Taxonomy & Evolution

Hybridisation of native and foreign Sorbus trees in the Polish Carpathian mountains

Sorbus is a highly diverse tree genus but is this the result of hybridisation and introgression between native and foreign species?

Hybridisation, polyploidisation and apomixis are important processes influencing the genetic diversity and evolution of species. They have been particularly important for Sorbus species and have resulted in the high taxonomic complexity found in this genus. The genus contains about 200 species of trees and shrubs that are found natively across Europe, Asia and north Africa.

The phenomenon of interspecific hybridisation between native and foreign species is frequently a consequence of human activity. It may lead to increased diversity of plants but conversely it may significantly reduce genetic variation if invasive genotypes of natural species participate in this process.

Comparison of shrubs and leaves’ shapes of tested Sorbus aria and S. intermedia and the hybrid form of S. carpatica growing in Tatra National Park in Poland. Image credits: T. Zwijacz-Kozica (photos) and M. Kempf (leaves).

In their new article published in AoBP, Hebda et al. report the results of their preliminary research on Sorbus species in natural and protected areas of Tatra National Park in Poland. They analysed the genetic and morphological variability of several Sorbus species including native (Sorbus aria), foreign (S. intermedia) and potentially hybrid (S. carpatica) individuals from the Polish Carpathian mountain range.

Morphological analyses of leaves were unable to distinguish between S. intermedia and S. carpatica. Variation patterns at nuclear microsatellites loci were however able to distinguish the two species and identify S. carpatica as a hybrid. The authors also found evidence of high genetic variation and complex evolutionary history of the native S. aria. They suggest protection of all its stands to facilitate their natural regeneration. The results of the study will advance the management and design of protective strategies within the Carpathian Mountains, facilitating the identification of native, hybrid and foreign Sorbus species.