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3. Graphs with total mutual-visibility number zero and total mutual-visibility in Cartesian productsJing Tian, Sandi Klavžar, 2024, izvirni znanstveni članek Povzetek: If $G$ is a graph and $X\subseteq V(G)$, then $X$ is a total mutual-visibility set if every pair of vertices $x$ and $y$ of $G$ admits a shortest $x,y$-path $P$ with $V(P) \cap X \subseteq \{x,y\}$. The cardinality of a largest total mutual-visibility set of $G$ is the total mutual-visibility number $\mu_{\rm t}(G)$ of $G$. Graphs with $\mu_{\rm t}(G) = 0$ are characterized as the graphs in which no vertex is the central vertex of a convex $P_3$. The total mutual-visibility number of Cartesian products is bounded and several exact results proved. For instance, $\mu_{\rm t}(K_n\,\square\, K_m) = \max\{n,m\}$ and $\mu_{\rm t}(T\,\square\, H) = \mu_{\rm t}(T)\mu_{\rm t}(H)$, where $T$ is a tree and $H$ an arbitrary graph. It is also demonstrated that $\mu_{\rm t}(G\,\square\, H)$ can be arbitrary larger than $\mu_{\rm t}(G)\mu_{\rm t}(H)$.
Ključne besede: mutual-visibility set, total mutual-visibility set, bypass vertex, Cartesian product of graphs, trees
Objavljeno v DiRROS: 26.08.2024; Ogledov: 103; Prenosov: 49
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4. Stakeholders' views on the global guidelines for the sustainableuse of non-native treesAna Novoa, Giovanni Vimercati, Giuseppe Brundu, David M. Richardson, Urs Schaffner, Antonio Brunori, Thomas Campagnaro, Susan Canavan, Laura Celesti-Grapow, Michele de Sá Dechoum, Marjana Westergren, 2024, izvirni znanstveni članek Povzetek: 1. A large number of non-native trees (NNTs) have been introduced globally andwidely planted, contributing significantly to the world's economy. Although someof these species present a limited risk of spreading beyond their planting sites, agrowing number of NNTs are spreading and becoming invasive leading to diversenegative impacts on biodiversity, ecosystem functions and human well- being. Tohelp minimize the negative impacts and maximize the economic benefits of NNTs,Brundu et al. developed eight guidelines for the sustainable use of NNTs glob-ally—the Global Guidelines for the Use of NNTs (GG-NNTs).2. Here, we used an online survey to assess perceptions of key stakeholders to-wards NNTs, and explore their knowledge of and compliance with the GG-NNTs.3. Our results show that stakeholders are generally aware that NNTs can providebenefits and cause negative impacts, often simultaneously and they consider thattheir organization complies with existing regulations and voluntary agreementsconcerning NNTs. However, they are not aware of or do not apply most of theeight recommendations included in the GG-NNTs.4. We conclude that effectively managing invasions linked to NNTs requires bothmore communication efforts using an array of channels for improving stakeholderawareness and implementation of simple measures to reduce NNT impacts (e.g. via GG-NNTs), and a deeper understanding of the barriers and reluctance ofstakeholders to manage NNT invasions.
Ključne besede: agroforestry, alien species, forestry, invasion risk, online survey, ornamental trees, perceptions, stakeholder engagement, sustainability, tree invasions
Objavljeno v DiRROS: 21.06.2024; Ogledov: 228; Prenosov: 439
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5. Maker-Breaker domination game on trees when Staller winsCsilla Bujtás, Pakanun Dokyeesun, Sandi Klavžar, 2023, izvirni znanstveni članek Povzetek: In the Maker-Breaker domination game played on a graph $G$, Dominator's goal is to select a dominating set and Staller's goal is to claim a closed neighborhood of some vertex. We study the cases when Staller can win the game. If Dominator (resp., Staller) starts the game, then $\gamma_{\rm SMB}(G)$ (resp., $\gamma_{\rm SMB}'(G)$) denotes the minimum number of moves Staller needs to win. For every positive integer $k$, trees $T$ with $\gamma_{\rm SMB}'(T)=k$ are characterized and a general upper bound on $\gamma_{\rm SMB}'$ is proved. Let $S = S(n_1,\dots, n_\ell)$ be the subdivided star obtained from the star with $\ell$ edges by subdividing its edges $n_1-1, \ldots, n_\ell-1$ times, respectively. Then $\gamma_{\rm SMB}'(S)$ is determined in all the cases except when $\ell\ge 4$ and each $n_i$ is even. The simplest formula is obtained when there are at least two odd $n_i$s. If ▫$n_1$▫ and $n_2$ are the two smallest such numbers, then $\gamma_{\rm SMB}'(S(n_1,\dots, n_\ell))=\lceil \log_2(n_1+n_2+1)\rceil$▫. For caterpillars, exact formulas for $\gamma_{\rm SMB}$ and for $\gamma_{\rm SMB}'$ are established.
Ključne besede: domination game, Maker-Breaker game, Maker-Breaker domination game, hypergraphs, trees, subdivided stars, caterpillars
Objavljeno v DiRROS: 08.04.2024; Ogledov: 428; Prenosov: 166
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6. Computational complexity aspects of super dominationCsilla Bujtás, Nima Ghanbari, Sandi Klavžar, 2023, izvirni znanstveni članek Povzetek: Let ▫$G$▫ be a graph. A dominating set ▫$D\subseteq V(G)$▫ is a super dominating set if for every vertex ▫$x\in V(G) \setminus D$▫ there exists ▫$y\in D$▫ such that ▫$N_G(y)\cap (V(G)\setminus D)) = \{x\}$▫. The cardinality of a smallest super dominating set of ▫$G$▫ is the super domination number of ▫$G$▫. An exact formula for the super domination number of a tree ▫$T$▫ is obtained, and it is demonstrated that a smallest super dominating set of ▫$T$▫ can be computed in linear time. It is proved that it is NP-complete to decide whether the super domination number of a graph ▫$G$▫ is at most a given integer if ▫$G$▫ is a bipartite graph of girth at least ▫$8$▫. The super domination number is determined for all ▫$k$▫-subdivisions of graphs. Interestingly, in half of the cases the exact value can be efficiently computed from the obtained formulas, while in the other cases the computation is hard. While obtaining these formulas, II-matching numbers are introduced and proved that they are computationally hard to determine.
Ključne besede: super domination number, trees, bipartite graphs, k-subdivision of a graph, computational complexity, matching, II-matching number
Objavljeno v DiRROS: 14.03.2024; Ogledov: 420; Prenosov: 156
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7. General position polynomialsVesna Iršič, Sandi Klavžar, Gregor Rus, James Tuite, 2024, izvirni znanstveni članek Povzetek: A subset of vertices of a graph $G$ is a general position set if no triple of vertices from the set lie on a common shortest path in $G$. In this paper we introduce the general position polynomial as $\sum_{i \geq 0} a_i x^i$, where $a_i$ is the number of distinct general position sets of $G$ with cardinality $i$. The polynomial is considered for several well-known classes of graphs and graph operations. It is shown that the polynomial is not unimodal in general, not even on trees. On the other hand, several classes of graphs, including Kneser graphs $K(n,2)$, with unimodal general position polynomials are presented.
Ključne besede: general position set, general position number, general position polynomial, unimodality, trees, Cartesian product of graphs, Kneser graphs
Objavljeno v DiRROS: 28.02.2024; Ogledov: 438; Prenosov: 227
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8. Resolvability and convexity properties in the Sierpiński product of graphsMichael A. Henning, Sandi Klavžar, Ismael G. Yero, 2024, izvirni znanstveni članek Povzetek: Let $G$ and $H$ be graphs and let $f \colon V(G)\rightarrow V(H)$ be a function. The Sierpiński product of $G$ and $H$ with respect to $f$, denoted by $G \otimes _f H$, is defined as the graph on the vertex set $V(G)\times V(H)$, consisting of $|V(G)|$ copies of $H$; for every edge $gg'$ of $G$ there is an edge between copies $gH$ and $g'H$ of $H$ associated with the vertices $g$ and $g'$ of $G$, respectively, of the form $(g,f(g'))(g',f(g))$. The Sierpiński metric dimension and the upper Sierpiński metric dimension of two graphs are determined. Closed formulas are determined for Sierpiński products of trees, and for Sierpiński products of two cycles where the second factor is a triangle. We also prove that the layers with respect to the second factor in a Sierpiński product graph are convex.
Ključne besede: Sierpiński product of graphs, metric dimension, trees, convex subgraph
Objavljeno v DiRROS: 16.02.2024; Ogledov: 424; Prenosov: 202
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9. Between but not within-species variation in the distribution of fitness effectsJennifer James, Chedly Kastallya, Katharina Budde, Santiago C. González-Martínez, Pascal Milesi, Tanja Pyhäjärvi, Martin Lascoux, 2023, izvirni znanstveni članek Povzetek: New mutations provide the raw material for evolution and adaptation. The distribution of fitness effects (DFE) describes the spectrum of effects of new mutations that can occur along a genome, and is, therefore, of vital interest in evolutionary biology. Recent work has uncovered striking similarities in the DFE between closely related species, prompting us to ask whether there is variation in the DFE among populations of the same species, or among species with different degrees of divergence, that is whether there is variation in the DFE at different levels of evolution. Using exome capture data from six tree species sampled across Europe we characterized the DFE for multiple species, and for each species, multiple populations, and investigated the factors potentially influencing the DFE, such as demography, population divergence, and genetic background. We find statistical support for the presence of variation in the DFE at the species level, even among relatively closely related species. However, we find very little difference at the population level, suggesting that differences in the DFE are primarily driven by deep features of species biology, and those evolutionarily recent events, such as demographic changes and local adaptation, have little impact.
Ključne besede: DFE, deleterious mutations, population structure, forest trees
Objavljeno v DiRROS: 12.12.2023; Ogledov: 574; Prenosov: 216
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10. Use of an arboretum and DNA barcoding for the detection and identification of leaf-mining insects on alien woody plantsNatalia I. Kirichenko, Stanislav Gomboc, Barbara Piškur, Maarten De Groot, 2023, izvirni znanstveni članek Povzetek: Arboreta serve as effective tools for identifying alien insect pests and novel trophic associations. In this study, we used an arboretum in Slovenia to survey woody plants and identify both alien and native leaf miners. The leaves and twigs of 50 woody plant species and their cultivars were examined for characteristic damage. We used an integrative approach that combined identification based on leaf mines and DNA barcoding of the larvae and pupae found in the mines. In total, 62 leaf-mining species were identified, including eight alien species, of which the heliozelid Coptodisca lucifluella (Clemens, 1860) and the agromyzid Cerodontha unisetiorbita Zlobin, 1992 were documented for Slovenia for the first time. Additionally, three presumably native Gracillariidae moths Phyllocnistis labyrinthella (Bjerkander, 1790), P. ramulicola Langmaid & Corley, 2007 and P. saligna (Zeller, 1839) represented the first record for Slovenia. Furthermore, we documented 23 novel-to-science trophic associations, 20 of which involved native insects and alien woody plants, primarily from Asia. This study highlights the importance of arboreta and botanical gardens for the interception of invasive alien insects and the early detection of trophic shifts of native insects to alien plants, which can aid in predicting their potential spread.
Ključne besede: botanical garden, sentinels, leaf miners, alien species, non-native trees, novel trophic associations, DNA barcoding, Slovenia
Objavljeno v DiRROS: 24.03.2023; Ogledov: 802; Prenosov: 348
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