Influence of macroclimate and local conservation measures on taxonomic, functional, and phylogenetic diversities of saproxylic beetles and wood-inhabiting fungi

Wood-inhabiting fungi and saproxylic beetles are threatened by habitat degradation. Our understanding of the importance of macroclimate and local factors determining their taxonomic diversity has increased, but determinants of functional and phylogenetic diversity are poorly understood. We investigated assemblages of wood-inhabiting fungi and saproxylic beetles along a 1000 m elevational gradient of a temperate low mountain range. We (i) tested the relative importance of macroclimate (i.e. elevation) and local variables (microclimate, i.e. canopy closure, amount and diversity of dead wood) in determining observed and rarefied diversities and (ii) explored whether determinants of observed functional and phylogenetic diversities match those of taxonomic diversity. For both taxa, the determinants of observed phylogenetic and functional diversities largely matched those of taxonomic diversity. The diversity of wood-inhabiting fungi was predominantly determined by local variables, whereas that of saproxylic beetles was determined by both local variables and elevation. Taxonomic and phylogenetic diversities of saproxylic beetles decreased with increasing elevation, but standardized functional richness and entropy of both groups increased with increasing elevation. Diversities of wood-inhabiting fungi increased with canopy closure, while diversities of saproxylic beetles decreased with increasing canopy closure. Microclimate and dead-wood amount and diversity affected the observed and rarefied diversity of both saproxylic taxa, which justifies conservation actions that focus on attributes of dead wood and canopy cover. The contrasting responses of fungi and beetles highlight the need for amounts of diverse dead wood in the various microclimates to preserve functional and phylogenetic diversities of saproxylic organisms.