Parent–offspring conflict
Therefore, any gene in an offspring that leads to additional PI decreases (to some extent) the number of surviving copies of itself that may be located in siblings.
In contrast, offspring benefits from low numbers of seeds per fruit, which reduces sibling competition before and after dispersal.
This conflict about resource allocation is most obviously manifested in the reduction of brood size (i.e. a decrease in the proportion of ovules matured into seeds).
(Although other explanations for this phenomenon exist, such as genetic load, resource depletion or maternal regulation of offspring quality, they could not be supported by experiments.)
In wild chimpanzees an abrupt increase in maternal rejections and a decrease in mother-offspring contact is found when mothers resume estrus and consort with males.
Consistency of this hypothesis has been shown for Japanese macaques where decreasing temperatures result in higher maternal rejections and increased number of contacts made by infants.
[9] In eusocial species, the parent-offspring conflict takes on a unique role because of haplodiploidy and the prevalence of sterile workers.
The conflict in social insects is about the level investment the queen should provide for each sex for current and future offspring.
[11] Females of certain poison frog species produce unfertilized, non-developing trophic eggs which provide nutrition to her tadpoles.
[12] In the neotropical, foam-nesting pointedbelly frog (Leptodactylus podicipinus), females providing parental care to tadpoles have reduced body condition and food ingestion.
This indicates that the cost of parental care in the pointedbelly frog has the potential to affect future reproduction of females due to the reaction in body condition and food intake.
[13] In the Puerto Rican common coqui, parental care is performed exclusively by males and consists of attending to the eggs and tadpoles at an oviposition site.
When brooding, males have a higher frequency of empty stomachs and lose a significant portion of their initial body mass during parental care.
This defense behavior includes aggressive calling, sustained biting, wrestling, and blocking directed against the nest intruder.
[14] Females of the Allegheny Mountain dusky salamander exhibit less activity and become associated with the nest site well in advance of oviposition in preparation for the reproductive season.
[15] Females of the red-backed salamander make a substantial parental investment in terms of clutch size and brooding behavior.
When brooding, females usually do not leave their eggs to forage but rather rely upon their fat reserves and any resources they encounter at their oviposition site.
A similar conflict happens in direct-developing frogs that care for clutches, with protected tadpoles having the advantage of a slower, safer development, but they need to be ready to reach independence rapidly due to the risks of predation or desiccation.
[12] An important illustration of POC within humans is provided by David Haig’s (1993) work on genetic conflicts in pregnancy.
The placenta, for example, secretes allocrine hormones that decrease the sensitivity of the mother to insulin and thus make a larger supply of blood sugar available to the fetus.
This results in hypertension and, significantly, high birth weight is positively correlated with maternal blood pressure.
