Morphological and genetic analysis supports three species in Central European Veronica complex

A multidisciplinary study of the Central European Veronica hederifolia group supports recognizing three distinct species: diploid Veronica triloba, tetraploid Veronica sublobata and diploid Veronica hederifolia. The researchers combined DNA sequence analysis, ploidy assessment, morphometric measurements of herbarium material and a controlled growth experiment involving variable light and water conditions to evaluate species boundaries within the weedy polyploid complex. Among the diagnostic traits, chromosome number provided a clear initial separation.

V. triloba was diploid, whereas V. sublobata was tetraploid. The researchers also identified morphological characters that can distinguish the species without relying on ploidy alone. V. triloba could be identified by a low pedicel-to-calyx length ratio, below 1.59.

V. sublobata had a longer ratio and could be distinguished more consistently from V. hederifolia by scattered hairs around the pedicel and shorter hairs on the calyx. These structural features allowed the three Central European species to be differentiated reliably using the combined evidence. Leaf characters, by contrast, were strongly influenced by light and therefore were not considered diagnostic at the species level.

The growth experiment examined plants under differing combinations of light and water availability, allowing the researchers to assess how environmental conditions affected their appearance. The results showed that leaf form was highly sensitive to light, while the pedicel-to-calyx ratio and the distribution and length of hairs supplied more dependable traits for identification. The findings therefore favor reproductive-structure measurements and hair characters over leaf shape when separating these Central European species.

The study also reported the first triploid plant found in the group and noted that such hybrids appear to be rare. The results apply most directly to the Central European material examined. The authors emphasized that phylogenetic and morphological variation within the wider group has not yet been analyzed sufficiently across the Mediterranean.

More intensive investigation is therefore needed to determine how species relationships and diagnostic characters vary across the full geographic range. Within its stated Central European scope, however, the study provides a practical framework for identifying the three recognized species and shows that chromosome state, floral measurements and hair morphology can be used together to resolve their boundaries.

Subject of Research: Species delimitation in the Central European Veronica hederifolia polyploid complex

Article Title: Species limits in Veronica hederifolia and relatives: experimental, morphometric, and phylogenetic approaches in a weedy polyploid complex

Article References: Albach, D. C., & Kúr, P. (2026). Species limits in Veronica hederifolia and relatives: experimental, morphometric, and phylogenetic approaches in a weedy polyploid complex. BMC Plant Biology, 26(1), Article 1819. https://doi.org/10.1186/s12870-026-10212-6

Image Credits: AI Generated

DOI: 10.1186/s12870-026-10212-6

Keywords: Veronica hederifolia, plant taxonomy, species delimitation, polyploidy, ploidy analysis, morphometrics, phylogenetics, DNA sequencing, growth experiment, Species, limits, Veronica