Convergent and lineage-specific genomic changes contribute to adaptations in sugar-consuming birds
High-sugar diets cause human metabolic diseases, yet several bird lineages convergently adapted to feeding on sugar-rich nectar or fruits. We investigated the underlying molecular mechanisms in hummingbirds, parrots, honeyeaters, and sunbirds by generating nine new genomes and 90 tissue-specific transcriptomes. Comparative screens revealed an excess of repeated selection in both protein-coding and regulatory sequences in sugar-feeding birds, suggesting reuse of genetic elements. Sequence or expression changes in sugar-feeders affect genes involved in blood pressure regulation, lipid, amino acid and carbohydrate metabolism, with experiments showing functional changes in honeyeater hexokinase 3. MLXIPL, a key regulator of sugar and lipid homeostasis, showed convergent sequence and regulatory changes across all sugar-feeding clades; experiments revealed enhanced sugar-induced transcriptional activity of hummingbird MLXIPL, highlighting its adaptive role in high-sugar diets. Summary Figure: Our comparative screens across four independent sugar-feeding bird groups identified both repeated and lineage-specific targets of selection O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=65 SRC="FIGDIR/small/610474v2_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@148f5c8org.highwire.dtl.DTLVardef@1005dbaorg.highwire.dtl.DTLVardef@1097facorg.highwire.dtl.DTLVardef@9d365c_HPS_FORMAT_FIGEXP M_FIG C_FIG