- Siblicide
Siblicide (attributed to behavioural ecologist
Doug Mock ), thedeath of an individual by its close relatives may occur directly betweensibling s or indirectly across the parent-offspring relationship and is seen to have beneficial indirect results for the genetic viability of apopulation or direct results for the recipient individuals.Cattle Egret s, "Bubulcus ibis", exhibit asynchronous hatching andandrogen loading (in the first two eggs) in its 3-egg clutch. This results in more aggressive chicks with the first having a developmental head start. If food is scarce the third chick often dies or is killed by the larger siblings and so parental effort is better distributed between the remaining chicks, more likely to survive to reproduce. Thus the investment in the older chicks is safeguarded for longest. This is possibly either due to the unforeseen possibility of food abundance or the chance of sterility in one egg, something suggested by studies into theCommon Grackle , "Quiscalus quiscula".In
Spotted Hyena s, "Crocuta crocuta", pups of the same sex exhibit siblicide more often than male-female twins.Sex ratio s may be manipulated in this way and the dominant status of a female and transmission ofgenes may be ensured through a son or daughter which inherits this solely, receiving much more parental nursing and decreased sexual competition. Siblicidal ‘survival of the fittest ’ is also exhibited in parasiticwasps , which lay multiple eggs in a host, after which the strongestlarva kills its rival sibling.The theory of
kin selection may be seen as a genetically-mediated altruistic response within closely-related individuals whereby the fitness conferred by the altruist to the recipient outweighs the cost to itself or the sibling/parent group. The fact that such a sacrifice occurs indicates an evolutionary tendency in some taxa toward improved vertical gene transmission in families or a higher percentage of the unit in reaching a reproductive age in a resource-limited environment.ee also
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Parent-offspring conflict
*Sibling rivalry
*Nazca Booby References
*Alcock, J. (1998). "Animal Behaviour". 6th Ed. Sinauer Associates.
*Smith RL & Smith TM (2001). "Ecology and Field Biology". 6th Ed. Benjamin Cummings.Further reading
* Michalski, R. L., Russell, D. P., Shackelford, T. K., & Weekes-Shackelford, V. A. (in press). Siblicide and genetic relatedness in Chicago, 1870-1930. "Homicide Studies". [http://www.toddkshackelford.com/downloads/Michalski-Russell-HS.pdf Full text]
* Russell, D. P., Michalski, R. L., Shackelford, T. K., & Weekes-Shackelford, V. A. (2007). A preliminary investigation of siblicide as a function of genetic relatedness. "Journal of Forensic Sciences, 52," 738-739. [http://www.toddkshackelford.com/downloads/Russell-et-al-JFS-2007.pdf Full text]
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