Transatlantic disjunctions in fleshy fungi III: Gymnopus confluens

Phylogeographic data indicate that DNA differences consistently exist between the North American and European allopatric populations of Gymnopus confluens. Conversely, pairing experiments show that collections from both populations were sexually compatible in vitro and detailed morphological examinations of numerous fresh and dried basidiomata do not produce qualitative differences. Percent ITS sequence divergence between Europe and North American collections of G. confluens was 3.25%. Species delineation metrics including Rosenberg’s PAB statistic, PID metrics, RRD (randomly distributed) and PTP (Poisson Tree Processes) gave mixed indications that North American and European populations were distinct at species rank. The North American populations are described as Gymnopus confluens subsp. campanulatus (Peck) R.H. Petersen.