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Title: Biogeographical plant-soil relations of invasive medusahead (Elymus caput-medusae)

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

Submitted to: Soil Ecology Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 5/15/2015
Publication Date: 6/8/2015
Citation: O'Neil, M., Morgan, T.A., Blank, R.R., Allen, E.B., Allen, M.F. 2015. Biogeographical plant-soil relations of invasive medusahead (Elymus caput-medusae)[abstract]. Soil Ecology Meeting Abstracts. p. 86.

Interpretive Summary:

Technical Abstract: Understanding the mechanisms that underlie the success of invasive plant species is integral to predicting and ameliorating their negative impacts. Many hypotheses have consequently been proposed to explain invasive behavior. This lack of consensus within invasion ecology can partially be attributed to an historical bias toward above- relative to belowground interactions. Importantly, recent investigations into biogeographical invasive plant species-soil interactions have revealed a consistent pattern – more positive growth responses in invasive than in native range soils. However, what soil component(s) drive this pattern remains equivocal. To address this issue we conducted a full factorial growth experiment in which each of 5 seed populations (2 native and 3 invasive) of the grass Elymus caput-medusae were exposed to sterile soil (nutrient treatment), microbial filtrate (‘pathogen’ treatment), or raw soil (‘mycorrhizal’ treatment) associated with each seed source. This design allowed us to test three prominent hypotheses in invasion ecology: increased resource availability, enemy release and enhanced mutualism hypotheses. Growth responses were significantly influenced by soil source (F = 5.45, p <0.001) and microbial treatments (F = 54.4, p < 0.001). Overall, plants grown in sterile invasive range soils out performed those grown in sterile native range soils. Invasive populations tended to demonstrate positive responses to both ‘pathogen’ and ‘mycorrhizal’ treatments (regardless of soil source), while native populations showed neutral and negative responses to ‘pathogen’ and ‘mycorrhizal’ treatments respectively. When responses were considered in a home vs. away context a few interesting patterns emerged. One, native populations were more negatively affected by ‘pathogens’ than invasive populations. Two, ‘mycorrhizal’ treatments were more positive in home soils than away soils. This suggests that invasive behavior in our system is primarily driven by resource availability, a lack of susceptibility to but not release from pathogens, and what appears to be enhanced mutualisms via local coadaptation.