Fig. 1: Evolutionary history of inversions.
From: Inversions maintain differences between migratory phenotypes of a songbird
A Alternative population scenarios for two inversions (lines changing from solid to dotted) appearing at separate loci (red and blue) at timepoints TI1 and TI2, respectively. In the left scenario, the inversions appear as polymorphisms within a single ancestral population and eventually get sorted into one of two subspecies (TS). The divergence times of the inverted and non-inverted haplotypes will, in this case, reflect the timepoints of the inversion events. In the right scenario, an ancestral population splits into two allopatric populations (TA) and inversions appear in one of them. The two populations later come into secondary contact and merge (TH), before the inversions get sorted into one of two subspecies (TS). In this scenario, the divergence times of the inverted and non-inverted haplotypes for the two loci will be similar as they do not reflect the time of the inversion events, but the time of the ancestral population split (TA). B Population modeling parameter estimates (maximum composite likelihood with 95CI) for the three divergent regions in the willow warbler. Orange, blue, and green boxes refer to ancestral, northern and southern effective population sizes, respectively, with numbers given in units of 103. For chromosome 3, simulations confirmed a better fit for a model including migration (IM2), and in this case the blue arrow indicates the direction of migration with the rate given in units of 10−7. All three divergent regions have similar split times (~1.2 Myrs), as expected from the right scenario in (A).
