Figure 7: Four alternative hypotheses to explain the origin of mtDNA paraphyly in Silver-backed Butcherbirds.
From: Australia’s arid-adapted butcherbirds experienced range expansions during Pleistocene glacial maxima
(a) Introgression from eastern Grey Butcherbirds into Silver-backed Butcherbirds, (b) introgression from Black-backed Butcherbirds into Silver-backed Butcherbirds, (c) incomplete lineage sorting, and (d) incorrect taxonomy. Green lines represent the mtDNA gene tree embedded within four alternative species trees that are scaled by time. C, Cape York Peninsula (CYP); N, New Guinea (NG); K, Kimberley (KIM); T, Top End (TE); E, eastern Grey Butcherbirds; W, western Grey Butcherbirds.
