Location: Range and Livestock ResearchTitle: Effects of soil biota from different ranges on Robinia invasion: acquiring mutualists and escaping pathogens Author
Submitted to: Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/22/2010
Publication Date: 5/12/2011
Citation: Callaway, R.M., Bedmar, E.J., Reinhart, K.O., Silvan, C.G., Klironomos, J. 2011. Effects of soil biota from different ranges on Robinia invasion: acquiring mutualists and escaping pathogens. Ecology 92(5):1027-1035. Interpretive Summary: • Range expansion by Robinia pseudoacacia corresponds with some predictions regarding changing interactions with soil biota. Specifically, invasive success corresponded with escaping belowground enemies, although not Pythium soil-borne pathogens, and the acquisition of important mutualistic nitrogen-fixing and nodule-forming bacteria. • Interactions occurring in the soil are often treated as a “black box.” This research is unique because it explored the total effect of the soil biota and three important subgroups: nitrogen-fixing bacteria, mycorrhizal fungi, and soil-borne pathogens (e.g. Pythium). • Basic science implications- This research illustrates the scientific challenge of trying to understand the effects of the whole soil community while attributing these effects to specific taxonomic groups. • Management implications- This research suggests that the invasive success of legumes, plants dependent on nitrogen-fixing bacteria, may not be limited by their failure to reacquire appropriate nodule forming bacteria in new ranges.
Technical Abstract: The net effects of soil biota from invaded ranges are often less inhibitory to exotic invasive plants than soil biota from native ranges. However, the net effects of soil biota on exotics are highly variable, in part because net effects are the products of complex effects of suites of interacting soil mutualists and antagonists. Here we compared the independent effects of mutualistic N-fixing, nodule-forming bacteria, mutualistic arbuscular mycorrhizal fungi (AMF), pathogenic Pythium taxa, and net soil feedback effects from biota among soils from the native range, expanded range, and invaded range of Robinia pseudoacacia, a tree native to the Appalachian and Ozark mountains in the USA, but now spread throughout North America, Europe and Asia. Robinia formed nodules in all soils, a very broad phylogenetic suite of N-fixing, nodule-forming bacteria were found in Robinia nodules, and leaf N did not differ among the different regional sources of soil. Together this suggests that the expansion potential of Robinia may not limited by the lack of appropriate mutualistic N-fixing bacteria. AMF from the native range stimulated stronger positive feedbacks than AMF from the expanded or invasive ranges, a biogeographic difference not described previously in the literature. Pythium collected in soils from different ranges did not vary in pathogenic effects; however, feedbacks produced by the total soil biota were much more negative from soils from the invaded range than the native range, overriding the effects of AMF, suggesting that escape from other pathogenic biota in the soil or the cumulative or synergistic negative effects of the whole soil community is a potential cause of superior performance in invaded regions. Our results suggest that important regional evolutionary relationships occur among plants and soil biota, and that the total biota of soil communities often affect invasion as a whole but in ways that are not easily explained by studying components of the soil biota.