| Title |
Investigators | Department | Objectives | Approach Keywords | Progress Reports | Impact Statements | Publications | |
Project * COL00638 | |
| Title | *The Ecology and Genetics of Invasions and Biological control |
| Investigator(s) | Hufbauer, RA; |
| Department | Bioagricultural Sciences and Pest Mgmt. |
| Objectives | 1. To control an invader we must know what enables it to invade. To this end, we are studying the genetics and ecology of the introduction of diffuse and spotted knapweeds (Centaurea diffusa and C. maculosa), two important invasive weeds in western North America . We plan to test the hypothesis that the weeds are more invasive here than in their native range. Also, we will examine the hypothesis that hybridization has contributed to the invasion, and will also explore whether allelopathic chemicals known to influence interactions with other plants and microbes in sterile culture and greenhouse experiments are effective in the field, and if so under what environmental conditions. 2. To understand and predict the risk of biological control it is vital to have valid estimates of how labile host range is. With this objective we propose to estimate quantitative genetic variation in oviposition preference for non-target hosts of three candidate biological control agents (Ceutorynchus spp.) of garlic mustard (Alliaria petiolata). |
| Approach | Objective 1: We are sampling broadly from the native and introduced ranges of C. diffusa and C. maculosa. We will use the samples in molecular genetic analyses, experimental hybridization, and ecological comparisons. The molecular analyses will include chloroplast DNA sequencing, and microsatellite surveys. For the ecological comparisons, three introduced North American populations of each species and a hybrid population will be compared to three native Eurasian populations of each species plus hybrids. The populations will be chosen based upon the genetic data. The introduced populations will be chosen to represent the range of variability found in the neutral molecular data. This is a powerful test of the hypothesis that native and introduced populations differ in their levels of general vigor (Blossey and Notzold 1995), because it explicitly controls for variation among individuals and populations that might otherwise obscure overall differences among native and introduced populations. Objective 2: We will explore population structure using microsatelite and mitochondrial DNA. Pending funding from competitive grants, we will initiate quantitative genetic experiments to measure levels of genetic variation of the weevils for use of non-target plants. |
| Keywords | Centaurea, Alliaria, biological control, invasion, exotic, genetics, host range |
| Progress Reports | |
| 2001 | Classical biological control of exotic weeds is the deliberate use of introduced, specialized herbivorous insects or pathogens to reduce the population size of the weeds below economic injury levels. When biological control of weeds is successful, millions of dollars can be saved each year through increases in overall land value, improved health and weight gain of livestock, and reduced herbicide usage. However, rates of success of weed biological control range from 10 to 18 percent. In order to improve success rates for the biological control of weeds, it is vital to understand the fundamental biological issues underlying interactions between weedy invasive plants and biological control agents. A critical component of biological control of weeds with herbivorous insects is using insect species with the appropriate level of specialization on the weedy host plant. The study of insect specialization on weedy plants comprises ecological measurements of insect preference and performance, genetic delimitation of insect population structure, and genetic characterization of introduced weed populations and the populations of that same weedy species within its native range. With this project, I will explore the ecological and genetic factors that determine host-plant specialization of biological control agents using two invasive weed, biological control agent systems. The first system is Brachypterolus pulicarius, a flower feeding beetle, and both yellow (Linaria vulgaris) and Dalmatian (Linaria dalmatica) toadflax. Both the beetle and the two host plants have invaded North America. Using this system my lab group and I are investigating genetic and ecological components of host use so that we may better understand the dynamics of host specialization. In this reporting period we examined the preference of beetles collected from each of the two host plants for each of the two host plants in behavioral assays. Beetles from both sources prefer yellow toadflax, but beetles from Dalmatian toadflax show less of a bias. These results indicate that there is either an environmental component to host preference or a genetic one. In future years we plan to tease those factors apart. In either case, those factors can be used to improve the biological control of these weeds. For example, if the bias has a genetic component, it may be possible to find beetles in the native range that prefer Dalmatian toadflax in order to better control that weed. The second system my lab group and I are studying as part of this Hatch project is the genetics of Centaura maculosa and Centaurea diffusa. We have collected samples from the native and introduced ranges of these weeds, have extracted DNA, and are studying the genetic effects of their introduction using ISSRs. We have also now isolated microsatellite loci, and are in the process of designing primers for them. These will provide a powerful tool for determining the areas of origin of the introduced populations. Once the populations of origin are known it will be possible to search those areas for specialized biological control agents. |
| 2002 | Most weedy plants in natural ecosystems, rangelands, and parks are exotic invaders. Invasive weeds reduce forage for wild animals and livestock, can increase fuels and therefore frequency and intensity of burns, and alter ecosystem function (e.g. nutrient cycling). Biological control is one of the only long-term approaches to managing invasive plants. However, controlling weeds with biological control agents has sporadic success. Our goal is to increase the success of biological control and decrease the risks associated with introductions of biological control agents. To accomplish that goal, we must have a better understanding of the fundamental ecology and biology of the interactions between biocontrol agents and their host weeds. Improving biological control of weeds (both efficacy and safety) is critical to national and state land managers, ranchers and farmers, and native plant conservationists. I am bringing the tools of population and ecological genetics to bear on three main weed biological control systems: diffuse and spotted knapweed and their control with Urophora flies , Dalmatian and yellow toadflax attacked by Brachypterolus pulicarius, and garlic mustard and it's Ceutoryncus biological control agents. For each of these systems I am exploring the parallel genetic structure of the weeds and the biological control agents. By fine-tuning the biological control of these noxious weeds, this project is relevant to conservationists and land managers in Colorado, and across North America. |
| 2003 | Most weedy plants in natural ecosystems, rangelands, and parks are exotic invaders. Invasive weeds reduce forage for wild animals and livestock, can increase fuels and therefore frequency and intensity of burns, and alter ecosystem function (e.g. nutrient cycling). Biological control is one of the only long-term approaches to managing invasive plants. However, controlling weeds with biological control agents has sporadic success. Our goal is to increase the success of biological control and decrease the risks associated with introductions of biological control agents. To accomplish this goal, we must have a better understanding of the fundamental ecology and biology of the interactions between biocontrol agents and their host weeds. Improving biological control of weeds (both efficacy and safety) is critical to national and state land managers, ranchers and farmers, and native plant conservationists. There is heightened concern about the long-term safety of biological control. I am bringing the tools of population and ecological genetics to bear on three main weed biological control systems: diffuse and spotted knapweed and their control with Urophora flies, Dalmatian and yellow toadflax attacked by Brachypterolus pulicarius, and garlic mustard and candidate Ceutorhynchus biological control agents. For each of these systems I am exploring the parallel genetic structure of the weeds and the biological control agents. We are estimating the genetic variation for oviposition preference within and among populations of three Ceutorhynchus weevil species that are being considered for biological control. This research will aid in choosing appropriately among the species, and populations within species, for introduction, and will help ensure that our biological control efforts are safe not only in the present, but also for future generations. By fine-tuning the biological control of these noxious weeds, this project is relevant to conservationists and land managers in Colorado, and across North America. |
| 2004 | Classical biological control is the control of exotic pests with specialized pathogens and parasites imported from the native range of the exotic pest. It is one of the most powerful and permanent solutions to the growing problems caused by invasive, weedy plants. An issue of overriding importance in biological control is efficacy. The genetics of both invasions and of plant-biological control agent interactions are thought to be and important component of efficacy. The main weeds we are working with are diffuse and spotted knapweed, and garlic mustard. With the knapweeds, we are focusing on discovering where in the native range the invasive populations originated, and how hybridization influences interactions with insects. A key finding from the knapweed work is that a cryptic species that looks like spotted knapweed appears to be present in North America. For garlic mustard, we are focusing on interactions between it and potential biological control agents. We have found significant genetic structuring of populations of the potential biological control agents in the native range using neutral loci. Pending external funding, the host ranges of these distinct populations will be evaluated to determine the risk of host-range evolution following release. |
| 2005 | Classical biological control is the control of exotic pests with specialized pathogens and parasites imported from the native range of the exotic pest. It is one of the most powerful and permanent solutions to the growing problems caused by invasive, weedy plants. An issue of overriding importance in biological control is efficacy. The genetics of both invasions and of plant-biological control agent interactions are thought to be and important component of efficacy. The main weeds we are working with are diffuse and spotted knapweed, yellow and Dalmatian toadflax, and garlic mustard. With the knapweeds, we are focusing on discovering where in the native range the invasive populations originated, and how hybridization influences interactions with insects. A key finding from the knapweed work is that the putative allelochemical is highly unstable in water and soil, and has minimal negative impacts on reportedly sensitive species. We have found that a biological control agent of the toadflaxes prefers and performs better on yellow toadflax. For garlic mustard, we are focusing on interactions between it and potential biological control agents. We have found significant genetic structuring of populations of the potential biological control agents in the native range using neutral loci. |
| 2006 | Invasive weeds threaten rangeland productivity and health. Understanding the genetic and ecological factors that facilitate invasions can lead to better options for long-term management. This year, we surveyed the genetic variation of the invasive weeds diffuse and spotted knapweed in both the U.S. and Europe using chloroplast DNA sequences and microsatellite locus 'genetic fingerprints'. Chloroplast DNA variation was reduced but microsatellite variation was not changed between the native and introduced ranges. This suggests that neither species has undergone a strong bottleneck in population size associated with the introductions. Indeed, they are both likely to have been introduced multiple times. The genotypes present in U.S. often appear to be mixtures of European genotypes. Thus, the introduction has led to new genetic variants that do not appear to exist in the native range. Additionally, some U.S. populations are genetically quite distinct. For example, an infestation in Vail, Colorado is quite unique, and does not even match our samples from the native range, making its origin a mystery. The patterns of relationships between populations in the U.S. suggests that new infestations are founded by long-distance dispersal from other areas, with likely means of transportation being fill dirt, trucks, and trains. |
| Impact | |
| 2001 | We expect to enhance our understanding of the fundamental biological issues underlying weed biological control systems, with the end goal of increasing the efficacy of weed biological control agents, while retaining their safety. |
| 2002 | This project will have several main impacts on the invasive weed problem facing Colorado and the US. (1) Economic. By fostering more efficient and effective biological control, the cost of controlling these invasive weeds will be reduced. Together these weeds cover over 200,000 acres in Colorado, and have vast populations in other states as well. Costs of control are prohibitive (e.g. $40 per acre), and thus any improvement in control through low-cost biological methods could save the state of Colorado hundreds of thousands of dollars, and the nation millions. (2) Social. By presenting my results at meetings for laypeople involved in weed control across the state, I contribute to their education and proper use of the tools at their disposal. (3) Environmental. By studying the factors involved in host use by biological control agents, this project will encourage safe use of biological control, reducing risk to non-target plants. (4) Scientific. This project has both applied and fundamental relevance. On the applied side, it advances the science biological control. The project is relevant to basic debates on the evolutionary and ecological consequences of small founding populations, and the factors that promote and inhibit coevolutionary arms races. |
| 2003 | This project will have several main impacts on the invasive weed problem facing Colorado and the US. (1) Economic. By fostering more efficient and effective biological control, the cost of controlling these invasive weeds will be reduced. (2) Social. By presenting my results at meetings for laypeople involved in weed control across the state, I contribute to their education and proper use of the tools at their disposal. (3) Environmental. By studying the factors involved in host use by biological control agents, this project will encourage safe use of biological control, reducing risk to non-target plants. (4) Scientific. This project has both applied and fundamental relevance. On the applied side, it advances the science of biological control. The project is relevant to basic debates on the evolutionary and ecological consequences of small founding populations, and the factors that promote and inhibit coevolutionary arms races. |
| 2004 | The finding that some populations thought to be spotted knapweed may in fact be a different species has lead these populations to be targeted for eradication. Preliminary population genetic work on the garlic mustard weevils will be used in the materials provided to the technical advisory group (TAG) that evaluates the risks and benefits of new biological control introductions, and makes recommendations to USDA APHIS PPQ officials regarding new releases. |
| 2005 | Our findings on the stability and effects of catechin, a putative allelochemical from spotted knapweed, suggest that allelochemistry does not explain invasion of this species, and that restoration of rangeland previously infested with knapweed will not be inhibited by residual catechin. Our findings in the toadflax system make it clear that the current practice of collecting beetles from yellow toadflax to establish populations on Dalmatian toadflax is ineffective. Other controls must be sought for Dalmatian toadflax. |
| 2006 | Knowing that long-distance dispersal is a key means by which new infestations are started is important to prevention efforts. New construction of roads or facilities should be watched closely to suppress new emergence of these noxious weeds before they grow dense and become difficult to eradicate. Our genetic data suggest that this is important to do even if other infestations of knapweed are nearby. A new site may be founded by genetically distinct plants, bringing new variation to the local knapweed populations. Because high genetic variation is associated with rapid adaptation, it might speed the evolution of resistance to herbicides or biological control agents. |
| Publications | |
| 2002 |
Bais, H. P, T. S. Walker, F. R. Stermitz, R. A. Hufbauer, and J. M. Vivanco. 2002. Enantiomeric dependent phytotoxic and antimicrobial activity of (+/-)-catechin; a rhizosecreted racemic mixture from Centaurea maculosa (spotted knapweed). Plant Physiology. 128:1173-1179. Hufbauer, RA, AP Norton, DK MacKinnon, AK Jackson. 2002. Population structure and host use of Brachypterolus pulicarius, an inadvertently introduced biological control agent of toadflaxes. Proceedings, International Organization for Biological Control Symposium: The Role of Genetics and Evolution in Biological Control. Marrs, RA, RA Hufbauer, SE Carney, L Smith. 2002. Population Structure and Ploidy Level in North American Spotted Knapweed, Centaurea maculosa. Proceedings, Western Society of Weed Science, Salt Lake City, Utah. Marrs, RA, RA Hufbauer, SE Carney, R Sforza. 2002. Genetic structuring and ploidy level in populations of spotted and diffuse knapweed. Proceedings, International Organization for Biological Control Symposium: The Role of Genetics and Evolution in Biological Control. |
| 2003 |
Hufbauer, RA, SM Bogdanowicz, and RG Harrison. 2004. The population genetics of a biological control introduction: microsatellite and mtDNA variation in native and introduced populations of Aphidius ervi, a parasitoid wasp. Molecular Ecology. 13:337-348. |
| 2004 |
Hufbauer, RA, Marrs,RA, Jackson,AK, Sforza,R, Bais,HP, Vivanco,JM and Carney, SE. 2004. Population structure, ploidy levels and allelopathy of spotted and diffuse knapweed Pp. 121-126 in North America and Eurasia. Proceedings of the XI International Symposium on Biological Control of Weeds, Cullen,JM, Briese,DT, Kriticos,DJ, Lonsdale,WM, Morin,L, Scott,JK eds. CSIRO Entomology, Canberra, Australia. McClay, AS, Crisp,MD, Evans,HC, Heard,T., Hufbauer,RA, Qin,T-K and Shaw,R. 2004. Centres of origin: do they exist, can we identify them, does it matter? Pp. 619-620 in Proceedings of the XI International Symposium on Biological Control of Weeds, Cullen,JM, Briese,DT, Kriticos,DJ, Lonsdale,WM, Morin,L, Scott,JK eds. CSIRO Entomology, Canberra, Australia. |
| 2005 |
Blair, A.C., Hanson, B.G., Brunk, G.R., Marrs, R.A., Westra, P., Nissen, S.J., and Hufbauer, R .A. 2005. New techniques and findings in the study of a candidate allelochemical implicated in invasion success. Ecology Letters. 8:1039-1047. Hufbauer, R.A. and Roderick, G.K. 2005. Microevolution in biological control: mechanisms, patterns and processes. Biological Control. 35:227-239. Lloyd, C.J., Hufbauer, R.A., Jackson, A.K., Nissen, S.J., and Norton, A.P. 2005. Pre- and post-introduction patterns in neutral genetic diversity in the leafy spurge gall midge. Biological Control 33:153-164. MacKinnon, D.K., Hufbauer, R.A., and Norton, A.P. 2005. Host-plant preference of an inadvertently introduced biological control agent. Entomologia Experimentalis et Applicata. 116:183-189. |