Behavioral Ecology Blog

So what are some of the potential benefits to multiple mating anyway? Here I am only speaking to the cases where matings are not forced or coerced by males.

Direct Benefits: Include the direct provisioning of females by males. Things like food, shelter, nest materials, territories, etc fall into this category. In addition, resources like sperm (in those species where male sperm supplies are frequently deplete) should be placed in the direct benefits category as well..

Direct benefits are generally better supported in the literature.

Indirect Benefits include genetic compatibility and heterozygosity based offspring vigor type arguments.

Indirect benefits are likely important in some systems, but likely small effect sizes make statistically significant results difficult..

What does the paper say?

Well in a nutshell, the authors found:
1. There was no difference in hatching success for females with 1 male, 2 males, or 4 males.
2. There was no difference in the adult mass of sons
3. There was no difference in the proportion of offspring that survived

Hmmm, so far the “multiple mating is beneficial” hypothesis is not doing so well… Here are the interesting results.

4. Monogamous females daughters matured sooner than the daughters of multiply
mated females.
5. The daughters of monogamous females were significantly heavier that those of multiply mated females.

So it turns out that the evidence suggests that not only is there no benefit to multiple mating, but that monogamy might actually be better. Think about a population where there are both monogamous and multiply mated females.. Ceteris parabis, the monogamous females will have left more descendants than multiply mated females.. This effect follow from result #4 alone. The fact that monogamous females daughters were heavier should only serve to reinforce this effect- as likely fecundity increases with female weight..

So the question becomes why? There are 4 possibilities… The 1st seems most plausible- that males force, coerce, or somehow manipulate females to mate at a rate higher then their optimum.. This behavior situation has been described elsewhere in the literature. 2nd- it is possible that monogamous females offspring themselves produce fewer offspring than do multiply mated females. 3rd- its possible that there are undescribed benefits of multiple mating such that they end up doing better then monogamous females. Lastly, it is possible that the heritability of mating behavior is essentially 0. Such that monogamous females daughters are just as likely to be monogamous as they are multiply mated…

Anyway- interesting paper… worth a read. I hope they follow up on the issues I speak of.