Mechanisms and Evolution of Reproductive Plasticity

In the anthropocene, our collective actions as human race cause the world to change rapidly. To mitigate dramatic consequences on biodiversity it is vital that we understand the different ways how organisms can adapt to changing environments. Genetic changes, such as mutations, enable species to adapt and respond to long-lasting, slow environmental trends. With todays rapid pace of environmental changes, such adaptations may not be fast enough. However, nature has a different trick in her toolbox: For sudden variations in their surrounding environment, some species use non-genetic adaptations, such as phenotypic plasticity, to adapt more quickly during transient unfavourable environmental conditions. One example of a species making use of phenotypic plasticity is the brine shrimp Artemia living in environments with very high salinity. To deal with such extreme conditions, Artemia females have evolved the remarkable ability to switch between two ways of reproduction depending on their environment. When conditions are good, Artemia are ovoviviparous they give birth to live young. However, when times are bad, females stop producing live young and become oviparous - they produce offspring encased in a highly resistant shell. When conditions improve, the offspring hatch and start a new population. While there is little doubt that phenotypic plasticity helps populations to respond to short-term environmental changes, it is less clear how costly it is for organisms to keep this ability and enable long-term adaptation. For example, the genes that enable phenotypic plasticity may bear fitness costs, such as decreased reproductive output. If phenotypic plasticity involves such important fitness trade-offs, it is not clear how it can evolve in the first place and be maintained. The reproductive shift of Artemia can easily be triggered in the lab, which makes it an ideal trait to explore phenotypic plasticity. In this project, we will measure and compare gene expression patterns to explore the molecular mechanisms underlying Artemias reproductive plasticity. We will then determine the fitness costs and benefits of each reproductive mode, and use this to develop theoretical predictions about the ability of phenotypic plasticity as a trait to evolve in response to long-lasting environmental changes. Furthermore, we will compare reproductive plasticity across 6 different Artemia species, which will help us to better understand the genetic basis of phenotypic plasticity. With this, we hope to gain a better understanding of the adaptive potential of biological species given the current challenges.