Seasonal and spatial variation of stream macroinvertebrate taxonomic and functional diversity across three boreal regions

Abstract

1. The exploration of biodiversity has predominantly been based on taxonomicmeasures, whereas functional diversity, a key component of biodiversity, is compar-atively understudied. Therefore, studies simultaneously investigating patterns oftaxonomic and functional diversity change in biological communities are of increas-ing interest. 2. We collated high-resolution macroinvertebrate and environmental data from 70 boreal headwater stream sites across three European countries (Germany,Finland, Sweden) to (1) investigate seasonal variation in taxonomic diversity, func-tional diversity, and redundancy, and (2) identify their potential drivers of spatialand seasonal variation. 3. Seasonal changes in boreal macroinvertebrate taxonomic diversity were decoupledfrom changes in functional diversity. Seasonal shifts in environmental conditions,including acidity and nutrient variability, drove fluctuations in taxonomic diversitywhich were far more pronounced than those of functional diversity. 4. Seasonal shifts in environmental conditions including variation in the quantity, quality, and state of organic carbon (dissolved vs particulate) facilitate an exchange of taxa, leading to taxonomically unique communities that exploit the pool of available seasonal resources. Thus, similar levels of functional diversity across seasons—evenas taxonomic diversity changes—suggest limited differences in interspecific changesin community function, potentially indicating functional resistance rooted inredundancy. 5. We highlight the spatial and seasonal discrepancies of freshwater communities,emphasising the need for both taxonomic and functional diversity patterns to beassessed in future biodiversity monitoring programmes. biological traits, community ecology, environmental drivers, freshwater ecosystems, functionalredundancy, inter-regional analysis, multivariate statistics, organic carbon

Seasonal and spatial variation of stream macroinvertebrate taxonomic and functional diversity across three boreal regions