What does not kill you can make you stronger: Variation in plasticity in response to early temporally heterogeneous hydrological experience

Temporally heterogeneous environments may drive rapid and continuous plastic responses, leading to highly variable plasticity in traits. However, direct experimental evidence for such meta-plasticity due to environmental heterogeneity is rare. Our objective was to investigate the effects of early experience with temporally heterogeneous water availability on the subsequent plasticity of plant species in response to water conditions. We subjected eight plant species from three habitats, four exotic and four native to North America, to initial exposure to either a first round of alternating drought and inundation treatment (E_het, temporally heterogeneous experience) or a consistently moderate water supply (E_hom, homogeneous experience), and to a second round of drought, moderate watering or inundation treatments. Afterwards the performance in a series of traits of these species, after the first and second rounds of treatments, was measured. Compared with E_hom, E_het increased final mean total mass of all species considered together but did not affect mean mortality. E_het relative to E_hom, decreased the initial total mass of native species as a group, but increased the mass of exotic species or species from hydric habitats; E_het also increased the late growth of natives, but did not for exotics, and increased the late growth of mesic species more than xeric and hydric species. Our results suggest that previous exposure to temporal heterogeneity in water supply may be not beneficial immediately, but can be beneficial for plant growth and response to water stress later in a plant's lifetime. Heterogeneous experiences may not necessarily enhance the degree of plasticity but may improve the expression of plasticity in terms of better performance later, effects of which differ for different groups of species, suggesting species-specific strategies for dealing with fluctuating abiotic environments. Synthesis. Previous temporally heterogeneous experience can benefits plant growth later in life though modulating the expression of plasticity, leading to adaptive meta-plasticity. Studies of meta-plasticity may improve our understanding not only on the importance of variable plasticity in relation to how plants cope with environmental challenges but also on the costs versus benefits of plastic responses and its limits over the long term.