Evol Ecol Res 6: 659-678 (2004)     Full PDF if your library subscribes.

Estimating reaction norms for age and size at maturation when age at first

reproduction is unknown

Sébastien Barot,1,2 Mikko Heino,2,3 Loretta O’Brien4 and Ulf Dieckmann2

1IRD-LEST, 32 Avenue H. Varagnat, 93143 Bondy cedex, France,  2Adaptive Dynamics Network, International Institute for Applied Systems Analysis, 2361 Laxenburg, Austria, 3Institute of Marine Research, PO Box 1870 Nordnes, 5817 Bergen, Norway and  4National Marine Fisheries Service, Northeast Fisheries Science Center, Woods Hole, MA 02543, USA.

Author to whom all correspondence should be addressed.
e-mail: barot@bondy.ird.fr


We describe a novel method to estimate the probabilities of maturing at age as a function of size; these probabilities can often be interpreted as probabilistic reaction norms for age and size at maturation. Such estimations are useful for describing the maturation process independently of the processes of growth and mortality, and they can also help to disentangle phenotypic plasticity from evolutionary changes in maturation. The estimation method can be used when mature and immature individuals are representatively sampled over two consecutive seasons, even when maturing individuals are not distinguished. Confidence intervals are derived for the reaction norm parameters using a bootstrap approach. Using simulated data, the method is shown to be asymptotically unbiased and robust to moderate violations of the main simplifying assumptions. However, it is relatively sensitive to small sample sizes: the method is not robust when fewer than about 100 individuals (mature and immature) are sampled from a cohort at a certain age. The method is illustrated by an application to Georges Bank cod stock (Gadus morhua) but can be used for any type of organism.

Keywords: maturation dynamics, phenotypic plasticity, probability of maturing, reaction norm, robustness assessment.

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        © 2004 Sébastien Barot. All EER articles are copyrighted by their authors. All authors endorse, permit and license Evolutionary Ecology Ltd. to grant its subscribing institutions/libraries the copying privileges specified below without additional consideration or payment to them or to Evolutionary Ecology, Ltd. These endorsements, in writing, are on file in the office of Evolutionary Ecology, Ltd. Consult authors for permission to use any portion of their work in derivative works, compilations or to distribute their work in any commercial manner.

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