Morphological and physiological sexual selection targets in a territorial damselfly

• 1 Several morphological and physiological traits may shape fitness through the same performance measure. In such cases, differentiating between a scenario of many‐to‐one mapping, where phenotypic traits independently shape fitness leading to functional redundancy, and a scenario where traits strongly covary among each other and fitness, is needed.
• 2 A multivariate approach was used, including morphological and physiological traits related to flight ability, a crucial performance measure in flying insects, to identify independent correlates of short‐term mating success (mated versus unmated males) in the territorial damselfly Lestes viridis.
• 3 Males with higher flight muscle mass, higher relative thorax mass, and more symmetrical hindwings, all traits presumably linked to manoeuvrability, were more likely to be mated. Unexpectedly, although relative thorax mass is often used as a proxy for flight muscle mass, both traits were selected for independently. Mated males had a higher thorax fat content than unmated males, possibly because of enhanced flight endurance.
• 4 The finding of several independent targets of sexual selection linked to flight ability is consistent with a scenario of many‐to‐one mapping between phenotype and performance. Identifying such a scenario is important, because it may clarify situations where animals may show suboptimal values for some phenotypic traits shaping a performance measure, while still having high performance and fitness. We argue in the discussion that the functional approach of sexual selection provides a potent tool for examining unresolved issues in both sexual selection theory, as well as life‐history theory.