SERPENTINE AND POLYPLOID DIFFERENTIATION WITHIN GALIUM-PUMILUM AGG. (RUBIACEAE) IN EASTERN C EUROPE

The local differentiation of a model group, Galium pumilum agg., was s tudied in serpentine versus non-serpentine habitats in the Czech Repub lic and adjacent regions in Austria, Germany and Poland. Serpentine ha bitats form ecologically distinct islands within the landscape; local micro-evolutionary processes may be important there, both because of s mall population sizes and the strong selection effects of the metal-ri ch soils. The Galium pumilum agg. is a group of taxa showing typical k aryological and ecological differentiation; the following species and cytotypes were studied: Galium pumilum MURRAY (2n=8x=88), G. valdepilo sum 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 inv estigation showed that serpentine versus non-serpentine habitats do no t play an important role in the differentiation of the species studied . (I) The examined populations of G. pumilum MURRAY were homogeneous i n 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 distribu tional difference. (3) G. sudeticum occupies special localities on ser pentine in western Bohemia, which are geographically isolated from its nearest localities in the Krkonose Mts. The plants coming from both l ocalities belong to the tetraploid cytotype. (4) A highly polyploid pl ant (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 tetraplo ids, but it is less suitable for separating the latter two ploidy leve ls. The occurrence of G. austriacum is reported for the Czech Republic for the first time with certainty. This record extends the known dist ribution area of G. austriacum in the NW direction.