| Title |
Investigators | Department | Objectives | Approach Keywords | Progress Reports | Impact Statements | Publications | |
Project * COL00680 | |
| Title | The Ecology and Genetics of Invasions and Biological Control |
| Investigator(s) | Hufbauer, RA; |
| Department | Bioagricultural Sciences and Pest Mgmt. |
| Objectives | 1) Explore the ecology and genetics of the invasions of Centaurea diffusa and C. stoebe to North America a) Examine the origin of these invasive weeds using molecular markers. b) Asses the role of hybridization in the invasion and interactions with biological control agents. 2) Evaluate genetic population structure in candidate biological control agents for garlic mustard (Alliaria petiolata) a) Characterize the structure of beetle populations using molecular markers. 3) Evaluate the relative roles of adaptive evolution, drift, propagule pressure and plasticity in the invasion of Bromus tectorum to high elevations a) Construct comparative demographic models of Bromus tectorum . b) Evaluate molecular population structure of B. tectorum from low and high elevation. c) Evaluate propagule pressure in high and low density habitats. 4) Study the role of harvester ants in preventing or facilitating invasion of Colorado rangelands. a) Document the preference of ants for seeds of different plant species. b) Determine the degree of seed vs. site limitation for certain key plant species. c) Set up ant exclosures to evaluate the long term consequences for plant community composition. |
| Approach | Objective 1. We are sequencing ITS data to add an ordered molecular marker to our data sets on origins of the two species. Additionally, we are using AFLPs to provide additional markers with which to study hybridization. The samples for this study have already been collected, and DNA has been extracted from most of them. The experimental work on hybridization includes first conducting crosses in the greenhouse and laboratory, and using the offspring in a common garden experiment and herbivory experiments. We are gathering first generation backcross seed currently, and will be setting up an experiment that includes parents from the native range, backcross individuals, hybrid individuals collected from the invasive range, and hybrid individuals collected from the native range. Plants will be grown with and without competition to simulate the more open, disturbed environments favored by C. diffusa and the more competitive environments used by C. stoebe. We will evaluate relative performance and phenotype using life history, physiological and morphological traits. A subset of the genotypes included in the common garden will be incorporated into experiments with one of the biological control agents that have been introduced. Objective 2. We will evaluate whether there appear to be cryptic species present in the regions being sampled for host-specificity testing using restriction digests , mtDNA sequencing, and AFLPs. We will use AFLPs to examine whether the regions being used represent single genetic groups (i.e. populations) or multiple groupings. Objective 3. Propagule pressure is thought to be a critical factor driving invasions. We will measure propagule pressure in low and high density habitats, and incorporate reproduction rates into comparative matrix population models. We will conduct experiments evaluating the competitive ability and phenology of plants from low and high density habitats. Objective 4 . We will conduct several experiments and sampling regimes to determine: 1) The number of viable seed available to granivores; 2) The proportion of viable seeds removed by granivores; 4) The relative proportion of seed types and sizes removed by rodents and ants; 5) How granivore foraging and caching behaviors redistribute seeds and possibly lead to secondary dispersal; 5) Whether four focal plant species are water limited, seed limited, or both, and how these limitations interact with granivore effects; and 6) Whether removal of one or both types of granivores changes the plant community over time. |
| Keywords | Centaurea, seed predation, Bromus tectorum, Aliaria, biological control, population genetics |
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