Environmental Determinants of Clonal Spread in Whitetop (Lepidium draba) in northeast Colorado
Amanda Stahlke1*, Natalie West2, John Gaskin2
1Bioinformatics and Computational Biology Program, Institute for Bioinformatics and Evolutionary Studies, University of Idaho; Moscow, ID 83843; astahlke@uidaho.edu
2USDA-ARS, Northern Plains Agricultural Research Lab; Sidney, MT 59270
Whitetop [Lepidium draba L. (Brassicaceae)] is a persistent and widespread monecious invasive weed in the western United States and Canada. To target management of invasive plants that may exploit either clonal or sexual reproduction such as whitetop, it is important to identify environmental factors that influence life history strategies and identify the scale at which these interactions vary. The value of either reproductive route to optimizing weed persistence or spread could vary due to local conditions, such as soil conditions, competitive interactions, or disturbance. In this field-based snapshot, we investigated the relationship between whitetop clonality and environmental heterogeneity across a series of floodplain areas in the South Platte River Basin of northeastern Colorado. Within 90 meter-squared subplots across six uncultivated sites, we characterized whitetop genetic diversity, soil nutrient and texture, and community structure and composition. Our nested sampling design revealed a scale-dependent pattern. We found that soil nutrients, the amount of bare ground, and grass were significant predictors of clonality at the small scale, in subplots. At the largest scale, we found that no clones spanned sites and genetic diversity across the drainage reflected hydrological patterns, suggesting sexual spread across the basin. We discuss opportunities for further study and implications for the recently approved classical biological control agent, Aceria drabae.