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A research group from Nitra is studying the evolution and genetics of pines in so-called hybrid zones – areas where the classical biological definition of a species begins to break down. Although two distinct species meet in these zones, they can interbreed and produce shared offspring.

“In Slovakia, such situations occur at a few very rare sites where Scots pine (Pinus sylvestris) and mountain pine (Pinus mugo) grow together under the extreme conditions of peatlands. These ecosystems function as natural laboratories where we can directly observe how species evolve, how their genes mix or, conversely, become isolated,” explains Miroslav Klobučník from the Institute of Plant Genetics and Biotechnology, Plant Biology and Biodiversity Research Center SAS, in Nitra. Here, a so-called hybrid swarm emerges—a population in which two related species or subspecies have been mixing for a long time. These are not isolated hybrids, but an entire community of individuals with varying proportions of genes from both parental species.

The fact that hybrid individuals survive in peatlands – and in some places even dominate – suggests that these extreme habitats provide suitable conditions for the formation and persistence of new evolutionary combinations.

Hybrid swarms are extremely valuable for evolutionary biology, as they allow scientists to observe evolutionary processes in real time: which genes are transferred, which are blocked, and which environmental factors influence species mixing.

“In Slovakia, pine hybrid swarms are found only in the peatlands of the Medzi Bormi Nature Reserve (Zuberec), Rudné Nature Reserve (Suchá Hora), and Tisovnica Nature Reserve (Oravská Polhora). Signs of hybridization were also reported at the rocky locality Obšívanka (Terchová), but current microsatellite analyses have questioned the hybrid character of this population,” adds Klobučník.

To obtain the most accurate picture of how pines behave and evolve in hybrid populations, researchers use several complementary methods – genetic, morphological, and physiological – together providing a comprehensive understanding of hybridization.

The home of these rare hybrids, the peatlands, are extremely scarce in Slovakia and were damaged for decades by drainage. As peatlands dry, they lose not only water but also entire communities of specialized species – including the pine hybrids, which are evolutionarily exceptional.

“Our genetic analyses show that the populations in the Medzi Bormi, Rudné, and Tisovnica peatlands are now genetically highly distinct and that they most likely formed much more extensive populations of a similar character in the past. The original area of these peatlands exceeded 100 hectares – today, Medzi Bormi covers ~6 ha, Rudné ~2 ha, and Tisovnica ~11 ha. Such contraction has led to population declines, loss of genetic diversity, and may affect their future viability,” says Klobučník.

Research on pine hybrid zones is therefore also important for nature conservation – genetic diversity is the basis of adaptability and an irreplaceable component of Slovakia’s biodiversity. Forests and peatlands with greater diversity are more resilient to drought, pests, and climate extremes; they store more carbon, regulate water, and protect soil from erosion and floods – providing tangible benefits for management and conservation efforts. Genetically diverse populations serve as “insurance” for the future – more resilient trees are better able to withstand climate change and new environmental challenges.  

“Even though peatland pine populations do not generate direct profit from timber production, they provide essential ecosystem services: water retention and filtration, carbon storage, and maintaining the microclimate of the landscape. Losing these systems represents not only biological but also economic damage. Protecting biodiversity and preserving hybrid pine populations is therefore important not only ecologically, but also practically,” Klobučník concludes.

The scientific team is currently studying the genetic structure of common juniper (Juniperus communis) in Slovakia, including its subspecies dwarf juniper (J. communis subsp. nana) and their natural hybrid J. communis nothovar. intermedia. The goal is to understand whether genetic factors contribute to its decline and to propose measures for the conservation of this ecologically and culturally significant woody species.

Edited by Monika Tináková

Foto: Martin Galgóci, Andrej Kormuťák, Miroslav Klobučník, Ústav genetiky a biotechnológií rastlín CBRB SAV, v. v. i.