Abstract -  Phenotypic plasticity is an important adaptation for organisms that live under fluctuating environmental conditions. However, investment in phenotypic plasticity may require complex molecular and physiological demands, potentially leading to trade-offs. Under sexual selection, different strategies can lead to the same fitness outcomes, allowing for the diversification of phenotypic plasticity. While plasticity can be exhibited at different life stages, the extent to which animals rely more on plasticity before or after maturity is unknown. For my PhD, I used a series of laboratory experiments to test how different environmental conditions affect phenotypic plasticity in guppies (Poecilia reticulata), a species under strong sexual selection. For chapters 1 and 2, I explored the effects of early-life food restriction on guppy life-history traits under two temperatures. I found that guppies can maintain a compensatory growth response after diet restriction even under high temperatures. However, patterns of size and time at maturation were sex specific. My results also showed that the combined effect of high temperature and diet restriction early in life stunted male size, persisting up to eight months after exposure to the treatment. In chapter 3, I conducted an experiment focusing on the effects of early-life social competition on developmental and sexual traits. I found that developing in a population of higher quality males did not affect either developmental or sexual traits in male guppies. Finally, in chapter 4, I explored the behavioural plasticity responses of adult guppies to an immune challenge. I found that an immune challenge did not affect anti-predatory responses; however, fish showed pronounced sexual differences in behaviour. Taken altogether, my results show that environmental conditions during guppy development affect only a limited group of traits, highlighting a possible resilience of guppies in maintaining traits at an optimal level. Although the overall phenotypic response appears restricted, the functional significance of the affected traits indicates that developmental conditions can still have meaningful impacts on individual fitness and population dynamics.

Biography - I am a Brazilian biologist and science educator. I obtained Bachelor of Science and Bachelor of Education degrees in Biological Sciences from the University of São Paulo (Brazil) in 2017. After that, I completed a master’s degree at the University of Campinas (Brazil), where I worked on the disease ecology of direct-developing amphibians in the Atlantic Rainforest. Since 2022, I have been pursuing a PhD at ANU, where my research focuses on sexual selection and environmental change. Throughout my academic career, I have also been involved in science education and teaching, particularly as a science ambassador for the game company Arludo and as an author of science and biology textbooks.