A systematic review of phenotypic plasticity in marine invertebrate and plant systems.

Marine organisms provide some of the most important examples of phenotypic plasticity to date. We conducted a systematic review to cast a wide net through the literature to examine general patterns among marine taxa and to identify gaps in our knowledge. Unlike terrestrial systems, most studies of plasticity are on animals and fewer on plants and algae. For invertebrates, twice as many studies are on mobile than sessile species and for both animals and plants most species are benthic intertidal zone taxa. For invertebrates, morphological plasticity is most common, while chemical plasticity is most common among algae. For algae, as expected, predators (inducible defences) are the primary cue for triggering plasticity. Surprisingly, for invertebrates the abiotic environment is the most common trigger for plasticity. Inducible defences in invertebrates have received great attention and predominate for a few well-studied species, which can bias perceptions; but, their predominance overall is not supported by the full data set. We also identified important research needs, including the need for data on non-temperate zone taxa, planned experiments to directly test the role of habitat variability and the prevalence of plasticity. We also need information on the lag time for induction of plastic traits, which is critical for determining the adaptive value of phenotypic plasticity. Studies of early life stages and studies that link plasticity to mechanisms that produce phenotypes are critically needed, as are phylogenetic comparative studies that can be used to examine responses of organisms to both short- and long-term change.