Optimal energy allocation tactics and indeterminate growth: Life-history evolution of long-lived bivalves

Abstract

The theory of optimal energy allocation among maintenance, somatic growth and reproduction forms the backbone of life-history theory. Allocation to each of these functions need not be equally important with respect to fitness. For example, for young individuals the allocation to maintenance (survival) may be more important than allocation to somatic growth or reproduction. The priority rank of allocation targets may depend on a multitude of factors, both external (e.g., seasonal environment) and internal (e.g. age) to the organism. Individuals that can identify the changes in the expected priority rank of allocation targets and respond accordingly will have a selective advantage. In other words, selection favors individuals whose allocation pattern is closer to the theoretical optimum than the mean allocation pattern of the population. A match of the observed and expected allocation patterns may be investigated by manipulating the availability of resources and measuring the response of the organism. I review the literature of energy allocation in long-lived, iteroparous, indeterminately growing bivalves. I discuss the relevant time scales of allocation decisions (among-season vs. within-season), the role of storage allocation in seasonal environments, and review the theory of optimal resource allocation for this type of life histories. Empirical and experimental studies suggest that priority ranks among allocation targets are an important part of life-history strategy in these long-lived bivalves.