Individual variation in age-dependent reproduction: fast explorers live fast but senesce young?

1. Adaptive integration of life history and behaviour is expected to result in variation in the pace-of-life. Previous work focused on whether "risky" phenotypes live-fast-but-die-young, but reported conflicting support. We posit that individuals exhibiting risky phenotypes may alternatively invest heavily in early-life reproduction but consequently suffer greater reproductive senescence. 2. We used a 7-year longitudinal dataset with >1200 breeding records of >800 female great tits assayed annually for exploratory behaviour to test whether within-individual age-dependency of reproduction varied with exploratory behaviour. We controlled for biasing effects of selective (dis)appearance and within-individual behavioural plasticity. 3. Slower and faster explorers produced moderate-sized clutches when young; faster explorers subsequently showed an increase in clutch size that diminished with age (with moderate support for declines when old), whereas slower explorers produced moderate-sized clutches throughout their lives. There was some evidence that the same pattern characterized annual fledgling success, if so, unpredictable environmental effects diluted personality-related differences in this down-stream reproductive trait. 4. Support for age-related selective appearance was apparent, but only when failing to appreciate within-individual plasticity in reproduction and behaviour. 5. Our study identifies within-individual age-dependent reproduction, and reproductive senescence, as key components of life history strategies that vary between individuals differing in risky behaviour. Future research should thus incorporate age-dependent reproduction in pace-of-life studies.BirdID Bird identity – individual-specific unique identifier Plot Plot identity – nest box plot-specific unique identifier (12 levels) BroodID Brood identity – brood-specific unique identifier associated with each nest attempt Year Year identity (2010-2016) MassSummer Female body mass (in .1 grams) at catching during focal breeding attempt ExpFieldScore Exploration score – total number of hops among cage locations; test during focal breeding attempt. Detailed by Araya-Ajoy et al. (2016). ClutchSize Clutch size – total number of eggs produced during focal breeding attempt NumberFledged Number of fledglings produced during focal breeding attempt; 0 = no fledglings ("failed") AvgDay14Mass Average fledgling mass at nestling age 14 PredTreat Predation risk treatment 0 = unmanipulated (all years except 2013 and 2014) 1 = blackbird treatment ("control"); 2 = sparrow-hawk treatement ("manipulated") Detailed in Abbey-Lee & Dingemanse (2019) AgeBreeder Age in calendar years. 0 = age in the year following birth. MinAge Minimum age over all the records of the focal individual MaxAge Maximum age over all the records of the focal individual Local Local recruit 1 = ringed as nestling in our populations 0 = all other birds Dead 1 = not recorded for two years following last observation in the dataset 0 = all other birds BSManip Brood size manipulation. For details see Nicolaus et al. (2015). 0 = unmanipulated 1 = reduced (3 nestlings removed) 2 = control (nestling swaps applied without changing brood size) 3 = enlarged (3 nestlings added) "NA" Missing values (applicable to multiple variables listed above). References Abbey-Lee, R.N. & Dingemanse, N.J. (2019) Adaptive individual variation in phenological responses to perceived predation levels. Nature Communications, 10, 1601. Araya-Ajoy, Y.G., Kuhn, S., Mathot, K.J., Mouchet, A., Mutzel, A., Nicolaus, M., Wijmenga, J.J., Kempenaers, B. & Dingemanse, N.J. (2016) Sources of (co)variation in alternative siring routes available to male great tits (Parus major). Evolution, 70, 2308-2321. Nicolaus, M., Mathot, K.J., Araya-Ajoy, Y.G., Mutzel, A., Wijmenga, J.J., Kempenaers, B. & Dingemanse, N.J. (2015) Does coping style predict optimization: an experimental test in a wild passerine bird. Proceedings of the Royal Society B-Biological Sciences, 282, 20142405