@article{EilersHeger2019,
  author    = {Eilers, Elisabeth Johanna and Heger, Tina},
  title     = {Past Competition Affects Offspring Foliar Terpenoid Concentrations, Seed Traits, and Fitness in the Invasive Forb Erodium cicutarium (Geraniaceae)},
  series = {Frontiers in Ecology and Evolution},
  volume    = {7},
  journal   = {Frontiers in Ecology and Evolution},
  publisher = {Frontiers Research Foundation},
  address   = {Lausanne},
  issn      = {2296-701X},
  doi       = {10.3389/fevo.2019.00392},
  pages     = {12},
  year      = {2019},
  abstract  = {(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.},
  language  = {en}
}
@article{HegerBernardVerdierGessleretal.2019,
  author    = {Heger, Tina and Bernard-Verdier, Maud and Gessler, Arthur and Greenwood, Alex D. and Grossart, Hans-Peter and Hilker, Monika and Keinath, Silvia and Kowarik, Ingo and K{\"u}ffer, Christoph and Marquard, Elisabeth and Mueller, Johannes and Niemeier, Stephanie and Onandia, Gabriela and Petermann, Jana S. and Rillig, Matthias C. and Rodel, Mark-Oliver and Saul, Wolf-Christian and Schittko, Conrad and Tockner, Klement and Joshi, Jasmin Radha and Jeschke, Jonathan M.},
  title     = {Towards an Integrative, Eco-Evolutionary Understanding of Ecological Novelty: Studying and Communicating Interlinked Effects of Global Change},
  series = {Bioscience},
  volume    = {69},
  journal   = {Bioscience},
  number    = {11},
  publisher = {Oxford Univ. Press},
  address   = {Oxford},
  issn      = {0006-3568},
  doi       = {10.1093/biosci/biz095},
  pages     = {888 -- 899},
  year      = {2019},
  abstract  = {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.},
  language  = {en}
}
@article{HegerNiklesJacobs2018,
  author    = {Heger, Tina and Nikles, Gabriele and Jacobs, Brooke S.},
  title     = {Differentiation in native as well as introduced ranges},
  series = {AoB PLANTS},
  volume    = {10},
  journal   = {AoB PLANTS},
  number    = {1},
  publisher = {Oxford Univ. Press},
  address   = {Oxford},
  issn      = {2041-2851},
  doi       = {10.1093/aobpla/ply009},
  pages     = {12},
  year      = {2018},
  abstract  = {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.},
  language  = {en}
}
@misc{HegerNiklesJacobs2018,
  author    = {Heger, Tina and Nikles, Gabriele and Jacobs, Brooke S.},
  title     = {Differentiation in native as well as introduced ranges},
  series = {Postprints der Universit{\"a}t Potsdam : Mathematisch Naturwissenschaftliche Reihe},
  journal   = {Postprints der Universit{\"a}t Potsdam : Mathematisch Naturwissenschaftliche Reihe},
  number    = {650},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-42464},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-424642},
  pages     = {12},
  year      = {2018},
  abstract  = {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.},
  language  = {en}
}