Attila I. Engloner

Annual growth dynamics and morphological differences of reed (Phragmites australis [Cav.] Trin. ex Steudel) in relation to water supply

Summary In a previous study (Engloner & Podani 2001, Flora 196) we have proposed to measure the distances between the tops of reed leaf sheaths as a new macromorphological character. Since these distances are highly correlated with the lengths of internodes, we can obtain further information on the annual growth dynamics of the same stems without disassembling them. The leaf sheath distances reached their maxima in a relatively short time and it did not change for the rest of the vegetation period. On the basis of all these, each internode can be linked to a well-defined period in which environmental conditions (e.g. humidity or water depth) affected its development. In the present paper macromorphological differences between reed ramets were also investigated in sample plots differing only in water supply (depths ranging from –30 to +200 cm). Greater shoot height in deeper water resulted from a higher number of internodes, since the majority of the internodes was longer in drier than in wetter habitats. Since different water supply can leave macromorphological marks on reed ramets, growth and morphology of reed may provide useful information on water supply of the habitat meaning that even a widespread species with a high tolerance to extremities of environmental factors may play a role in bioindication.

Multilevel Comparison of Dendrograms: A New Method with an Application for Genetic Classifications

Procedures are currently available for the evaluation of hierarchical classifications of produce tree dissimilarities or consensus dendrograms. Some tests of cluster validity operate by comparing all possible partitions from a tree with a reference partition. We propose an exhaustive search procedure to compare all partitions from one dendrogram with all partitions derived from the other to detect hierarchical levels at which the two dendrograms show maximum agreement. The method is illustrated using RAPD and microsatellite data in order to detect clones in reed populations. The utility of our approach is its ability to reveal extra information in different genetic data sets which would be hidden otherwise. The method is also useful in any field of science where hierarchical clustering is the main research tool and comparison of results is an objective. Artificial and actual dendrograms, together with randomly simulated trees were used to compare the performance of five classical coefficients of partition dissimilarity. The simulations showed that when meaningful group structure is lacking, then the five coefficients are in full disagreement, but they perform similarly otherwise.

A new approach in evaluating the efficiency of macromorphological description of reed (Phragmites australis (Cav.) Trin. ex Steudel) stands

Summary Newly proposed macromorphological characters and methods are presented and tested by canonical variates analysis and principal components analysis. Dividing ramets into “growth sections” avoids the problem that, depending on the environment and age, reed ramets are composed of different numbers of nodes. If the objective is to examine selected features of as many reed stands as possible, new characters are useful. The length and location of the longest internode provide stronger separation between different reed stands than the use of an increased number of internodes. To monitor the morphological changes of the same reed ramets in situ during the whole vegetation period, we proposed to measure the distances between the tops of leaf sheaths. Reed ramets need not be cut and disassembled, because between-leaf sheath distances are highly correlated with the lengths of internodes, and they explain the strong separation of the different stands. Using our formula, these distances can also be calculated, which provides opportunity for collecting further information from previous morphological data or for comparing them with newly obtained data.

Proposal for estimating volume based relative abundance of aquatic macrophytes

In aquatic macrophyte ecology, species abundance is usually estimated by cover values expressed on the ordinal scale. Recently, there has been increasing demand for three-dimensional estimates of plant abundance. To extend ordinal cover data into three dimensions, a new formula is proposed which considers the vertical developmental types of plants. In this, a constant k is used with three different values reflecting three groups of macrophytes, namely the “free floating leaved”; “rooted, floating leaved” and “submersed leaved” species. By using the new formula, inappropriate conversion and evaluation of ordinal abundance data occurring frequently in the literature may also be avoided.