Some reasons for differences in the rate of range expansion by tree squirrels have been suggested by Signorile (2014) and include size of the founding population
, genetic diversity and population structure.
On average, all three indexes of genetic variability decreased as the effective size of the founding population
All non-Africans stem from one major founding population
, the studies agree.
Information about the origin of the founding population
is also important and can help to elucidate the history and spread of the invasion (Fitzpatrick et al.
LiveScience reports on the international team's new study, which found that "the central and eastern European Jewish population, known as Ashkenazi Jews, from whom most American Jews are descended, started from a founding population
of about 350 people between 600 and 800 years ago.
Their hypothesis is a somewhat complicated one: that the combination of a small founding population
at the end of the Dark Ages and a narrow concentration in the profession of moneylending created powerful selection pressures on Ashkenazi Jews for high intelligence, and more specifically the kind of intelligence needed for symbolic manipulation as opposed to spatial manipulation.
A single migration of humans introduced the majority of the founding population
of the Americas south of the ice sheet at the close of the last Ice Age.
Also, although the SA Lemba and Zimbabwean Remba originated from the same founding population
, several differences were observed in the composition and frequencies of their Y chromosome pools, perhaps a consequence of drift and human contacts the groups may have had following their split.
As far as men are concerned, previous research on Madagascans, specifically on the Y sex chromosome (passed from father to son), indicates that the males of this founding population
were also from Southeast Asia, though they don't know how many there were.
The original founding population
was diverse and generalized, both morphologically and genetically, and its descendent populations, affected by changing environments, produced variant characteristics and newly derived traits.
Introduced populations often act as natural experiments in that regard, particularly when founding population
size is known, as well as demographic trends since founding.
is older and may have been the founding population