Genet size and distribution of Amanita muscaria in a suburban park, Dunedin, New Zealand

Amanita muscaria is a common ectomycorrhizal (ECM) fungus introduced to New Zealand. It most commonly forms associations with introduced host trees, but is also known to form ECM associations with native Nothofagus species. It may act as a "mycorrhizal weed" and could potentially have far-reaching consequences for the diversity of indigenous fungal taxa in New Zealand. Little is known about its population biology. By analysing the banding patterns produced from randomly amplified microsatellite (RAMS) primed polymerase chain reactions, we examined the genetic structure of an established population of A. muscaria in a park in Dunedin, New Zealand. The primer BDB(ACA)(5) was found to have a higher number of polymorphisms than the either of the primers DDB(CCA)(5) or DHB(CGA)(5), and it is possible that within any given area the number of genets detected might be greater, and the size of genets smaller, with the use of more primers. Within a 40 x 40 m area the population was found to comprise 28 genotypes, both small (< 6.0 m across) and large (> 6.0 m across). The distribution of genotypes showed no clear pattern of spatial segregation, indicating that single genotypes may comprise multiple ramets rather than contiguous genets. The presence of both small and large genets (or widely separated ramets) indicates that establishment through sexually derived basidiospores and through mycelial spread may play important roles in populations of A. muscaria such as the one studied. A. muscaria may employ a strategy combining attributes of C, S, and r-selected ecological strategies. Frequent disturbance at the site may mean that establishment by basidiospore plays a more important role than at other sites with low levels of disturbance.