Figure 1.

Map of the location of the study and the study ponds. Map of Sweden showing A) the location of the study region (square) and study ponds (black dots) in relation to geographic variation in anthropogenic acidification in 1990 and B) the study region with nine populations and their pond pHs (in brackets). The pond Nitta (*) was only used for environmental variation. (Source: Swedish Environmental Protection Agency: http://www.naturvardsverket.se/en/In-English/Start/State-of-the-environment/Acidification/.