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Parent-offspring conflict and selection on egg size in turtles
1Department of Ecology, Evolution and Organismal Biology, Iowa State University, Ames, IA 50011, USA. fjanzen@iastate.edu
Journal of Evolutionary Biology
|October 3, 2009
Summary
Parental and offspring fitness goals conflict over egg size. Maternal fitness, not offspring fitness, drives optimal egg size in turtles, balancing egg number and size.
Area of Science:
- Evolutionary biology
- Reproductive strategies
- Parent-offspring conflict
Background:
- The trade-off between offspring size and number is a key factor in reproductive strategies.
- Optimal egg size for offspring fitness may differ from that maximizing parental fitness due to constraints.
Purpose of the Study:
- To investigate selection on egg size in three turtle species: Apalone mutica, Chelydra serpentina, and Chrysemys picta.
- To determine if optimal egg sizes differ between offspring and maternal fitness.
Main Methods:
- Evaluated selection gradients on egg size in natural populations.
- Assessed hatching success in relation to egg size.
- Compared optimal egg sizes for offspring and maternal fitness.
Main Results:
- Hatching success generally increased with egg size, but selection strength and form varied among species.
- The egg size maximizing offspring fitness was typically larger than that maximizing maternal fitness.
- Population mean egg sizes more closely reflected maternal optima than offspring optima.
Conclusions:
- Maternal fitness, rather than offspring fitness, appears to be the primary driver of selection on egg size in these turtle species.
- Selection favors an optimal balance between egg size and number to maximize maternal fitness.
- Results support evolutionary optimality theory in reproductive allocation.
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