Evoluční a ochranářské důsledky mezidruhové hybridizace u vzácných druhů rostlin

Vít, Petr

3 Summary Hybridization plays an important role in the evolution of vascular plants. It can have both positive and negative consequences, ranging from the origin of new species on the one hand to the extinction of taxa through introgression on the other. These effects may be pronounced in geographically restricted or rare species. The core of this thesis are three case studies addressing interspecific hybridization involving rare angiosperm species. Finally, the thesis is completed with a study considering hybridization as a source of variation and new species. The coexistence of frequent primary hybrids with their parental taxa was revealed in the system comprising the rare species Cerastium alsinifolium and its widespread counterpart C. arvense. The spatial distribution of the endemic species and its habitat preferences were elucidated. In contrast, comparatively rare hybridization events were found in the Nymphaea alba - N. candida complex. Although it has been assumed that water lilies hybridize freely, our karyological data do not support this hypothesis. Hybrids therefore do not present a serious risk to either of these rare species. The third study describes interspecific hybridization in the spore-bearing genus Diphasiastrum. Traditionally, three basic and three hybridogenous species are recognized...

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