Evolution of resource generalism via generalized stress response confers increased reproductive thermal tolerance in a pest beetle

Abstract Generalism should be favoured evolutionarily when there is no genetic constraint or loss of fitness across alternative environments. However, evolution generalism can require substantial evolutionary change, which confer a general stress response to other aspects the environment. We created generalist lineages from an ancestral, resource-specialized laboratory population seed beetles (Callosobruchus maculatus) by rearing lines over 60 generations on mixture both ancestral and novel host species test for costs associated with involving changes in gene expression correlated phenotypic responses during shift generalism. Evolved had higher resource, indicating that they overcame initial trade-offs. This involved upregulation major (heat shock protein) genes coding metabolic enzymes, suggesting underpinning physiological cost. Resource populations also evolved greater thermal tolerance breadth, highlighting resource might pre-adapt respond favourably environmental stressors, following selection generalized upregulation. The rapid gain hosts pest invasion resilience ongoing climate change.