Rhamnus fallax Boiss. is a distinctive calciphyte and pioneer species. It ranges from southeastern outskirts of Alps throughout the Balkan Peninsula to Greece and Bulgaria. The goals of this study were identification of the sex ratio of the sampled populations, existence of morphologic variability, influence of environmental factors on variability and occurrence of eventual sexual dimorphism in this species. We have chosen 6 populations in the area of Julian Alps. We analyzed 600 shrubs. Of these, we randomly selected 180 specimens from which we gathered 1407 leaves for morphometric analysis. Sex ratio was male biased on all 6 populations. On average, there were around 55 % males, 40 % females and the sex determination was not possible on 5 % of the shrubs. We carried out the hierarchical test to demonstrate the impact of individual factors (altitudinal belt, population, sex, specimen) on the variability of the measured characteristics. The greatest influence on the overall variability of leaves came from the intra-specimen level and the greatest influence on the overall variability of shrubs came from the specimen level. The gender had the weakest influence on leaves and shrubs variability. We used principal component analysis for determine average values of all characteristics for female in male plants. Leaves size on first 4 populations was pretty similar. The last two populations had smaller leaves because locations were more exposed. Sexual dimorphism was not clearly expressed in this study.
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