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Abstract Detail


Juliano, Steven A. [1], Borowicz, Victoria A. [2], Yannarell, Anthony C. [3].

Direct and indirect effects of the hemiparasite Pedicularis canadensis on invasions of a prairie community by Lespedeza cuneata.

The factors contributing to successful invasion and impacts on native species by non-native organisms remain an important topic for understanding ecology in human-dominated landscapes. A prominent hypothesis is that species and functional diversity of the invaded community contribute to the resistance of the community to successful invasion and reduce impacts of invaders. The direct and indirect pathways by which species and functional diversity have these effects remain mostly unknown. Hemiparasites are photosynthetic plants that parasitize the roots of other plants, drawing water and mineral nutrition from their hosts. Hemiparasites as a functional group can have important effects on plant communities. We investigated the direct and indirect effects of the hemiparasite Pedicularis canadensis on invasion of Midwestern prairie communities by Lespedeza cuneata. We used structural equation modeling to test hypotheses that: 1) P. canadensis indirectly enhances invasion success of L. cuneata by suppressing dominant grasses and forbs; 2) Species richness (excluding P. canadensis) reduces invasion success of L. cuneata; 3) P. canadensis indirectly affects the community by increasing soil N via concentrating nutrients in its litter; and 4) P. canadensis affects soil microbial communities. We used data from 90 experimental plots. Measured soil variables were: NH4 and NO3; and Nonmetric Multidimensional Scaling Scores describing microbial assemblages. Measured plant variables were: cover of grasses, forbs, and P. canadensis, and biomass of L. cuneata. There was strong support for direct effects of P. canadensis on its victims, though not on L. cuneata. There was no support for the hypothesis that P. canadensis indirectly facilitated L. cuneata by suppressing native species, largely because native grasses and forbs had little direct effect on L. cuneata. The hypothesis that P. canadensis has indirect effects via enriching the soil could not be formally tested because the data set was of inadequate size to estimate reciprocal causal paths from soil latent variables to the plant cover variables; however P. canadensis did have a significant positive direct effect on soil N. There was also no support for the hypothesis of strong competitive effects of L. cuneata on other plants. Indirect effects of L. cuneata on other plants via increasing soil N seem likely, as L. cuneata had a relatively strong positive effect on soil N. Species richness had no effect on L. cuneata and no direct effects on any other variable. Omitting species number yielded a substantial improvement in AIC over the full model.

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1 - Illinois State University, School of Biological Sciences, Normal, IL, 61790-4120, USA
2 - Illinois State University, School Of Biological Sciences, Campus Box 4120, Normal, IL, 61790-4120, USA
3 - University of Illinois, Natural Resources & Environmental Sciences , Urbana, IL, 61810, USA

invasive species
community ecology
indirect effects

Presentation Type: Poster
Session: P, Ecology Section Posters
Location: Exhibit Hall/Savannah International Trade and Convention Center
Date: Monday, August 1st, 2016
Time: 5:30 PM This poster will be presented at 5:30 pm. The Poster Session runs from 5:30 pm to 7:00 pm. Posters with odd poster numbers are presented at 5:30 pm, and posters with even poster numbers are presented at 6:15 pm.
Number: PEC011
Abstract ID:314
Candidate for Awards:None

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