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Berlin Brandenburg

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  • 1
    Language: English
    In: Science (New York, N.Y.), 18 May 2012, Vol.336(6083), pp.904-7
    Description: Conspecific negative density-dependent establishment, in which local abundance negatively affects establishment of conspecific seedlings through host-specific enemies, can influence species diversity of plant communities, but the generality of this process is not well understood. We tested the strength of density dependence using the United States Forest Service's Forest Inventory and Analysis database containing 151 species from more than 200,000 forest plots spanning 4,000,000 square kilometers. We found that most species experienced conspecific negative density dependence (CNDD), but there was little effect of heterospecific density. Additionally, abundant species exhibited weaker CNDD than rarer species, and species-rich regions exhibited stronger CNDD than species-poor regions. Collectively, our results provide evidence that CNDD is a pervasive mechanism driving diversity across a gradient from boreal to subtropical forests.
    Keywords: Biodiversity ; Ecosystem ; Trees
    ISSN: 00368075
    E-ISSN: 1095-9203
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  • 2
    Article
    Article
    In: Nature, 2004, Vol.427(6973), p.401
    Description: A recent study by Arnold et al on the cacao tree shows that a poorly understood group of microbes provide their host plants with an effective defense against pathogens. The microbes are "endophytes," fungi that live inside leaves without causing disease, and they appear to be ubiquitous associates of...
    Keywords: Cacao–Microbiology ; Festuca–Microbiology ; Phytophthora–Pathogenicity ; Phytophthora–Physiology ; Plant Diseases–Microbiology ; Symbiosis–Microbiology ; Fungi ; Flowers & Plants ; Plant Ecology;
    ISSN: 0028-0836
    E-ISSN: 14764687
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  • 3
    Article
    Article
    In: Nature, 2003, Vol.421(6923), p.585
    Description: Invasive species can be a real bother. These are plants or animals that, when they are accidentally or deliberately moved from one region to another, flourish to the extent of getting out of hand and becoming pests in their naturalized environment. They tend to reduce biodiversity, and can have adverse effects on human well-being. Much effort is devoted to controlling them after they are established, but a better understanding of why species become invasive offers the possibility of taking pre-emptive measures. In companion papers on pages 625 and 628 of this issue, Mitchell and Power and Torchin et al. illuminate the biology of invasiveness. They report the results of surveying parasite loads of invasive plants and animals in their naturalized and native ranges. They find that parasitism is significantly reduced in organisms in the introduced range, so supporting the 'enemy release hypothesis' -- the idea that species are more likely to become invasive when they are released from control by their natural enemies.
    Keywords: Parasites ; Population Control ; Biotic Pressure ; Introduced Species ; Freshwater ; Brackish ; Marine ; Species Interactions: Parasites and Diseases ; Ecology/Community Studies ; Conservation, Wildlife Management and Recreation;
    ISSN: 0028-0836
    E-ISSN: 1476-4687
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  • 4
    In: Ecology, April 2014, Vol.95(4), pp.1045-1054
    Description: Biotic interactions play primary roles in major theories of the distribution and abundance of species, yet the nature of these biotic interactions can depend upon the larger ecological community. Leguminous plants, for example, commonly associate with both arbuscular mycorrhizal fungi (AMF) and rhizobia bacteria, and the pairwise interactions may depend upon the presence or identity of the third partner. To determine if the dynamics of plant–AMF and plant–rhizobia interactions are affected by the alternate symbiont, we manipulated the presence and identity of each symbiont, as well as levels of the nutrients supplied by each symbiont (nitrogen and phosphorus), on the growth of prairie legume . We found strong synergistic effects of AMF and rhizobia inoculation on plant biomass production that were independent of nutrient levels. AMF and rhizobia responses were each influenced by the other, but not in the same direction. AMF infection increased root nodule number and mass, but rhizobia inoculation decreased AMF hyphal colonization of roots. The relative benefits of each combination of symbionts depended upon phosphorus level. The effect of nitrogen was also contingent on the biotic environment where nitrogen addition decreased nodulation, but this decrease was reduced with coinfection by AMF. Our results demonstrate a strong contingency on the co‐occurrence of AMF and rhizobia for the long‐term fitness of , and suggest that the belowground community is critical for the success of this species in tallgrass prairies.
    Keywords: Amorpha Canescens ; Arbuscular Mycorrhizal Fungi ; Biotic Context Dependency ; Interspecific Plant Interactions ; Mutualism ; Rhizobia ; Rhizobia–Amf Interactive Effects ; Symbiosis ; Tallgrass Prairie
    ISSN: 0012-9658
    E-ISSN: 1939-9170
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  • 5
    In: Ecology, December 2011, Vol.92(12), pp.2248-2257
    Description: Plant species introduced into novel ranges may become invasive due to evolutionary change, phenotypic plasticity, or other biotic or abiotic mechanisms. Evolution of introduced populations could be the result of founder effects, drift, hybridization, or adaptation to local conditions, which could enhance the invasiveness of introduced species. However, understanding whether the success of invading populations is due to genetic differences between native and introduced populations may be obscured by origin × environment interactions. That is, studies conducted under a limited set of environmental conditions may show inconsistent results if native or introduced populations are differentially adapted to specific conditions. We tested for genetic differences between native and introduced populations, and for origin × environment interactions, between native (China) and introduced (U.S.) populations of the invasive annual grass (stiltgrass) across 22 common gardens spanning a wide range of habitats and environmental conditions. On average, introduced populations produced 46% greater biomass and had 7.4% greater survival, and outperformed native range populations in every common garden. However, we found no evidence that introduced exhibited greater phenotypic plasticity than native populations. Biomass of was positively correlated with light and resident community richness and biomass across the common gardens. However, these relationships were equivalent for native and introduced populations, suggesting that the greater mean performance of introduced populations is not due to unequal responses to specific environmental parameters. Our data on performance of invasive and native populations suggest that post‐introduction evolutionary changes may have enhanced the invasive potential of this species. Further, the ability of to survive and grow across the wide variety of environmental conditions demonstrates that few habitats are immune to invasion.
    Keywords: Common Garden ; Evolution ; Phenotypic Plasticity ; Plant Invasion ; Specific Leaf Area
    ISSN: 0012-9658
    E-ISSN: 1939-9170
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  • 6
    Language: English
    In: Forest Ecology and Management, Jan 1, 2012, Vol.263, p.268(7)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.foreco.2011.09.038 Byline: Kurt O. Reinhart (a), Daniel Johnson (b), Keith Clay (b) Keywords: Community structure; Recruitment patterns; Forest Inventory and Analysis Database (FIADB); Janzen-Connell Hypothesis; Recruitment dynamics; Distance-dependent mortality Abstract: a* Distance-dependent mortality judged from forest inventory database. a* Survival varied for 4 of 9 species planted near parent or other tree species. a* Experimental results did not support groupings by distance-dependent effects. a* Species group predicted to suffer most from enemies had greatest survival. Author Affiliation: (a) USDA-ARS, Fort Keogh Livestock & Range Research Laboratory, Miles City, MT 59301-4016, USA (b) Indiana University, Department of Biology, Bloomington, IN 47405-3700, USA Article History: Received 10 August 2011; Revised 26 September 2011; Accepted 27 September 2011
    ISSN: 0378-1127
    Source: Cengage Learning, Inc.
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  • 7
    Language: English
    In: Oecologia, 2010, Vol.164(4), pp.1029-1038
    Description: Multiple factors can affect the process of forest succession including seed dispersal patterns, seedling survival, and environmental heterogeneity. A relatively understudied factor affecting the process of succession is invasions by non-native plants. Invasions can increase competition, alter abiotic conditions, and provide refuge for consumers. Functional traits of trees such as seed size and life history stage may mediate the effects of invasions on succession. We tested the effects of the forest invader Microstegium vimineum on planted and naturally regenerating trees in a multi-year field experiment. We established plots containing nine species of small- and large-seeded tree species planted as seeds or saplings, and experimentally added Microstegium to half of all plots. Over 3 years, Microstegium invasion had an overall negative effect on small-seeded species driven primarily by the effect on sweetgum, the most abundant small-seeded species, but did not affect large-seeded species such as hickory and oak species, which have more stored seed resources. Natural regeneration was over 400% greater in control than invaded plots for box elder, red maple, and spicebush, and box elder seedlings were 58% smaller in invaded plots. In contrast to the effects on tree seedlings, invasion did not affect tree sapling survival or growth. Microstegium may be directly reducing tree regeneration through competition. Invaded plots had greater overall herbaceous biomass in 2006 and 2008 and reduced light availability late in the growing season. Indirect effects may also be important. Invaded plots had 120% more thatch biomass, a physical barrier to seedling establishment, and significantly greater vole damage to tree saplings during 2006 and 2007. Our results show that two tree functional traits, seed size and life history stage, determined the effects of Microstegium on tree regeneration. Suppression of tree regeneration by Microstegium invasions may slow the rate of forest succession and alter tree species composition.
    Keywords: Life history stage ; Forest composition ; Tree regeneration ; Microstegium vimineum ; Japanese stiltgrass
    ISSN: 0029-8549
    E-ISSN: 1432-1939
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  • 8
    Language: English
    In: Oecologia, 2012, Vol.170(4), pp.1089-1098
    Description: Due to their complementary roles in meeting plant nutritional needs, arbuscular mycorrhizal fungi (AMF) and nitrogen-fixing bacteria (N 2 -fixers) may have synergistic effects on plant communities. Using greenhouse microcosms, we tested the effects of AMF, N 2 -fixers (symbiotic: rhizobia, and associative: Azospirillum brasilense ), and their potential interactions on the productivity, diversity, and species composition of diverse tallgrass prairie communities and on the productivity of Panicum virgatum in monoculture. Our results demonstrate the importance of AMF and N 2 -fixers as drivers of plant community structure and function. In the communities, we found a positive effect of AMF on diversity and productivity, but a negative effect of N 2 -fixers on productivity. Both AMF and N 2 -fixers affected relative abundances of species. AMF shifted the communities from dominance by Elymus canadensis to Sorghastrum nutans , and seven other species increased in abundance with AMF, accounting for the increased diversity. N 2 -fixers led to increases in Astragalus canadensis and Desmanthus illinoense , two legumes that likely benefited from the presence of the appropriate rhizobia symbionts. Sorghastrum nutans declined 44 % in the presence of N 2 -fixers, with the most likely explanation being increased competition from legumes. Panicum monocultures were more productive with AMF, but showed no response to N 2 -fixers, although inference was constrained by low Azospirillum treatment effectivity. We did not find interactions between AMF and N 2 -fixers in communities or Panicum monocultures, indicating that short-term effects of these microbial functional groups are additive.
    Keywords: Symbiosis ; Diversity ; Panicum virgatum ; Azospirillum ; Rhizobia
    ISSN: 0029-8549
    E-ISSN: 1432-1939
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  • 9
    Language: English
    In: Oikos, Dec, 2012, Vol.121, p.2090(7)
    Description: To purchase or authenticate to the full-text of this article, please visit this link: http://onlinelibrary.wiley.com/doi/10.1111/j.1600-0706.2012.20153.x/abstract Byline: Anna L. Larimer(1), James D. Bever(1), Keith Clay(1) Plants simultaneously associate with multiple microbial symbionts throughout their lifetimes. To address the question of whether the effects of simultaneous symbionts are contingent on the specific identities, we conducted a greenhouse experiment manipulating the presence and identities of arbuscular mycorrhizal fungi (AMF) and fungal endophytes on the shared host grass Elymus hystrix. Each plant host was inoculated with one of two AMF species having varying effects on host growth, or a sterile soil control. Further, we used naturally occurring endophyte-infected (E+) and uninfected (E-) individuals from two populations of the endophyte Epichloe elymi that varied in their interaction with E. hystrix. We then measured responses of plants, AMF, and fungal endophytes. Overall, we found that the combined effects of AMF and fungal endophytes on plant growth were additive, reflecting the mutualistic quality of each symbiont independently interacting with host plants. However, fungal endophyte infection differentially altered hyphal colonization of the two AMF species and the identity of the coinfecting AMF species affected fungal endophyte fitness traits. The results of this study demonstrate that the outcome of interspecific symbiotic interactions varies with partner identity such that the effects of simultaneous symbioses can not be generalized. Author Affiliation: (1)Dept of Biology, Jordan Hall, 1001 East Third Street, Indiana Univ., Bloomington, IN 47405-3700, USA Correspondence: A. L. Larimer, Dept of Biology, Jordan Hall, 1001 East Third Street, Indiana Univ., Bloomington, IN 47405-3700, USA. E-mail: allarime@indiana.edu Paper manuscript accepted 7 February 2012
    Keywords: Fungi ; Atmospheric Carbon Dioxide ; Plants (Organisms)
    ISSN: 0030-1299
    Source: Cengage Learning, Inc.
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  • 10
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 30 August 2005, Vol.102(35), pp.12465-12470
    Description: Microbial symbioses are ubiquitous in nature. Hereditary symbionts warrant particular attention because of their direct effects on the evolutionary potential of their hosts. In plants, hereditary fungal endophytes can increase the competitive ability, drought tolerance, and herbivore resistance of their host, although it is unclear whether or how these ecological benefits may alter the dynamics of the endophyte symbiosis over time. Here, we demonstrate that herbivores alter the dynamics of a hereditary symbiont under field conditions. Also, we show that changes in symbiont frequency were accompanied by shifts in the overall structure of the plant community. Replicated 25- m 2 plots were enriched with seed of the introduced grass, Lolium arundinaceum at an initial frequency of 50% infection by the systemic, seed-transmitted endophyte Neotyphodium coenophialum. Over 54 months, there was a significantly greater increase in endophyte-infection frequency in the presence of herbivores (30% increase) than where mammalian and insect herbivory were experimentally reduced by fencing and insecticide application (12% increase). Under ambient mammalian herbivory, the above-ground biomass of nonhost plant species was reduced compared with the mammal-exclusion treatment, and plant composition shifted toward greater relative biomass of infected, tall fescue grass. These results demonstrate that herbivores can drive plant-microbe dynamics and, in doing so, modify plant community structure directly and indirectly.
    Keywords: Biological sciences -- Ecology -- Ecological processes ; Biological sciences -- Ecology -- Ecological processes ; Health sciences -- Medical conditions -- Infections ; Biological sciences -- Agriculture -- Agricultural sciences ; Biological sciences -- Ecology -- Biomass ; Biological sciences -- Ecology -- Ecological processes ; Biological sciences -- Biology -- Botany ; Biological sciences -- Ecology -- Ecological processes ; Arts -- Applied arts -- Architecture ; Biological sciences -- Biology -- Zoology
    ISSN: 00278424
    E-ISSN: 10916490
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