Phylogeny of chromosome inversion polymorphism in Drosophila pseudoobscura

The Standard (ST) arrangement of the third chromosome is related to the Arrowhead (AR) pattern by a paracentric inversion involving about a third of the chromosome. Other chromosome polymorphisms involve multiple inversions, and inversions-within-inversions. Reconstruction of the pattern of inversions allows the phylogeny of the inversions patterns to be reconstructed (below). [chromosome figures after Dobzhansky & Sturtevant (1938)]