| Abstrakt: |
Abstract: Mode of reproduction and presence of reproductive barriers were studied in two closely related members of the genus Cyanus: the C. triumfetti (diploid 2n = 22) and C. montanus (tetraploid 2n = 44) groups. Based on results from isolation and emasculation experiments, taxa of these groups can be considered allogamous with a low selfing rate (0.07 %-0.21 % of achenes developed after selfing). Taxa of the C. triumfetti group hybridize easily and produce viable progeny. Differences in the percentage of well-developed achenes per capitulum obtained from interspecific crosses between members of the C. triumfetti group suggested different levels of reproductive isolation. The percentage of well-developed achenes of most homoploid crosses was 3.47 %-8.87 %. Higher percentages of well-developed achenes were obtained from crosses between Eastern Carpathian C. pinnatifidus and Alpine C. triumfetti s. str. (18.36 % ; 26.56 %) and between geographically close taxa in Central Europe (C. dominii, C. strictus and ‘intermediate morphotype'; 12.75 % -17.60 %), which indicate their overall close relatedness. Crossing geographically remote C. strictus and C. triumfetti s. str. yielded no or only few (0.99 %) well-developed achenes, indicating an increased degree of incompatibility in allopatry. The success of heteroploid crosses between plants belonging to different groups was reduced (2.96 %) and suggested reproductive incompatibilities between ploidy levels. The progeny of heteroploid crosses comprised 63 % of triploids of presumable hybrid origin on tetraploid as well as diploid maternal plants. Another 15.22 % of progeny had the maternal cytotype, probably resulting from selfing. Low viability of heteroploid hybrids supports the existence of post-zygotic mechanisms. |
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