Founder population
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When a species invades a new area, especially an island, the original, small population is called a founder population. The concept of a founder population is usually used in a context of subsequent population growth, and populations that have recently arisen from small founder populations will exhibit reduced variation due to the genetic drift implied by such a population bottleneck. The genetics of Easter Islanders and those native to Pitcairn Island provide examples of such a gene pool of limited variation.
Founder populations are essential to the study of island biogeography. A natural tabula rasa is not easily found. Classic series of studies on founder population effects were done following the catastrophic eruption in 1883 of Krakatau, ('Krakatoa'), which erased all life on the island remnant. Another ongoing study has been following the biocolonization of Surtsey, Iceland, a new volcanic island that erupted offshore between 1963 and 1967.
An effective founder population consists only of those whose genetic prinmt is identifiable in subsequent populations. Because in sexual reproduction, genetic recombination ensures that with each generation only half the genetic material of a parent is represented in the offspring, some genetic lines may die out entirely, even though there are numerous progeny. The misinterpretations of "Mitochondrial Eve" are a case in point. A recent study (Hey 2005) concluded that of the people migrating across the Bering land bridgeat the close of the ice age, only 70 left their genetic print in modern descendents, a minute effective founder population— which is easily misread as though implying that only 70 people crossed to North America.
The effective founder population of Quebec was only 2,600. After twelve to sixteen generations, with an eighty-fold growth but minimal gene dilution from intermarriage, Quebec has what geneticists call optimal linkage disequilibrium (genetic sharing)[1] (http://www.genizon.com/html/content.asp?node=14). The result: far fewer genetic variations, including those that have been well studied because they are connected with inheritable diseases.
A cultural meme may die out in a comparable way, as when a surname or title becomes extinct through lack of Y chromosomes, even though there is a flourishing population of descendants, all through female lines.
External link
- Genizon.com: (http://www.genizon.com/html/content.asp?node=14) Quebec Founder Population
References
- Hey, Jody, 2005. "On the Number of New World Founders: A Population Genetic Portrait of the Peopling of the Americas" in PLoS Biol 2005 May 24;3(6):e193 [2] (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15898833&query_hl=1)