MEPS 634:199-211 (2020)  -  DOI: https://doi.org/10.3354/meps13207

ABSTRACT: Phenotypic plasticity has the potential to influence environmental adaptation on extremely short evolutionary timescales. Transgenerational plasticity (TGP) allows parents to provision their offspring for rapid environmental shifts in as little as one generation. We hypothesized that organisms that produce multiple generations of offspring each year use TGP to maximize their fitness under predictable fluctuations in seasonal environments. Using the direct-developing bivoltine eelgrass sea hare Phyllaplysia taylori as a test case, we examined the impacts of seasonal thermal variation (i.e. average temperature and acute heat stress) on physiological tolerance, maternal provisioning, and developmental plasticity across multiple generations. In the laboratory, we acclimated seasonally acclimatized adults from successive generations at 13, 17, and 21°C in order to assess plasticity of thermal tolerance limits. We also examined the effects of thermal acclimation and heat stress on reproductive output within a single generation in order to characterize TGP. Physiological plasticity, including but not limited to TGP, successfully maintained the viability of offspring under 2 seasonal conditions regularly experienced in the wild, despite differences in the density of offspring per clutch and large individual differences in offspring numbers under these conditions. These results indicate that warmer conditions (21°C) disrupt current patterns of plasticity and warrant further investigation of the long-term effects of chronic stress on TGP under climate change.

KEY WORDS: Phyllaplysia taylori · Physiological plasticity · Seasonal variation · Estuarine invertebrate · Thermal tolerance