Phylogeny and chemophenetics of the newly described Doronicum × longeflorens and related Doronicum taxa (Senecioneae, Asteraceae)

Untargeted Metabolomics for Integrative Taxonomy: Metabolomics, DNA Marker-Based Sequencing, and Phenotype Bioimaging

Integrative taxonomy is a fundamental part of biodiversity and combines traditional morphology with additional methods such as DNA sequencing or biochemistry. Here, we aim to establish untargeted metabolomics for use in chemotaxonomy. We used three thallose liverwort species Riccia glauca, R. sorocarpa, and R. warnstorfii (order Marchantiales, Ricciaceae) with Lunularia cruciata (order Marchantiales, Lunulariacea) as an outgroup. Liquid chromatography high-resolution mass-spectrometry (UPLC/ESI-QTOF-MS) with data-dependent acquisition (DDA-MS) were integrated with DNA marker-based sequencing of the trnL-trnF region and high-resolution bioimaging. Our untargeted chemotaxonomy methodology enables us to distinguish taxa based on chemophenetic markers at different levels of complexity: (1) molecules, (2) compound classes, (3) compound superclasses, and (4) molecular descriptors. For the investigated Riccia species, we identified 71 chemophenetic markers at the molecular level, a characteristic composition in 21 compound classes, and 21 molecular descriptors largely indicating electron state, presence of chemical motifs, and hydrogen bonds. Our untargeted approach revealed many chemophenetic markers at different complexity levels that can provide more mechanistic insight into phylogenetic delimitation of species within a clade than genetic-based methods coupled with traditional morphology-based information. However, analytical and bioinformatics analysis methods still need to be better integrated to link the chemophenetic information at multiple scales.

Seasonal variations in phenolic natural products in Fagus sylvatica (European beech) leaves

Fagus sylvatica L. (Fagaceae), European beech, is one of the most important deciduous tree species in Central Europe and the most common broadleaved tree species in Germany. We investigated the leaves of six individual Fagus sylvatica trees growing in a beech forest in Kiel, Schleswig-Holstein, Germany, for seasonal variations in the content of phenolic natural products over three consecutive growing seasons. The investigated compound classes comprised hydroxycinnamic acid and flavonoid derivatives. The content of phenolic compounds showed clear trends in all years. A sharp decline in the total content of phenolic substances was observed from mid-April to the end of May. During the summer months, the content of phenolic compounds remained stable with only slight fluctuations until fall. The values for individual trees deviated more pronouncedly from one another in spring, but converged during the course of the growing period. These trends, despite differences in absolute values, were identical in three consecutive growing seasons (2016-2018). Our results contribute to a better understanding of the dynamics of plant natural products of deciduous trees in temperate climates caused by seasonal variations.