Extended Data Fig. 2: QTL mapping of other spine lengths and axial traits.

a. Schematic of Gasterosteus anatomical features. Most Gasterosteus have three dorsal spines that in this study are referred to as dorsal spine 1 (DS1), dorsal spine 2 (DS2), and dorsal spine last (DSL). The dorsal side of the fish also has median bony plates known as pterygiophores, some of which underlie dorsal spines. Typical A-P midline pattern: two non-spine bearing/blank pterygiophores (Pter1 and Pter 2), dorsal spine 1 on pterygiophore 3 (Pter3), dorsal spine 2 on pterygiophore 4 (Pter4), non-spine bearing pterygiophore 5 (Pter5), and dorsal spine last on pterygiophore 6 (Pter6). The three unpaired fins are shown in light gray: dorsal fin (DF), caudal fin (CF), and anal fin (AF). The anal spine (AS) is also indicated on the ventral side of the fish. The standard length shown with the dotted line is from the anterior tip of the jaw to the posterior of the hypural plates. b. QTL plot of DS1 length c. QTL plot of DSL length d. QTL plot of pterygiophore number e. QTL plot of total vertebral number f. QTL plot of caudal vertebral number. Dotted lines represent genome-wide significance thresholds. Abdominal vertebral number and anal spine length were also tested, but they did not result in any peaks that passed the genome wide significance threshold. The significance threshold (dashed line) is based on LOD scores obtained in 1,000 permutations of the phenotype data (α = 0.05).