Evol Ecol Res 14: 207-221 (2012) Full PDF if your library subscribes.
The evolution of developmental dependence, or ‘Why do my kids need me so much?’
Rebecca E. Hale1 and Joseph Travis2
1Department of Biology, University of North Carolina Asheville, Asheville, North Carolina, USA and 2Department of Biological Science, Florida State University, Tallahassee, Florida, USA
Correspondence: R.E. Hale, Department of Biology, University of North Carolina Asheville, Asheville, NC 28804, USA.
e-mail: rhale@unca.eduABSTRACT
Question: The young of some species depend utterly on care by their parents. How does such extreme dependence evolve?
Methods: Dependence is defined as the minimum effort offspring need for survival; thus, greater minimum effort is equivalent to greater dependence. We study a state-dependent life-history model with forward-iterating simulations of a brooding individual. We identify the optimal parental effort given the fitness consequences of that effort for offspring and the offspring’s level of dependence. We manipulate the level of dependence and evaluate its effect on parental effort, mean offspring fitness, and mean parental fitness.
Key assumptions: Individual parents must decide daily how many offspring to birth and, consequently, how many remaining offspring will share the parent’s acquired resources. A female’s offspring all have the same level of dependence. Daily resource availability varies and parents can rear multiple broods in sequence.
Results: Greater altriciality results in smaller broods, larger birth sizes, and prolonged care. The selection gradient on offspring altriciality suggests altriciality can evolve despite negative consequences for parental fitness.
Keywords: altricial, birth asynchrony, brood reduction, developmental dependence, parental care, parental effort.
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