On species richness estimates, climate change and host shifts in wood-inhabiting fungi

In a recent paper in Fungal Ecology, Gange et al. (2011) concluded that the wood-inhabiting basidiomycote Auricularia auricula-judae has widened its host range and changed its phenology since 1980 in the study area in southern England, most likely as a response to global warming. At the same time the authors report, that the number of macrofungi fruiting on Sambucus nigra, the most common host of A. auricula-judae, has tripled, while another fungus preferring S. nigra, Hyphodontia sambuci, has remained constant. We challenge these conclusions and point out that the reported changes may just as well reflect a change in foraying quality over time. To support this statement we present an analysis of data from an ongoing mapping project in Denmark. We show that species accumulation curves and species richness estimators are highly context specific, and that random sampling by amateurs and specialists provide very different representations of actual patterns in nature. We show that the three species analysed by Gange et al. (2011) behave very differently in this context, and are hence not straight forward to compare over time based on data from amateur forays. We conclude that more rigorous standardising procedures are needed to reach sound scientific conclusion based on analyses of foray data over time.