The Adaptive Value of Sexual Dimorphism: I, Anisogamy

Making a number of simplifying assumptions, the rate of unions in a population of gametes has been calculated both for the case of anisogamy (union between a macro- and microgamete) and the case of isogamy (union between gametes of one kind). In anisogamy the rate of unions depends, other things bei...

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Bibliographic Details
Published in:Evolution 1967-06, Vol.21 (2), p.285-291
Main Author: Scudo, Francesco M.
Format: Article
Language:English
Subjects:
Animal genetics
Differential equations
Evolution
Gametes
Life tables
Mass ratio
Particle collisions
Particle interactions
Population distributions
Population genetics
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Summary:Making a number of simplifying assumptions, the rate of unions in a population of gametes has been calculated both for the case of anisogamy (union between a macro- and microgamete) and the case of isogamy (union between gametes of one kind). In anisogamy the rate of unions depends, other things being equal, on the bulk (mass) proportion between the two kinds. Neglecting the chemical differences between the two kinds and assuming that a given mass of them can be produced per unit time and volume, one can calculate the rate of unions as a function of the mass of microgametes to the total mass and thus determine which proportion is the most favorable. It turns out that the maximum number of unions occurs when the microgametes constitute rather less than 1/2 of the bulk gametic mass. It appears also, from a comparison of isogamy with anisogamy (and in agreement with Kalmus), that gametic dimorphism only assumes a greater adaptive value than isogamy when it exceeds a certain degree. Some considerations are discussed under which evolution towards gametic differentiation could have occurred.
ISSN:0014-3820
1558-5646
DOI:10.1111/j.1558-5646.1967.tb00156.x