Two new tropical Russula species associated with Quercus show evidence of diversification across the Isthmus of Panama

Abstract

Russula floriformis and R. symphoniae are described as two new sister species of Russula subsection Substriatinae from montane forest of Colombia and Panama and associated with Quercus and Oreomunnea trees. Very similar field environmental conditions and an ITS sequence similarity higher than 99% with only 3 different positions indicate that these species are closely related and nearly cryptic. Detailed observations of microscopic structures and analyses of more DNA loci revealed more morphological and molecular characters distinguishing collections of R. floriformis from Colombia and R. symphoniae from Panama. Spatial distribution and phylogenetic proximity of Russula species and their ectomycorrhizal host Quercus tree suggests their speciation as a result of migration, adaptation and climatic isolation across the Panama Isthmus of their host tree during the Pliocene and Pleistocene events. Then we hypothesize that this could be evidence of coevolution between Russula and Quercus. Analysis of publicly available ITS sequence data suggests that there are more locally adapted species of this lineage in Central and North America.