Footprints of introgression inferred across the southern skua complex. Population names are colored according to the 7 phylogeographic groups defined based on the topology of the ML tree a) Unrooted ML tree inferred by TreeMix; the arrows denote 3 migration events from the origin to the recipient locality. Migration arrows are colored according to their weight. b) Southern South America, Subantarctica, and Antarctic Peninsula map showing the admixed populations: 2 from the Antarctic Peninsula (LGTL, DEVL) with a high percentage of South Polar Skua and 3 in the maritime Antarctic (BOUV, SHET, GEOR) with a higher percentage of Brown Skua ancestry. c) Genomic introgression results for Southern Hemisphere skua using the f-branch method. Darker colors in the heat map represent increasing evidence of specific gene flow events between lineages, and gray data points in the matrix correspond to tests that are not applicable to the provided phylogeny. Dashed lines in the phylogeny represent the ancestral lineage. The D statistic and f4-ratio reflect evidence of excess allele exchange between P3 and P2 for each trio.