Life‐history traits and phylogeny structure taxon‐specific species–substrate relationships in deadwood

To understand the structuring of species assemblages, integrating life‐history traits and evolutionary heritage in analyses is vital. This allows the assessment of a mechanistic link between species and their environment. Deadwood systems are vital for nutrient cycling and biodiversity support, governed by complex intra‐ and inter‐specific fungal and insect species interactions. However, trait‐ and phylogeny‐based approaches to studying species–substrate and species‐to‐species relationships in deadwood community assembly have received little attention. We link life‐history traits and phylogeny to species‐substrate and species‐to‐species relationships of saproxylic beetles and fungi in 256 Scots pine Pinus sylvestris deadwood substrates derived from a forest experiment in central Sweden. We test how the characteristics of deadwood substrates shape beetle and fungal assemblages through their ecological traits (body size, feeding guild and primary lifestyle) and phylogenetic relatedness. We compare substrates that differ in posture (standing or lying) and origin (machine‐created or burned). Trait composition differed among substrate types for both taxa, but only fungi revealed a phylogenetic relationship with substrate type. Lying substrates were characterized by smaller bodied and fungivore beetles while standing substrates supported larger beetle species. Lichenized fungi were more prevalent on machine‐created than burned substrates. After accounting for substrate type, traits and phylogenetic signal, we found one species‐to‐species association between beetles and numerous fungus–fungus associations. Differences in trait composition and phylogeny, and lack of detected species‐to‐species associations, suggest that life history traits and phylogeny explain community assembly patterns in deadwood, with inter‐specific relationships playing a minimal role for beetles but a larger role for fungi at later stages of wood decay. Together, these findings suggest that community assembly in deadwood is shaped by different processes in beetles and fungi, emphasizing the value of integrating traits and phylogeny when studying saproxylic communities.