Figure 6

GC3 is more conserved between pairs of large-bodied species. Each point on the plot represents one species pair. GC3 is less conserved between genes evolving in small-bodied species pairs (see Additional file 6). The hummingbird/swift (CALAN/CHAPE) pair appears to be an outlier with high conservation (approximately 4.75), possibly owing to hummingbird having a low, and therefore more conserved, GC for its size (GC: 0.4929, body mass 4.25 g).