THERMOPLAST · Adaptive plasticity meets unpredictability: how do organisms cope with changing environmental variability?

Adaptive plasticity meets unpredictability: how do organisms cope with changing environmental variability?

Species and populations tolerate a finite range of temperatures, the breadth of which is a critical determinant of their distribution and abundance. Natural populations can respond to changes in temperature in the short-term via non-genetic, ‘plastic’, mechanisms and over longer time periods by genetic adaptation. Both plastic and genetic responses to changes in the mean temperature are well understood. However, organismal responses to the variation and stochasticity in temperature that is inherent in natural environments are less known. Given that patterns of temperature variability are projected to become increasingly unpredictable in the near future, understanding how organisms will adapt to changing patterns of environmental variability is of vital importance because the previously adaptive responses of organisms to temperature change may be rendered ineffective. Thus, understanding responses to such changes in environmental variability requires detailed knowledge about how organisms can detect levels and predictability of variation, how they can respond to this through non-genetic, plastic mechanisms and if there is potential for such ‘plasticity’ to evolve given its specific costs and benefits. In this project, using the widespread clonally reproducing zooplankter Daphnia magna, I therefore investigated plastic, non-genetic changes in thermal tolerance, the ability to maintain basic body function at high temperature, in response to different patterns of temperature variability. The major aims of this project were: 1.) Investigate if temperature variability can cause a plastic response in thermal tolerance 2.) Are plastic shifts in thermal tolerance fixed or flexible and does this type of plasticity correspond to natural patterns of temperature variability? 3.) Is there genetic variation in thermal tolerance plasticity and does this carry a physiological cost?

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