Effects of Heat Stressors on Phenotypic Plasticity and Thermal Tolerance in the Tigriopus californicus System

Adaptations, both evolutionary and physiological, are essential to the continuation of species across generations within changing environments. Plasticity, a key mechanism of adaptation, enables rapid phenotypic changes within a single generation or across short generational timescales. We sought to understand the potential for phenotypic plasticity of temperature tolerance within one generation using the small marine copepod model system Tigriopus californicus. Previous work in the T. californicus system has not examined the capacity for change in temperature tolerance within one generation including the difference in resulting temperature tolerances along a temperature cline. To understand the potential for an increased temperature tolerance across the cline due to early exposure to thermal stress, maternal T. californicus individuals with egg sacs underwent a heat stressor, and the offspring of these maternal copepods underwent the same heat stressor to determine whether the copepods developed tolerance to higher temperatures. An increase in temperature tolerance was seen across one generation in some populations studied, while others showed no increase or a decrease. No clear pattern emerged along the cline. This work is applicable to understanding the capacity for plasticity in the T. californicus system in the context of warming climates, and the results can be applied to other species using T. californicus as a model system.