. Peter and Burdick (2010) postulated that native plant competition would reduce the success of Phragmites to invade a tidal salt marsh. They tested whether native plant diversity and composition changed the invasive plant’s ability to survive, and analyzed the growth of Phragmites for a single growing season when planted among different native plant communities. In general, they found that in the presence of any native grass, Phragmites’ ability to thrive was reduced as a result of resource competition. Acadia Tucker
Peter, C., Burdick D., 2010. Can plant competition and diversity reduce the growth and survival of exotic Phragmites australis invading a tidal marsh? Estuaries and Coasts 33, 1225–1236

Species in diverse and productive salt marshes are highly competitive in regards to resource partitioning. Different native plants inhabit different spatial niches and capture all the available nutrients, space, and light for each area within an ecosystem. However once an ecosystem is disrupted the balance of resources can shift to allow new species to colonize. Phragmites easily conquers a disturbed landscape, creating a homogenous distribution of plants that offers fewer ecosystem services than a landscape scattered with a multitude of native grasses. Restricted tides blocked by jetties, increased runoff, and eutrophication all reduce the health of a salt marsh but promote the invasion of Phragmites. This reed has a strong competitive ability, with shoots up to 3 meters tall, that block the sun from smaller native plants once it has taken root. It can also survive in hyper-saline and waterlogged soils more competitively than native grasses. The invasion of Phragmites has decreased the numbers of birds, reduced nekton diversity, and diminished benthic invertebrate colonization for many salt marsh communities.

 Peter and Burdick tested the effect of native grass competition on the growth of Phragmites in Meadow Marsh Pond in Hampton, New Hampshire, because it has a history of human obstruction. The irregular flooding in the north section caused by restricted tides has led to the invasion of Phragmites. Peter and Burdick planted 30 cm x 30 cm plots of densely vegetated Phragmites among two distinct communities of native plants. Phragmites was planted with one native competitor (S. patens in the high marsh or S. alterniflora in the low marsh) or a mixture of several native competitors. The plots with multiple competitors represented the effects of species richness (the number of different species in a given area), species evenness (a measure of biodiversity) and species composition on the success of Phragmites. Results were quantified by the amount of dried aboveground biomass, shoot length and density, shoot survival, and aphid damage (aphids only feed on healthy plants).
Phragmites planted alone always outgrew Phragmites planted with native competitors. Shoot length, density, and survival as well as the presence of aphids were all significantly diminished when Phragmites was planted with native plants, with the most dramatic decline occurring among multiple competitors. Above ground biomass decreased 83.7%, shoot length decreased 60.0%, shoot density decreased 48.3%, shoot survival decreased 58.8% and the amount of aphid damage decreased 74.2% in the presence of one native competitor. The greater the species richness and evenness, the less Phragmite’s ability to thrive. For example, shoot density decreased an additional 31.5% in the presence of multiple competitors compared to a single competitor.
Native plants inhibit the expansion of Phragmites by competing for space, nutrients, and light. In a well-established salt mash ecosystem, native plants have a monopoly on all of the resources within a particular niche. For example, native grasses prevent the proliferation of Phragmites roots limiting the amount of nutrients a given plant can absorb. Native canopies also severely reduce the amount of light germinating shoots receive. Native grasses have the capacity to inhibit invasion as long as the ecosystem remains healthy. Therefore if the impacts of climate change or human disturbances remove native plants, it is far easier for invasive species to colonize an area
In this study, it was inconclusive if species composition had an overall effect on the growth of Phragmites. Competitive relationships can reverse with excessive nutrient loading or along resource gradients by changing the interspecific competitive relationships within a salt marsh. S. alterniflora had a greater capability of reducing the growth of Phragmites than S. patens. Peter and Burdick predicted that species with taller canopies and that are normally weaker competitors for nutrients may be the best opponent against invasive species in disturbed salt marshes.
Past restoration techniques have focused on the removal of specific species by controlled burning or mowing but physical plant damage is only temporary when environmental conditions are ripe for invasive species. Restoration should focus on and mitigate the human disturbances and impacts of climate change that create the favorable conditions for invasive species to thrive. It is more effective to reestablish routine flooding and maintain dense populations of native plants after the removal of Phragmites to help prevent reinvasion by increasing native plant competition for available nutrients. 

Invasive Cuban Treefrog and its Potential Dis-tribution with Climate Change

The Cuban treefrog (Osteopilus septentrionalis) is an invasive species which, in the last couple of decades, has begun to spread to many different areas of the Americas. The natural distribution of the frog includes Cuba and the Bahamas, Isla de la Juventud, San Salvador, the Acklins Islands, and the Cayman Islands. Recently, the Cuban treefrog’s habitat has expanded to include Anguilla, the British Virgin Islands, Florida, the French Antilleans, Puerto Rico, and the Virgin Islands. The frog was probably introduced in the 1930s, by accident, as an undetected stowaway in imported vegetables from Cuba. Right now breeding populations can be found as far north as Jacksonville and individuals have been reported in places as far as coastal Georgia and South Carolina. The high invasiveness of the Cuban treefrog can be attributed to its high fecundity, short larval period, broad diet, and broad habitat and dietary niches. The frog may have major impacts on native species because it is the biggest hylid in the US and could easily outcompete other species. Also, the tadpoles are omnivorous, cannibalistic, and could potentially eat the eggs of indigenous frogs. One feature limiting the distribution of the Cuban treefrog is climatic suitability, however, with the onset of anthropogenic climate change, range-size patterns for the treefrog are expected to increase even further. Geographic information systems-based climate envelope models (CEMs) are used to assess the potential distribution of species derived from their climate niches. The models were used to predict potential distribution of the frog under current climate conditions and as well as potential distribution due to anthropogenic global warming. Models suggest that global warming is very likely to increase the range of the Cuban treefrog. — Patricio Ku
Rodder, D., Weinsheimer, F., 2009. Will future anthropogenic climate change increase the potential distribution of the alien invasive Cuban treefrog (Anura: Hylidae). Journal of Natural History 43, 1207–1217

Rődder and Weinsheimer used 6665 records of the Cuban treefrog that were available thought the Global Biodiversity Information Facility (GBIF) for their model. The climate information was taken from the WorldClim database where the cumulative frequency of biolimatic parameters was plotted with DIVA-GIS. The CEM used was Maxent 3.2.1 where the model assessed the potential distribution of the Cuban treefrog. The Maxent model allows for model testing by calculation of the Area Under the Curve (AUC) which uses either the invasive records as test points and the native records for training, or all native records for training and background points for testing.
The CEM suggests that the Cuban treefrog can find suitable regions all over the Caribbean and the countries adjacent to the Gulf of Mexico. Projections onto anthropogenic climate-change scenarios indicate an extension of the current distribution of the Cuban treefrog in Northern America. In addition to natural propagation, human-facilitated propagation is an important factor to consider when mapping the distribution of the frog. The national and international plant trade can displace species in remote places and encourage their spread. Means of control must focus on prevention rather than trying to avoid further spreading through human activities. Regional differences in population structure and fitness may also require different regulation or eradication approaches. As a result of increased climatic suitability, a more aggressive control strategy must be put in to place in order to help control the population of the Cuban treefrog.

Invasive Species in the Mongla Port of Bangladesh

Invasive species are life forms that have evolved elsewhere and were then intentionally or unintentionally introduced into a new ecosystem (Amin et al. 2009). Although many of the species have invaded environments on their own, an increasing number are introduced into new areas because of anthropogenic forces—human exploration, colonization, and commercial trade. Specifically, coastal aquatic ecosystems have had a large increase in introduced species through industries such as the aquarium trade and aquaculture, and thousands of species are carried all across the world unknowingly in and on ships. The invasive species, with a lack of natural predators in their new environment, thrive and many times outcompete the native species. The invaded habitats can be degraded and food supplies depleted, which poses problems environmentally, economically, and for human health. In the Mongla port of Bangladesh, instances such as the one described have caused 54 indigenous fishes to become threatened. For this reason an impact analysis on invasive species in the Mongla sea port was carried out and proved to be valuable. The Mongla seaport habitat was found to be under threat due to invasive species such as catfish, which according to a survey, were found by almost all fisherman. Native fish were found to be rare in the area and to have little chance to reintegrate into the aquatic ecosystem. The organisms that live in brackish water ecosystems were found to be outcompeted and have no place to spawn. — Patricio Ku
Amin, Md., Ali, Mohd., Salequzzaman, Md, 2009. Identification and impact analysis of invasive species: A case study in the Mongla sea port area of Bagerhat district of Bangladesh. Daffodil International University Journal of Science and Technology 4, 35–41
Amin and colleagues from Khulna University did an exploratory study in the Mongla seaport where three major rivers meet (the Ganges, the Padma and the Lower Meghna). The purpose of the study was to discover problems occurring in the seaport in order to develop more precise investigations. Biological samples studied ranged from plankton to higher vertebrates, which were collected through the fisherman working around the area. The occurrence of ship movement in the area was also analyzed and compared to the frequency and distribution of invasive species.
Some fish and other aquatic faunal samples collected are of deformed maybe because of the changed environment in the seaport. The factors found to be potentially responsible for causes of invasion were also studied. The research found that vessels were the primary vector for introducing aquatic life at such an unprecedented rate. Arriving vessels can contain hundreds of species living on and within the ship. There is no regulation to prevent the thousands of ships that pass through the port from discharging their ballast water along with whatever exotic species it contains. Water diversion for shrimp practices was also deemed a significant cause to the spread of invasive species. This practice occurs predominantly during the time of the first monsoon when water levels in the Pussur River rise near the Mongla port opening up a pathway to the port. These exotic-introducing-practices cause many changes in coastal biodiversity, such as, habitat alteration, chemical pollution, over-enrichment, fisheries impacts, and the introductions themselves. Finally, it was found that the invasion of species taking place in the Mongla region will have long lasting effects. As a result, preventative measures are essential and must be undertaken for the sustainable good of the Mongla port area of Bangladesh.

Invasive Pests, Pathogens, and Plants in the forests of northeastern North America

Native and nonnative pest, pathogen, and plant species in the northeastern forests of North America all contain the capacity to alter and damage the ecological processes of the forest. This damage can lead to ecological and economic damage such as, among other things, causing tree mortality (Dukes et al. 2009).  The northeastern forests of North America are being increasingly affected by invasive species in the form of fruit-bearing shrubs and vines that are altering young or physically disturbed forests. Essentially, the alien species create dense thickets that eliminate tree regeneration and reduce native understory shrub and herb diversity. These alien species are highly responsive to changes in the climate through changes in host distribution, population dynamics, nutrition, defense compounds, and evolving land use. Temperature increases in the northeastern US of 0.25 °C will increase the metabolism, reproductive rates, and survival of invasive species. In the case study, the possible responses of six key species were analyzed according to the effects of projected future climate change on the forests. For insect pests, climatic warming was found to accelerate insect consumption, development, and movement, which in turn can also influence fecundity, survival, generation time, and dispersal. The spread of pathogens in response to climate change is more difficult to predict because less is known about viral or bacterial sensitivity to climate in forest systems. However, likely affects of climate change on forest pathogens include increased growth and reproduction, altered dispersal, transmission rates, infection phenology, and changes in overwinter survival. And it is not just the temperature that affects the pathogens, precipitation, storm severity, nitrogen deposition, atmospheric ozone and CO2 concentration, and UV-B radiation all can affect forest pathogens. Plants also respond directly to changes in the climate. Direct effects to plants in the northeastern US forests as a result of climate change include: temperature, frost-free period length, and magnitude and duration of climate extremes. Indirect affects could also occur by altering ecosystem processes which could affect soil nutrients and moisture.—Patricio Ku
Dukes, J., Pontius, J., Orwig, D., Garnas, J., Rodger, V., Brazee, N., Cooke, B., Theoharides, K., Stange, E., Harrington, R., Ehrenfeld, J., Gurevitch, J., Leradu, M., Stinson, K., Wick, R., Ayres, M. 2009. Responses of insect pests, pathogens, and invasive plant species to climate change in the forests of northeastern North America: What can we predict?. Canadian Journal of Forest Research 39, 231–248

            The species chosen to represent a sample of invasive aliens in northeastern US forests were selected because they represent a good sample of invasives and are not necessarily the most damaging species. The six case studies include two pests: Adelges tsuga (hemlock woolly adelgid) and the Malacosoma disstria (forest tent caterpillar); two common diseases: Armillaria (Armillaria root rot) and Cryptococcus fagisuga + Neonectria spp. (beech bark disease); and two invasive plant species: Frangula alnus Mill. (glossy buckthorn) and Celastrus orbiculatus (oriental bittersweet).
            The result of almost all the case studies showed that climate change in almost certain to be a strong driver of evolutionary change in plant and pathogen populations. Although it is clear that invasive species are among the primary agents of biotic disturbance in northeastern US forests, it is unclear how exactly these forest dynamics will be played out. Uncertainties associated with internal ecosystem processes, climate projections, future human actions, and those arising from a lack of data on the invasive species themselves all make predicting the manifestations of these species more difficult. Nonetheless, the case studies did show that three of the six studied species (hemlock woolly adelgid, beech bark disease, and oriental bittersweet) are likely to become more widespread or abundant in northeastern US forests under projected climate change. None of the species that were studied were found to become less problematic as a result of climate change, but this does not mean that such species do not exist. The results were also difficult to interpret because of the relatively low statistical confidence level of the information on five of the six species studied. In the future it will be more useful and accurate to use whole-systems modeling of invasives to anticipate the range of possible responses of these complex systems as opposed to each individual species.

Elevated CO2 Levels and Competitive Interactions Between Native and Invasive Exotic Plant Species

Exotic plants have been identified as a major threat to biodiversity as well as a significant management and economic concern. One factor that becomes increasingly relevant when studying interactions between exotic and native species is the increasing amount of atmospheric CO2 available to plants (Manea and Leishman 2010). The reason exotic plants take over and become dominant in the ecosystems they invade is largely because of their superior competitive ability.  Carbon capture strategies in invasive species attributed to certain leaf traits make for fast plant growth.  Thus, it was hypothesized that elevated CO2 levels will affect invasive exotic plants more than native ones. Competitive outcomes were tested for 14 different species, which measured relative competitive ability, rather than inferring competitive ability based on a plant’s abundance and growth. Results indicated that the competitive rankings within each species pair were not altered by differing CO2 treatments. However, results did show that the competitive response of the native species decreased under elevated CO2 compared to ambient CO2.—Patricio Ku
Manea, A., Leishman, M., 2010. Competitive interactions between native and invasive exotic plant species are altered under elevated carbon dioxide. Community Ecology 10.1007/s00442-010-1765-3

            Manea and Leishman, from the Department of Biological Sciences, Macquarie University, grew fourteen different species of native and invasive exotic plants in a series of competition experiments under ambient (380–420ppm) and elevated (675–715) CO2 concentrations. The ambient CO2 concentration represents that of the beginning of the twenty-first century and the elevated one represents the predicted atmospheric CO2 concentrations by 2100. The method used to determine competitive ability was the corrected index of relative competition intensity (CRCI). Plant species used in the study are common species of the Cumberland Plain Woodland in western Sydney, Australia. Species pairs were selected based on: being from the same functional group (grass, vine, herb or shrub/tree), utilizing the same photosynthetic pathway (C3 or C4), and having the same life history (annual or perennial).
            Competitive rankings within species-pairs were not affected by CO2, but the strength of the competitive interactions was affected. Native species had, on average, a reduced competitive response under elevated compared with ambient CO2. This could also be interpreted as an increased competitive effect of invasive exotic species under elevated CO2. These results could suggest that under future CO2 levels, competitive rankings among species may not change substantially, but the relative success of invasive exotic species may be increased. Results also showed that, in general, traits associated with growth and allocation can enable predictions of outcomes of competition under particular environmental conditions.