Hidden diversity in the non-caryophyllaceous plant-parasitic members of Microbotryum (Pucciniomycotina: Microbotryales)

Members of the fungal genus Microbotryum are well-known parasites on eudicotyledonous plant hosts. However, recent studies focused exclusively on Microbotryum species being parasites in the anthers of Caryophyllaceae in which strong host-specificity was confirmed by molecular analyses. Consequently, species numbers have risen considerably as multi-host parasites were split up in so-called cryptic species. We subjected three non-caryophyllaceous Microbotryum groups to molecular phylogenetic analyses to see whether we would confirm multi-host morphospecies or if host-specific cryptic species in these selected groups could be revealed as welt (i.e. a group of non-caryophyllaceous anther smuts, parasites on different Fallopia species, and parasites on Polygonum bistorta and Polygonum viviparum). We applied a multiple analysis strategy to correct for varying alignment effects on a two-locus dataset (ITS and LSU rDNA). The results obtained by the different approaches are uniform; high host-specificity exists in the non-caryophyllaceous anther smuts, but overlapping host ranges occur in the parasites of Fallopia species. Results for the parasites of Polygonum are similar, with Microbotryum bistortarum being separated into three lineages and M. marginale forming a lineage on P. bistorta which apparently is conspecific with M. bistortarum p.p. Our study shows that phylogenetic patterns within Microbotryum are much more complicated than deduced from morphological observations alone. Even though Microbotryum species are highly host-specific, it is impossible to identify species based solely on host taxa affiliation. Species status is reinstated for the anther smut on Salvia pratensis.