Genomic Evidence for Convergent Adaptation through Tandem Gene Duplications in Carnivorous Butterworts and Bladderworts

Cases of convergent adaptation, especially between close relatives within a lineage, provide insights into constraints underlying the mechanisms of evolution. We examined this in the carnivorous plant family Lentibulariaceae, with its highly divergent trap designs but shared need for prey digestion, by generating a chromosome-level genome assembly for Pinguicula gigantea, the giant butterwort. Our work confirms a history of whole-genome duplication in the genus and provides strong phylogenomic evidence for a sister-group relationship between Lentibulariaceae and Acanthaceae. The genome also reveals that a key digestive adaptation, the expansion of cysteine protease genes active in digestion, was achieved through independent tandem duplications in the butterwort (Pinguicula) and its close relative, the bladderwort (Utricularia). Most of these parallel expansions arose in non-homologous regions of the two genomes, with a smaller subset located on homologous blocks. This study provides clear genomic evidence for convergent evolution and illustrates how similar selective pressures can repeatedly shape genomes in analogous ways.