Interactive effects of immediate and ancestral salt stress on fitness in duckweed

We took a demographic approach to examine whether ancestral exposure to salt stress affects the ability of duckweed offspring to tolerate immediate exposure to the same stress. Methodology We placed three consecutive clonal generations of duckweed in an environment with 2 g L-1 NaCl (non-lethal salt stress) or 0 g L-1 NaCl (control), followed by an additional 0-3 generations in the control environment to vary the presence and schedule of ancestral stress.

After these treatments, we used the offspring produced as focal plants for the experiment. Half were placed into the salt-stress environment, and half were placed in control conditions, and focal plants were tracked longitudinally. Pivotal Results Immediate stress decreased fitness, due to a slowing of reproduction, suggesting a cost of stress tolerance.

The effects of ancestral stress, and the interaction of immediate and ancestral stress, were more complex. Specifically, recent ancestral stress induced plants to produce offspring more quickly, but with the potential cost of lowered offspring quality. Conclusions Our results amplify findings that responses to, and fitness consequences of, current stressors can be contingent on past exposure.

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