Evol Ecol Res 10: 867-892 (2008)     Full PDF if your library subscribes.

Dioecy as a specialization promoting sperm delivery

Priya Iyer and Joan Roughgarden

Department of Biological Sciences, Stanford University, Stanford, California, USA

Correspondence: P. Iyer, Department of Biological Sciences, Stanford University, Herrin 424 Serra Mall, Stanford, CA 94305, USA.
e-mail: priyai@stanford.edu


Question: Is dioecy primitive to metazoans? When should hermaphrodism or dioecy be selected?

Data description: Classification of animal phyla as hermaphroditic/dioecious, broadcast spawning/localized fertilizing.

Analysis method: Ancestral trait reconstruction using the maximum parsimony method.

Hypothesis: Specialization to dioecy is selected when males are more effective than hermaphrodites in concentrating sperm.

Mathematical method: Population genetic model to derive ESS conditions for hermaphrodism and dioecy.

Assumptions: Trade-off between resources available for gamete production and sperm concentrating capability.

Conclusions: Dioecy evolves from hermaphrodism when increasing sperm concentration is adaptive, even though total resources available for sperm and egg production decrease.

Keywords: broadcast spawning, dioecy, evolution of sexes, fertilization behaviour, hermaphrodism, internal fertilization.

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