Balázs András Lukács

Aquatic macrophytes as bioindicators of water chemistry in nutrient rich backwaters along the Upper-Tisza river (in Hungary)

We assessed the relationship of vegetation composition and water chemical parameters in fi ve nutrient rich backwaters in NE Hungary. We used 126 plots and water samples analysed for 19 water chemical parameters. Our hypothesis was that environmental variables might be decisive for macrophyte species composition in waters with different nutrient content. We also supposed that community-environment and species-environment relationship of nutrient rich water may differ from nutrient poor ones. TWINSPAN analysis was used to reveal the main vegetation units, and detrended canonical correspondence analysis (DCCA) was used to explore the water chemical demands of these communities and the species-water chemical parameters relationships. We found 8 communities by TWINSPAN. Among the water chemical parameters Ca 2+ , COD, NO2, Mg 2+ , Cl - were important in differentiating the communities. In the nutrient rich backwaters we found similar results as other authors found in nutrient poor waters and fens. Glycerietum maximae association found in waters with high amount of COD and NO2 - , Typhetum angustifoliae association correlated negatively with these water chemi- cal parameters and Sparganietum erecti and Potametum lucentis associations prefer both habitats. Bolbo- schoenion and Schoenoplectetum lacustris associations have been found to prefer waters with high amount of Cl - . Trapetum natantis and Ceratophyllo-Nymphaeetum albae associations found to prefer waters with low amount of Ca 2+ , COD, NO2 - , Mg 2+ and Cl - , which proved the vulnerability of these protected associations in nutrient rich waters. In the case of species-water chemical parameters relationship we found high nitrogen correla- tion of Ceratophyllum demersum and high Ca 2+ correlation of Potamogeton lucens.

Which factors affect phytoplankton biomass in shallow eutrophic lakes

The restoration and management of shallow, pond-like systems are hindered by limitations in the applicability of the well-known models describing the relationship between nutrients and lake phytoplankton biomass in higher ranges of nutrient concentration. Trophic models for naturally eutrophic small, shallow, endorheic lakes have not yet been developed, even though these are the most frequent standing waters in continental lowlands. The aim of this study was to identify variables that can be considered as main drivers of phytoplankton biomass and to build a predictive model. The influence of potential drivers of phytoplankton biomass (nutrients, other chemical variables, land use, lake use and lake depth) from 24 shallow eutrophic lakes was tested using data in the Pannonian ecoregion (Hungary and Romania). By incorporating lake depth, TP, TN and lake use as independent and Chl-a as dependent variables into different models (multiple regression model, GLM and multilayer perception model) predictive models were built. These models explained >50% of the variance. Although phytoplankton biomass in small, shallow, enriched lakes is strongly influenced by stochastic effects, our results suggest that phytoplankton biomass can be predicted by applying a multiple stressor approach, and that the model results can be used for management purposes.

Rainfall fluctuations and vegetation patterns in alkali grasslands - using self-organizing maps to visualise vegetation dynamics

Knowledge about the drivers of vegetation dynamics in grasslands is fundamental to select appro-priate management for conservation purposes. In this study, we provide a detailed analysis of vegeta-tion dynamics in alkali grasslands, a priority habitat of the Natura 2000 network. We studied vegetation dynamics in five stands of four alkali grassland types in the Hortobagy National Park (eastern Hunga-ry), between 2009 and 2011. We analysed the effect of fluctuations in precipitation on both the overall vegetation composition and on the cover of each species using Self Organizing Map neural networks (SOM). We found that SOM is a promising tool to reveal plant community dynamics. As we analysed species cover and overall vegetation composition separately, we were able to identify the species re-sponsible for particular vegetation changes. Fluctuations in precipitation (a dry season, followed by a wet and an average season) caused quick shifts in plant species composition because of an increasing cover of halophyte forbs, probably because of salinisation. We observed a similar effect of stress from waterlogging in all studied grassland types. The species composition of Puccinellia grasslands was the most stable over the three years with varying precipitation. This was important as this grassland type contained many threatened halophyte species. Self-organising maps revealed small-scale vegetation changes and provided a detailed visualisation of short-term vegetation dynamics, thus we suggest that the application of this method is also promising to reveal community dynamics in more species-rich habitat types or landscapes.

Phytoplankton-based shallow lake types in the Carpathian basin: steps towards a bottom-up typology

As lake biota are basically determined by hydromorphological characteristics of the lake basin, estab- lishment of a lake typology is the first step in lake quality assessment and management. Based on descriptor vari- ables (size, depth, lake bed material, water-regime and macrophyte coverage), 16 hydromorphological lake-types were established for the Pannonian Ecoregion. Our analyses revealed that descriptor variables have considerable effect both on biomass and composition of phytoplankton. As the phytoplankton biomass of several lake-types can be merged, a simplified typology can be proposed. Since the phytoplankton composition of various lake-types dif- fered significantly in terms of diversity and relative abundance of functional groups, well delineated composition- based types cannot be established for Pannonian lakes. Although the Pannonian Ecoregion is the westernmost part of the Eurasian steppe zone, the proposed typology of the studied area can be extended to lakes of the greater Pannonian region.

Flood induced phenotypic plasticity in amphibious genus Elatine (Elatinaceae)

Vegetative characters are widely used in the taxonomy of the amphibious genus Elatine L. However, these usually show great variation not just between species but between their aquatic and terrestrial forms. In the present study we examine the variation of seed and vegetative characters in nine Elatine species (E. brachysperma, E. californica, E. gussonei, E. hexandra, E. hungarica, E. hydropiper, E. macropoda, E. orthosperma and E. triandra) to reveal the extension of plasticity induced by the amphibious environment, and to test character reliability for species identification. Cultivated plant clones were kept under controlled conditions exposed to either aquatic or terrestrial environmental conditions. Six vegetative characters (length of stem, length of internodium, length of lamina, width of lamina, length of petioles, length of pedicel) and four seed characters (curvature, number of pits / lateral row, 1st and 2nd dimension) were measured on 50 fruiting stems of the aquatic and on 50 stems of the terrestrial form of the same clone. MDA, NPMANOVA Random Forest classification and cluster analysis were used to unravel the morphological differences between aquatic and terrestrial forms. The results of MDA cross-validated and Random Forest classification clearly indicated that only seed traits are stable within species (i.e., different forms of the same species keep similar morphology). Consequently, only seed morphology is valuable for taxonomic purposes since vegetative traits are highly influenced by environmental factors.

Molecular phylogenetics, seed morphometrics, chromosome number evolution and systematics of European Elatine L. (Elatinaceae) species

The genus Elatine contains ca 25 species, all of which are small, herbaceous annuals distributed in ephemeral waters on both hemispheres. However, due to a high degree of morphological variability (as a consequence of their amphibious life-style), the taxonomy of this genus remains controversial. Thus, to fill this gap in knowledge, we present a detailed molecular phylogenetic study of this genus based on nuclear (rITS) and plastid (accD-psaI, psbJ-petA, ycf6-psbM-trnD) sequences using 27 samples from 13 species. On the basis of this phylogenetic analysis, we provide a solid phylogenetic background for the modern taxonomy of the European members of the genus. Traditionally accepted sections of this tree (i.e., Crypta and Elatinella) were found to be monophyletic; only E. borchoni—found to be a basal member of the genus—has to be excluded from the latter lineage to achieve monophyly. A number of taxonomic conclusions can also be drawn: E. hexandra, a high-ploid species, is most likely a stabilised hybrid between the main sections; E. campylosperma merits full species status based on both molecular and morphological evidence; E. gussonei is a more widespread and genetically diverse species with two main lineages; and the presence of the Asian E. ambigua in the European flora is questionable. The main lineages recovered in this analysis are also supported by a number of synapomorphic morphological characters as well as uniform chromosome counts. Based on all the evidence presented here, two new subsections within Elatinella are described: subsection Hydropipera consisting of the temperate species of the section, and subsection Macropodae including the Mediterranean species of the section.

Distribution, morphology and habitats of Elatine triandra (Elatinaceae) in Europe, with particular reference to the central part of the continent

Abstract Elatine triandra Schkuhr is the most variable and widespread species within the genus Elatine L.; it has been recorded in all continents, except Antarctica, but it is mainly located in Europe. The study is based on an extensive data set of European literature, herbaria and web data that covers the period 1828–2012. The range of the species in Europe is disjunctive, covering the southern and western parts of the Central European Plain and the southern part of the Fennoscandian Shield. At a smaller scale, the species can also be found along some river valleys. In Central Europe many localities, particularly isolated ones in the northern part of the range, are now only historical. From the data set we determined that E. triandra may be best observed between May and October. We found that species records show a near-significant shift since 1828. Depending on the environmental conditions, individuals of the taxon develop as one of two morphs: terrestrial or aquatic. The aquatic morph is characterized by stems, internodes, lamina and petiole that are twice as long as those of the terrestrial form. Elatine triandra seeds show consistent characteristics, both in terms of morphs and populations. Our studies show that the best diagnostic features, in addition to the construction of flowers, are the size, shape and surface structure of seeds. In Central Europe, E. triandra occurs exclusively in communities classified as Isoëto-Nano-Juncetea.

Diatom composition of the rheoplankton in a rhithral river system

Abstract Diatom composition of the rheoplankton (phytoplankton) in the Sajó-Hernád river system (Slovakia and Hungary) was studied. Forty two sample sites were designated on the watershed from source to mouth of the two rivers and their tributaries. Samples were taken in July 2012. Altogether, 258 diatom taxa were identified. The microflora was dominated by tychoplanktonic elements. According to the relative abundance of the occurring taxa, four groups could be distinguished. Differentiation of these groups was confirmed by differences in the habitat characteristics, viz. altitude, width of watercourse, macrophyte coverage and river bed material. Diversity of diatom taxa in the phytoplankton was also studied. A positive relationship was found between the macrophyte coverage and the Simpson and the Shannon indices. In contrast, a negative relationship was shown between the macrophyte coverage and Berger-Parker diversity, in which metric the role of the dominant taxa is emphasized. Although the phytoplankton in rhithral rivers is influenced by stochastic events, our results reveal that geographical and hydromorphological characteristics of the rivers and coverage of macrophytes can also play role in shaping the composition and diversity of the phytoplankton.

Growth‐form and spatiality driving the functional difference of native and alien aquatic plants in Europe

Abstract Trait‐based approaches are widely used in community ecology and invasion biology to unravel underlying mechanisms of vegetation dynamics. Although fundamental trade‐offs between specific traits and invasibility are well described among terrestrial plants, little is known about their role and function in aquatic plant species. In this study, we examine the functional differences of aquatic alien and native plants stating that alien and native species differ in selected leaf traits. Our investigation is based on 60 taxa (21 alien and 39 native) collected from 22 freshwater units of Hungarian and Italian lowlands and highlands. Linear mixed models were used to investigate the effects of nativeness on four fundamental traits (leaf area, leaf dry matter content, specific leaf area, and leaf nitrogen content), while the influence of growth‐form, altitude, and site were employed simultaneously. We found significantly higher values of leaf areas and significantly lower values of specific leaf areas for alien species if growth‐form was included in the model as an additional predictor.We showed that the trait‐based approach of autochthony can apply to aquatic environments similar to terrestrial ones, and leaf traits have relevance in explaining aquatic plant ecology whether traits are combined with growth‐forms as a fixed factor. Our results confirm the importance of traits related to competitive ability in the process of aquatic plant invasions. Alien aquatic plants can be characterized as species producing soft leaves faster. We argue that the functional traits of alien aquatic plants are strongly growth‐form dependent. Using the trait‐based approach, we found reliable characteristics of aquatic plants related to species invasions, which might be used, for example, in conservation management.

The occurrence of Spiraea crenata and other rare steppe plants in Pannonian graveyards

Abstract Spiraea crenata was categorised as a species extinct from Hungary at the end of the 20th century. This stepperelic species was rediscovered in 2000 in a rural graveyard (Pusztamonostor). As a result of our recent survey of 294 Pannonian graveyards, we found further 12 localities of S. crenata. We also found 27 populations of further protected plant species, mainly with pontic, pontic-pannonian, Eurasian or continental distribution. We found that the total scrub cover of graveyards with S. crenata was significantly higher than graveyards without this species; this is obviously related to the fact that the individuals of S. crenata were found mostly in edges of the graveyards, where they could survive mowing among high and dense scrubs or small trees. Other factors (geographic position, altitude above sea level, area of graveyards, proportion of grasslands, and proportion of territory covered by graves) were not related to the presence of the species. The total number of other protected species was significantly higher in graveyards with S. crenata. Most of the sites with S. crenata functioned as graveyards during the 2nd Military Survey of the Austrian Empire (1806–1869; 10 out of 13 sites), and the 3rd Military Survey (1869–1887; 12 of 13 sites). The long usage history of these graveyards suggests that the S. crenata individuals – along with other remarkable species – might be remnants of the original steppe vegetation rather than the result of plantations for ornamental purposes. Our results highlight the role of graveyards in the preservation of steppe flora, one of the most endangered component of the European flora.