Neurological adaptation and ecological specialisation

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We live amidst a cacophony of sensory information. It is the job of the brain to make sense of the environment we live in. It must extract the most relevant cues and combine this information with memories of past experiences to trigger appropriate behavioural responses. For animals living in different environments the most reliable sensory information may come from different sources, the experiences they have may vary, and what passes as appropriate behaviour can be radically different. The brain must therefore evolve to meet the demands of a changing environment. My research asks how brains accommodate adaptive change, how these changes are brought about, and why one evolutionary solution is favoured over another. For over 150 years biologists have studied mimetic butterflies to gain insights into the evolutionary process. Mimicry evolves when distantly related species converge on the same colour pattern to warn predators that they are toxic and to be avoided. This has dramatic knock-on effects, driving changes in habitat preference, sensory environment, foraging and reproductive behaviour. In many cases it results in butterflies that evolved to look the same also behaving in similar ways and occupying similar habitats. This makes them an ideal system to study how brains function and evolve because they are behaviourally diverse and the same behaviours have evolved multiple times.My project leverages these features to explore how brain structure changes as species diverge into different environments. I will measure the size of distinct components of the brain that have different functions, for example in vision, olfaction or memory. Changes in their relative size imply a change in the importance of that function. By comparing brains of different species I can therefore identify differences in their structure that reflect adaptations to the particular demands of a species' environment. I will then ask how these changes occur: are they are the result of genetic changes or flexibility in the way the brain develops? And how do changes at the cellular level alter the way the brain processes and stores information? Understanding how brains evolve is central to understanding the diverse range of behaviour observed in the animal kingdom, a major axis of biodiversity. It can also tell us how quickly animals are able to change their behaviour to respond to rapid environmental change, and whether this requires selection for genetically-encoded adaptations, or if it can be facilitated by flexibility in the way brains and behaviour develop. Evolutionary comparisons also provide insightful models for general problems in understanding brain function. For example, what types of cells contribute to changes in brain size? How is brain development controlled? And how do different brain cells connect and communicate with one another? This can tell us about our own biology, and the origin of disorders caused by disruption of these developmental processes.I will tackle these questions by homing in on specific changes in the way species perceive and remember information about their environment. For example, I have previously shown that one brain region, called the mushroom body, has trebled in size in passion-vine butterflies. The mushroom bodies are implicated in learning and memory, and this explosive expansion may be linked to the skill with which these species navigate their environment. Similarities in the genetic control and functional organisation of the insect mushroom body make it directly comparable to the mammalian forebrain, providing a novel framework for studying general principles in cell proliferation and communication. By considering how mushroom body expansion occurred at multiple biological levels, from genes to cells to behaviour and ecology, I will investigate how processes at these different scales interact to facilitate, or restrict, the way brains function.