@article{LeifsoMacDougallHusbandetal.2012, author = {Leifso, A. and MacDougall, A. S. and Husband, B. and Hierro, J. L. and K{\"o}chy, Martin and P{\"a}rtel, M. and Peltzer, D. A.}, title = {Expansion of a globally pervasive grass occurs without substantial trait differences between home and away populations}, series = {Oecologia}, volume = {170}, journal = {Oecologia}, number = {4}, publisher = {Springer}, address = {New York}, issn = {0029-8549}, doi = {10.1007/s00442-012-2370-4}, pages = {1123 -- 1132}, year = {2012}, abstract = {The global expansion of species beyond their ancestral ranges can derive from mechanisms that are trait-based (e.g., post-establishment evolved differences compared to home populations) or circumstantial (e.g., propagule pressure, with no trait-based differences). These mechanisms can be difficult to distinguish following establishment, but each makes unique predictions regarding trait similarity between ancestral ('home') and introduced ('away') populations. Here, we tested for trait-based population differences across four continents for the globally distributed grass Dactylis glomerata, to assess the possible role of trait evolution in its worldwide expansion. We used a common-environment glasshouse experiment to quantify trait differences among home and away populations, and the potential relevance of these differences for competitive interactions. Few significant trait differences were found among continents, suggesting minimal change during global expansion. All populations were polyploids, with similar foliar carbon:nitrogen ratios (a proxy for defense), chlorophyll content, and biomass. Emergence time and growth rate favored home populations, resulting in their competitive superiority over away populations. Small but significant trait differences among away populations suggest different introductory histories or local adaptive responses following establishment. In summary, the worldwide distribution of this species appears to have arisen from its pre-adapted traits promoting growth, and its repeated introduction with cultivation and intense propagule pressure. Global expansion can thus occur without substantial shifts in growth, reproduction, or defense. Rather than focusing strictly on the invader, invasion success may also derive from the traits found (or lacking) in the recipient community and from environmental context including human disturbance.}, language = {en} } @article{NottebrockEslerSchurr2013, author = {Nottebrock, Henning and Esler, Karen J. and Schurr, Frank Martin}, title = {Effects of intraspecific and community density on the lifetime fecundity of long-lived shrubs}, series = {Perspectives in plant ecology, evolution and systematics}, volume = {15}, journal = {Perspectives in plant ecology, evolution and systematics}, number = {3}, publisher = {Elsevier}, address = {Jena}, issn = {1433-8319}, doi = {10.1016/j.ppees.2013.03.003}, pages = {150 -- 161}, year = {2013}, abstract = {Intra- and interspecific density dependence has profound consequences for plant population and community dynamics. In long-lived plants, however, lifetime patterns and mechanisms of density dependence are difficult to study. Here, we examine effects of intraspecific and community density on the lifetime fecundity of two long-lived shrub species from South African Fynbos: Protea repens (animal-pollinated, hermaphroditic) and Leucadendron rubrum (wind-pollinated, dioecious). Both species are serotinous, retaining seeds in cones until fire kills the mother plant. We measured lifetime fecundity as the product of cone number, proportion of cones that are not damaged by predation and seed set (fertile seeds per intact cone). Intraspecific and community densities were quantified by counting individuals of target species and all Proteaceae in small- and large-scale neighbourhoods (10 m and 50 m radius) around each focal individual. Additionally, we determined the age and size of focal individuals. We found that lifetime fecundity of the wind-pollinated L rubrum is density independent. In contrast, the lifetime fecundity of the animal-pollinated P. repens increases with large-scale intraspecific density and shows a hump-shaped relationship to large-scale community density. Community density has a hump-shaped effect on seed set (probably through partial absence of generalized pollinators at low and competition for pollinators at high densities) and negatively affects cone number per individual. For both species, plant age decreases seed set while increasing lifetime fecundity. The qualitative differences in the density dependence of lifetime fecundity may arise from differences between animal and wind pollination. In particular, interactions with generalized animal pollinators may cause community-level Allee effects with profound consequences for the future dynamics of long-lived plant populations and communities.}, language = {en} } @article{CaronDeFrenneBrunetetal.2015, author = {Caron, Maria Mercedes and De Frenne, Pieter and Brunet, J{\"o}rg and Chabrerie, Olivier and Cousins, Sara A. O. and Decocq, Guillaume and Diekmann, Martin and Graae, Bente Jessen and Heinken, Thilo and Kolb, Annette and Lenoir, Jonathan and Naaf, Tobias and Plue, Jan and Selvi, Federico and Wulf, Monika and Verheyen, Kris}, title = {Divergent regeneration responses of two closely related tree species to direct abiotic and indirect biotic effects of climate change}, series = {Forest ecology and management}, volume = {342}, journal = {Forest ecology and management}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0378-1127}, doi = {10.1016/j.foreco.2015.01.003}, pages = {21 -- 29}, year = {2015}, abstract = {Changing temperature and precipitation can strongly influence plant reproduction. However, also biotic interactions might indirectly affect the reproduction and recruitment success of plants in the context of climate change. Information about the interactive effects of changes in abiotic and biotic factors is essential, but still largely lacking, to better understand the potential effects of a changing climate on plant populations. Here we analyze the regeneration from seeds of Acer platanoides and Acer pseudoplatanus, two currently secondary forest tree species from seven regions along a 2200 km-wide latitudinal gradient in Europe. We assessed the germination, seedling survival and growth during two years in a common garden experiment where temperature, precipitation and competition with the understory vegetation were manipulated. A. platanoides was more sensitive to changes in biotic conditions while A. pseudoplatanus was affected by both abiotic and biotic changes. In general, competition reduced (in A. platanoides) and warming enhanced (in A. pseudoplatanus) germination and survival, respectively. Reduced competition strongly increased the growth of A. platanoides seedlings. Seedling responses were independent of the conditions experienced by the mother tree during seed production and maturation. Our results indicate that, due to the negative effects of competition on the regeneration of A. platanoides, it is likely that under stronger competition (projected under future climatic conditions) this species will be negatively affected in terms of germination, survival and seedling biomass. Climate-change experiments including both abiotic and biotic factors constitute a key step forward to better understand the response of tree species' regeneration to climate change. (C) 2015 Elsevier B.V. All rights reserved.}, language = {en} }