Figure 2.

Abundance of three Daphnia pulex populations after exposure to either no salt (control), or two elevated concentrations of either NaCl, CaCl₂ or MgCl₂. The naive population had no prior history of exposure to high salt concentrations. In a prior experiment, population 1 (P1) evolved a tolerance to 833 µS cm⁻¹ (250 mg Cl⁻ l⁻¹) of NaCl and population 2 (P2) evolved a tolerance to 2662 µS cm⁻¹ (1000 mg Cl⁻ l⁻¹) of NaCl. Abundances were quantified on days 21, 44 and 60.