Title : Old descriptions, new evidence: Polyploid hybrids of Mercurialis perennis and M. Ovata revealed by genome size and stomatal traits
Abstract:
Hybridization and polyploidization play a key role in plant evolution, yet their impact in perennial species of the genus Mercurialis remains underexplored. In North Bohemia, we investigate natural hybridization between Mercurialis perennis and the rare, legally protected M. ovata. Putative hybrids of these species were first noted in early 20th-century Central European floristic surveys, described as Mercurialis × paxii and M. longistipes, but their taxonomic status has remained unclear due to a lack of cytogenetic and molecular data. Using flow cytometry and digital morphometry, we analyzed genome sizes, leaf shape, and stomatal density in several populations. Our results confirm genome sizes for M. ovata (3.39 ± 0.27 pg/2C) and M. perennis (7.24 ± 0.17 pg/2C), while morphologically intermediate individuals showed a mean genome size of 5.62± 0.66 pg/2C, consistent with hybrid origin. These plants also differed significantly in stomatal density and epidermal cell morphology, suggesting that stomatal traits may serve as a reliable diagnostic marker. The combined data support the existence of at least two distinct hybrid or polyploid forms in regions where both parental species co-occur. Our findings not only shed light on historical taxonomic ambiguities but also open new avenues for field identification and conservation of M. ovata. Ongoing cytological and molecular analyses aim to refine these preliminary conclusions and contribute to a practical identification key and distribution map.
Audience Take Away Notes:
- How flow cytometry and stomatal analysis can be combined to identify natural plant hybrids—with Mercurialis as a case study highlighting genome size and morphological traits as diagnostic tools
- Evidence for the existence of polyploid hybrids between M. perennis and M. ovata in North Bohemia, including novel data that confirm and extend early 20th-century observations
- The taxonomic and conservation implications of hybridization in rare and protected plant species, particularly the challenges of recognizing cryptic diversity in field settings
