David A. Andow

Biological invasions: recommendations for U.S. policy and management.

The Ecological Society of America has evaluated current U.S. national policies and practices on biological invasions in light of current scientific knowledge. Invasions by harmful nonnative species are increasing in number and area affected; the damages to ecosystems, economic activity, and human welfare are accumulating. Without improved strategies based on recent scientific advances and increased investments to counter invasions, harm from invasive species is likely to accelerate. Federal leadership, with the cooperation of state and local governments, is required to increase the effectiveness of prevention of invasions, detect and respond quickly to new potentially harmful invasions, control and slow the spread of existing invasions, and provide a national center to ensure that these efforts are coordinated and cost effective. Specifically, the Ecological Society of America recommends that the federal government take the following six actions: (1) Use new information and practices to better manage commercial and other pathways to reduce the transport and release of potentially harmful species; (2) Adopt more quantitative procedures for risk analysis and apply them to every species proposed for importation into the country; (3) Use new cost-effective diagnostic technologies to increase active surveillance and sharing of information about invasive species so that responses to new invasions can be more rapid and effective; (4) Create new legal authority and provide emergency funding to support rapid responses to emerging invasions; (5) Provide funding and incentives for cost-effective programs to slow the spread of existing invasive species in order to protect still uninvaded ecosystems, social and industrial infrastructure, and human welfare; and (6) Establish a National Center for Invasive Species Management (under the existing National Invasive Species Council) to coordinate and lead improvements in federal, state, and international policies on invasive species. Recent scientific and technical advances provide a sound basis for more cost-effective national responses to invasive species. Greater investments in improved technology and management practices would be more than repaid by reduced damages from current and future invasive species. The Ecological Society of America is committed to assist all levels of government and provide scientific advice to improve all aspects of invasive-species management.

Managing the Evolution of Insect Resistance to Transgenic Plants

The evolution of resistance in pests such as the European corn borer will imperil transgenic maize varieties that express insecticidal crystal proteins of Bacillus thuringiensis. Patchworks of treated and untreated fields can delay the evolution of pesticide resistance, but the untreated refuge fields are likely to sustain heavy damage. A strategy that exploits corn borer preferences and movements can eliminate this problem. Computer simulation indicates that this approach can delay the evolution of resistance and reduce insect damage in the untreated fields of a patchwork planting regime.

GENETICALLY ENGINEERED ORGANISMS AND THE ENVIRONMENT: CURRENT STATUS AND RECOMMENDATIONS1

The Ecological Society of America has evaluated the ecological effects of current and potential uses of field-released genetically engineered organisms (GEOs), as described in this Position Paper. Some GEOs could play a positive role in sustainable agriculture, forestry, aquaculture, bioremediation, and environmental management, both in developed and developing countries. However, deliberate or inadvertent releases of GEOs into the environment could have negative ecological effects under certain circumstances. Possible risks of GEOs could include: (1) creating new or more vigorous pests and pathogens; (2) exacerbating the effects of existing pests through hybridization with related transgenic organisms; (3) harm to nontarget species, such as soil organisms, non-pest insects, birds, and other animals; (4) disruption of biotic communities, including agroecosystems; and (5) irreparable loss or changes in species diversity or genetic diversity within species. Many potential applications of genetic engineering extend beyond traditional breeding, encompassing viruses, bacteria, algae, fungi, grasses, trees, insects, fish, and shellfish. GEOs that present novel traits will need special scrutiny with regard to their environmental effects. The Ecological Society of America supports the following recommendations. (1) GEOs should be designed to reduce environmental risks. (2) More extensive studies of the environmental benefits and risks associated with GEOs are needed. (3) These effects should be evaluated relative to appropriate baseline scenarios. (4) Environmental release of GEOs should be prevented if scientific knowledge about possible risks is clearly inadequate. (5) In some cases, post-release monitoring will be needed to identify, manage, and mitigate environmental risks. (6) Science-based regulation should subject all transgenic organisms to a similar risk assessment framework and should incorporate a cautious approach, recognizing that many environmental effects are GEO- and site-specific. (7) Ecologists, agricultural scientists, molecular biologists, and others need broader training and wider collaboration to address these recommendations. In summary, GEOs should be evaluated and used within the context of a scientifically based regulatory policy that encourages innovation without compromising sound environmental management. The Ecological Society of America is committed to providing scientific expertise for evaluating and predicting the ecological effects of field-released transgenic organisms.

Multifunctional Agriculture in the United States

Abstract We evaluated possible changes to current farming practices in two Minnesota watersheds to provide insight into how farm policy might affect environmental, social, and economic outcomes. Watershed residents helped develop four scenarios to evaluate alternative future trends in agricultural management and to project potential economic and environmental outcomes. We found that environmental and economic benefits can be attained through changes in agricultural land management without increasing public costs. The magnitude of these benefits depends on the magnitude of changes to agricultural practices. Environmental benefits include improved water quality, healthier fish, increased carbon sequestration, and decreased greenhouse gas emissions, while economic benefits include social capital formation, greater farm profitability, and avoided costs. Policy transitions that emphasize functions of agriculture in addition to food production are crucial for creating change. We suggest that redirecting farm payments by using alternative incentives could lead to substantial environmental changes at little or no extra cost to the taxpayer.

Plant structural complexity and host-finding by a parasitoid

SummaryThere are three major components to plant structure relevant to searching parasitoids: 1) plant size or surface area, 2) the variation among plant parts (structural heterogeneity), such as seed heads, flowers and nectaries, and heterogeneous surfaces (e.g. glabrous, hirsute), and 3) the connectivity of parts or plant form (structural complexity). We examined the effect of structural complexity, while controlling for size and structural heterogeneity, on searching behaviors of Trichogramma nubilale in controlled environments. Females were presented with a structurally simple surface and a structurally complex one. Parasitism rates were 2.9 times higher on simple surfaces than on complex ones. Unexpectedly, when no hosts were present, searching time on simple surfaces was 1.2 times higher than on complex surfaces. This implies that structural complexity per se can affect the giving-up-time of a searching parasitoid. Searching efficiency, however, was the dominant process, and females found hosts on simple surfaces 2.4 times faster than on complex surfaces. Structural complexity can have a dramatic effect on the success of parasitoid search.

Success of the high-dose/refuge resistance management strategy after 15 years of Bt crop use in North America

Transgenic maize and cotton expressing Bacillus thuringiensis (Bt) toxins were first commercialized in 1996. By 2009, Bt crops were planted on ca. 47.6 Mha in 22 countries worldwide, with the USA and Canada accounting for 54% of this area. Resistance (virulence) development in target insect pests is a major threat to the sustainable use of Bt crops. Four major target pests of Bt crops in the USA and Canada – European corn borer, Ostrinia nubilalis (Hübner), southwestern corn borer, Diatraea grandiosella Dyar (both Lepidoptera: Crambidae), tobacco budworm, Heliothis virescens Fabricius (Lepidoptera: Noctuidae), and pink bollworm, Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae) – remain susceptible to Bt toxins after 15 years of intensive use of Bt maize and Bt cotton. The success in sustaining susceptibility in these major pests is associated with successful implementation of the ‘high‐dose/refuge’ insecticide resistance management (IRM) strategy: (i) Bt crop cultivars express a ‘high dose’, (ii) initial frequency of resistance alleles is very low, and (iii) a refuge is maintained nearby in the environment. Field resistance (including control failure) to a Bt crop has been clearly documented in three situations: fall armyworm [Spodoptera frugiperda JE Smith] in Puerto Rico, African stem borer [Busseola fusca Fuller (Lepidoptera: Noctuidae)] in South Africa, and P. gossypiella in India. Factors associated with these cases of field resistance include: failure to use high‐dose Bt cultivars and lack of sufficient refuge. These observations support the claim that implementation of the ‘high‐dose/refuge’ IRM strategy has been successful in substantially delaying field resistance to Bt crops.

Science-Based Risk Assessment for Nontarget Effects of Transgenic Crops

Abstract Nontarget risk assessment for transgenic crops should be case specific, depending on the plant, the transgene, and the intended release environment. We propose an ecological risk-assessment model that preserves the strengths and avoids the deficiencies of two other commonly used models, the ecotoxicology and nonindigenous-species models. In this model, locally occurring nontarget species are classified into groups according to their ecological function. Within each group, ecological criteria are used to select the species that are most likely to be affected by the transgenic crop. Initial experimental assessments are conducted in the laboratory and consist of two kinds of test: toxicity tests using purified transgene product, and whole-plant tests using intact transgenic plants. For nontarget natural enemy species, it will also be important to evaluate both direct bitrophic impacts and indirect tritrophic impacts.

Consequences of recurrent gene flow from crops to wild relatives

Concern about gene flow from crops to wild relatives has become widespread with the increasing cultivation of transgenic crops. Possible consequences of such gene flow include genetic assimilation, wherein crop genes replace wild ones, and demographic swamping, wherein hybrids are less fertile than their wild parents, and wild populations shrink. Using mathematical models of a wild population recurrently receiving pollen from a genetically fixed crop, we find that the conditions for genetic assimilation are not stringent, and progress towards replacement can be fast, even for disfavoured crop genes. Demographic swamping and genetic drift relax the conditions for genetic assimilation and speed progress towards replacement. Genetic assimilation can involve thresholds and hysteresis, such that a small increase in immigration can lead to fixation of a disfavoured crop gene that had been maintained at a moderate frequency, even if the increase in immigration is cancelled before the gene fixes. Demographic swamping can give rise to ‘migrational meltdown’, such that a small increase in immigration can lead to not only fixation of a disfavoured crop gene but also drastic shrinkage of the wild population. These findings suggest that the spread of crop genes in wild populations should be monitored more closely.

Transgenic Insecticidal Crops and Natural Enemies: A Detailed Review of Laboratory Studies

ABSTRACT This review uses a data-driven, quantitative method to summarize the published, peer-reviewed literature about the impact of genetically modified (GM) plants on arthropod natural enemies in laboratory experiments. The method is similar to meta-analysis, and, in contrast to a simple author-vote counting method used by several earlier reviews, gives an objective, data-driven summary of existing knowledge about these effects. Significantly more non-neutral responses were observed than expected at random in 75% of the comparisons of natural enemy groups and response classes. These observations indicate that Cry toxins and proteinase inhibitors often have non-neutral effects on natural enemies. This synthesis identifies a continued bias toward studies on a few predator species, especially the green lacewing, Chrysoperla cornea Stephens, which may be more sensitive to GM insecticidal plants (16.8% of the quantified parameter responses were significantly negative) than predators in general (10.9% significantly negative effects without C. cornea). Parasitoids were more susceptible than predators to the effects of both Cry toxins and proteinase inhibitors, with fewer positive effects (18.0%, significant and nonsignificant positive effects combined) than negative ones (66.1%, significant and nonsignificant negative effects combined). GM plants can have a positive effect on natural enemies (4.8% of responses were significantly positive), although significant negative (21.2%) effects were more common. Although there are data on 48 natural enemy species, the database is still far from adequate to predict the effect of a Bt toxin or proteinase inhibitor on natural enemies.

COMMUNITY GENETICS: EXPANDING THE SYNTHESIS OF ECOLOGY AND GENETICS

Community genetics synthesizes community ecology and population genetics and yields fresh insights into the interplay between evolutionary and ecological processes. A community genetics framework proves especially valuable when strong selection on traits results from or impinges on interspecific interactions, an increasingly common phenomenon as more communities are subject to direct management or anthropogenic disturbances. We draw illustrations of this perspective from our ongoing studies of three representative communities, two managed and one natural, that have recently undergone large perturba- tions. The studied communities are: (1) insect pests of crop plants genetically engineered to produce insecticidal toxins; (2) insect-pollinated plants in habitats severely fragmented by agriculture and urbanization; and (3) a pathogen and its crop host now grown extensively outside their native ranges. We demonstrate the value of integrating genetic and ecological processes to gain a full understanding of community dynamics, particularly in nonequilib- rium systems that are subject to strong selection.