Effects of soil biota from different ranges onRobiniainvasion: acquiring mutualists and escaping pathogens

Abstract

The net effects of soil biota on exotic invaders can be variable, in part, because net effects are produced by many interacting mutualists and antagonists. Here we compared mutualistic and antagonistic biota in soils collected in the native, expanded, and invasive range of the black locust tree, Robinia pseudoacacia. Robinia formed nodules in all soils with a broad phylogenetic range of N-fixing bacteria, and leaf N did not differ among the different sources of soil. This suggests that the global expansion of Robinia was not limited by the lack of appropriate mutualistic N-fixers. Arbuscular mycorrhizal fungi (AMF) from the native range stimulated stronger positive feedbacks than AMF from the expanded or invasive ranges, a biogeographic difference not described previously for invasive plants. Pythium taxa collected from soil in the native range were not more pathogenic than those from other ranges; however, feedbacks produced by the total soil biota were more negative from soils from the native range than from the other ranges, overriding the effects of AMF. This suggests that escape from other pathogens in the soil or the net negative effects of the whole soil community may contribute to superior performance in invaded regions. Our results suggest that important regional evolutionary relationships may occur among plants and soil biota, and that net effects of soil biota may affect invasion, but in ways that are not easily explained by studying isolated components of the soil biota.

Help from under ground: soil biota facilitate knotweed invasion

“…As knotweed is the species most negatively affected by the fine filtrate, some of the microbial organisms in this filtrate have the potential to limit knotweed spread and thus in principle to be candidates for biocontrol agents (Stubbs and Kennedy 2012). More generally, our study suggests that, in contrast to what has been found for other aggressive plant invaders (e.g., Reinhart et al 2010, Callaway et al 2011, soil pathogens from the introduced range can at least sometimes have strong negative effects on exotic species, even though they do not share a coevolutionary history (see also Nijjer et al 2007, Parker andGilbert 2007).…”

“…The outcome of these altered or novel interactions is likely to influence invasion success (Klironomos 2002, Levine et al 2004, Wolfe and Klironomos 2005, Pringle et al 2009), by promoting the invader, or by enhancing community resistance to invasion (Stampe and Daehler 2003). Invasion success will be promoted if exotic plants profit more from the presence of mutualists than native plants (mutualism facilitation hypothesis; Richardson et al 2000b, Mitchell et al 2006, or if they suffer less from soil pathogens than the natives (Reinhart et al 2010, Callaway et al 2011. Recent research has shown that for several highly invasive exotic plants such effects are chemically mediated (e.g., Callaway et al 2008, Mangla et al 2008.…”

In their native range, invasive plants are held in check by negative soil-feedbacks

“…It suggests that these species are not dominant in their native range partially because they are held in check by negative soil-feedbacks. Bever (2002) and Callaway et al (2011) observed that negative feedbacks could override beneficial effects of native-range arbuscular mycorrhizal fungi. This may be why the invasive species in our study did not show any benefit from soil mutualists in native range soil inocula.…”

“…Negative soil feedbacks can enhance species coexistence due to a form of a Janzen-Conell effect (Bever et al 1997, Packer and Clay 2000, Petermann et al 2008, McCarthy-Neumann and Kobe 2010. Kulmatiski et al (2008) and Callaway et al (2011) suggested that missing plant-soil feedbacks may explain why some non-native plants become invasive and dominant in a new biogeographical range whereas others do not. The advantage of invasive species over native species in new ranges may, in addition, be due to negative soilfeedbacks affecting the native, but not the invasive plants (Klironomos 2002, van Grunsven et al 2007, although this effect may weaken over time in the new ranges as new enemies adjust to invasive species (Diez et al 2010).…”

Role and influence of soil microbial communities on plant invasion

“…The majority of the plants form the symbiotic association with AM fungi (Allen, 1991;Smith & Read, 2008), nitrogen fixing bacteria (Richardson et al, 2000;Ehrenfled, 2003) and with the wide range of other endophytes (Shipunov et al, 2008;Newcombe et al, 2009). Callaway et al (2011) studied the impact of soil biota of an invasive tree, Robinia pseudoacacia L., from native, expanded and invasive ranges on nodulation and the nitrogen fixation and found the absence of mutualist and nitrogen fixing organisms in the invaded and expanded soil. In contrast, R. pseudoacacia formed nodules with nitrogen fixing bacteria in the native soil.…”