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Enemy Release (enemy + release)

Distribution by Scientific Domains

Life Sciences	100%

Terms modified by Enemy Release

enemy release hypothesis

Selected Abstracts

The role of enemy release, tolerance and resistance in plant invasions: linking damage to performance

ECOLOGY LETTERS, Issue 8 2010
Young Jin Chun
Ecology Letters (2010) 13: 937,946 Abstract An explanation for successful invasion is that invasive alien species sustain less pressure from natural enemies than co-occurring native species. Using meta-analysis, we examined whether invasive species: (1) incur less damage, (2) exhibit better performance in the presence of enemies, and (3) tolerate damage more than native species. Invasive alien species did not incur less damage than native species overall. The performance of invasive alien species was reduced compared to natives in the presence of enemies, indicating the invasive alien species were less tolerant to damage than native species. However, there was no overall difference in performance of invasive alien and native species with enemies present. The damage and degree of reduction in performance of invasive alien relative to native species did not depend on relatedness to natives. Our results suggest aliens may not always experience enemy release, and enemy release may not always result in greater plant performance. [source]

Parasites can cause selection against migrants following dispersal between environments

FUNCTIONAL ECOLOGY, Issue 4 2010
Andrew D. C. MacColl
Summary 1.,The potential for selection against migrants to promote population divergence and speciation is well established in theory, yet there has been relatively little empirical work that has explicitly considered selection against migrants as a form of reproductive barrier, and its importance in the accumulation of reproductive isolation between populations has been overlooked until recently. 2.,Parasites often differ between environments and can be an important source of selection on hosts, yet their contribution to population divergence in general, and selection against migrants in particular, is poorly understood. 3.,Selection against migrants might be reduced if organisms escape parasitism when they disperse (natural enemy release). Alternatively, parasites could increase selection against migrants if, when they disperse, organisms encounter parasites to which they are poorly adapted. 4.,Here we test experimentally the contribution that parasites could make to selection against migrants in the adaptive radiation of three-spined sticklebacks. These fish have repeatedly colonized freshwater environments from marine ones, and this has repeatedly lead to rapid speciation. 5.,We use transplant experiments of lab-raised fish to simulate dispersal, and antihelminthic treatment to show that ancestral-type marine sticklebacks contract higher burdens of novel parasites when introduced to freshwater, than in saltwater, and suffer a growth cost as a direct result. 6.,Susceptibility to parasites and their detrimental effect is less in derived, freshwater fish from evolutionarily young populations, possibly as a result of selection for resistance. 7.,Our results support a role for parasites in selection against migrants and population diversification. They do not support the hypothesis of ,natural enemy release'. [source]

Approaches for testing herbivore effects on plant population dynamics

JOURNAL OF APPLIED ECOLOGY, Issue 5 2006
STACEY L. HALPERN
Summary 1As plant invasions pose one of the greatest threats to biodiversity, it is critical to improve both our understanding of invasiveness and strategies for control. Much research into plant invasions and their management, including biological control, assumes strong demographic effects by natural enemies, including herbivores. However, the importance of natural enemies in the regulation of plant populations remains controversial: some ecologists contend that they rarely affect plant populations, and others that they can strongly limit plant population sizes. 2We briefly review the conflicting views and suggest that new approaches to gather and analyse data are needed before the effects of natural enemies on plant populations can be fully characterized. 3We outline experimental and analytical approaches that incorporate density dependence into population models and thus provide a more complete test of the long-term effects of natural enemies on plant populations. We also introduce new methods for obtaining stochastic estimates of equilibrium density, which will provide a key test of enemy effects on plant population size. 4Synthesis and applications. Designing effective strategies for invasive plant management requires information about the factors that limit plant population size. Together, the experiments and analyses we describe measure more clearly how natural enemies influence plant population dynamics. They will provide an important tool in evaluating the role of enemy release in plant invasions and for predicting the potential success of biological control. Such information should help to prioritize strategies that are most likely to control invasive plants effectively and will contribute to risk assessment when considering the release of non-native natural enemies as biological control agents. [source]

Release from foliar and floral fungal pathogen species does not explain the geographic spread of naturalized North American plants in Europe

JOURNAL OF ECOLOGY, Issue 3 2009
Mark Van Kleunen
Summary 1During the last centuries many alien species have established and spread in new regions, where some of them cause large ecological and economic problems. As one of the main explanations of the spread of alien species, the enemy-release hypothesis is widely accepted and frequently serves as justification for biological control. 2We used a global fungus,plant host distribution data set for 140 North American plant species naturalized in Europe to test whether alien plants are generally released from foliar and floral pathogens, whether they are mainly released from pathogens that are rare in the native range, and whether geographic spread of the North American plant species in Europe is associated with release from fungal pathogens. 3We show that the 140 North American plant species naturalized in Europe were released from 58% of their foliar and floral fungal pathogen species. However, when we also consider fungal pathogens of the native North American host range that in Europe so far have only been reported on other plant species, the estimated release is reduced to 10.3%. Moreover, in Europe North American plants have mainly escaped their rare, pathogens, of which the impact is restricted to few populations. Most importantly and directly opposing the enemy-release hypothesis, geographic spread of the alien plants in Europe was negatively associated with their release from fungal pathogens. 4Synthesis. North American plants may have escaped particular fungal species that control them in their native range, but based on total loads of fungal species, release from foliar and floral fungal pathogens does not explain the geographic spread of North American plant species in Europe. To test whether enemy release is the major driver of plant invasiveness, we urgently require more studies comparing release of invasive and non-invasive alien species from enemies of different guilds, and studies that assess the actual impact of the enemies. [source]

Do virus-resistant plants pose a threat to non-target ecosystems?

AUSTRAL ECOLOGY, Issue 5 2009

Abstract One key environmental risk associated with the release of novel disease-resistant plants is the potential for non-target host populations to acquire resistance genes and undergo enemy release, leading to damage to associated native plant populations in high conservation-value ecosystems. Unfortunately, the dynamics of most natural pathosystems are poorly understood, and risk assessment of disease-resistant plants remains a challenge. Here we describe the first stage of a multi-tiered risk assessment strategy aimed at quantifying potential ecological release in a model pathosystem (the weedy pasture species Trifolium repens infected with Clover yellow vein virus; ClYVV) in order to assess the level of risk posed by genetically modified and conventionally bred disease-resistant host genotypes to non-target plant communities in south-eastern Australia. Glasshouse inoculation and growth experiments using 14 ClYVV isolates and 20 wild T. repens lines collected from high conservation-value montane grassland and woodland communities show that viral infection reduces the survival and growth of host plants by on average 10,50%. However, T. repens lines exhibited variable levels of resistance and tolerance to virus infection and ClYVV isolates differed in infectivity and aggressiveness, with grassland isolates having a greater pathogenic effect on associated host plants than woodland isolates. We conclude that ClYVV potentially plays an important role in limiting the size of T. repens populations in some at-risk non-target ecosystems and that second-tier field experiments are required to adequately quantify the risk associated with the commercial release of V-R T. repens genotypes in Australia. [source]