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ECOEVODEVO Sintesi della relazione

Project ID: 322814
Finanziato nell'ambito di: FP7-IDEAS-ERC
Paese: Netherlands

Mid-Term Report Summary - ECOEVODEVO (Eco-evolutionary dynamics of community self-organization through ontogenetic asymmetry)

This project focuses on the aspect of life that the majority of animal species are characterized by a life history full of complexities. Individuals need to grow during their life, sometimes over impressive ranges of body size, and these changes in body size change their energy requirements for subsistence, growth and reproduction. In many species these changing energy demands are met by changing the use of available resources during juvenile development (ontogeny) or by changing the habitat individuals live in. Examples of the former are piscivorous fish species that start out eating zooplankton as newborn but switch to hunting for other fish when large. Examples of the latter are amphibians with an aquatic, juvenile life stage and a terrestrial, adult life stage and species of salmonoids that migrate from the river to the ocean and back for growth and reproduction, respectively. In this project the possible drivers are investigated that have resulted in the evolution of such life cycle complexities.

With increasing body size the efficiency changes, with which individuals can use available resources to grow or reproduce, often resulting in asymmetric competition between juveniles and adults when they forage on a shared resource. We have theoretically shown that natural selection would by default minimize such asymmetric competition, which occurs when individuals of different sizes are equally efficient in their use of available energy. Other factors must hence be responsible for the asymmetry in intraspecific competition that is generally observed in nature. One such factor relevant for fish species is the occurrence of cannibalism. Indeed, cannibalism can be shown to evolve and give rise to evolutionary coexistence in the same population of a slow, large-sized cannibalistic life history type and a faster growing smaller non-cannibalistic life history type. The evolution of cannibalism, however, makes the population more vulnerable to harvesting and may even result in increased risk of population collapse.

In this project we have also shown that a change in diet during juvenile development is likely to evolve when an alternative resource is available in abundance, but that adaptation to this new foraging niche will not occur if it has negative effects for the foraging success as a newborn. This trade-off between early and late foraging efficiency is generally postulated, because each of the foraging niches is likely to pose its own morphological constraints. It turns out to be evolutionary more important to produce a few offspring that are excellent competitors than to produce many offspring that are not very efficient in feeding during the first part of their lives. The trade-off between early and large foraging success thus impedes the evolution of an ontogenetic niche shift. However, our studies have also revealed that if alternative resources are available in abundance a change in resource use is expected to evolve hand in hand with metamorphosis, during which process individuals invest stored energy to change their morphology and thereby their foraging efficiency. Metamorphosis thus breaks up the trade-off between early and late foraging. The most remarkable finding of the project is that once metamorphosis is fixated in the population reductions of the supply of alternative resources will not lead to loss of this life history trait.

Other studies in the project have focused on the plasticity of individuals to adopt different life history strategies, for example salmonoid species, in which part of the population migrates out to the marine environment before reproduction, while an other part of the population stays behind and completes its juvenile phase in freshwater. In general these studies have shown that under a given set of environmental conditions only one of the possible life history strategies is really successful and hence supports population persistence, but that the environmental conditions determines which is this productive strategies. These findings suggest that the coexistence of alternative life history strategies may ensure population persistence in the face of changing environmental conditions.

This project is theoretical in nature and uses population dynamic models to answer fundamental questions in ecology and evolutionary biology. As part of the project we also develop generic methodology and software to analyze population dynamic models that explicitly represent complex life histories of individual organisms. As such these models contrast with the classic models in ecology that tend to ignore individual life history altogether. The tools developed are made publicly available as open-source software.

Research results have furthermore been presented in a large number of presentations by team members at national and international conferences in Europe (the Netherlands, France, England, Germany) and the United States. These are conferences in the field of evolutionary biology, ecology, and theoretical biology, attesting of the interdisciplinary nature of the project. The first publications resulting from the project have been published in prominent journals or are currently in submission. Several more papers are in final stage of preparation and will be submitted in the near future.

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