Romain Richard André de Roos Population dynamics with multiple limiting nutrients: Life history mediated effects Romain Richard André de Roos

From individual development to population dynamics Life history & Co Growth Fecundity Mortality Feeding Being fed upon Population / community processes Development Physiology Ingestion Maturation Allocation Maintenance Development is a major determinant of population dynamics

Dynamical effects of development Makes competition between individual asymmetric: Individuals are not equally good at producing biomass Population cycles Alternative dynamical attractors Coexistence Biomass overcompensation Catastrophic collapses Facilitation Allee effects Juveniles Adults Total

Ecological stoichiometry Individual experiencing different environment may be limited by different currency: energy vs mineral limitation Focus on environmental and inter-specific variation Intra-specific variation due to ontogenetic development

Mechanisms likely to induce changes in the limiting nutrient through development Changes at maturation Allometric scaling of body composition Changes due to ontogenetic diet-shift / metamorphosis Size-specific changes in physiological rates (ingestion, maintenance, maturation…) How do multiple nutrient limitations affect individual life histories and what are the implications for ecological dynamics?

Individual model Differences in assimilation efficiency Maintenance Growth Reproduction Biomass Overhead cost of growth Overhead cost of reproduction (includes provisioning of nutrients for embryogenesis) Carbon is for structural and energetic purposes Phosphorus is for structural purpose only Differences in assimilation efficiency Differences in specific maintenance rate Differences in overhead costs

P-rich food (=> Carbon limitation) P-poor food (=> Phosphorus limitation)

TER is size-dependent TER = critical C:P ratio in the food at which individual switches from C- to P-limitation Carbon-limitation Phosphorus-limitation P-rich food P-poor food

(some) Population consequences Population extinction with resource enrichment (dilution effect) Alternative stable states: [low food density, high food quality] vs [high food density, low food quality] Dampening / stabilization of population cycles

Biomass overcompensation Total Juveniles Adults Decrease in phosphorus concentration = decrease in adult performance (but not juveniles) Decrease in population abundance Carbon limitation Phosphorus limitation Increase in food density (Much) increase in both juvenile performance More transition of biomass to adult stages Increase in adult biomass

Conclusions Numerous potential implications of biomass overcompensation Interactions between stoichiometric- and size- dependent effects Can reverse the scaling of competition predicted by allometric scaling of ingestion and maintenance

(Personn and de Roos 2013)