Janos Podani

Janos Podani

Eötvös Loránd Tudományegyetem

H-index: 49

Europe-Hungary

About Janos Podani

Janos Podani, With an exceptional h-index of 49 and a recent h-index of 27 (since 2020), a distinguished researcher at Eötvös Loránd Tudományegyetem, specializes in the field of Numerical ecology, systematics.

His recent articles reflect a diverse array of research interests and contributions to the field:

Analysis of SIRT1 Gene SNPs and Clinical Characteristics in Medication-Related Osteonecrosis of the Jaw

Multivariate study of lice (Insecta: Psocodea: Phthiraptera) assemblages hosted by hummingbirds (Aves: Trochilidae)

Components of functional diversity revisited: A new classification and its theoretical and practical implications

A new statistical method for the comparison of biplots with the same objects and variables

The ternary diagram of functional diversity

Correlating variables with different scale types: A new framework based on matrix comparisons

Bryoflora and landscapes of the eastern Andes of central Peru: II. Understory epiphyllous bryophyte assemblages of the Cordillera El Sira

A bibliometric analysis of the publications by Tamás Pócs

Janos Podani Information

University

Eötvös Loránd Tudományegyetem

Position

Professor

Citations(all)

10916

Citations(since 2020)

3264

Cited By

8715

hIndex(all)

49

hIndex(since 2020)

27

i10Index(all)

117

i10Index(since 2020)

61

Email

University Profile Page

Eötvös Loránd Tudományegyetem

Janos Podani Skills & Research Interests

Numerical ecology

systematics

Top articles of Janos Podani

Analysis of SIRT1 Gene SNPs and Clinical Characteristics in Medication-Related Osteonecrosis of the Jaw

Authors

Bence Bojtor,Mihaly Vaszilko,Richard Armos,Balint Tobias,Janos Podani,Szofia Szentpeteri,Bernadett Balla,Balazs Lengyel,Henriett Piko,Anett Illes,Andras Kiss,Zsuzsanna Putz,Istvan Takacs,Janos P Kosa,Peter Lakatos

Journal

International Journal of Molecular Sciences

Published Date

2024/3/25

Certain genetic factors, including single-nucleotide polymorphisms (SNPs) in the SIRT1 gene, have been linked to medication-related osteonecrosis of the jaw (MRONJ). This study examined four SNPs in the SIRT1 gene and implemented multivariate statistical analysis to analyze genetic and clinical factors in MRONJ patients. Genomic DNA was isolated from peripheral blood samples of 63 patients of European origin treated for MRONJ, and four SNP genotypes in the gene encoding the SIRT-1 protein were determined by Sanger sequencing. The allele frequencies measured in the MRONJ population were compared with allele frequencies measured in the European population in the National Center for Biotechnology Information Allele Frequency Aggregator (NCBI ALFA) database. Genetic and clinical factors were examined with multivariate statistical analysis. A C:A allele distribution ratio of 77.8:22.2 was measured in the rs932658 SNP. In the ALFA project, a C:A allele distribution ratio of 59.9:40.1 was detected in the European population, which was found to be a significant difference (p = 4.5 × 10−5). Multivariate statistical analysis revealed a positive correlation (0.275) between the genotype of SNP rs932658 and the number of stages improved during appropriate MRONJ therapy. It is concluded that allele A in SNP rs932658 in the SIRT1 gene acts as a protective factor in MRONJ.

Multivariate study of lice (Insecta: Psocodea: Phthiraptera) assemblages hosted by hummingbirds (Aves: Trochilidae)

Authors

Oldřich Sychra,Lajos Rózsa,János Podani,Vojtěch Sychra,Ivan Literák,Miroslav Capek

Journal

Parasitology

Published Date

2024/2

Lice were collected from 579 hummingbirds, representing 49 species, in 19 locations in Brazil, Costa Rica, Honduras, Paraguay and Peru, at elevations 0–3000 m above sea level. The following variables were included in an ecological analysis (1) host species' mean body mass, sexual size dimorphism, sexual dichromatism, migratory behaviour and dominance behaviour; (2) mean elevation, mean and predictability of temperature, mean and predictability of precipitation of the host species' geographic area; (3) prevalence and mean abundance of species of lice as measures of infestation. Ordination methods were applied to evaluate data structure. Since the traits are expressed at different scales (nominal, interval and ratio), a principal component analysis based on d-correlations for the traits and a principal coordinates analysis based on the Gower index for species were applied. Lice or louse eggs were found on …

Components of functional diversity revisited: A new classification and its theoretical and practical implications

Authors

Dénes Schmera,Carlo Ricotta,János Podani

Published Date

2023/10

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 according to the multivariate technique on which they rely, but more recent studies suggest that several multivariate techniques, providing different functional representations (such as dendrograms and ordinations) of the community can in fact express the same functional component. Here, we review the relevant literature and find that (1) general ecological acceptance of the field is hampered by ambiguous terminology and (2) our understanding of the role of multivariate techniques in defining components is unclear. To address these issues, we provide new definitions …

A new statistical method for the comparison of biplots with the same objects and variables

Authors

Attila István Engloner,János Podani

Journal

Ecological Indicators

Published Date

2023/10/1

Ordinations are compared most commonly by Procrustes methods applicable to points belonging to the same domain, either the objects or the variables describing them. However, no published approach applies to biplots which visualize principal component ordinations of objects and variables simultaneously.To fill this gap, this paper provides a new procedure based on two fundamental, scale-invariant properties of biplots: the cosine of the angle between the vectors pointing to every pair of objects and variables and the mean of the relative length of the two vectors. The method applies to situations in which the number of objects is the same in all ordinations, the number of variables is also the same and, additionally, there is one-to-one correspondence between the points in the different ordinations. The new method is illustrated with two artificial examples and is also applied to the comparison of biplots obtained …

The ternary diagram of functional diversity

Authors

Carlo Ricotta,János Podani,Dénes Schmera,Giovanni Bacaro,Simona Maccherini,Sandrine Pavoine

Journal

Methods in Ecology and Evolution

Published Date

2023/5

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 given community into three complementary fractions: functional diversity, functional redundancy and species dominance. These three components sum up to one. Therefore, they can be used to portray the community structure in a ternary diagram. Since the identification of community‐level patterns is an essential step to investigate the main drivers of species coexistence, the ternary diagram of functional diversity can be used to relate different facets of diversity to community assembly processes more exhaustively than looking only at one index at a time. The value of the …

Correlating variables with different scale types: A new framework based on matrix comparisons

Authors

János Podani,Dénes Schmera,Simonetta Bagella

Journal

Methods in Ecology and Evolution

Published Date

2023/4

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 application of standard multivariate techniques. The essence of the new approach is to derive a so‐called difference semimatrix for all pairs of observations for each variable, and then to calculate the matrix correlation based on two such semimatrices. The advantage of this function, termed d‐correlation, is that comparisons are made on the same logical basis regardless of the measurement scale, allowing for the use of principal components analysis to visualize interrelationships among many variables simultaneously. Further advantages are that missing values in …

Bryoflora and landscapes of the eastern Andes of central Peru: II. Understory epiphyllous bryophyte assemblages of the Cordillera El Sira

Authors

James G Graham,János Podani,Armin Niessner,Margaux Fischer,Tamás Pócs

Journal

Cryptogamie, Bryologie

Published Date

2023/3

We document the makeup of four understory epiphyllous (leaf-inhabiting) bryophyte assemblages along an elevational gradient on the eastern slopes of the Cordillera El Sira in Ucayali, Peru. Epiphylls from two lowland rainforest (250 and 350 m) and two upland cloud forest (1550 and 1800 m) sites were sampled along a transect spanning 6.8 km horizontal and 1.6 km vertical distance, with 74 epiphyllous taxa (69 liverworts and 5 mosses) identified. Change in community composition along the elevational gradient and factors affecting the diversity and distribution of understory epiphyllous bryophytes are explored using various approaches to diversity measurement and multivariate analysis.

A bibliometric analysis of the publications by Tamás Pócs

Authors

János Podani

Journal

ACTA BIOLOGICA PLANTARUM AGRIENSIS: A JOURNAL OF PLANT BIOLOGY

Published Date

2023

This paper provides a statistical evaluation of the publication record of Tamás Pócs, from 1954 to 2022. During this period, he contributed to 550 publications of which 232 were authored only by himself. Frequency histograms are used to demonstrate the distribution of the number of his articles, books and book chapters for six variables: topic, document type, number of authors, year of appearance, geographical scope and language. It is remarkable that his publication activity was the highest in the past 20 years. Principal components analysis is used to reveal the correlation structure between ten features characterizing the publications.

Basal phylogenetic asymmetry in species-rich natural taxa of plants: a multivariate study

Authors

Bálint Czuppon,János Podani

Journal

Plant Biosystems-An International Journal Dealing with all Aspects of Plant Biology

Published Date

2022/9/3

Sister groups at the root of large plant clades (with ≥1000 extant species) are described in terms of variables expressing species richness, geographical distribution, age, diversification rate and speed of molecular evolution. Standard statistical tools and principal component analysis are used to determine and visualize their relationships. In the majority of the 167 groups examined, one clade (the minor) has many fewer species than its sister (the major clade). A striking phenomenon is that many minor clades (17%) contain four or fewer species only. Asymmetry is largely, but not generally reflected by proportions in geographical range and relative speed of molecular evolution: species in the minor clade are more widely distributed than the major clade in 8 groups and – based on available information – we detected longer maximum branch lengths on the minor lineage in 14 cases. The basal lineages considerably …

Characterising functional strategies and trait space of freshwater macroinvertebrates

Authors

Dénes Schmera,Jani Heino,János Podani

Journal

Scientific Reports

Published Date

2022/7/19

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 were used to compare observed occupancy with theoretical models, and randomization-based analyses were performed to test whether taxonomic relatedness, a proxy of phylogenetic signal, constrains the functional trait space of freshwater macroinvertebrates. We identified four major strategies along which functional traits of the taxa examined show trade-offs. In agreement with expectations and in contrast to existing evidence we found that life cycles and aquatic strategies are important in shaping functional structure of freshwater macroinvertebrates. Our results showed …

Coefficients of association between nominal and fully ranked ordinal variables with applications to ecological network analysis

Authors

János Podani,Katalin Patonai,Péter Szabó,András Szilágyi

Journal

Ecological Modelling

Published Date

2022/4/1

A central issue of ecological data analysis is the pairwise comparison of variables describing biological entities and the environment. Difficulties arise with calculations if the measurement scales of the variables differ. In particular, no method is available for measuring the association between a nominal and a fully ranked ordinal variable. Here two coefficients are suggested by reducing this problem to the evaluation of pattern in string representations. The first one is a topological measure that counts the number of other types of elements occurring between pairs of elements of a given state along the entire length of the string, thus providing a global coefficient of aggregation/segregation. The second coefficient is based on counting the number of different elements within substrings generated from the complete string with the moving window technique. Thus, it is a local measure. There is no compact and general …

New measures for quantifying directional changes in presence-absence community data

Authors

Dénes Schmera,Pierre Legendre,Tibor Erős,Mónika Tóth,Enikő K Magyari,Bruno Baur,János Podani

Journal

Ecological Indicators

Published Date

2022/3/1

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 meaningfully studied from past to present. Although a wide variety of methods exist for partitioning variation and related community-level phenomena such as similarity, richness difference and nestedness, approaches evaluating species turnover along geographic or temporal gradients, based on an analogous conceptual framework, are rare. We therefore look into the possibilities for examining different aspects of directional changes along a gradient when presence-absence community data are available. Measures of community overlap, as well as species loss and gain …

Who is where in marine food webs? A trait-based analysis of network positions

Authors

Anett Endrédi,Katalin Patonai,János Podani,Simone Libralato,Ferenc Jordán

Journal

Frontiers in Marine Science

Published Date

2021/9/22

Networks of trophic interactions provide a lot of information on the functioning of marine ecosystems. Beyond feeding habits, three additional traits (mobility, size, habitat) of various organisms can complement this trophic view. The combination of traits and food web positions are studied here on a large food web database. The aim is a better description and understanding of ecological roles of organisms and the identification of the most important keystone species. This may contribute to develop better ecological indicators (e.g., keystoneness) and help in the interpretation of food web models. We use food web data from the Ecopath with Ecosim (EwE) database for 92 aquatic ecosystems. We quantify the network position of organisms by 18 topological indices (measuring centrality, hierarchy and redundancy) and consider their three, categorical traits (e.g., for mobility: sessile, drifter, limited mobility, mobile). Relationships are revealed by multivariate analysis. We found that topological indices belong to 6 different categories and some of them nicely separates various trait categories. For example, benthic organisms are richly connected and mobile organisms occupy higher food web positions.

In memoriam Simon Tibor (1926–2020)

Authors

Péter Csontos,Tibor Kalapos,Tamás Pócs,János Podani

Journal

Botanikai Közlemények

Published Date

2021/6/15

2 részt doktori védéseken, tanszéki rendezvényeken és kirándulásainkon–természetes volt, hogy mindig velünk van, ami még fájóbbá teszi eltávozását. Debrecenben született 1926. július 26-án. Édesapja, Simon István nyomdász és műkedvelő énekes (akinek csodálatos basszus hangjától zengett a templom) ez utóbbi képességet fiának is továbbadta, hiszen Tibor Bátyánk közismert volt nótás kedvéről, jellegzetes orgánumáról. Édesanyja, Hriczó Mária, háztartásbeliként oltotta fiába a könyvek és a zene iránti szeretetet. Minden iskoláját a szülővárosában végezte, a Jókai utcai elemi iskolában, a Református Kollégiumban, a Fazekas Mihály Gimnáziumban és a Debreceni Magyar Királyi Tudományegyetemen. Egész életében nagy szeretettel emlékezett meg első mestereiről, elsősorban Horváthy Dezső biológia–földrajz szakos gimnáziumi tanárról, akinek szertárosként is segédkezett, és osztályfőnökéről, Murányi Kálmánról, aki a humán tárgyak iránti vonzódását erősítette benne. Természetszeretete igen hamar, már általános iskolás korában kialakult–és főleg ez határozta meg későbbi pályafutását. Sokat kirándult a város zöldterületein és közvetlen környékén; egyformán lenyűgözték az állatok, a növények és az életközösségek is, mint például a szikes rétek növényzete. Középiskolás éveinek egyik nagy élménye volt, amikor az iskola szervezésében Jakucs Pállal egyetemben, gyantát gyűjtöttek az Észak-Erdéllyel visszacsatolt Radnai-havasokban. Tanári pályára készült, és egyértelmű volt számára, hogy az érettségi után a háborús sebeket éppen kiheverő, frissen induló felsőoktatásban a biológia–földrajz szakot választja. Egyetemi …

Annual plants, pigeons and flies: first signs of quantitative ecological thinking in Linnaeus's works

Authors

János Podani,Lajos Rózsa,András Szilágyi

Journal

Archives of Natural History

Published Date

2021/4

Thinking about the dynamics of populations of plants and animals goes back to Linnaeus. He used at least three examples to show what happens when the population of a species grows without limitations and to illustrate the potential reproductive capacity of organisms. We examined the mathematical precision of calculations Linnaeus used in presenting these examples and reviewed the assumptions under which Linnaeus's conclusions are valid. In the case of a slowly reproducing annual plant, additionally cited by Darwin, the final result was incorrect, although little different from the true value. In the example of a pair of pigeons, the calculations were accurate, although the well-known fact that pigeons breed several times throughout their lifetime was ignored. Though the input parameters must have been unknown to Linnaeus, a short statement in Systema naturae regarding the population increase and feeding …

Principal component analysis of incomplete data–A simple solution to an old problem

Authors

János Podani,Tibor Kalapos,Barbara Barta,Dénes Schmera

Journal

Ecological Informatics

Published Date

2021/3/1

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 arbitrary, and restriction of the analysis to either the variables or observations, thereby losing the advantages of biplot diagrams. We describe a minor modification of eigenanalysis-based PCA in which correlations or covariances are calculated using different numbers of observations for each pair of variables, and the resulting eigenvalues and eigenvectors are used to calculate component scores such that missing values are skipped. This procedure avoids artificial data imputation, exhausts all information from the data and allows the preparation of biplots for the simultaneous …

Generalizing resemblance coefficients to accommodate incomplete data

Authors

János Podani,Dénes Schmera

Journal

Ecological Informatics

Published Date

2021/12/1

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 potentially applied in multivariate data analysis. We provide a general framework for a precise mathematical redefinition of a large set of resemblance functions originally developed for complete data sets with presence-absence (binary) or ratio-scale variables. Included are coefficients which consider double absences in abundance data. Potential problems with the use of these functions are discussed, with the conclusion that incompleteness of data would rarely if ever influence greatly the interpretability of ordinations and classifications. An R function described in the …

The wonder of the Jaccard coefficient: From alpine floras to bipartite networks

Authors

János Podani

Journal

Flora Mediterr. J

Published Date

2021/1/2

The similarity index suggested by Paul Jaccard 120 years ago has been one of the best-known coefficients in statistical ecology and other research fields in which the objects to be compared are described in terms of the presence or absence of many characters. Jaccard and his immediate followers used the coefficient for the comparison of floras of different localities and phytosociological relevés, based on the list of constituting species. A historical and mathematical overview reveals that, in addition to applications in ordinations and classifications, partitioning the coefficient into additive fractions opens unlimited opportunities for evaluating taxonomic, phylogenetic and functional diversity and related phenomena of ecological communities.

Phylogeny of Crataegus (Rosaceae) based on 257 nuclear loci and chloroplast genomes: evaluating the impact of hybridization

Authors

Aaron Liston,Kevin A Weitemier,Lucas Letelier,János Podani,Yu Zong,Lang Liu,Timothy A Dickinson

Journal

PeerJ

Published Date

2021/10/26

BackgroundHawthorn species (Crataegus L.; Rosaceae tribe Maleae) form a well-defined clade comprising five subgeneric groups readily distinguished using either molecular or morphological data. While multiple subsidiary groups (taxonomic sections, series) are recognized within some subgenera, the number of and relationships among species in these groups are subject to disagreement. Gametophytic apomixis and polyploidy are prevalent in the genus, and disagreement concerns whether and how apomictic genotypes should be recognized taxonomically. Recent studies suggest that many polyploids arise from hybridization between members of different infrageneric groups.MethodsWe used target capture and high throughput sequencing to obtain nucleotide sequences for 257 nuclear loci and nearly complete chloroplast genomes from a sample of hawthorns representing all five currently recognized subgenera. Our sample is structured to include two examples of intersubgeneric hybrids and their putative diploid and tetraploid parents. We queried the alignment of nuclear loci directly for evidence of hybridization, and compared individual gene trees with each other, and with both the maximum likelihood plastome tree and the nuclear concatenated and multilocus coalescent-based trees. Tree comparisons provided a promising, if challenging (because of the number of comparisons involved) method for visualizing variation in tree topology. We found it useful to deploy comparisons based not only on tree-tree distances but also on a metric of tree-tree concordance that uses extrinsic information about the relatedness of the terminals in …

A study of community structure and beta diversity of epiphyllous liverwort assemblages in Sabah, Malaysian Borneo

Authors

Tamás Pócs,Gaik Ee Lee,János Podani,Elizabeth Pesiu,Judit Havasi,Hung Yung Tang,Andi Maryani A Mustapeng,Monica Suleiman

Journal

PhytoKeys

Published Date

2020

We evaluated the species richness and beta diversity of epiphyllous assemblages from three selected localities in Sabah, ie Mt. Silam in Sapagaya Forest Reserve, and Ulu Senagang and Mt. Alab in Crocker Range Park. A total of 98 species were found and a phytosociological survey was carried out based on the three study areas. A detailed statistical analysis including standard correlation and regression analyses, ordination of species and leaves using centered principal component analysis, and the SDR simplex method to evaluate the beta diversity, was conducted. Beta diversity is very high in the epiphyllous liverwort assemblages in Sabah, with species replacement as the major component of pattern formation and less pronounced richness difference. The community analysis of the epiphyllous communities in Sabah makes possible their detailed description and comparison with similar communities of other …

See List of Professors in Janos Podani University(Eötvös Loránd Tudományegyetem)

Janos Podani FAQs

What is Janos Podani's h-index at Eötvös Loránd Tudományegyetem?

The h-index of Janos Podani has been 27 since 2020 and 49 in total.

What are Janos Podani's top articles?

The articles with the titles of

Analysis of SIRT1 Gene SNPs and Clinical Characteristics in Medication-Related Osteonecrosis of the Jaw

Multivariate study of lice (Insecta: Psocodea: Phthiraptera) assemblages hosted by hummingbirds (Aves: Trochilidae)

Components of functional diversity revisited: A new classification and its theoretical and practical implications

A new statistical method for the comparison of biplots with the same objects and variables

The ternary diagram of functional diversity

Correlating variables with different scale types: A new framework based on matrix comparisons

Bryoflora and landscapes of the eastern Andes of central Peru: II. Understory epiphyllous bryophyte assemblages of the Cordillera El Sira

A bibliometric analysis of the publications by Tamás Pócs

...

are the top articles of Janos Podani at Eötvös Loránd Tudományegyetem.

What are Janos Podani's research interests?

The research interests of Janos Podani are: Numerical ecology, systematics

What is Janos Podani's total number of citations?

Janos Podani has 10,916 citations in total.

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