Genetic diversity of Pisolithus in New Zealand indicates multiple long-distance dispersal from Australia

Pisolithus is a common ectomycorrhizal (EcM) associate of prostrate kanuka Kunzea ericoides var. microflora (Myrtaceae) in New Zealand geothermal areas. Here, we report the genetic diversity and phylogeny of Pisolithus and interpret the results in relation to the origin of this fungus in New Zealand. We determined the genetic variation of Pisolithus on the basis of ITS gene sequences and spore morphology. We identified three Pisolithus species in New Zealand, each matching Australian species associated with eucalypts and acacias. All three species co-occurred locally in thermal areas, with two species sometimes colonizing root tips in the same soil volume, indicating co-occurrence of species on a smaller scale. We propose that Pisolithus fungi were introduced to New Zealand from Australia by trans-Tasman airflow during recent geological times. The success of this long-distance dispersal of EcM fungi may be related to the capacity of kanuka to act as a 'nurse plant' for wind-blown spores.