Fig. 1

Distribution of long-lived Y-linked genes and their X-linked and autosomal homologs in eight mammals. a Species distribution and characteristics of the 14 longest-lived mammalian Y-linked genes. Phylogenetic tree representing evolutionary relationships among eight mammals is shown at top. Branch lengths are proportional to lineage divergence times; time scale in millions of years (mya) at left. The presence of a Y-linked gene in a given species is indicated by a blue circle; gene loss events are indicated by white circles. Blank squares in the opossum lineage represent seven genes that became Y-linked after the divergence of the eutherian and marsupial lineages. Genes are ranked according to total branch length, which is the sum of branch lengths for each species possessing an intact Y-linked homolog of that gene. The seven genes that were considered for further study met both of the criteria shown at the right side of the table: loss from the Y chromosome in one or more lineages and single-copy presence on the Y chromosome. Autosomal copies were found in one or more species for four of the seven genes. b Distribution of X-linked, Y-linked, and autosomal homologs of four genes in eight mammals. Filled circles indicate presence of gene in given species: X-linked (pink), Y-linked (blue), or autosomal (green). Autosomal copies are either ancestral (A), retrotransposed (R), or translocated (T), as indicated. White circles represent gene loss events