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When do mixotrophs specialize? Adaptive dynamics theory applied to a dynamic energy budget model
Tineke A Troost1, Bob W Kooi, Sebastiaan A L M Kooijman
1Faculty of Earth and Life Sciences, Department of Theoretical Biology, Vrije Universiteit, De Boelelaan 1087, 1081 HV Amsterdam, The Netherlands. tineke@bio.vu.nl
Mathematical Biosciences
|March 8, 2005
Summary
Mixotrophs can evolve into specialized autotrophs or heterotrophs, but only under specific conditions. Evolutionary branching occurs at intermediate costs and when pure strategies offer an advantage, influenced by complex cost functions.
Area of Science:
- Evolutionary Biology
- Theoretical Ecology
- Physiological Ecology
Background:
- Mixotrophs, organisms capable of both autotrophy and heterotrophy, represent a significant ecological strategy.
- Evolutionary history shows instances where mixotrophs have specialized into distinct autotrophic and heterotrophic lineages.
- Understanding the drivers of such specialization is key to comprehending ecosystem dynamics and evolutionary pathways.
Purpose of the Study:
- To investigate the conditions under which mixotrophic populations diverge into specialized autotrophs and heterotrophs.
- To model the evolutionary dynamics of mixotrophs using established theoretical frameworks.
- To identify intrinsic and extrinsic factors influencing the potential for evolutionary branching in mixotrophs.
Main Methods:
- Utilized the Dynamic Energy Budget (DEB) theory to model organismal metabolism and physiological rules.
- Employed Adaptive Dynamics (AD) theory to simulate the evolutionary trajectories of trait values within a mixotrophic population.
- Developed a model of mixotrophs with adjustable affinities for autotrophic and heterotrophic nutrient uptake.
Main Results:
- Evolutionary branching, leading to specialization, was found to be contingent on specific conditions, not a universal outcome.
- Branching occurred primarily at intermediate cost levels and when pure strategies (either autotrophy or heterotrophy) were advantageous over mixed strategies.
- The emergence of branching points was sensitive to the complexity of cost functions and constraints on affinities, with simpler functions or external factors like nutrient/light levels having no impact.
Conclusions:
- The specialization of mixotrophs is a complex evolutionary process influenced by internal biological constraints and strategies.
- Specific intrinsic properties, particularly intermediate costs and advantages for pure strategies, are critical for evolutionary branching.
- External environmental factors do not appear to drive the evolutionary specialization of mixotrophs in this model.