Dating divergence of Polystigma and other Sordariomycetes

Studies on the evolutionary history of ascomycetes in terms of time scale will help to understand historical patterns that shape their biodiversity. Until now most of dating studies of ascomycetes have focused on major events in fungal evolution but not on divergence events within smaller groups of fungi e.g. within Sordariomycetes. We used molecular dating to estimate the time of separation of Polystigma from other groups of Sordariomycetes with a Bayesian approach using a relaxed clock model and secondary calibration. Sequences from ITS region and SSU gene of rDNA were used for this purpose. We inferred evolutionary dates in Sordariomycetes particularly for Xylariomycetidae. Dating analyses showed that Polystigma diverged from Xylariales approximately 90 Million years ago in the late Cretaceous in which most other diversification events occurred. Our results also suggest that Polystigma amygdalinum and P. rubrum diverged in early Eocene concurrently with the divergence of their hosts, also providing a base for speculation on the location of evolution of these pathogens.