2.1.3 | Recurring decreasing admixture scenarios
For a given source population S, scenarios S-DE consider a
recurring monotonically decreasing admixture from population S at each
generation between generation 1 (after founding at generation 0) and
generation 20 (sampled population) (Figure 1 , Table
1 ). In these scenario, s S,g, with g in
[1..20], are the discrete numerical solutions of a rectangular
hyperbola function over the 20 generations of the admixture process
until present as described in Supplementary Note S2 . In brief,
this function is determined by parameter u S, the
“steepness” of the curvature of the decrease, in [0,1/2],s S,1, the admixture proportion from population S
at generation 1 (after founding), in [0,1], ands S,20, the last admixture proportion in the
present, in [0,s S,1/3]. Note that we chose
the boundaries for s S,20 in order to reduce the
parameter space and nestedness among competing scenarios, by explicitly
forcing scenarios S-DE into a substantially decreasing admixture
process. Furthermore, note that parameter u Svalues close to 0 create pulse-like scenarios of intensitys S,1 occurring immediately after founding,
followed by constant recurring admixture of intensitys S,20 at each generation until present.
Alternatively, parameter u S values close to 1/2
create scenarios with a linearly decreasing admixture betweens S,1 and s S,20 from
population S at each generation after founding.