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Intraspecific competition for host resources in a parasite
Paul D Nabity1, Greg A Barron-Gafford2, Noah K Whiteman3
1Department of Botany and Plant Sciences, University of California, Riverside, 900 University Avenue, Riverside, CA 92125, USA.
Current Biology : CB
|February 24, 2021
Summary
Intraspecific competition among desert mistletoe parasites exists for host resources. This competition influences virulence, with trophic flexibility potentially reducing negative impacts in stressful environments.
Area of Science:
- Ecology
- Plant Biology
- Parasitology
Background:
- Intraspecific competition in parasites is theorized to increase virulence, but empirical evidence from natural settings is scarce.
- Parasitic plants offer a unique model to study competition's role in host-parasite dynamics due to their dual autotrophic and heterotrophic resource acquisition.
- Desert mistletoe (Phoradendron californicum) is a xylem hemiparasite with significant heterotrophic reliance on its host.
Purpose of the Study:
- To experimentally investigate the role of intraspecific competition for xylem resources among desert mistletoe individuals.
- To assess how competition influences the virulence of desert mistletoe on its host, velvet mesquite (Prosopsis velutina).
- To determine the impact of host performance and climate variation on parasite competition and virulence.
Main Methods:
- Field manipulation of desert mistletoe individuals on co-infected velvet mesquite branches in the Sonoran Desert.
- Removal experiments to alter parasite density and spatial position within the host's xylem stream.
- Measurement of host and parasite physiological performance, resource availability, and resource use over time.
Main Results:
- Evidence of intraspecific competition for xylem resources, including host carbon, between desert mistletoe individuals.
- Host performance and seasonal climate (monsoon) influenced the intensity of competition and parasite virulence.
- Experimental parasite removal demonstrated density- and location-dependent effects on the host, impacting mistletoe autotrophy and resource availability.
Conclusions:
- Intraspecific competition among hemiparasitic desert mistletoes affects resource acquisition and virulence.
- Trophic flexibility in mistletoes can mitigate intraspecific competition and reduce virulence.
- Mistletoe co-infections may attenuate virulence as a strategy to maintain resource access, especially in challenging ecological conditions.
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