Abstract
Carex buekii is a highly adaptive species showing a fairly wide ecological spectrum. It belongs to the group of river corridor plants which are vulnerable to any human activity directed at transformation of river valley habitats worldwide. This study was aimed at: determining the phenotypic variability of the species in the central part of its range, examining effects of soil conditions on the sedge's morphological traits, and finding out whether the phenotypic plasticity observed may have taxonomic implications. A total of 487 specimens from 26 populations were collected in Hungary, Poland and Slovakia and tested by univariate, bivariate, and multivariate statistical methods. The analysis involved 16 morphological traits and 7 soil parameters (organic matter, pH, potassium, phosphorus, nitrogen, magnesium, calcium). Soil conditions were shown to affect the C. buekii morphology; particularly important was potassium, the only soil parameter that was indicated as a factor affecting intra-specific variability. Sites with lower contents of bioavailable potassium hosted C. buekii individuals which were generally smaller than those at sites showing higher soil potassium contents. The relationship held true also with respect to generative traits important in sedge taxonomy, i.e. utricle and beak lengths. Consideration of morphological differences only, without analysing relationships between morphology and soil conditions, could have resulted in distinguishing new entities at the level of species, subspecies or variety. Thus, knowledge on the range of phenotypic plasticity in field populations seems to be of a key importance in taxonomic studies.