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Illustration inspired by the Jean de la Fontaine fable "the grasshopper and the ant" using copepod characters, where the grasshopper is described as enjoying the summer, relying on the food available at that time but does not have anything when the winter comes (as the income breeders relies on food availability to fuel their egg production but does not store reserve to survive the winter), while the ant works hard to store reserves during the summer but can rely on them to survive the winter (as the capital breeders store reserve to which allow them to survive the winter and spawn at a time that is disconnected with the timing of the spring bloom, and is beneficial for their offspring).

New Ocean Life article in American Naturalist: Capital versus income breeding in a seasonal environment

Thursday 04 Sep 14

In this latest contribution from Ocean Life, Sainmont and co-authors show that optimal breeding strategy is tied to size at maturity and varies with latitude and the duration of the spring bloom.

An abiding challenge of organisms living in seasonal environments is when to produce their offspring with respect to the annual cycle of food abundance and scarcity. Even closely related species can differ radically in their reproductive strategy with implications for their distribution in space and time. Thus, one can ask: What is the best breeding strategy as a function of seasonal conditions? Sainmont and co-authors investigated how the duration of the feeding season influences optimal breeding strategy and adult size in short lived species. As illustrated by fairytale of Jean de la Fontaine; is it better to base everything on the current food availability and thus spawn during the feeding season like the grasshopper, termed income breeding? Or should individuals store reserves and spawn detached from the feeding season like the ant, termed capital breeding? An individual following an income breeding strategy will ensure high offspring production, while an individual following a capital breeding strategy, while producing fewer young, will have the opportunity to do so at a time which maximizes the success of their offspring. Associated with this question is how big an individual should be when they start reproducing (also called size at maturation)? Based on zooplankton studies and with a mathematical model, Sainmont and co-authors show that individuals should be large capital breeders when the feeding season is short, but small income breeders when the feeding season is prolonged. This transition between small and large adult size is observed on a latitudinal gradient, with large species found at high latitude where seasonal fluctuations in food availability and other factors are particularly pronounced. This study also relates to the ability of species to cope with environmental change: large capital breeders are expected to cope better with highly variable feeding seasons of short duration while small income breeders will be favored by long stable feeding seasons.

Reference:
Julie Sainmont, Ken H. Andersen, Øystein Varpe, André W. Visser. (2014) Capital versus income breeding in a seasonal environment. The American Naturalist. Vol. 184, no. 4, October 2014