Fig. 7: Haplotype network for the β-globin cluster showing the 3′ coding region of capillary-sequenced HBB (β^A), including 291 bp spanning part of intron 2 and all of exon 3 including the Alaβ^A116Ser and Leuβ^A116Met amino-acid substitutions previously characterized experimentally by Natarajan et al. (2015).

Bold edged circles represent haplotypes with putatively adaptive amino-acid substitutions appearing identical by descent (IBD) between high-altitude populations of the two duck species. Six β^A116Ser-β^A116Met haplotypes were identified. One haplotype (at the center) is common, and the other five are singletons or occur at low frequency and radiate from the central common haplotype in a star-like pattern. Five of these rare β^A116Ser-β^A116Met haplotypes are present in speckled teal, whereas only one is present in yellow-billed pintail, consistent with the coalescent model data indicating that speckled teal has an older ancestry in the highlands.