Outlook for the original common yew population in the Podyjí region
Historically, the common yew was gradually displaced to less accessible, extreme habitats, leading to its status as a highly endangered plant species. Currently, only a few significant natural areas and numerous small localities where it thrives remain in the Czech Republic, primarily within protected regions.
Photo: Massive male common yew, Podyjí, Bítov Castle area, author J. Ponikelský, 31. 5. 2022
Common yews of cultural origin, often from unspecified sources, have been planted in ornamental gardens and parks both in the past and present. However, their widespread presence poses a risk to nature and landscape protection. This is due to the potential negative impacts they can have, such as crossbreeding and genetic erosion, on the preserved gene pool of natural populations. These populations rely on local pollen and seeds, which contain DNA with alleles from genes that may not be native to the area.
The wind pollinates common yew, and its seeds are spread when birds or mammals eat them. The seeds pass through their digestive tracts and are excreted undigested in the faeces.
Scientists from the VÚLHM, v. v. i., Department of Biology and Forest Tree Breeding conducted genetic research on the original common yew population in the Podyjí region and its protection. They published their findings in the paper titled “Genetic characterization of common yew (Taxus baccata L.) In the wider area of the Podyjí/Thayatal and the Svitavy region with a link to conservation management.” (Genetická charakterizace tisu červeného v širší oblasti Podyjí/Thayatal a na Svitavsku s vazbou na ochranářský management). This paper appeared in the journal Reports of Forestry Research, issue 3, in 2024.
The scientists aimed to analyse DNA to assess the genetic diversity, structure, and differentiation of three nearby natural populations of common yew—specifically, those in Podyjí National Park, the surrounding area outside the park, and Thayatal National Park. They also compared these populations to regional yew groups with presumed cultural origins and other remaining domestic subpopulations. This research aims to provide solid evidence for developing an effective regional action plan for the conservation and management of the Podyjí yew population in the future.
Some remnant populations of common yew in the Czech Republic continue to experience negative effects, such as decreased vitality and abundance, due to a previously applied conservation approach known as the “static” concept. This method operated on the principle of minimal human intervention, essentially aiming to let the natural development of the protected species unfold without interference.
However, modern species protection is informed by a solid base of expert knowledge in conservation biology. This is evident in contemporary in situ and ex situ practices that incorporate active (dynamic) population management, which routinely utilizes molecular genetic analysis techniques.
Photo: Common yew in Hřebečov silver fir and European beech forest stands, Svitavy Region, PP “Pod skálou”, author J. Ponikelský, 5. 11. 2024
The current distribution of yew trees in the Podyjí region is documented in the Czech flora and vegetation database Pladias (www.pladias.cz), which includes data from the mapping of biotopes in the Czech Republic. In the Podyjí National Park and Thayatal National Park, the common yew is currently found infrequently on the shaded foothills of scree slopes, specifically in inverted positions on the right bank of the Dyje River between Braitava and Hardegg. Additionally, it can be found on the left bank near the localities known as “Hardeggské vyhlídky” and “Široké pole.”
In 2015, when active management began, the residual yew population in Podyjí National Park comprised only two dry trees, one drying tree, and approximately 20 healthy individuals, mostly male, spread across four locations: Braitava, Gáliš, Široké Pole, and the area on the left bank of the Dyje River opposite Hardegg. Only the Gáliš and Braitava locations had seedlings, with around 40 of these seedlings later protected by fencing.
Before initiating rescue management, the population was relatively weak but still viable, consisting of approximately 30–100 individuals in terms of both characteristics and risk. From 2015 to 2023, a total of 340 plants of local, primarily generative origin were planted in suitable locations to strengthen this population.
In contrast, much larger natural populations are found on the opposite side of the Thaya River in the Austrian Thayatal National Park, where at least dozens of vital adult yews, primarily female, have been identified. It is likely that there are hundreds of tree-like individuals growing in this area.
In the Moravian part of the Dyje Valley, outside of the National Park, there are several adult yew trees growing in rubble forests. These include around 15 trees in the Bílý Kříž Nature Reserve (PR) and approximately 30 trees in the Tisová Stráň Nature Reserve. Both reserves are part of a larger vegetation belt with a more natural character that extends along both banks of the Dyje River, roughly from Uherčice to Vranov nad Dyjí. This belt also features a single mature male yew tree located at the Kolikron locality, across from the Babka promontory in the Jazovice cadastral area.
In 2021 and 2022, scientists collected samples of sprouting needles from naturally growing common yews. This work was conducted with the consent of the relevant nature conservation authorities in the Czech Republic and Austria. The samples were gathered from various locations, including the Podyjí National Park, the Dyje Valley, and Fugnitz, as well as the Einsiedler site in the Thayatal National Park. Additionally, samples were collected from the Bílý Kříž Nature Reserve, the Tisová Stráň Nature Reserve, and the Kolikron site. Further samples were taken from yews of cultural origin at the Lukov and Znojmo sites in the Podyjí National Park and its surrounding areas, including locations below Mitrov, opposite the Babka promontory, near Bítov Castle, and on Cínová hora near Znojmo.
Photo: Planting of common yew of local provenance, 10 years old, Podyjí National Park, author J. Ponikelský, 30. 5. 2022
Conclusion
Although some scientists suggest that most naturally growing yews in the Czech Republic originated from a single refuge, the significant differences observed among individual isolated populations are the result of long-term adaptations to their specific local conditions. It is essential to consider these adaptations when transferring reproductive materials.
Even domestically transferring reproductive material could, in some cases, introduce undesirable genetic traits into the isolated populations that have adapted to their local environments.
Understanding the genetic makeup of yew populations is essential for implementing effective conservation management strategies in the Podyjí and Hřebeč areas.
The interest of forest owners and managers in planting yew trees is highlighted by the planting of 89 trees, whose origins were not specified, across suitable sites in the Znojmo Forest Administration during 2011 and 2012.
These commendable efforts by management entities to enhance biodiversity underscore the importance of sharing fundamental information about the genetic structure of our tree species populations with the professional community.
Subpopulations of yew in the Czech Republic have undergone genetic differentiation during their isolated development.
Despite their relatively low abundance, these subpopulations have managed to maintain a sufficient level of internal genetic diversity. To facilitate comparison, scientists collected samples from a geographically distant subpopulation in the „Hřebečský hřbet“ area, cultural occurrences in the Svitavy region, the „Jílovské tisy“ nature reserve near Děčín, and the Vývěry Punkvy national nature reserve (NPR) in the Moravian Karst.
The scientists chose the „Hřebečský hřbet“, Svitavy region, and Moravian Karst based on existing literature suggesting a genetic affinity among these occurrences with Podyjí. In contrast, the „Jílovské tisy“ area was selected due to its relative isolation and the assumption of a greater genetic distance.
In total, analyses were conducted on samples taken from 270 individuals.
Photo: Protection of natural rejuvenation of yew against damage by wildlife, Podyjí National Park, author J. Ponikelský, 26. 7. 2022
The intentional mixing of alleles in small remnant populations can lead to undesirable homogenization of the existing gene pool and the potential loss of unique alleles.
In small yew populations, management efforts should primarily focus on promoting rapid generative reproduction of local genetic resources and increasing effective population sizes to a range of approximately 50 to 500 individuals.
If there is a decision to strengthen populations, particularly in small remnant groups, genetic analyses can guide the appropriate transfer of reproductive material.
The newly acquired knowledge should act as a crucial foundation for potential proposals for the conservation management of yew, including regional action plans and updated care strategies for small-scale specially protected areas.
The paper “Genetic characterization of common yew (Taxus baccata L.) In the wider area of the Podyjí/Thayatal and the Svitavy region with a link to conservation management.” (Genetická charakterizace tisu červeného v širší oblasti Podyjí/Thayatal a na Svitavsku s vazbou na ochranářský management) can be downloaded here.
Authors of original paper: Petr Novotný, Martina Komárková, Helena Cvrčková, Jaroslav Dostál, Pavlína Máchová, VÚLHM, v. v. i.; Jaroslav Ponikelský, Správa národního parku Podyjí; e-mail: pnovotny@vulhm.cz
Prepared by Jan Řezáč, VÚLHM, v. v. i., e-mail: rezac@vulhm.cz, based on the original