Distribution of fourfold degenerate site (4dTv) distances of duplicate gene pairs in pear, apple, and strawberry. A total of 1085 synteny blocks in pear (726 in apple and 262 in strawberry) are selected to calculate 4dTv values. The distribution of 4dTv values in pear (in blue) and those of apple (in red) are similar, while those of strawberry (in black) are different, with a single peak around 0.65, suggesting that there is no recent whole-genome duplication (WGD) in strawberry. (Green groups) Synteny blocks (557) between pear and apple, revealing that these groups are closer to the y-axis, and suggesting a more recent divergence event must have occurred between pear and apple.
