Paxillus is an ectomycorrhizal genus with introduced trees. Paxillus involutus was recently shown to be a species complex. See this record for more info ...
https://inaturalist.nz/observations/1291556

So far in NZ we have confirmed P. cuprinus and P. ammoniavirescens, P. involutus and it is likely that we have P. obscurosporus (it is common in Australia). These are all commonly associated with introduced street/park trees. The real Paxillus involutus is not said to be associated with trees in urban environments in its home range, but we do have confirmed records. In general P. cuprinus appears to be associated with birch, alder and lime whereas P. ammoniavirescens favours oaks, poplars and conifers. P. involutus has been recorded with birch. Unfortunately P. obscurosporus is not so specific.

Posted on April 11, 2015 06:44 AM by cooperj