Reproductive senescence and mating tactic interact and conflict to drive reproductive success in a passerine

• Published in: The Journal of animal ecology 2023-04, Vol.92 (4), p.838-849
• Main Authors: Riecke, Thomas V., Hegelbach, Johann, Schaub, Michael
• Format: Article
• Language: English
• Subjects: Age; Age factors; Aging; Animal reproduction; Animals; Breeding success; Cinclus cinclus; Ecology; Evolution; Female; Females; Fitness; Hatching; Heterogeneity; individual heterogeneity; Male; Males; Mate selection; Mating; Monogamy; Nesting; Offspring; Passeriformes; Polygyny; Reproduction; reproductive allocation; Reproductive fitness; Senescence; Sexual Behavior, Animal; sex‐specific senescence; Success; Survival; white‐throated dipper
• ISSN: 0021-8790; 1365-2656
• DOI: 10.1111/1365-2656.13893

An understanding of the drivers of individual fitness is a fundamental component of evolutionary ecology and life‐history theory. Reproductive senescence, mate and mating tactic choice and latent heterogeneity in individual quality interact to affect individual fitness. We sought to disentangle the effects of these fitness drivers, where longitudinal data are required to understand their respective impacts. We used reproductive allocation and success data from a long‐term (1989–2018) study of white‐throated dippers Cinclus cinclus in Switzerland to simultaneously examine the effects of female and male age, mating tactic, nest initiation date and individual heterogeneity on reproductive performance. We modelled quadratic and categorical effects of age on reproductive parameters. The probability of polygyny increased with age in both sexes before declining in older age classes. Similarly, hatching probability in monogamous pairs and the number of nestlings hatched in both monogamous and polygynous pairs increased with female age before declining later in life. As predicted, offspring survival in monogamous pairs increased with male age before declining in older age classes, but male age had no effect on offspring survival in polygynous nesting attempts. Our results demonstrate that parental age, mating tactic and individual heterogeneity all affect reproductive success, and that the impacts of senescent decline are expressed across different demographic components as a function of sex‐specific senescent decline and mating tactic. The effects of both senescence and mate choice and mating tactic on individual fitness have been the focus of a tremendous amount of ecological inquiry. The authors assess reproductive senescence for monogamous and polygynous mating attempts, and demonstrate that the effects of parental age differ among mating tactics.