Systematics provides the foundation for understanding plant diversity. It investigates evolutionary relationships among plants and establishes the principles for naming and classifying them. This framework is essential to many areas of biology, from evolutionary research and ecology to nature conservation.
Genetic data alone do not determine how plants should be classified. Modern DNA analyses, however, make it possible to reconstruct increasingly well-resolved phylogenetic trees, revealing evolutionary relationships with greater precision. These trees do not, in themselves, determine which evolutionary lineages should be recognized as distinct plant families. In their article, Böhnert and Weigend argue that classification should take into account not only evolutionary relationships, but also diagnosability and interpretability of external characteristics, stability and practical utility. In other words, can a family be recognized by a set of external characteristics—or is it defined so broadly that the diversity of the species it contains becomes difficult to grasp? The international classification of flowering plants known as “APG V” (2026) incorporates extensive genetic evidence, yet the boundaries of numerous plant families remain controversial. Such disagreements often arise not from conflicting data, but different interpretations of the evidence. Böhnert and Weigend therefore emphasize the importance of transparent decision-making and involving specialists in the relevant fields.
Chives and daffodils provide one example: Although they look distinctly different and were formerly assigned to separate families, under the APG classification they now belong to the same plant family. Both classifications are compatible with the known evolutionary relationships. Böhnert and Weigend therefore argue that decisions of this kind should be justified transparently. What are the benefits of merging the families? Which biological differences become less apparent as a result? And how does the relevant scientific community assess the alternatives?
As part of their studies, students learn to identify, distinguish and compare plant families on the basis of shared characteristics. The Botanic Gardens provide an opportunity to put this knowledge into context and deepen their understanding. At the same time, the gardens demonstrate that scientific classifications are not fixed, but evolve as new research findings emerge. Thus, they connect traditional botanical knowledge with current insights from evolutionary biology and phylogenomics.
The Systematics Section of the Botanic Gardens shows visitors not only how different plants can look, but also which species are related and which characteristics they share. Visitors can discover and compare familiar garden and wild plants alongside less familiar species. The collection illustrates how the plant world has evolved over time and how new scientific findings continue to shape our understanding of its diversity.