Individual heterogeneity in reproductive rates and cost of reproduction in a long-lived vertebrate
Article first published online: 31 MAY 2013
© 2013 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.
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Ecology and Evolution
Volume 3, Issue 7, pages 2047–2060, July 2013
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How to Cite
Ecology and Evolution 2013; 3(7): 2047–2060
- Issue published online: 10 JUL 2013
- Article first published online: 31 MAY 2013
- Manuscript Accepted: 24 APR 2013
- Manuscript Revised: 18 APR 2013
- Manuscript Received: 24 JAN 2013
- National Science Foundation
- Bayesian statistics;
- individual variation;
- life-history theory;
- marine mammals;
- population dynamics;
- posterior predictive checks
Individual variation in reproductive success is a key feature of evolution, but also has important implications for predicting population responses to variable environments. Although such individual variation in reproductive outcomes has been reported in numerous studies, most analyses to date have not considered whether these realized differences were due to latent individual heterogeneity in reproduction or merely random chance causing different outcomes among like individuals. Furthermore, latent heterogeneity in fitness components might be expressed differently in contrasted environmental conditions, an issue that has only rarely been investigated. Here, we assessed (i) the potential existence of latent individual heterogeneity and (ii) the nature of its expression (fixed vs. variable) in a population of female Weddell seals (Leptonychotes weddellii), using a hierarchical modeling approach on a 30-year mark–recapture data set consisting of 954 individual encounter histories. We found strong support for the existence of latent individual heterogeneity in the population, with “robust” individuals expected to produce twice as many pups as “frail” individuals. Moreover, the expression of individual heterogeneity appeared consistent, with only mild evidence that it might be amplified when environmental conditions are severe. Finally, the explicit modeling of individual heterogeneity allowed us to detect a substantial cost of reproduction that was not evidenced when the heterogeneity was ignored.