Changes in ecological preference, often driven by spatial and temporal variation in resource distribution, can expose populations to environments with divergent information content. This can lead to adaptive changes in the degree to which individuals invest in sensory systems and downstream processes, to optimize behavioural performance in different contexts. At the same time, environmental conditions can produce plastic responses in nervous system development and maturation, providing an alternative route to integrating neural and ecological variation. Here, we explore how these two processes play out across a community of Heliconius butterflies. Heliconius communities exhibit multiple Mullerian mimicry rings, associated with habitat partitioning across environmental gradients. These environmental differences have previously been linked to heritable divergence in brain morphology in parapatric species pairs. They also exhibit a unique dietary adaptation, known as pollen feeding, that relies heavily on learning foraging routes, or trap‐lines, between resources, which implies an important environmental influence on behavioural development. By comparing brain morphology across 133 wild‐caught and insectary‐reared individuals from seven Heliconius species, we find strong evidence for interspecific variation in patterns of neural investment. These largely fall into two distinct patterns of variation; first, we find consistent patterns of divergence in the size of visual brain components across both wild and insectary‐reared individuals, suggesting genetically encoded divergence in the visual pathway. Second, we find interspecific differences in mushroom body size, a central component of learning and memory systems, but only among wild caught individuals. The lack of this effect in common‐garden individuals suggests an extensive role for developmental plasticity in interspecific variation in the wild. Finally, we illustrate the impact of relatively small‐scale spatial effects on mushroom body plasticity by performing experiments altering the cage size and structure experienced by individual H. hecale. Our data provide a comprehensive survey of community level variation in brain structure, and demonstrate that genetic effects and developmental plasticity contribute to different axes of interspecific neural variation.

Most multicellular organisms reproduce sexually despite the costs associated with sexuality. This has been explained as the result of selection favouring the ability to recombine the genome. The lack of recombination in asexual species constrains their adaptability and leads to the accumulation of deleterious mutations, ultimately increasing their risk of extinction. Nonetheless, successful asexual life histories persist among multicellular organisms, and explanatory mechanisms which may help limit the cost of asexuality remain enigmatic. In search of these mechanisms, we looked at that the molecular evolutionary changes in sexual and obligate asexual strains of the planarian flatworm, Schmidtea mediterranea. We find that the accumulation of deleterious mutations is largely avoided in the asexual strain. We find evidence that this is achieved by somatic gene conversion in stem cells allowing for the restoration of fit alleles and the purification of deleterious mutations. Our analyses provide a potential mechanism for the maintenance of asexuality in a metazoan. Taken together, these findings suggest that gene conversion may be used by asexual lineages to unlink loci, counteracting some of the key challenges facing obligate asexual species.

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