Deadwood priority and colonization

Quantification of ecological community assembly processes, especially in species-rich systems, remains challenging. While the role of environmental filtering is well acknowledged, understanding how biotic filtering shapes communities is less explored. We investigated the relative roles of these processes in colonization success and community succession of wood-inhabiting fungi. In a field experiment, we simulated natural colonization by inoculating nine fungal species across habitat patches with varying abiotic and biotic conditions and tracked the colonization success of inoculated species and resident community succession via DNA metabarcoding. All nine species successfully colonized the habitat patches but the factors affecting colonization success varied. While four species were primarily affected by abiotic conditions, three were additionally influenced by resident fungal communities. Moreover, we found that the succession of resident fungal communities was shaped by immigration of inoculated species in addition to abiotic environmental conditions, indicative of priority effects where the species immigration history affects species interactions and community dynamics. The strength and type of priority effects depended on the identity of inoculated species. Our study demonstrates the joint impact of abiotic and biotic filtering on structuring species-rich communities, emphasizing the importance of species-level responses in understanding community-level changes. Furthermore, it advances our understanding of priority effects in species-rich systems by experimentally quantifying the role of immigrating species in community succession.