Phylogenomics reveals reticulate evolution in the <i>Chenopodium album</i> complex

Abstract Background and Aims Complex genomic histories driven by hybridization and polyploidy can shape key plant traits such as defense, stress tolerance, and toxicity, particularly in Amaran-thaceae, which includes crops such as quinoa and spinach. Within this family, white goosefoot ( Chenopodium album ) is both a widespread agricultural weed and a traditional food resource. However, its evolutionary history is complicated by discordant signals among genomic markers within the C. album complex, comprising diploid, tetraploid, and hexaploid taxa. Here, we tested whether reticulate evolution underlies this genome-wide discordance. Methods Using genome-scale phylogenomic data, we analysed 2,298 conserved nuclear loci (BUSCO genes) across 27 Amaranthaceae genomes. Both single- and multicopy gene families were included to capture signals of gene duplication, incomplete lineage sorting, and hybridization. Complementary phylogenomic approaches were used to evaluate whether the evolutionary history is best supported by strictly bifurcating relationships or by reticulate evolution. Key Results A consistent C. album lineage was recovered, comprising tetraploid and hexaploid C. album cytotypes together with C. suecicum , C. strictum , C. formosanum , C. acuminatum , and C. opulifolium . Phylogenetic discordance was concentrated within Chenopodium , particularly around the C. album and C. quinoa lineages. Models incorporating hybridization fit better than strictly bifurcating relationships, supporting at least two reticulation events. Hybridization signals were detected in 271 loci in tetraploid and 270 in hexaploid C. album , of which 232 were shared, indicating a shared hybrid origin rather than independent lineages. Conclusions The evolutionary history of the C. album lineage is best explained by reticulate processes involving hybridization and polyploidy. Conserved nuclear loci retain persistent signatures of these events, helping to resolve complex evolutionary histories in polyploid plant systems.