Gary P. Fitt

Evolutionary principles and their practical application

Evolutionary principles are now routinely incorporated into medicine and agriculture. Examples include the design of treatments that slow the evolution of resistance by weeds, pests, and pathogens, and the design of breeding programs that maximize crop yield or quality. Evolutionary principles are also increasingly incorporated into conservation biology, natural resource management, and environmental science. Examples include the protection of small and isolated populations from inbreeding depression, the identification of key traits involved in adaptation to climate change, the design of harvesting regimes that minimize unwanted life‐history evolution, and the setting of conservation priorities based on populations, species, or communities that harbor the greatest evolutionary diversity and potential. The adoption of evolutionary principles has proceeded somewhat independently in these different fields, even though the underlying fundamental concepts are the same. We explore these fundamental concepts under four main themes: variation, selection, connectivity, and eco‐evolutionary dynamics. Within each theme, we present several key evolutionary principles and illustrate their use in addressing applied problems. We hope that the resulting primer of evolutionary concepts and their practical utility helps to advance a unified multidisciplinary field of applied evolutionary biology.

Field evaluation and potential ecological impact of transgenic cottons (Gossypium hirsutum) in Australia.

The first field trials in Australia of transformed cottons expressing the CryIA(b) insecticidal protein from Bacillus thuringiensis subsp. kurstaki (Bt) were completed during the 1992–93 season. The trials showed good efficacy of the plants against field populations of Helicoverpa, but there were indications of a declining level of Bt expression once plants began to senesce. Laboratory assays showed that larger instars could survive on the transgenic tissues although their growth was severely retarded. The introduction of Bt transgenic cottons may have several ecological impacts, apart from their direct impact on target pests. These include the risk of resistance development, effects on beneficial and non‐target arthropod species and changes in pest status associated with altered patterns of pesticide usage. Chief among the potential pests are sucking insects (e.g. Miridae) which appear not to be regulated by beneficial agents and are currently suppressed by sprays applied for Helicoverpa Transgenic Bt pl...

A Comparison of Arthropod Communities in Transgenic Bt and Conventional Cotton in Australia

Abstract Transgenic Bacillus thuringiensis (Bt) cotton has had a major impact on the Australian cotton industry by largely controlling lepidopteran pests. However, it also may have other impacts on the invertebrate community that need to be identified. We compared the canopy invertebrate community in sprayed conventional, unsprayed conventional, and unsprayed Bt cotton over three seasons using suction sampling methods. We found that the diversity or species richness of the beneficial communities was reduced in the sprayed crops at two sites. Although spraying had the strongest effect on the community, there was a slight difference between the total community in unsprayed conventional and Bt crops, with crop type accounting for 4.5% of the variance between these communities. Out of over 100 species groups examined, the most consistent differences between unsprayed Bt and conventional communities were higher numbers of Helicoverpa in conventional crops (as would be expected) and slightly higher numbers of Chloropidae and Drosopillidae (Diptera), damsel bugs (Hemiptera, Nabidae), and jassids (Hemiptera, Cicadellidae) in conventional crops. With the advent of Bollgard II and the possibility that 80% of the cotton crop in Australia could be transgenic, the effects of these small differences in the transgenic and conventional communities should be monitored over the long-term to assess if any modifications to cotton management practices need to be made.

Ecology of Helicoverpa armigera (Hübner) and H. punctigera (Wallengren) in the Inland of Australia: larval sampling and host plant relationships during winter and spring

Extensive surveys during the winter months in inland areas of Australia have greatly extended both the range and known hosts of Australias two pest Helicoverpa species. H. punctigera was the more common species, being collected from c. half of the sites sampled. Here a further 47 plant species in 8 families are recorded as possible host plants; the majority (all except two) are new records of native hosts, and greatly extend the existing lists. H. armigera was less common, being recorded from c. 10% of the 554 sites sampled. This species was reared from 28 species in 10 plant families. Both moth species are recorded for the first time from various native plant species, predominantly in the Asteraceae and Fabaceae. The Goodeniaceae is also added to the host list of both species. Determination of the status of host plants is discussed.

An Australian approach to IPM in cotton: integrating new technologies to minimise insecticide dependence

Abstract Insect pests represent a severe limitation for cotton production in many regions of the world. Key pests include several Heliothine moths, which are well adapted to exploit cropping systems associated with cotton and often evolve resistance to pesticides. While many components of IPM have been implemented, the main intervention for the management of key pests continues to be insecticides. This reliance on pesticides brings significant environmental liabilities of off-target drift, chemical residues and resistance. IPM must be founded on a thorough understanding of the ecology of pest and beneficial species and their interaction with the crop. The emerging era of insect resistant transgenic cottons offers real prospects to provide a foundation for more sustainable, economically acceptable IPM with the integration of a range of non-chemical tactics and much less reliance on pesticides.

Evolution in agriculture: the application of evolutionary approaches to the management of biotic interactions in agro-ecosystems

Anthropogenic impacts increasingly drive ecological and evolutionary processes at many spatio‐temporal scales, demanding greater capacity to predict and manage their consequences. This is particularly true for agro‐ecosystems, which not only comprise a significant proportion of land use, but which also involve conflicting imperatives to expand or intensify production while simultaneously reducing environmental impacts. These imperatives reinforce the likelihood of further major changes in agriculture over the next 30–40 years. Key transformations include genetic technologies as well as changes in land use. The use of evolutionary principles is not new in agriculture (e.g. crop breeding, domestication of animals, management of selection for pest resistance), but given land‐use trends and other transformative processes in production landscapes, ecological and evolutionary research in agro‐ecosystems must consider such issues in a broader systems context. Here, we focus on biotic interactions involving pests and pathogens as exemplars of situations where integration of agronomic, ecological and evolutionary perspectives has practical value. Although their presence in agro‐ecosystems may be new, many traits involved in these associations evolved in natural settings. We advocate the use of predictive frameworks based on evolutionary models as pre‐emptive management tools and identify some specific research opportunities to facilitate this. We conclude with a brief discussion of multidisciplinary approaches in applied evolutionary problems.

Pollen dispersal from two field trials of transgenic cotton in the Namoi Valley, Australia

The testing of transgenic crops in the field is a necessary part of the validation of genetically engineered cultivars, but in the early stages of testing, biosafety procedures must be carefully monitored to ensure that the modified plants do not have deleterious effects on the environment. This study was carried out over two seasons to determine the effectiveness of containment procedures under australian environmental conditions by measuring the dispersal of pollen amay from a test plot of transgenic cotton into a surrounding buffer field of non-transgenic cotton plants whose function was to act as a sink for pollen carried by nectar feeding and pollen-gathering insects. Dispersal was estimated by measuring the frequency of the dominant selectable marker transgene, neomycin phosphotransferase (NptII) in the progeny of the buffer plants. The presence of nptii was determined by a sensitive radioactive enzyme assay. Pollen dispersal was low in both years, but increased with an increase in the size of the source plot in the second year. In the first year outcrossing averaged from 0.15% of progeny at 1 m to below 0.08% at 4 m from the test plot. Outcrossing was highest within the central test plot where progeny from non-transgenic control plants, immediately adjacent to transgenic plants, had transgenic progeny at frequencies of up to 1.7%. In the second year, with a bigger source of transgenic plants, outcrossing declined on average from 0.4% at 1 m to below 0.03% at 16 m into the buffer zone. These results indicate that 20 m buffer zones would serve to limit dispersal of transgenic pollen from small-scale field tests.

Adaptive management of pest resistance by Helicoverpa species (Noctuidae) in Australia to the Cry2Ab Bt toxin in Bollgard II® cotton

In Australia, monitoring Helicoverpa species for resistance to the Cry2Ab toxin in second generation Bacillus thuringiensis (Bt) cotton has precisely fulfilled its intended function: to warn of increases in resistance frequencies that may lead to field failures of the technology. Prior to the widespread adoption of two‐gene Bt cotton, the frequency of Cry2Ab resistance alleles was at least 0.001 in H. armigera and H. punctigera. In the 5 years hence, there has been a significant and apparently exponential increase in the frequency of alleles conferring Cry2Ab resistance in field populations of H. punctigera. Herein we review the history of deploying and managing resistance to Bt cotton in Australia, outline the characteristics of the isolated resistance that likely impact on resistance evolution, and use a simple model to predict likely imminent resistance frequencies. We then discuss potential strategies to mitigate further increases in resistance frequencies, until the release of a third generation product. These include mandating larger structured refuges, applying insecticide to crops late in the season, and restricting the area of Bollgard II® cotton. The area planted to Bt‐crops is anticipated to continue to rise worldwide; therefore the strategies being considered in Australia are likely to relate to other situations.

Have Bt Crops Led to Changes in Insecticide Use Patterns and Impacted IPM

GM crops have now been commercialised for over ten years and currently over 114 million hectares are grown in 23 countries (James, 2007). By incorporating a powerful pest management tactic within the plant these Bt crops overcome some, but not all of the problems with timing and variable rates of application of insecticides, which reduce efficacy and often result in higher than necessary concentrations being applied than is necessary. The aim of this chapter is to gather the current evidence for impacts of Bt crops, largely Bt cotton and Bt maize, on insecticide use and to reflect on their role in IPM. Analyses of Bt crop performance across a range from large-scale intensive production to smallholder production systems of varying levels of sophistication indicate significant reductions in insecticide input and in some systems, highly significant improvements in yield. However, economic performance is highly variable and seems dependent more on the market characteristics, support structures and culture of the systems in which Bt crops are deployed than on the Bt crops themselves. Given their specificity for key target pests and well demonstrated lack of impact on beneficial insects, Bt crops provide an important new platform for sustainable IPM systems, one that is compatible with a full range of other tactics. However, achieving that IPM outcome will often require ongoing education and extension support for farmers, particularly in smallholder systems, to ensure they can build confidence and gain sustainable benefit from a mix of new and established technologies in pest management.

Field performance and seasonal changes in the efficacy against Helicoverpa armigera (Hübner) of transgenic cotton expressing the insecticidal protein vip3A

1 Three years of field experiments in Eastern Australia were carried out on transgenic cotton (Gossypium hirsutum L.) event Cot102 expressing the insecticidal protein gene vip3A from Bacillus thuringiensis to evaluate performance against Helicoverpa armigera Hübner. Efficacy, defined as the capacity of plant tissues to induce larval mortality, was determined with a well‐validated leaf bioassay fortnightly through the growth cycle of the cotton in each season.