Diaptomid species richness and candidate correlates. A. Species richness per ecoregion. The remaining scatterplots indicate the relationship between species richness and candidate correlates, namely area (B), altitude (C), annual mean temperature (D), maximum temperature of warmest month (E), minimum temperature of the coldest month (F), annual precipitation (G), precipitation of driest month (H), and precipitation of wettest month (I). See text for details, and also Additional file 1: Table S2 for average climatic raw data.