Dénes Schmera

HUN-REN Balaton Limnological Research Institute

Several theoretical models have been proposed as the underlying mechanisms behind occupancy frequency distribution (OFD) patterns. For instance, the metapopulation dynamic model predicts bimodal OFD pattern indicating the dominance of dispersal processes in structuring the assemblages, while the niche‐based model predicts unimodal right‐skewed OFD...

Context Human-induced landscape modification, such as urbanization, creates new environments that can have adverse effects on flora and fauna, posing threats to biodiversity. Understanding how reptiles respond to urbanization is crucial, especially in light of their ongoing population declines. Objectives We examined the influence of landscape-sca...

Exposure to synthetic chemicals, such as pesticides and pharmaceuticals, affects freshwater communities at broad spatial scales. This risk is commonly managed in a prospective environmental risk assessment (ERA). Relying on generic methods, a few standard test organisms, and safety factors to account for uncertainty, ERA determines concentrations t...

Transitioning from perennial to non-perennial flow regimes causes ecological shifts in aquatic communities. Aquatic macroinvertebrates deploy resistance and resilience strategies to cope with flow intermittency, crucial in rivers with long-term seasonal dry episodes. Less is known, about how these strategies support community persistence in streams...

A ten-year-long examination of macroinvertebrate community recovery was conducted following a catastrophic spill of highly alkaline red sludge (pH >13) into lowland streams. Our primary objective was to compare recovery patterns after coarse- and fine-grain disturbances, focusing on two aspects: i) trend analysis to reveal long-term changes of six...

The expansion of urban areas leads to a decrease in natural habitats, resulting some species to live in urban environments. Novel environmental factors might influence their size, body condition and development stability. The environmentally induced developmental instability can be indicated by fluctuating symmetry, which means random deviations fr...

Functional diversity is regarded as a key concept in understanding the link between ecosystem function and biodiversity, and is therefore widely investigated in relation to human-induced impacts. However, information on how the intersection of roads and streams (hereafter road crossings, representing a widespread habitat transformation in relation...

Functional diversity is regarded as a key concept for understanding the link between ecosystem function and biodiversity. The different and ecologically well-defined aspects of the concept are reflected by the so-called functional components, for example, functional richness and divergence. Many authors proposed that components be distinguished acc...

Semi-natural, nutrient-poor calcareous grasslands are local biodiversity hotspots that are increasingly threatened by land use intensification, abandonment, or indirect effects from adjacent habitats. The habitat quality of these grasslands is often influenced by neighbouring forests or intensively managed agricultural land. For example, shrubs enc...

Several theoretical models have been proposed as the underlying mechanisms behind occupancy frequency distribution (OFD) patterns. For instance, the metapopulation dynamic model predicts bimodal OFD pattern indicating the dominance of dispersal processes in structuring the assemblages, while the niche-based model predicts unimodal right-skewed OFD...

Among the many diversity indices in the ecologist toolbox, measures that can be partitioned into additive terms are particularly useful as the different components can be related to different ecological processes shaping community structure. In this paper, an additive diversity decomposition is proposed to partition the diversity structure of a giv...

The aim of our study was to compare the richness and composition of macroinvertebrate assemblages in natural reed and artificial rip-rap habitats in a shallow lake 50+ years after shoreline modifications. Lake Balaton (Hungary) provided a unique study system as approximately half of its shoreline (c.105 km) has been modified. Littoral macroinverteb...

Motivation Aquatic insects comprise 64% of freshwater animal diversity and are widely used as bioindicators to assess water quality impairment and freshwater ecosystem health, as well as to test ecological hypotheses. Despite their importance, a comprehensive, global database of aquatic insect occurrences for mapping freshwater biodiversity in macr...

Ecological variables may be expressed on four basic measurement scales (nominal, ordinal, interval or ratio), whereas circular variables and those combining a nominal state with other scale types are also common. However, existing methods are not suited to calculate correlations between all pairwise combinations of such variables, preventing the ap...

Urbanization is one of the most serious threats to stream ecosystems worldwide. It is crucial to understand its effects on stream organisms as a prerequisite for the mitigation of urban degradation. Our aim was to investigate the general effects of urbanization in a moderately urbanized landscape and to assess the relationship between local environ...

Motivation: Aquatic insects comprise 64% of freshwater animal diversity and are

Motivation: Aquatic insects comprise 64% of freshwater animal diversity and are widely used as bioindicators to assess water quality impairment and freshwater ecosystem health, as well as to test ecological hypotheses. Despite their importance, a comprehensive, global database of aquatic insect occurrences for mapping freshwater biodiversity in mac...

We examined the functional strategies and the trait space of 596 European taxa of freshwater macroinvertebrates characterized by 63 fuzzy coded traits belonging to 11 trait groups. Principal component analysis was used to reduce trait dimensionality, to explain ecological strategies, and to quantify the trait space occupied by taxa. Null models wer...

Humans have severely altered freshwater ecosystems globally, causing a loss of biodiversity. Regulatory frameworks, like the Water Framework Directive, have been developed to support actions that halt and reverse this loss. These frameworks use typology systems that summarize freshwater ecosystems into environmentally delineated types. Within types...

Variation in community composition and species turnover are different types of beta diversity, expressing non-directional and directional changes, respectively. While directional changes (e.g. turnover) along geographic gradients can be studied in any direction depending on the hypothesis of interest to researchers, temporal changes can only be mea...

To secure the ecosystem services forests provide, it is important to understand how different management practices impact various components of these ecosystems. We aimed to uncover how silvicultural treatments affected the ground-dwelling spider communities during the first five years of a forest ecological experiment. In an oak-hornbeam forest st...

Large ecological data matrices may be incomplete for various reasons, preventing the use of standard multidimensional scaling (ordination) and cluster analysis packages. Although there exist a few resemblance functions that allow missing scores, there is no theoretical background and software support for most distance and similarity coefficients po...

The recreational use of water bodies presents new challenges and pressures on lake ecosystems. We focused on how recreational beaches influence the shoreline biodiversity of Lake Balaton, Hungary. Taking into account the establishment of beaches, we examined natural reed vegetated shorelines (representing natural situation), open areas (representin...

Roads threaten animal species through habitat loss, fragmentation and degradation, and direct mortality. It is crucial to understand how species respond to linear infrastructure for effective conservation of animal communities in fragmented landscapes. We assessed relationships between amphibian abundance and roads/ railways and habitat fragmentati...

A fundamental goal of community ecology is to understand species–habitat relationships and how they shape metacommunity structure. Recent advances in occupancy modeling enable habitat relationships to be assessed for both common and rare species within metacommunities using multi‐species occupancy models (MSOM). These models account for imperfect s...

A long-standing problem in biological data analysis is the unintentional absence of values for some observations or variables, preventing the use of standard multivariate exploratory methods, such as principal component analysis (PCA). Solutions include deleting parts of the data by which information is lost, data imputation, which is always arbitr...

The study of the diversity of animal signals on within‐ and among‐species levels is the key to uncover mechanisms that shape the evolution of communication systems. However, the methods used to quantify acoustic diversity (like repertoire size) lack to grasp several aspects of acoustic diversity. Here, we propose a new framework for the study of an...

Extracting meaningful information from community data is among the most challenging tasks of community ecology. Whereas presence-absence data matrices are commonly used in different analytical frameworks, we argue that the conceptual distinction among community patterns (on which inference is made), pairwise pattern components (PPCs, which reflect...

We examined the effects of regional scale land use and local scale environmental and biotic stressors on alpha, beta and zeta diversities of native fish communities in wadeable streams and non-wadeable rivers in the Danube basin, Hungary. Relationships among land use and local scale environmental and biotic stressors were weak both in streams and r...

Although it is well known that the increasing size of the human population has a negative effect on freshwater biodiversity, the subject of whether or how the intersection of roads and streams (hereafter road crossings) influence the diversity of stream macro-invertebrates is under-researched. To fill this gap in our knowledge, we collected stream...

World‐wide decreases of insect abundance and diversity are of major concern because of their importance for ecosystem functioning and the stability of ecosystems. Various studies reported dramatic declines of butterflies, wild bees and beetles in agricultural areas. Yet, evidence for decreasing abundance in cryptic insect species is scarce. Using a...

Experimental streams are bounded and partly enclosed lotic units that facilitate the simulation of certain aspects of natural stream ecosystems under controlled conditions. We summarized the current knowledge regarding experimental streams in order to support researchers in designing and undertaking future studies using experimental streams. We obs...

Aerobic anoxygenic phototrophs (AAPs) are a group of photoheterotrophic bacteria common in natural waters. Here, AAP abundance, and contribution to total bacterial abundance and biomass were investigated to test whether the trophic status of a lake or content of coloured dissolved organic matter (CDOM) play a role in determining AAP distribution an...

Understanding the effects of urbanization on the diversity of freshwater macroinvertebrates is an important topic of biodiversity research and has direct conservation relevance. The absence of evidence-based systematic overviews on this topic motivated us to perform meta-analyses and to synthetize the present state of knowledge. We observed signifi...

Aim: We examined the responses of the beta diversity of aquatic and terrestrial beetles to ecogeographical variables, including climate, land cover and land use, across Northern Europe. Location: Northern Europe (Denmark, Sweden, Norway and Finland). Methods: Information on the occurrence of ground beetles and diving beetles across Northern Europ...

Partition of beta diversity into components is a modern method that allows inferences about the underlying processes driving metacommunities. Based on two alternative approaches, we examined the patterns of beta diversity components of chironomids in relation to environmental and spatial gradients in three contrasting freshwater ecosystems. Beta di...

Limestone cliffs in the Jura Mountains harbour species-rich plant and animal communities including rare species. Sport climbing has recently increased in popularity in this habitat and several studies have reported damage to cliff biodiversity. However, so far how damage levels vary with climbing intensity has not been investigated. We evaluated th...

Methods that quantify multiple-site resemblance are basic toolkits of ecology for studying community variation in space and time. Although both pairwise and multiple-site coefficients have received increasing attention in the past decade, the high variety of methodologies combined with the absence of a systematic review prevents full understanding...

The Elements of Metacommunity Structure (EMS) framework originally suggested by Leibold and Mikkelson (2002) in Oikos is a popular approach to identify idealized metacommunity patterns (i.e. checkerboard, nested, evenly spaced, Clementsian, Gleasonian), and hereby to infer the existence of structuring processes in metacommunities. Essentially, the...

• Quantifying the relative importance of how local (environmental or niche‐based) and regional (dispersal‐related or spatial) processes regulate the assembly of communities has become one of the main research avenues of community ecology. It has been shown that the degree of isolation of local habitats in the landscape may substantially influence t...

Although overlap of communities is a key issue in studies ranging from community ecology to biogeography, a clear definition of community overlap and related terms hinder the development of the field. The absence of a unified terminology is remarkable even when the overlap of a pair or multiple communities is characterized. As a remedy, I suggest a...

Although several studies have examined the functional diversity of freshwater macroinvertebrates, the variety of methodologies combined with the absence of a synthetic review make our understanding of this field incomplete. Therefore, we reviewed the current methodology for assessing functional diversity in freshwater macroinvertebrate research. Ou...

Exposed limestone cliffs in the Swiss Jura Mountains harbour a diverse gastropod community with some rare species. Sport climbing has recently increased in popularity on these cliffs. We examined the effects of sport climbing and microtopographical features of rock faces on terrestrial gastropods by assessing species diversity and abundance on clim...

Background: Sperm size and quality are key factors for fertilization success. There is increasing empirical evidence demonstrating that sperm form and function are influenced by selective pressures. Theoretical models predict that sperm competition could favour the evolution of longer sperm. In hermaphrodites, self-fertilizing species are expected...

The metacommunity framework has shed light upon the significance of local and regional processes in shaping ecological communities. However, our knowledge is limited how landscape context (i.e. type and positioning of habitats) influences the structuring of metacommunities. We examined the role of environmental selection (niche‐based species sortin...

A recent study (1) reports the spatial clustering patterns of the global distribution of human infectious diseases. However, there are some controversial issues that arise from the beta diversity partitioning method used in the paper. To further debate these issues, we follow the same notations in the paper (1) by writing the Sorensen beta diversit...

Headwater stream macroinvertebrates play an important role in processing allochthonous leaf litter, which suggests that bottom-up forces control macroinvertebrates. However, because larvae of stream-breeding salamanders are predators of macroinvertebrates and are abundant consumers in these ecosystems, macroinvertebrates in fishless head-water stre...

Rock-dwelling land snails, feeding on algae and lichens that grow on stone surfaces, may influence the structure and function of these ecosystems. Yet, little is known about the life history of rock-dwelling snails. We performed a 30-month mark–release–resight study in four populations of Chondrina clienta (Westerlund, 1883) inhabiting vertical wal...

Traits-based community analyses are receiving increasing attention. However, consistent interpretation of empirical results and ecological understanding in stream ecology are limited by ambiguous terminology. Furthermore, the measurement scales used to analyze trait data, especially ordinal-scale data, are often inappropriately applied. We identify...

The hypotheses that beta diversity should increase with decreasing latitude and increase with spatial extent of a region have rarely been tested based on a comparative analysis of multiple datasets, and no such study has focused on stream insects. We first assessed how well variability in beta diversity of stream insect metacommunities is predicted...

The hypotheses that beta diversity should increase with decreasing latitude and increase with spatial extent of a region have rarely been tested based on a comparative analysis of multiple datasets, and no such study has focused on stream insects. We first assessed how well variability in beta diversity of stream insect metacommunities is predicted...

The hypotheses that beta diversity should increase with decreasing latitude and increase with spatial extent of a region have rarely been tested based on a comparative analysis of multiple datasets, and no such study has focused on stream insects. We first assessed how well variability in beta diversity of stream insect metacommunities is predicted...

The hypotheses that beta diversity should increase with decreasing latitude and increase with spatial extent of a region have rarely been tested based on a comparative analysis of multiple datasets, and no such study has focused on stream insects. We first assessed how well variability in beta diversity of stream insect metacommunities is predicted...

The hypotheses that beta diversity should increase with decreasing latitude and increase with spatial extent of a region have rarely been tested based on a comparative analysis of multiple datasets, and no such study has focused on stream insects. We first assessed how well variability in beta diversity of stream insect metacommunities is predicted...

Alpine grasslands harbour species-rich communities of plants and invertebrates. We examined how environmental variables and anthropogenic impact shape species richness and community structure of terrestrial gastropods in alpine grass- lands in the Val Müstair (Eastern Alps, Switzerland). Gastropods were sampled using a standardised method at 76 sit...

Sperm morphology can be highly variable among species, but less is known about patterns of population differentiation within species. Sperm morphology is under strong sexual selection, may evolve rapidly, and often co-varies with other reproductive traits that differ between populations. We investigated variation in sperm morphology in the simultan...

In field trapping tests in Hungary cinnamyl alcohol (3-phenyl-2-propen-l-ol) and transanethole [(1-methoxy-4-(1-propenyl)benzene)] attracted significantly more adult Epicometis (Tropinota) hirta (Coleoptera, Scarabaeidae, Cetoniinae) when presented together in the same bait compared to the single compounds Best attraction was recorded by a 1:1 mixt...

We propose the use of a new methodological scheme for exploring and quantifying structure in bipartite ecological networks. In this, graphical visualization and numerical measurement are combined, offering a unique possibility for network analysis on a coherent conceptual basis. Dissimilarity between all species pairs in either group of constitutin...

In promiscuous species with sperm storage, males are expected to show a preference for mating with virgin and young females to reduce the risk of sperm competition. In the simultaneous hermaphrodite land snail Arianta arbustorum, sperm production precedes egg production by 2–4 weeks, resulting in a short period of protandric hermaphroditism before...

Monaghan and Soares (2014) suggested that combining traits with log‐transformed abundance of taxa may cause anomalies in analyses of stream macroinvertebrate communities. While they addressed an important issue in stream ecology, here we present an opposite view. To identify the causes of these contrasting opinions, we carefully examined the exampl...