Does freshwater macroinvertebrate diversity along a pH‐gradient reflect adaptation to low pH?

• Published in: Freshwater Biology
• Main Authors: PETRIN, ZLATKO, LAUDON, HJALMAR, MALMQVIST, BJÖRN
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2007
• Subjects: Northern Sweden
• Online Access: http://dx.doi.org/10.1111/j.1365-2427.2007.01845.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1365-2427.2007.01845.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2427.2007.01845.x

Summary 1. The impacts of anthropogenic surface water acidification are much better known than those of natural acidity. Recent studies have indicated biodiversity is not degraded and species composition unaltered in naturally acidic compared to circumneutral watercourses. 2. Here, we use a geographically extensive dataset comprising sites in more than 200 Swedish streams to test whether the lack of effects on macroinvertebrate species diversity is due to exaptation and adaptation to natural acidity. 3. To this end, we modelled pH associated with spring flood episodes, which inflict the most challenging hydrochemical conditions to the biota. We compared taxonomic richness and species composition along the modelled pH gradient in northern Sweden, where acidity is largely natural, with southern Sweden, a region influenced by significant anthropogenic acidification. 4. We found Plecoptera richness did not respond to varying pH either in northern or southern Sweden. Ephemeroptera richness was sensitive to pH in both regions, while that of Trichoptera increased with increasing pH in southern Sweden, but decreased in the north. The taxonomic composition of Plecoptera changed along the pH gradient in both regions, whereas that of Ephemeroptera and Trichoptera changed more strongly with pH in southern Sweden. 5. Our results support the hypothesis that stream invertebrates are able to tolerate low pH through exaptation or adaptation, but that this capability varies among taxonomic groups.