The observed DDG is clearly hump-shaped for meso- and eutraphentic
species across all lake types, whereas oligotraphentic species have a
linear DDG in clear and intermediate lakes and are not present in turbid
lakes (Figure 2a). The potential depth diversity gradient (DDG) is
hump-shaped across all lake types and species groups (Figure 2b). By
comparing the observed species richness with the potential species
richness for all lake types and species groups (Figure 2c), we find the
highest correlations within turbid lakes for meso- (R = 0.71) and
eutraphentic species (R = 0.65). Within those lakes, the observed
species richness is smaller than the potential species richness (below
the line) almost in all lakes and species groups. Intermediate and clear
lakes, also contain lakes where observed species richness is higher than
the potential species richness (above the line). In intermediate lakes
in all species groups observed species richness and potential species
richness correlate slightly positive (Figure 2c). In clear lakes,
potential species richness correlates negatively with observed species
richness for oligo- and mesotraphentic species. The DDG for all
individual lakes can be found in the Appendix 2 as in Supporting
Information (Figures S2.1-2.10).