Reponse of Giant Ragweed (Ambrosia trifida) Source Populations to Varying Soil Moisture Conditions
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Date
2024-05
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The Ohio State University
Abstract
Giant ragweed (Ambrosia trifida) is native to North America and an emerging invasive species in Europe and Asia. Giant ragweed is typically found in riparian areas, which are located near water sources and have relatively high soil moisture. Giant ragweed often escapes into agricultural fields where it is highly competitive with corn and soybean crops and the soil is much drier. Such incursions into crop fields have been occurring for much longer in the eastern part of the U.S. Corn Belt than in the western Corn Belt, which has led to evolved population differences in the east that are more pronounced than in the west. We hypothesized that giant ragweed populations would differ in drought tolerance due to variable abiotic conditions where they occur. Specifically, we predicted that populations of giant ragweed from crop fields would be more drought tolerant than non-crop populations and that populations from the drier western region would be more drought tolerant than populations from the east. We sourced seeds from agricultural and riparian populations in Ohio and Nebraska. In a greenhouse, we grew each population type and source under three conditions that spanned a soil moisture gradient, from saturated to dry soil moisture conditions. Performance was greatest in the driest conditions for all source populations, with higher germination percentages, higher total biomass, and earlier emergence than in either of the wetter treatments. However, Nebraska populations had a much higher germination percentage and emerged earlier than Ohio populations, which was exacerbated in drier conditions. Additionally, crop populations showed higher germination percentages than non-crop populations, especially in the driest conditions (habitat x treatment). These findings suggest that Nebraska and crop populations may be more drought tolerant than Ohio and non-crop populations, respectively. Overall, giant ragweed is more successful in areas with lower soil moisture content, such as agricultural fields, in comparison to areas with saturated soils. Furthermore, soil moisture similarly affects giant ragweed from varying population types and seed sources. The germination data suggests that there have been adaptive changes in crop populations of giant ragweed in response to soil moisture. This indicates that adaptive changes across the range of giant ragweed may be more extensive than previously thought.
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Keywords
giant ragweed, soil moisture, agricultural weed, drought tolerance