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Gametic conflict versus contact in the evolution of anisogamy. - Abstract - Europe PMC

But there are a few organisms that reproduce by the combination of one gamete from each of two individuals, and those two gametes are the same isogamy. These are still gametes: they have half the number of chromosomes of an adult cell. They must combine with another gamete to make a new, genetically complete individual.

But they are the same size, the same shape, equally mobile or immobile. There are no sexes. All the adult individuals are the same type. They are not "all female" or "all male. Think of the difference between a point and a line. A point has no dimensions, no right and left or up and down. A line has one dimension, a side-by-side stringing together of points.

The evolution of sexes: A specific test of the disruptive selection theory

It has two ends, this way and that way. Even if it is an infinite line, we can say that it goes this way forever and that way forever. There are two ways. And that is the issue I'm raising with the concept of anisogamy. Many plants are true hermaphrodites. They have fully developed and functioning "male" and "female" sex organs and produce "male" and "female" gametes. They reproduce, sometimes by fertilizing themselves, but more often by a difference of timing or by using helpers like those proverbial birds and bees, so that the male gametes pollen fertilize the female gametes of a different individual.

The Sperm Struggle is Real

There are a number of animals, notably some fishes and mollusks, which display a different kind of hermaphroditism. They change their "sex" during their lives depending on their state of maturation or conditions in the environment. They are fully functional "males" sperm producers at one time, and fully functional "females" egg producers at another time. In humans, individuals are more likely to be intersex than hermaphrodites.

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Ann Herendeen

Abstract Anisogamy refers to gametes that differ in size, and characterizes the difference between males and females. The evolution of aniosgamy is widely interpreted as involving conflict between gamete producers with small sperm parasitizing on the investment made by the eggs. Using a population genetic model for evolution at a locus that codes jointly for sperm and egg sizes of a hermaphrodite, we show that the origin of anisogamy in an externally spawning population need not involve conflict between gamete producers.

Gamete size dimorphism may be an adaptation that increases gamete encounter rates when large zygotes are selected, and we show this in a mechanistically general individual selection model. We use the Vance survival function without specific allometric assumptions to model the zygote fitness dependence on its size, and hence obtain ecological and life-history correlates of isogamy and anisogamy, which we successfully compare with data from Volvocales.

Read Article at publisher's site. Selection for high gamete encounter rates explains the evolution of anisogamy using plausible assumptions about size relationships of swimming speed and duration.

David Brock Dusenbery. Sexual conflict over mating and fertilization: an overview. Survival and anisogamy.

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James P. Randerson , Laurence D. The evolution of anisogamy: a game-theoretic approach. Michael Bulmer , G. The uncertain evolution of the sexes James P.

Nuclear condensation in protozoan gametes and the evolution of anisogamy

Randerson , Laurence D Hurst. Sexual conflict resulting from adaptations to sperm competition. Paula Stockley. By clicking accept or continuing to use the site, you agree to the terms outlined in our Privacy Policy , Terms of Service , and Dataset License.

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