LAUSR

Understanding the drivers of community structure is an important topic in ecology. We examined whether different species trait groups of stream diatoms (ecological guilds and specialization groups) show divergent responses to spatial and environmental factors in a subarctic drainage basin. We used local- and catchment-scale environmental and spatial variables in redundancy analysis and variation partitioning to examine community structuring. Local and catchment conditions and spatial variables affected diatom community structure with different relative importance. Local-scale environmental variables explained most of the variation in the low-profile and motile guilds, whereas local and spatial variables explained the same amount of the variation in the high-profile guild. The variations in the planktic guild and the specialist species were best explained by spatial variables, and catchment variables explained most variation only in generalist species. Our study showed that diatom communities in subarctic streams are a result of both environmental filtering and spatial processes. Our findings also suggested that dividing whole community into different groups by species traits can increase understanding of metacommunity organization.