Trade‐off between male and female allocation in the simultaneously hermaphroditic flatworm Macrostomum sp

Sex allocation theory for simultaneous hermaphrodites assumes a direct trade‐off between the allocation of resources to the male and female reproductive functions. Empirical support for this basic assumption is scarce, possibly because studies rarely control for variation in individual reproductive...

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Bibliographic Details
Published in:Journal of evolutionary biology 2005-03, Vol.18 (2), p.396-404
Main Authors: Schärer, L., Sandner, P., Michiels, N. K.
Format: Article
Language:English
Subjects:
Adaptation, Physiological
Analysis of Variance
Animal reproduction
Animals
Body Weights and Measures
Disorders of Sex Development
Evolutionary biology
Female
Fertility - physiology
Food Deprivation - physiology
Gender
local mate competition
Macrostomum
Male
mating group size
platyhelminthes
Population Density
Reproduction - physiology
resources
sex allocation
simultaneous hermaphrodite
sperm competition
Turbellaria - growth & development
Turbellaria - physiology
Worms
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Summary:Sex allocation theory for simultaneous hermaphrodites assumes a direct trade‐off between the allocation of resources to the male and female reproductive functions. Empirical support for this basic assumption is scarce, possibly because studies rarely control for variation in individual reproductive resource budgets. Such variation, which can have environmental or genetic sources, can generate a positive relationship between male and female investment and can thus obscure the trade‐off. In this study on the hermaphroditic flatworm Macrostomum sp. we tried to control for budget effects by restricting food availability in a standardized way and by using an inbred line. We then manipulated mating group size in a two‐way design (two group sizes × two enclosure sizes) in order to induce phenotypic variation in male allocation, and expected to find an opposing correlated response in female allocation. The results suggest that we only managed to control the budget effects under some conditions. Under these the sex allocation trade‐off emerged. Under the other conditions we found a strongly positive correlation between male and female allocation. We discuss possible causes for the observed differences.
ISSN:1010-061X
1420-9101
DOI:10.1111/j.1420-9101.2004.00827.x