Facultative mycorrhizal associations promote plant naturalization worldwide

Abstract

Mycorrhizal symbiosis has received relatively little attention as a mechanism explaining plant naturalizations at a global scale. Here, we combined data on vascular plant species occurrences in over 840 mainland and island regions from the Global Naturalized Alien Flora (GloNAF) database with up-to-date databases of mycorrhizal associations. We tested whether the mycorrhizal type (arbuscular, AM; ectomycorrhizal, ECM; and non-mycorrhizal, NM) and status (facultative and obligate) were associated with two measures of naturalization success, (1) naturalization incidence (reflecting the ability to naturalize, and expressed as whether or not a plant species is recorded as naturalized anywhere in the world) and (2) naturalization extent (expressed as the number of GloNAF regions where the species occurs). In total, we found information on mycorrhizal type and status for 3211 naturalized plant species and 4200 non-naturalized plant species. Mycorrhizal plant species, both AM and ECM, were more likely to be naturalized and naturalized to a greater extent than NM plants. The effect of being an AM species was always stronger, with AM species having a greater naturalization extent than ECM species. Being the same mycorrhizal type or status, annual species were generally more likely to be naturalized than perennials. Species with facultative mycorrhizal associations were more successful than those with obligate mycorrhizal associations, but both groups tended to have a greater chance of being naturalized than NM species. These results indicate that being NM is generally less favorable for naturalization. Overall, our results confirm, at the global scale, those of regional studies that facultative association with AM provides plant species with a naturalization advantage. For the first time, we have shown that being mycorrhizal contributes not only to the size of the naturalized range, reflecting the ability to spread, but also to the ability to become naturalized in the first instance.

Below‐ and aboveground traits explain local abundance, and regional, continental and global occurrence frequencies of grassland plants

“…On the last line are the R 2 values for models with all 10 traits used as predictors. results of a recent global analysis (Pyšek et al 2019), although this effect was not statistically significant. In return for carbon, mycorrhizal fungi provide plants with nutrients and improve their resistance against various stresses.…”

How and where do disturbances promote the establishment of nonnative mycorrhizal plants at high elevations?

“…The ability of invasive plants to disperse and establish in new habitats has been related to their mycorrhizal traits: plant mycorrhizal type, mainly focusing on AM, ectomycorrhizal (ECM), or nonmycorrhizal (NM) plants, whilst plant mycorrhizal status focuses on obligately mycorrhizal (OM) and facultatively mycorrhizal (FM) plants (Pyšek et al ., 2019). Plants of different mycorrhizal types differ in the symbiotic fungal taxa involved which dictates the nature and functionality of the association, whereas the plant mycorrhizal status informs about the frequency of the association.…”

“…Besides, a recent global assessment of the mycorrhizal traits of nonnative plant species suggests that being AM or ECM, and in particular, having a facultative status, i.e. forming the symbiosis with AM fungi optionally, leads more often to successful naturalizations (Pyšek et al ., 2019). While the study of plant naturalizations concerning plant mycorrhizal traits does not include any analysis along elevational gradients, Clavel et al .…”

Evidence for Elton's diversity–invasibility hypothesis from belowground

“…Second, if plant diversity dilutes the prevalence of mutualists, species‐rich communities will be better able to resist alien plants. Third, if alien plants miss their mutualists (Mitchell et al 2006) or are not tightly associated with mutualists (Pyšek et al 2019), plant diversity will not affect resistance to alien plants. Given the contrasting predictions, empirical tests are necessary to test whether and how soil microbes contribute to the diversity–invasibility relationship.…”