With pure epistasis, the increase in additive genetic variance is not restricted to the founder event
but continues through succeeding generations until populations fixed at both loci become common.
The results of the allozyme cluster analysis may be distorted by the effect of fixation of polymorphic alleles during the founder event
. Most gigantea fly populations are fixed for two loci polymorphic in altissima fly populations (Waring et al.
The theoretical prediction of increased responsiveness to selection at the modifier loci has been elaborated and confirmed by subsequent theoretical work showing that founder events
can indeed convert epistatic variance into additive genetic variance, thereby increasing - not diminishing - the overall levels of additive genetic variance and hence selective responsiveness immediately after the founder event
(Goodnight 1988; Wagner et al.
If the founder event
caused the large differentiation observed between Lab and P1 or P2, this should be reflected in the corrected measure of genetic divergence.
Although there is general agreement on the core of these ideas (e.g., see Provine 1989, Mayr 1992), opinions differ on whether founder events
ever lead to much loss of genetic variation (Lande 1980), or to major genetic reorganizations (Barton and Charlesworth 1984; Charlesworth and Rouhani 1988) and whether populations persist long enough at low density for strong inbreeding effects to occur (Parsons 1989).
The neutral effects of founder events
on the mean phenotype of a population have been well studied.
The expected heritability following a founder event
, making the assumptions listed above, is equal to the expected [V.sub.A], divided by the sum of the expected [V.sub.G] and [V.sub.E]:
We conclude that although founder events
may occasionally lead to the evolution of assortative mating and hence to speciation, our results do not support the claim that the founder-flush-crash model identifies conditions very likely to result in speciation events.
Rare conditions are therefore disproportionately common in populations with strong founder events
. Among Finns, for instance, congenital nephrotic syndrome, a relatively rare kidney disease, is uniquely prevalent.
However, the distance separating recolonized locations indicates that multiple founder events
likely occurred from streams east of the Wabash River.
Researchers can also use this information to develop an understanding of how the loss of genetic diversity often associated with founder events
may influence the evolution of invasive populations.
This has caused many researchers to doubt the importance of peak shift and founder events