Abstract
The local differentiation of a model group, Galium pumilum agg., was studied in serpentine versus non-serpentine habitats in the Czech Republic and adjacent regions in Austria, Germany and Poland. Serpentine habitats form ecologically distinct islands within the landscape; local micro-evolutionary processes may be important there, both because of small population sizes and the strong selection effects of the metal-rich soils. The Galium pumilum agg. is a group of taxa showing typical karyological and ecological differentiation; the following species and cytotypes were studied: Galium pumilum MURRAY (2n=8x=88), G. valdepilosum HEINR. BRAUN (2n=2x=22, 2n=4x=44), G. sudeticum TAUSCH (2n=4x=44) and G. austriacum JACQ. (2n=4x=44). The karyological and taxonomic investigation showed that serpentine versus non-serpentine habitats do not play an important role in the differentiation of the species studied. (1) The examined populations of G. pumilum MURRAY were homogeneous in chromosome numbers, belonging to the octoploid (2n=88) cytotype only. (2) G. valdepilosum consists of two cytotypes. Both of them occur on and off serpentine sites, but they show pronounced East-West distributional difference. (3) G. sudeticum occupies special localities on serpentine in western Bohemia, which are geographically isolated from its nearest localities in the Krkonose Mts. The plants coming from both localities belong to the tetraploid cytotype. (4) A highly polyploid plant (2n=12x=ca. 132) from the G. pumilum group was found on serpentine. From the methodological point of view, pollen size turned out to be reliable only for distinguishing octoploids from diploids and tetraploids, but it is less suitable for separating the latter two ploidy levels. The occurrence of G. austriacum is reported for the Czech Republic for the first time with certainty. This record extends the known distribution area of G. austriacum in the NW direction.
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