Abstract
The fitness of any evolutionary unit can be understood in terms of its two basic components: Fecundity (reproduction) and viability (survival). Trade-offs between these fitness components drive the evolution of life-history traits in extant multicellular organisms. We argue that these trade-offs gain special significance during the transition from unicellular to multicellular life. In particular, the evolution of germ-soma specialization and the emergence of individuality at the cell group (or organism) level are also consequences of trade-offs between the two basic fitness components, or so we argue using a multilevel selection approach. During the origin of multicellularity, we study how the group trade-offs between viability and fecundity are initially determined by the cell level trade-offs, but as the transition proceeds, the fitness trade-offs at the group level depart from those at the cell level. We predict that these trade-offs begin with concave curvature in single-celled organisms but become increasingly convex as group size increases in multicellular organisms. We argue that the increasingly convex curvature of the trade-off function is driven by the cost of reproduction which increases as group size increases. We consider aspects of the biology of the volvocine green algae - which contain both unicellular and multicellular members - to illustrate the principles and conclusions discussed.
Original language | English (US) |
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Pages (from-to) | 967-987 |
Number of pages | 21 |
Journal | Biology and Philosophy |
Volume | 20 |
Issue number | 5 |
DOIs | |
State | Published - Nov 2005 |
Keywords
- Body size
- Cost of reproduction
- Evolutionary transitions
- Fitness
- Germ-soma specialization
- Individuality
- Life-history evolution
- Multi-level selection
- Multicellularity
- Volvox
ASJC Scopus subject areas
- Philosophy
- General Agricultural and Biological Sciences
- History and Philosophy of Science