I did a half-day of internet sleuthing for rhizobia-symbiosis in exotic nitrogen-fixers and from that I ascertained that exotics will bond with rhizobia but won't fix the maximum amount of nitrogen.
Here are two quotes that may be interesting to some:
- SourceThere are many cases of introduced woody legumes nodulating abundantly (and presumably also invading) without rhizobium inoculation when introduced to new habitats (Allen & Allen, 1981). De Faria et al. (1989) document this for Australian Acacia spp., Cytisus spp., Leucaena spp. and Robinia spp. in Brazil. The lack of nodulation after in- troduction appears to be the exception rather than the rule with woody legumes. This suggests that either effective rhizobia for woody species are widely distributed between continents, and}or that many legume trees can be nodulated by a wide range of strains of rhizobia.
There are, however, isolated cases of legumes failing to nodulate following introduction. Halliday & Somasegaran (1983) note that Leucaena leucocephala failed when introduced to Australia and eastern Colombia until inoculated with effective Rhizobium strains. In a study of seven sites on Jamaica, Zimpfer, Smyth & Dawson (1997) found rhizobia able to nodulate L. leucocephala at only one site.
Rhizobium Research Laboratory FAQ - further reading.Specificity in nodulation: Specificity in nodulation can affect benefits to inoculation for closely related species. As example rhizobia nodulating white clover will also nodulate subterranean clover, but will not fix nitrogen with this host.
What are the qualities of a good inoculant strain? Able to compete with less effective indigenous soil rhizobia, and so form most of the nodules produced.
Competition: Because each plant only forms a finite number of nodules, the ability of indigenous rhizobia to form nodules will limit the number produced by inoculant strains. This can limit nitrogen fixation, and in the American Midwest can mean that the plant derives less than 50% of its nitrogen from symbiosis. While this is generally seen as a competition between inoculant and indigenous rhizobia, various factors play a role. These include the great numerical superiority of the indigenous rhizobia in the bulk soil, and the limited mobility of the inoculant rhizobia. It is also assumed that indigenous rhizobia are also better adapted to soil conditions.