Ontogenetic development characterizes the life history of all organisms on Earth. The different kinds of individual growth patterns observed in different organisms are reviewed, and an overview is given of the possible consequences of ontogenetic development on population and community dynamics. Finally, the question whether a general ecological theory taking ontogenetic development into account may be reached is addressed.  

Community ecology has traditionally treated species as homogenous entities and thereby implicitly assumed that individuals within species are functionally equivalent. Yet, increasing evidence indicates that developmental stages can differ substantially in their ecological interactions. Recent work indicates that these ontogenetic shifts are ubiquitous in natural communities and can fundamentally alter the structure and dynamics of communities and ecosystem processes.

Community theory currently ignores ontogenetic development, even though it characterizes the life history of all species. Development, in particular growth in body size, leads to ontogenetic asymmetry in energetics between differently sized individuals. We discuss the community consequences of such ontogenetic asymmetry, illustrating how it overturns basic ecological principles by inducing population size structure to change with changing environmental conditions.

Previous work has shown that structured dynamics can influence selection among asexual genotypes in consumer-resource systems. One question raised by this work is how to characterize the variation and covariation among life-history traits for novel genotypes. Here I present experimental results in freshwater zooplankton that suggest an energy budget model to capture this life-history trait (co)variation.

Intraspecific interference competition gives a competitive advantage to larger individuals through social interactions (as opposed to exploitative competition which usually favours small individuals). We show how interference competition first dampens juvenile-driven generation cycles and then leads to the emergence of giant individuals and high amplitude cycles, using both experiments and a size-structured model.

We study interactive effects of different types of phenotypic plastic responses on the successful development of early stages of organisms. In marine shrimps, thermal and food-dependent maternal effects and larval developmental plasticity interact and determine patterns of pelagic larval duration (PLD). PLD is a trait that affects dispersal, survival and recruitment in marine species with complex life cycles.   

Using time-series analysis and stage-structured population models, we show that biomass overcompensation by juveniles occurred in a natural fish population in response to increased adult mortality induced by a severe pathogen outbreak. The compensatory response occurs due to release from competition among adults leading to higher age-specific fecundity and reproduction, and release from cannibalism leading to higher juvenile survival.

Stage- and spatial structure have major consequences for populations but their interaction is unexplored. We manipulated stage-structure in closed and open habitats using egg mortality. In open populations, stage-specific spill-over effects in opposite directions compensated the negative mortality effect on juveniles and increased adult densities in unharvested reserves. Habitat status as a source or sink therefore depended on life-history stage.

The properties of marine communities, and the traits of populations nested within them, can affect how resilient they are to human induced and environmental change. The goal of this paper is to explore ideas that link the role of size-dependent traits with community resilience, including testing theoretical predictions with empirical data from a wide range of marine ecosystems.

The mystery posed by the lack of recovery after marine predator population collapses has evoked many hypotheses to explain this phenomenon. Fisheries impact complex ecological systems, formed by the integrated dynamics at small scales. By the analysis of  size-structured predator-prey models we test some postulated explanations for the lack of recovery of marine predator populations, starting from individual level processes.

Habitat complexity has been suggested to promote the persistence of intraguild predation (IGP) systems through weakening trophic interactions particularly the predation link. Here we show that, in a size-structured IGP system, the presence of habitat structure does not promote the coexistence of IG-predator and IG-prey despite a major decrease in the IG-predator’s capture rate.

Theory on predator-mediated coexistence has so far ignored the role of stage structure at the predator level. We show that ontogenetic diet shifts at the predator level have a high potential to enlarge coexistence between competing prey along a productivity gradient. Furthermore only a slight niche shift is necessary to lead to qualitatively different patterns compared to the unstructured case.