Phd Project
My dissertation focused on the evolutionary processes shaping age-specific demographic rates, with a particular emphasis on ageing rates. I was involved in research on the evolution of trade-offs (or lack thereof) between early-life breeding decisions, future reproduction, and survival chances in a long-lived seabird, the black-legged kittiwake.
Recruitment (i.e., age at first reproduction) is often assumed to initiate mechanisms that impede somatic repair, resulting in a decline in reproductive and survival abilities with age, i.e., senescence. If so, different recruitment tactics, such as early versus delayed recruitment, could lead to contrasting reproductive and survival trajectories, including divergent senescence patterns.
We addressed this 'long-term trade-off', while taking into account opportunities for (1) breeding experience, (2) temporal variation, and (3) heterogeneity in individual quality to improve or diminish breeding success and survival chances across ages. We also estimated individual-based measures of fitness to quantify the benefits associated to each recruitment strategy. Finally, we calculated selection gradients to determine the direction and strength of selection operating on the age at first reproduction while accounting for its effects on senescence.
The Data
The Kittiwake project in Brittany (France) was initiated by Jean-Yves Monnat in 1979, and is still active thanks to Jean-Yves and Emmanuelle Cam's love of the field, and to students and friends helping out every summer. This unique follow-up provides long-term data on large numbers of color-marked individuals. Five colonies located in the Cap Sizun, a few kilometers apart, are followed extensively through each breeding season, such that all breeding events are covered, and presence in the colonies is recorded almost all-year round. This allows for the identification of the very first reproductive event for each individual returning to the study area. The age of most individuals is known, and each individual’s presence is recorded as well as demographic and behavioral information at each resighting period. Hence, this is a superb dataset to examine long-term trade-offs.
Research questions and associated methods
1/ Are the decisions of when (i.e., age at first reproduction) and where (i.e., habitat selection) to start breeding intimately linked, and do they have immediate effects on reproductive success? Methods: Capture-Mark-Recapture Multistate Models; Generalized Linear Models.
2/ Do recruitment decisions (i.e., early versus delayed recruitment) and heterogeneity affect age-specific breeding success trajectories and reproductive senescence? Methods: Generalized Linear and Additive Mixed Models.
3/ Are recruitment timing (i.e., early versus delayed recruitment) and breeding history the main factors influencing ageing rates, or does unobserved heterogeneity play a role as well? Methods: Time-to-Failure Survival analysis.
4/ What are the fitness benefits associated to the different recruitment strategies identified earlier (i.e., early versus delayed recruitment). Methods: integrative model involving CMR Multi-State Models, Time-to-Failure Survival analysis, Matrix Population Models, and Jack-knifing (or 'delifing' to estimate individually-based fitness). | Emmanuelle Cam
Jean-Yves Monnat
|
