The pupal stage shapes life-history trade-offs across metamorphosis

Dealing with ecological stressors during development often comes at the expense of later-life performance. Although such trade-offs are well studied as two-stage systems such as larva-adult trade-offs, they are rarely examined across multiple developmental stages, limiting our understanding of how ecological effects are integrated throughout complex life cycles. We addressed this gap using a multistage experimental framework in Aedes aegypti, where we exposed individuals to predation risk during the larval stage, the pupal stage, both stages, or neither, and quantified developmental, physiological, and adult fitness traits. Contrary to expectations, predation risk across successive stages did not produce cumulative fitness costs, and traits varied in their responses. Both males and females emerged faster when exposed to risk, with lighter bodies, but males paid an additional cost of reduced starvation resistance when the pupal stage was exposed. Surprisingly, despite their lower body mass, females showed enhanced reproductive performance when both stages were exposed to risk. Overall, responses were stage- and sex-specific, with exposure during the non-feeding pupal stage imposing greater life-history costs than larval exposure alone. Measurements across the larva-pupa-adult continuum further revealed that traits such as body mass and energy reserves respond differently before and after metamorphosis, highlighting the role of the pupa in mediating trade-offs. Our findings identify the pupal stage as a critical mediator of life-history trade-offs and demonstrate the value of a multistage framework for understanding the role of each stage in life-history evolution.