TY - JOUR A1 - Heger, Tina A1 - Bernard-Verdier, Maud A1 - Gessler, Arthur A1 - Greenwood, Alex D. A1 - Grossart, Hans-Peter A1 - Hilker, Monika A1 - Keinath, Silvia A1 - Kowarik, Ingo A1 - Küffer, Christoph A1 - Marquard, Elisabeth A1 - Mueller, Johannes A1 - Niemeier, Stephanie A1 - Onandia, Gabriela A1 - Petermann, Jana S. A1 - Rillig, Matthias C. A1 - Rodel, Mark-Oliver A1 - Saul, Wolf-Christian A1 - Schittko, Conrad A1 - Tockner, Klement A1 - Joshi, Jasmin Radha A1 - Jeschke, Jonathan M. T1 - Towards an Integrative, Eco-Evolutionary Understanding of Ecological Novelty: Studying and Communicating Interlinked Effects of Global Change JF - Bioscience N2 - Global change has complex eco-evolutionary consequences for organisms and ecosystems, but related concepts (e.g., novel ecosystems) do not cover their full range. Here we propose an umbrella concept of "ecological novelty" comprising (1) a site-specific and (2) an organism-centered, eco-evolutionary perspective. Under this umbrella, complementary options for studying and communicating effects of global change on organisms, ecosystems, and landscapes can be included in a toolbox. This allows researchers to address ecological novelty from different perspectives, e.g., by defining it based on (a) categorical or continuous measures, (b) reference conditions related to sites or organisms, and (c) types of human activities. We suggest striving for a descriptive, non-normative usage of the term "ecological novelty" in science. Normative evaluations and decisions about conservation policies or management are important, but require additional societal processes and engagement with multiple stakeholders. KW - Anthropocene KW - eco-evolutionary experience KW - global change KW - novel ecosystems KW - shifting baselines Y1 - 2019 U6 - https://doi.org/10.1093/biosci/biz095 SN - 0006-3568 SN - 1525-3244 VL - 69 IS - 11 SP - 888 EP - 899 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Braga, Raul Renno A1 - Gomez-Aparicio, Lorena A1 - Heger, Tina A1 - Simoes Vitule, Jean Ricardo A1 - Jeschke, Jonathan M. T1 - Structuring evidence for invasional meltdown BT - broad support but with biases and gaps JF - Biological invasions : unique international journal uniting scientists in the broad field of biological invasions N2 - Negative interactions have been suggested as a major barrier for species arriving in a new habitat. More recently, positive interactions drew attention from community assembly theory and invasion science. The invasional meltdown hypothesis (IMH) introduced the idea that positive interactions among non-native species could facilitate one another’s invasion, even increasing their impact upon the native community. Many studies have addressed IMH, but with contrasting results, reflecting various types of evidence on a multitude of scales. Here we use the hierarchy-of-hypotheses (HoH) approach to differentiate key aspects of IMH, organizing and linking empirical studies to sub-hypotheses of IMH. We also assess the level of empirical support for each sub-hypothesis based on the evidence reported in the studies. We identified 150 studies addressing IMH. The majority of studies support IMH, but the evidence comes from studies with different aims and questions. Supporting studies at the community or ecosystem level are currently rare. Evidence is scarce for marine habitats and vertebrates. Few sub-hypotheses are questioned by more than 50% of the evaluated studies, indicating that non-native species do not affect each other’s survival, growth, reproduction, abundance, density or biomass in reciprocal A ↔ B interactions. With the HoH for IMH presented here, we can monitor progress in empirical tests and evidences of IMH. For instance, more tests at the community and ecosystem level are needed, as these are necessary to address the core of this hypothesis. KW - Facilitation KW - Mutualism KW - Review KW - Nonindigenous KW - Exotic Y1 - 2018 U6 - https://doi.org/10.1007/s10530-017-1582-2 SN - 1387-3547 SN - 1573-1464 VL - 20 IS - 4 SP - 923 EP - 936 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Yannelli, Florencia A. A1 - Karrer, Gerhard A1 - Hall, Rea A1 - Kollmann, Johannes A1 - Heger, Tina T1 - Seed density is more effective than multi-trait limiting similarity in controlling grassland resistance against plant invasions in mesocosms JF - Applied vegetation science : official organ of the International Association for Vegetation Science N2 - QuestionDisturbed areas offer great opportunities for restoring native biodiversity, but they are also prone to invasion by alien plants. Following the limiting similarity hypothesis, we address the question of whether or not similarity of plant functional traits helps developing seed mixtures of native communities with high resistance to invasive species at an early stage of restoration. LocationCentre of Greenhouses and Laboratories Durnast, Technische Universitat Munchen, Freising, Germany. MethodsUsing a system of linear equations, we designed native communities maximizing the similarity between the native and two invasive species according to ten functional traits. We used native grassland plants, two invasive alien species that are often problematic in disturbed areas (i.e., Ambrosia artemisiifolia and Solidago gigantea) and trait information obtained from databases. The two communities were then tested for resistance against establishment of the two invaders separately in a greenhouse experiment. We measured height of the invasive species and above-ground biomass, along with leaf area index, 4 and 8months after sowing respectively. ResultsBoth invasive species were successfully reduced by the native community designed to suppress S. gigantea dominated by small-seeded species. These results could be considered as partial support for the limiting similarity hypothesis. However, given the success of this mixture against both invasive species, suppression was better explained by a seed density effect resulting from the smaller seed mass of the native species included in this mixture. Further, the dominance of a fast-developing competitive species could also contribute to its success. ConclusionsThere was no unequivocal support for the limiting similarity hypothesis in terms of the traits selected. Instead we found that increasing seeding density of native species and selecting species with a fast vegetative development is an effective way to suppress invasive plants during early stages of restoration. If limiting similarity is used to design communities for restoration, early life-history traits should be taken into account. KW - Achillea millefolium KW - Ambrosia artemisiifolia KW - biotic resistance KW - competition KW - density-driven suppression KW - disturbed areas KW - restoration KW - seed mixtures KW - Solidago gigantea Y1 - 2018 U6 - https://doi.org/10.1111/avsc.12373 SN - 1402-2001 SN - 1654-109X VL - 21 IS - 3 SP - 411 EP - 418 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Eilers, Elisabeth Johanna A1 - Heger, Tina T1 - Past Competition Affects Offspring Foliar Terpenoid Concentrations, Seed Traits, and Fitness in the Invasive Forb Erodium cicutarium (Geraniaceae) JF - Frontiers in Ecology and Evolution N2 - (1) Environmental conditions experienced in the past may lead to intraspecific differences in ecological and chemical traits of plants, which likely affect future responses to altered or new environments. Whether competition by neighbors is such a trait-shaping factor is not yet well-known. We aimed to understand how the level of ancestral plant competition affects traits related to plant fitness and resource allocation, reproduction, and (phyto-)toxin accumulation in offspring, and whether a potential differentiation in these traits can be found in different geographic origins of which one belongs to the native and one to the invaded range. (2) We compared differentiation of the following traits in offspring plants of multiple populations in Erodium cicutarium (Geraniaceae): biomass, seed production, seed traits related to dispersal and germination, and concentrations of foliar mono- and sesquiterpenes. We tested the allelopatic potential of aqueous extracts of the same E. cicutarium plants on seeds of five different plant families. (3) In plants originating from populations that experienced high levels of competition, we found twice as high monoterpene concentrations. These plants also produced more biomass and a higher proportion of ripe to unripe seeds until harvesting. Seeds originating from high competition sites were shorter. Aqueous E. cicutarium leaf extracts with high terpenoid content reduced radicle length of Zea mays and radicle and hypocotyl length of E. cicutarium seedlings. (4) The results of this study provide first evidence that the surrounding vegetation may shape chemo-ecological plant traits that may be fundamental for competitive ability. Our study calls for more research testing whether competition experienced in the native range may lead to an enhanced capability of plants to establish populations and spread in a new range. KW - resource allocation KW - specialized metabolites KW - gas chromatography-mass spectrometry KW - seed morphology KW - plant interactions KW - eco-evolutionary experience Y1 - 2019 U6 - https://doi.org/10.3389/fevo.2019.00392 SN - 2296-701X VL - 7 PB - Frontiers Research Foundation CY - Lausanne ER - TY - JOUR A1 - Latimer, Andrew M. A1 - Jacobs, Brooke S. A1 - Gianoli, Ernesto A1 - Heger, Tina A1 - Salgado-Luarte, Cristian T1 - Parallel functional differentiation of an invasive annual plant on two continents JF - AoB PLANTS N2 - Rapid local adaptation frequently occurs during the spread of invading species. It remains unclear, however, how consistent, and therefore potentially predictable, such patterns of local adaptation are. One approach to this question is to measure patterns of local differentiation in functional traits and plasticity levels in invasive species in multiple regions. Finding consistent patterns of local differentiation in replicate regions suggests that these patterns are adaptive. Further, this outcome indicates that the invading species likely responds predictably to selection along environmental gradients, even though standing genetic variation is likely to have been reduced during introduction. We studied local differentiation in the invasive annual plant Erodium cicutarium in two invaded regions, California and Chile. We collected seeds from across strong gradients in precipitation and temperature in Mediterranean-climate parts of the two regions (10 populations per region). We grew seeds from maternal families from these populations through two generations and exposed the second generation to contrasting levels of water and nutrient availability. We measured growth, flowering time and leaf functional traits across these treatments to obtain trait means and plasticity measures. We found strong differentiation among populations in all traits. Plants from drier environments flowered earlier, were less plastic in flowering time and reached greater size in all treatments. Correlations among traits within regions suggested a coordinated evolutionary response along environmental gradients associated with growing season length. There was little divergence in traits and trait intercorrelations between regions, but strongly parallel divergence in traits within regions. Similar, statistically consistent patterns of local trait differentiation across two regions suggest that local adaptation to environmental gradients has aided the spread of this invasive species, and that the formation of ecotypes in newly invaded environments has been relatively consistent and predictable. KW - Erodium cicutarium KW - flowering time KW - functional trait correlations KW - invasive species KW - life-history strategy KW - local adaptation KW - parallel evolution KW - phenotypic plasticity Y1 - 2019 U6 - https://doi.org/10.1093/aobpla/plz010 SN - 2041-2851 VL - 11 IS - 2 PB - Oxford University Press CY - Oxford ER - TY - JOUR A1 - Ryo, Masahiro A1 - Jeschke, Jonathan M. A1 - Rillig, Matthias C. A1 - Heger, Tina T1 - Machine learning with the hierarchy-of-hypotheses (HoH) approach discovers novel pattern in studies on biological invasions JF - Research synthesis methods N2 - Research synthesis on simple yet general hypotheses and ideas is challenging in scientific disciplines studying highly context-dependent systems such as medical, social, and biological sciences. This study shows that machine learning, equation-free statistical modeling of artificial intelligence, is a promising synthesis tool for discovering novel patterns and the source of controversy in a general hypothesis. We apply a decision tree algorithm, assuming that evidence from various contexts can be adequately integrated in a hierarchically nested structure. As a case study, we analyzed 163 articles that studied a prominent hypothesis in invasion biology, the enemy release hypothesis. We explored if any of the nine attributes that classify each study can differentiate conclusions as classification problem. Results corroborated that machine learning can be useful for research synthesis, as the algorithm could detect patterns that had been already focused in previous narrative reviews. Compared with the previous synthesis study that assessed the same evidence collection based on experts' judgement, the algorithm has newly proposed that the studies focusing on Asian regions mostly supported the hypothesis, suggesting that more detailed investigations in these regions can enhance our understanding of the hypothesis. We suggest that machine learning algorithms can be a promising synthesis tool especially where studies (a) reformulate a general hypothesis from different perspectives, (b) use different methods or variables, or (c) report insufficient information for conducting meta-analyses. KW - artificial intelligence KW - hierarchy-of-hypotheses approach KW - machine learning KW - meta-analysis KW - synthesis KW - systematic review Y1 - 2019 U6 - https://doi.org/10.1002/jrsm.1363 SN - 1759-2879 SN - 1759-2887 VL - 11 IS - 1 SP - 66 EP - 73 PB - Wiley CY - Hoboken ER - TY - GEN A1 - Ryo, Masahiro A1 - Jeschke, Jonathan M. A1 - Rillig, Matthias C. A1 - Heger, Tina T1 - Machine learning with the hierarchy-of-hypotheses (HoH) approach discovers novel pattern in studies on biological invasions T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - Research synthesis on simple yet general hypotheses and ideas is challenging in scientific disciplines studying highly context-dependent systems such as medical, social, and biological sciences. This study shows that machine learning, equation-free statistical modeling of artificial intelligence, is a promising synthesis tool for discovering novel patterns and the source of controversy in a general hypothesis. We apply a decision tree algorithm, assuming that evidence from various contexts can be adequately integrated in a hierarchically nested structure. As a case study, we analyzed 163 articles that studied a prominent hypothesis in invasion biology, the enemy release hypothesis. We explored if any of the nine attributes that classify each study can differentiate conclusions as classification problem. Results corroborated that machine learning can be useful for research synthesis, as the algorithm could detect patterns that had been already focused in previous narrative reviews. Compared with the previous synthesis study that assessed the same evidence collection based on experts' judgement, the algorithm has newly proposed that the studies focusing on Asian regions mostly supported the hypothesis, suggesting that more detailed investigations in these regions can enhance our understanding of the hypothesis. We suggest that machine learning algorithms can be a promising synthesis tool especially where studies (a) reformulate a general hypothesis from different perspectives, (b) use different methods or variables, or (c) report insufficient information for conducting meta-analyses. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1171 KW - artificial intelligence KW - hierarchy-of-hypotheses approach KW - machine learning KW - meta-analysis KW - synthesis KW - systematic review Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-517643 SN - 1866-8372 IS - 1171 SP - 66 EP - 73 ER - TY - GEN A1 - Higgs, Eric S. A1 - Harris, Jim A. A1 - Heger, Tina A1 - Hobbs, Richard J. A1 - Murphy, Stephen D. A1 - Suding, Katharine N. T1 - Keep ecological restoration open and flexible T2 - Nature Ecology & Evolution Y1 - 2018 U6 - https://doi.org/10.1038/s41559-018-0483-9 SN - 2397-334X VL - 2 IS - 4 SP - 580 EP - 580 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Heger, Tina A1 - Nikles, Gabriele A1 - Jacobs, Brooke S. T1 - Differentiation in native as well as introduced ranges BT - germination reflects mean and variance in cover of surrounding vegetation JF - AoB PLANTS N2 - Germination, a crucial phase in the life cycle of a plant, can be significantly influenced by competition and facilitation. The aim of this study was to test whether differences in cover of surrounding vegetation can lead to population differentiation in germination behaviour of an annual grassland species, and if so, whether such a differentiation can be found in the native as well as in the introduced range. We used maternal progeny of Erodium cicutarium previously propagated under uniform conditions that had been collected in multiple populations in the native and two introduced ranges, in populations representing extremes in terms of mean and variability of the cover of surrounding vegetation. In the first experiment, we tested the effect of germination temperature and mean cover at the source site on germination, and found interlinked effects of these factors. In seeds from one of the introduced ranges (California), we found indication for a 2-fold dormancy, hindering germination at high temperatures even if physical dormancy was broken and water was available. This behaviour was less strong in high cover populations, indicating cross-generational facilitating effects of dense vegetation. In the second experiment, we tested whether spatial variation in cover of surrounding vegetation has an effect on the proportion of dormant seeds. Contrary to our expectations, we found that across source regions, high variance in cover was associated with higher proportions of seeds germinating directly after storage. In all three regions, germination seemed to match the local environment in terms of climate and vegetation cover. We suggest that this is due to a combined effect of introduction of preadapted genotypes and local evolutionary processes. KW - Bet-hedging KW - competition KW - eco-evolutionary experience KW - facilitation KW - genetic adaptation KW - physical and physiological dormancy KW - preadaptation Y1 - 2018 U6 - https://doi.org/10.1093/aobpla/ply009 SN - 2041-2851 VL - 10 IS - 1 PB - Oxford Univ. Press CY - Oxford ER - TY - GEN A1 - Heger, Tina A1 - Nikles, Gabriele A1 - Jacobs, Brooke S. T1 - Differentiation in native as well as introduced ranges BT - germination reflects mean and variance in cover of surrounding vegetation T2 - Postprints der Universität Potsdam : Mathematisch Naturwissenschaftliche Reihe N2 - Germination, a crucial phase in the life cycle of a plant, can be significantly influenced by competition and facilitation. The aim of this study was to test whether differences in cover of surrounding vegetation can lead to population differentiation in germination behaviour of an annual grassland species, and if so, whether such a differentiation can be found in the native as well as in the introduced range. We used maternal progeny of Erodium cicutarium previously propagated under uniform conditions that had been collected in multiple populations in the native and two introduced ranges, in populations representing extremes in terms of mean and variability of the cover of surrounding vegetation. In the first experiment, we tested the effect of germination temperature and mean cover at the source site on germination, and found interlinked effects of these factors. In seeds from one of the introduced ranges (California), we found indication for a 2-fold dormancy, hindering germination at high temperatures even if physical dormancy was broken and water was available. This behaviour was less strong in high cover populations, indicating cross-generational facilitating effects of dense vegetation. In the second experiment, we tested whether spatial variation in cover of surrounding vegetation has an effect on the proportion of dormant seeds. Contrary to our expectations, we found that across source regions, high variance in cover was associated with higher proportions of seeds germinating directly after storage. In all three regions, germination seemed to match the local environment in terms of climate and vegetation cover. We suggest that this is due to a combined effect of introduction of preadapted genotypes and local evolutionary processes. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 650 KW - bet-hedging KW - competition KW - eco-evolutionary experience KW - facilitation KW - genetic adaptation KW - physical and physiological dormancy KW - preadaptation Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-424642 SN - 1866-8372 IS - 650 ER -