Capital versus Income Breeding in a Seasonal Environment

Abstract

The allocation of resources between growth, storage, and reproduction is a key trade-off in the life-history strategies of organisms. A central dichotomy is between capital breeders and income breeders. Capital breeders build reserves that allow them to spawn at a later time independently of food availability, while income breeders allocate ingested food directly to reproduction. Motivated by copepod studies, we use an analytical model to compare the fitness of income with capital breeding in a deterministic seasonal environment. We analyze how the fitness of breeding strategies depend on feeding season duration and size at maturity. Small capital breeders perform better in short feeding seasons but fall behind larger individuals when the length of the feeding season increases. Income breeding favors smaller individuals as their short generation time allows for multiple generations within a year and thereby achieve a high annual growth rate, outcompeting capital breeders in long feeding seasons. Therefore, we expect to find a dominance of small income breeders in temperate waters, while large capital breeders should dominate high latitudes where the spring is short and intense. This pattern is evident in nature, particularly in organisms with a generation time of a year or less.

The effects of seasonal processes on size spectrum dynamics

“…In reality, reproduction is sometimes subject to spatial and temporal variations and is independent of instantaneous growth (capital as opposed to income breeding; see Jönsson 1997;Jager et al 2008;Sainmont et al 2014). Such a reproduction function should be both massdependent (Wootton 1977;Duarte and Alcaraz 1989;Blanchard 2000) and time-dependent, depending on the species (Fig.…”

“…The reproductive rate is dependent on the predation rate, in keeping with the dynamic energy budget methods (Kooijman 2009) commonly used in size spectrum models to allocate incoming mass to somatic and reproductive mass (e.g., Maury et al 2007a;Blanchard et al 2011). Thus we consider mature individuals to be income rather than capital breeders, the latter having spawning that is relatively independent of current prey availability but strongly dependent upon lagged average availability (Sainmont et al 2014). The physiology of egg production is not explicitly modelled, and simple size-based fecundity is assumed.…”

“…A recent paper by Sainmont et al (2014) used an ordinary differential equation (ODE) model approach to investigate alternative strategies for seasonal reproduction (capital versus income breeding) in environments with varying feeding seasons and maturity masses. In short, income breeding allocates incoming mass directly to reproduction, whereas capital breeding stores reserves that may be used for spawning at a later time, independent of food availability.…”

“…Clearly, a comprehensive simulation of the impacts of seasonality should include capital breeding, as this strategy can be both optimal theoretically (Sainmont et al 2014;Ejsmond et al 2015) and, more importantly, common empirically in seasonal environments (e.g., Lambert and Dutil 2000). However, the purpose of this study is to conduct an initial exploration of the consequences, for the consumer size spectrum, of seasonality in both resource availability and consumer spawning times.…”

Traits controlling body size in copepods: separating general constraints from species-specific strategies

“…that trade energy gain and fecundity for reduced mortality (Kiørboe & Hirst 2014). At the opposite end of the size spectrum, the largest, high-latitude calanoid species such as C. hyperboreus and Neocalanus flemingeri/ plumchrus also take low-energy strategies compared with C. finmarchicus, surviving short, unpredictable seasons of prey availability through adap tations like multi-year life cycles and high starvation tolerance (Conover 1988, Falk-Petersen et al 2009, Sainmont et al 2014. These examples hint at the variety of ways in which copepod diversity might be generated, across the entire size spectrum, by adjusting one or another process relative to a metabolically determined maximum.…”