Invasive annuals respond more negatively to drought than native species
Justin M Valliere1,2, Evelin B Escobedo2, Gary M Bucciarelli2
1La Kretz Center for California Conservation Science, Institute of the Environment and Sustainability, University of California, Los Angeles, CA, 90095, USA.
The New Phytologist
|April 21, 2019
Summary
Invasive plants in California grasslands may be more negatively impacted by drought than native species. However, invasives can capitalize on well-watered conditions, increasing their reproductive output.
Area of Science:
- Ecology
- Botany
- Environmental Science
Background:
- Baker's (1965) hypothesis suggests weedy plants maximize reproduction under high resources.
- Invasive species are thought to be more responsive to resource fluctuations than native species.
- Few studies have examined reproductive output in relation to resource responsiveness in invasive plants.
Purpose of the Study:
- To test Baker's hypothesis in the context of plant invasion and drought in California grasslands.
- To compare the growth and reproductive responses of invasive and native annual wildflowers to water availability.
- To determine if invasive species exhibit greater responsiveness to fluctuating resources, particularly water.
Main Methods:
- An outdoor potted study was conducted using eight native and eight invasive annual species from California grasslands.
- Plants were grown to reproductive maturity under two conditions: well-watered and drought.
- Key growth and reproductive traits were measured and compared between native and invasive species under varying water availability.
Main Results:
- Drought negatively affected overall plant performance for both native and invasive species.
- Invasive species showed more pronounced negative responses in growth and reproductive traits under drought conditions compared to natives.
- Invasive species exhibited larger growth, particularly under well-watered conditions, and produced seeds with higher germination rates than native species.
Conclusions:
- While invasives may be more susceptible to drought stress, they possess an opportunistic strategy.
- Invasive plants can significantly enhance reproductive output under favorable, high-resource conditions.
- These opportunistic responses to variable precipitation may explain the fluctuating abundance of invasive species in grasslands.
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