Skip to main content
ARS Home » Pacific West Area » Reno, Nevada » Great Basin Rangelands Research » Research » Publications at this Location » Publication #343718

Title: Why is Taeniatherum caput-medusae (medusahead) Invasive in North America and not in its Native Eurasia?

item Morgan, Tye
item O'NEIL, MATTHEW - University Of California
item Blank, Robert - Bob
item ALLEN, EDITH - University Of California
item ALLEN, MICHAEL - University Of California

Submitted to: Ecological Society of America (ESA)
Publication Type: Abstract Only
Publication Acceptance Date: 6/21/2017
Publication Date: N/A
Citation: N/A

Interpretive Summary: Not applicable

Technical Abstract: Taeniatherum caput-medusae (medusahead) is an exotic annual grass introduced to North America in 1887 that has since invaded an estimated four million ha of rangelands. Contrary, in its native ranges of Eurasia, T. caput-medusae is not considered to be invasive. Why is it that T. caput-medusae expresses invasive traits in foreign regions, but not in its native lands? Invasion ecology allows separation of mechanistic invasion approaches with two prominent hypotheses: enemy release and resource availability. Previous research (Blank and Sforza, 2006) provides evidence that increased resource availability in soils of eastern CA, where T. caput-medusae is invasive, offers a partial explanation of its invasiveness. This new study was designed to test the effect of soil (three Eurasian native soils and three North American invasive soils), seed source (three native and invasive collections from where soil was collected), and treatment (sterile, filtrate, inoculum) on growth, tissue nutrient concentrations, and mycorrhize and pathogen root counts of T. caput-medusae. We hypothesized: 1) T. caput-medusae invaded soils of North America are more fertile than native soils in Eurasian and thus support growth and expansion of medusahead; 2) Invaded soils of western North America lack pathogenic organisms, which in native environments, reduce the growth and invasiveness of medusahead. Interactions among seed source, soil source, and treatment significantly influenced growth of T. caput-medusae. Overall, soil and seed from its invasive range produced significantly larger plants. North American populations had a greater response to filtrate treatments with higher mycorrhizae counts, whereas Eurasain populations had a negative response with higher amounts of pathogen counts.