Identifying the dominant drivers of fungal biogeographical patterns is an important question from both an ecological and ecosystem perspective. Although -omics approaches can increasingly provide unparalleled insight into the structure and function of complex microbial systems, unifying trends remain elusive, in part due to the hyper-diversity of terrestrial fungal communities. This lack of clear spatial patterns has partially contributed to the expectation that fungal community composition is governed largely by neutral processes (e.g., dispersal limitation), with environmental filtering and local adaptation having weak roles in structuring the functional capacity of fungal communities. Yet whether or not an organism survives in a given environment is largely dictated by its functional traits, not by its taxonomic identity, such that traits should more strongly capture biogeographic patterns. Here, we explore this question by taking a trait-based approach to identifying fungal biogeographical patterns, measuring the expression of >100 functional traits on 23 species of basidiomycete wood-decay fungi from across North America. For each if 37 isolates, we quantify the thermal and moisture niches, competitive ability, enzymatic potential, wood decomposition rate, and organic volatile production; and we explore the relationships among functional traits, phylogeny, and the climate conditions from where the fungi were collected.
Results/Conclusions
Our results demonstrate a clear functional trait trade-off between abiotic stress tolerance and competitive ability. Fungi with high thermal and moisture stress tolerances (wide niches) exhibited slower growth rates, lower temperature and moisture optima, and higher hyphal density, with PC1 explaining approximately 23% of the variation in this trade-off. In contrast, fungi with low abiotic stress tolerance exhibited high competitive ability, rapid hyphal extension rate, and higher thermal and moisture optima. More importantly, the magnitude of this dominance-tolerance trade-off is partially linked to the environmental conditions from where each fungus was collected (R2=0.31, p<0.001), leading to a predictive dominance-tolerance pattern at the continental scale. Phylogenetic analysis suggests that these relationships are due to a combination of environmental filtering along taxonomic lines in tandem with local adaption at the level of the individual. Finally, we show that this dominance-tolerance trade-off is correlated with fungal decomposition rate (R2=0.39, p=0.03), allowing us to translate these life-history patterns into functional outcomes. Collectively, this work contributes to our core understanding of the functional biogeography of wood-decay fungi.