Fig. 2

Overview of the evolutionary history of gene gain and gene loss from brown algal SDRs. The maximum likelihood phylogenetic tree based on cox1–cox3 sequences (PhyML, HKY85 model, 500 bootstraps) represents the evolutionary relationships among species analysed in the current study. Branch lengths are proportional to lineage divergence times. Genes at the base of the tree are predicted to be ancestral in the SDR; the estimated timing of proposed gene gain and gene loss events is indicated by names placed above or below specific branches of the tree, respectively. Gene names, which are indicated based on the Ectocarpus sp. orthologue, are colour-coded to indicate the current chromosomal location—male SDR (blue), female SDR (pink), autosomal (green)—or to indicate gene loss (grey). The two genes for which SDR ancestry is unclear are marked in light pink