Rapid adaptation of a rotifer prey population to non-consumptive predation pressures

To test the hypothesis that non-consumptive predation pressures favor genotypes that have higher equilibrium densities or mictic ratios, we expose replicate populations of the rotifer Brachionus angularis to low (LK) and high (HK) concentrations of predator Asplanchna kairomones. Over 75 days (25 asexual generations) of selection, LK-treated populations have higher equilibrium densities and lower mictic ratios than the control populations. The opposite occurs for HK-treated populations. These results suggest that compared with the control, LK and HK select for genotypes with higher equilibrium densities and mictic ratios, respectively. Common garden bioassays reveal that in the absence of Asplanchna kairomones, populations with an LK selection history have a higher average intrinsic rate of population increase, and those with an HK selection history have a higher average mictic ratio than those with the control selection history, which suggest that adaptations to LK and HK increase average intrinsic rate of population increase and mictic ratio of prey populations, respectively. Increased intrinsic rate of population increase and mictic ratio can serve as strategies of offsetting mortality from predation and escaping the predator, and thus enable prey to survive low and high predation pressures, respectively.

Automated summary

To test the hypothesis that non-consumptive predation pressures favor genotypes with higher equilibrium densities or mictic ratios, populations of rotifer Brachionus angularis were exposed to different concentrations of predator Asplanchna kairomones. The results showed that low concentrations selected for higher equilibrium densities while high concentrations selected for higher mictic ratios. Additionally, common garden bioassays revealed that populations with low concentration selection history had higher intrinsic rate of population increase, and populations with high concentration selection history had higher mictic ratios.