Differential Patterns in β‐Diversity Among Plants, Soil Fungi and Insects Across Two Subarctic Landscapes

Aim Whether different organism groups show similar β‐diversity across space has major implications for biotic interactions. Nonetheless, apparent β‐diversity can also be caused by mere sampling, calling for an explicit separation of random vs. non‐random contributions to compositional differences across samples. We compared β‐diversity patterns of three kingdoms across the same set of 40 sites, while explicitly accounting for sampling effects. Location Two mountainous tundra landscapes (~14 km 2 each) located 350 km apart: the Kilpisjärvi region (north‐western Finland; 20 sampling sites centred on 69°03′N, 20°51′ E) and the western Varanger Peninsula (north‐eastern Norway; 20 sampling sites centred on 70°31′N, 29°05′ E). Time Period 2020 (fungi, arthropods); 2021 (arthropods); 2022 (vascular plants). Major Taxa Studied Flying and ground‐dwelling arthropods, vascular plants, soil fungi. Methods For each taxonomic group, we examined the increase in β‐diversity (i.e., pairwise community dissimilarity) with increasing distance. To account for sampling effects, we subsampled abundance data to equal sample coverage and presence–absence data to equal species richness. To test the significance of the rate of distance decay, we compared observed patterns to permuted patterns expected under random placement. Results Overall, we find larger differences between local communities than are attributable to mere sampling. The level of β‐diversity differed among organism groups. Further distances were associated with a larger rate of dissimilarity in plants and fungi than in arthropods, and this difference persisted even after standardizing samples to equal coverage. Main Conclusions Our findings suggest that at the landscape level, different organism groups will be differentially impacted by physical distances. Pairwise community similarity will be strongly patterned by distance even in vagile groups, such as fungi and flying insects. Differential rates of species turnover suggest that different species will meet in different locations, causing strong turnover in pairwise species interactions.