Journal Article
Subtropical streams harbour higher genus richness and lower abundance of insects compared to boreal streams, but scale matters
Jani Heino; Adriano S. Melo; Jenny Jyrkänkallio‐Mikkola; Danielle Katharine Petsch; Victor Satoru Saito; Kimmo T. Tolonen; Luis Mauricio Bini; Victor Lemes Landeiro; Thiago Sanna Freire Silva; Virpi Pajunen; Janne Soininen; Tadeu Siqueira
Journal of Biogeography · Vol. 45, Issue 9 · pp. 1983-1993 · 2018
Abstract
Aim Biological diversity typically varies between climatically different regions, and regions closer to the equator often support higher numbers of taxa than those closer to the poles. However, these trends have been assessed for a few organism groups, and the existing studies have rarely been based on extensive identical surveys in different climatic regions. Location We conducted standardized surveys of wadeable streams in a boreal (western Finland) and a subtropical (south‐eastern Brazil) region, sampling insects identically from 100 streams in each region and measuring the same environmental variables in both regions. Taxon Aquatic insects. Methods Comparisons were made at the scales of local stream sites, drainage basins and entire regions. We standardized the spatial extent of the study areas by resampling regional richness based on subsets of sites with similar extents. We examined differences in genus richness and assemblage abundance patterns between the regions using graphical and statistical modelling approaches. Results We found that while genus accumulation and rank‐abundance curves were relatively similar at the regional scale between Finland and Brazil, regional genus richness was higher in the latter but regional abundance much higher in the former region. These regional patterns for richness and abundance were reproduced by basin and local genus richness that were higher in Brazil than in Finland, and assemblage abundance that was much higher in Finland than in Brazil. The magnitude of the difference in genus richness between Brazil and Finland tended to increase from local through basin to regional scales. Main conclusions Our findings suggest that factors related to evolutionary diversification might explain differences in genus richness between these two climatically different regions, whereas higher nutrient concentrations of stream waters might explain the higher abundance of insects in Finland than in Brazil.