Out of sync: Quinolizidine alkaloid evolution does not track phylogenetic relationships in Genisteae (Fabaceae)

Quinolizidine alkaloids (QAs) are specialized plant metabolites with antiherbivore defense functions and pharmaceutical applications. They occur frequently across the Fabaceae Genistoid clade especially in the tribe Genisteae. Previous literature that explored QA distribution utilized a limited number of taxa. This study provides the most taxonomically comprehensive survey of QAs in Genisteae to examine their evolution across a highly resolved phylogenomic tree of the tribe. Chemical compounds were extracted from fresh or herbarium tissue for 41 taxa, including one species each from 24 of the 25 Genisteae genera. Expanded species sampling was performed in the Lupinus and Teline/Genista clades. Resulting liquid chromatography-tandem mass spectrometry (LC-MS/MS) data enabled detailed analyses of QA presence/absence, chemical similarity, potential grouping factors, and phylogenetic signal. Quinolizidine alkaloids were found in all Genisteae clades and in every taxon sampled, underscoring their widespread occurrence. The QA distribution in Genisteae indicated very little pattern with regard to clade, sample origin, New/Old World Lupinus species, or species historically classified as Teline. All alkaloids considered together showed weak chemical grouping regarding clade and tissue type between herbarium and fresh samples. Neither QAs nor alkaloids in general displayed phylogenetic signal. This study afforded a more complete view of QAs in Genisteae, revealing that QA chemical diversity does not track the phylogeny with respect to compound types. The analyses supported this result in terms of grouping factors and chemical similarity, although there is a significant effect of tissue type at the alkaloid level.