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ARS Home » Plains Area » Miles City, Montana » Livestock and Range Research Laboratory » Research » Publications at this Location » Publication #323042

Research Project: Adaptive Rangeland Management of Livestock Grazing, Disturbance, and Climatic Variation

Location: Livestock and Range Research Laboratory

Title: Testing fundamental ecological concepts with a Pythium-Prunus pathosystem

Author
item Reinhart, Kurt
item Rinella, Matthew - Matt
item CLAY, KEITH - Indiana University

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 12/1/2016
Publication Date: N/A
Citation: N/A

Interpretive Summary: n/a

Technical Abstract: The study of plant-pathogen interactions has enabled tests of basic ecological concepts on plant community assembly (Janzen-Connell Hypothesis) and plant invasion (Enemy Release Hypothesis). We used a field experiment to (#1) test whether Pythium effects depended on host (seedling) density and/or distance to (tree) hosts. Next, we used lab pathogenicity trials to (#2) compare the virulence of Pythium isolates associated with Prunus (tree host) in its native and non-native ranges. Coinciding with this research, we observed a proliferation of related studies and study designs. This led us to (#3) compare and contrast two competing bioassay methodologies of field experiments. We used data on spatial variation in Pythium density and relationships between Pythium density and Prunus biomass to simulate the results for two competing soil handling techniques and rates of Type I statistical error. We found (#1) that pathogenic activity varied by host tree distance but not host seedling density thereby indicating a mechanism for maintaining tree species coexistence. We isolated Pythium spp. (#2) associated with Prunus in its native (North America) and invaded ranges (Europe). Isolates from Prunus’s native range were consistently more virulent thereby indicating that its invasive success was partly attributed to it having escaped its virulent enemies. Lastly, a review (#3) of the literature indicates that >50% of relevant studies use methods that result in overly precise inferences with greater rates (10×) of type I statistical error. Our research indicates that plant-Pythium associations and interactions have produced important tests of fundamental ecological concepts and will help improve future studies on plant-soil biota interactions. The study of plant-pathogen interactions have enabled us to test basic ecological concepts on plant community assembly (Janzen-Connell Hypothesis) and plant invasion (Enemy Release Hypothesis). We used a field experiment to test whether or not Pythium effects depended on host (seedling) density and/or distance to (tree) hosts. Next, we used pathogenicity trials in the lab to compare the virulence of Pythium isolates associated with Prunus (tree host) in its native and non-native ranges. Finally, we compared and contrasted two competing bioassay methodologies of field experiments. We used data on spatial variation of Pythium density and relationships between Pythium density and Prunus biomass to simulate the results for two competing soil handling techniques and quantify rates of Type I statistical error. We found that pathogenic activity varied by host tree distance but not host seedling density thereby indicating a mechanism for maintaining tree species coexistence. We isolated Pythium spp. associated with Prunus in its native (North America) and invaded ranges (Europe). Isolates from Prunus’s native range were consistently more virulent than isolates from Europe thereby suggesting that invasive Prunus populations are less regulated by soil-borne enemies. Lastly, a review of the literature indicates that >50% of relevant studies used flawed methods with overly precise inferences and with greater rates (10×) of type I statistical error. Our research indicates that plant-Pythium associations and interactions have produced important tests of fundamental ecological concepts and will help improve future studies on plant-soil biota interactions.