It posits that, in addition to the initial inbreeding due to the founder effect
, the density of related individuals increases with limited gene flow within a cluster over time, leading to an increased frequency of crosses between related neighbors.
It was postulated at the time that this increased incidence could be attributed to a founder effect
. This hypothesis was later proved to be correct when Tipping et al.
Key words.--Colonization, floral polymorphism, founder effect
, frequency-dependent selection, gene flow, genetic drift, Lythrum salicaria, metapopulations, purple loosestrife, tristyly.
(3) SCA7 is the most common dominant ataxia in Sweden, Norway, Denmark and Finland, as a result of a founder effect
. (9) A similar experimental approach to that of the Jonasson et al.
In order for founder effect
speciation models to produce adaptive evolutionary change and speciation, the founder event must cause a large change in the genetic environment through drift or increased inbreeding but at the same time allow sufficient additive genetic variation for a significant evolutionary response to the altered genetic and external environment (Templeton 1980a, b).
A common SNP haplotype provides molecular proof of a founder effect
of Huntington disease linking two South African populations.
Two speciation modes, that is, speciation via peripheral isolation (or "founder effect
"; Mayr 1954) and local sympatric speciation (Bush 1975), can produce a pattern of allele relationships distinguished by all haplotypes of the widespread ("ancestral") species forming a paraphyletic group, whereas alleles of the newly formed ("derived") species arise from within the ancestral species clade [ILLUSTRATION FOR FIGURE 1 OMITTED].
A high frequency has been reported in South African white Afrikaners owing to a founder effect
. (2,3) In South Africans of mixed ancestry (coloureds), frequencies comparable to other world populations have been reported, but with an increased proportion of juvenile cases.
Under genetic transilience, there is no radical overall reduction in levels of genetic variation in the founding population as in the genetic revolution model, but the initial founder effect
can occasionally induce severe allele frequency alterations at one or more of the major loci, including fixation.
(2) A higher-than-expected number of subjects with homozygous FH suggested a founder effect
Under the founder-flush model of speciation proposed by Carson (1971), the first step in the speciation process is usually thought to be an incidental genetic change through founder effect
affecting mating behavior so that sexual premating isolation evolves.
or small population size probably explain several cases of reduced genetic variability in dimorphic species.