A LIGHT MICROSCOPICAL INVESTIGATION AND MULTIVARIATE STATISTICAL ANALYSES OF HETEROVALVAR CELLS OF CYCLOTELLA-SPECIES (BACILLARIOPHYCEAE) FROM LAKES OF THE BERLIN-BRANDENBURG REGION

Abstract

113 randomly selected frustules of Cyclotella taxa, taken from the plankton of four lakes, have been investigated with respect to variation between the two thecae of each frustule and also variation within and between populations occurring in the different lakes. Multivariate statistical analyses of phenetic similarity of the 226 thecae were based on a data matrix recording the status of 11 characters drawn from the structure of the siliceous wall. From the cluster analysis, 55% of the frustules could be characterized as heterovalvar. In these cases, the phenetically dissimilar thecae of a single frustule were allocated to different clusters. Principle component analyses showed that the variation in the relative length of the marginal striae, and also the number of marginal striae on the entire valve face, are correlated with valve circumference. The arrangement of depressions on central valve and the development of the central valvar undulation appear to be unrelated to valve size. Due to the existence of different patterns of markings within one frustule (“Cyclotella kuetzingiana var. radiosa”-pa.ttem, “C. kuetzingiana var. planetophora“-paltem, “C. ocellata“-pattern, “C. comensis“-paltem), these patterns have limited or no taxonomie value. Thus, as far as one can judge from LM observation alone, it seems reasonable to assign all the investigated frustules to the same species, which thus shows great phenotypic plasticity in cell wall structure.