An Exploration of Hypotheses that Explain Herbivore and Pathogen Attack in Restored Plant Communities

<div><p>Many hypotheses address the associations of plant community composition with natural enemies, including: (i) plant species diversity may reduce enemy attack, (ii) attack may increase as host abundance increases, (iii) enemy spillover may lead to increased attack on one host species due to transmission from another host species, or enemy dilution may lead to reduced attack on a host that would otherwise have more attack, (iv) physical characteristics of the plant community may influence attack, and (v) plant vigor may affect attack. Restoration experiments with replicated plant communities provide an exceptional opportunity to explore these hypotheses. To explore the relative predictive strengths of these related hypotheses and to investigate the potential effect of several restoration site preparation techniques, we surveyed arthropod herbivore and fungal pathogen attack on the six most common native plant species in a restoration experiment. Multi-model inference revealed a weak but consistent negative correlation with pathogen attack and host diversity across the plant community, and no correlation between herbivory and host diversity. Our analyses also revealed host species-specific relationships between attack and abundance of the target host species, other native plant species, introduced plant species, and physical community characteristics. We found no relationship between enemy attack and plant vigor. We found minimal differences in plant community composition among several diverse site preparation techniques, and limited effects of site preparation techniques on attack. The strongest associations of community characteristics with attack varied among plant species with no community-wide patterns, suggesting that no single hypothesis successfully predicts the dominant community-wide trends in enemy attack.</p></div

Average Partial Correlations from Multiple Regression Models of 14 Predictor Variables Regressed against Herbivore/Pathogen Attack.

<p>Error bars (standard error) are shown among partial correlations of each variable across all models in which that variable was selected. Numbers above each bar represent the proportion of models in which that variable was selected. Error bars represent variation in magnitude of partial correlation among selected models. R² values represent the average predictive power of the multiple selected models for each host species-natural enemy combination. Figs. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0116650#pone.0116650.g002" target="_blank">2</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0116650#pone.0116650.g003" target="_blank">3</a> depict subsets of the data shown in this figure, arranged according to hypothesis rather than host species. Predictor variables are defined as follows; the first seven predictor variables represent relative abundance of each species denoted as percent of total plant cover, Introduced Species: relative abundance of introduced plant species as percent of total plant cover, Total: total plant cover (see manuscript for method of recording total plant cover), Simpsons: Simpson’s diversity index, Standing Thatch and Ground Thatch: percent cover of thatch, Shoot Mass: above-ground individual shoot biomass, Plant Chlorophyll: leaf chlorophyll content.</p

Community Factors that Were Measured and Entered into AIC Analysis.

<p>Community Factors that Were Measured and Entered into AIC Analysis.</p

Interpretive Diagram: Partial Correlations of Changes in Herbivore/Pathogen Attack versus Abundance of Plant Species.

<p>Diagram is based on the results of our AIC analyses, and represents interactions that were in all or most resulting selected models. Width of arrows indicates approximate magnitude of partial correlation, ranging from 0.06 to 0.40. The arrow with a dashed border was selected in 89% of the models selected. All other relationships shown were selected in 100% of the models.</p

Partial Correlations of Variables with Herbivore and Pathogen Attack to Six Native Species.

<p>Title of each panel is the variable of interest for that panel. Panels <b>b</b>, <b>c</b>, and <b>d</b> represent relative abundance of the variable of interest. Panels <b>f</b> and <b>g</b> represent percent cover of the variable of interest. Mean partial correlations with the variable of interest and percent herbivore or pathogen attack on each of six species are represented by bars. Error bars represent variation (standard error) in magnitude of partial correlation among selected models. Numbers along x axes below each bar represent the percent of models in which that variable was selected (herbivory, pathogen).</p

Ecologie et gestion de la maladie de l'enroulement de la vigne.

International audienceGrapevine leafroll disease (GLD) is caused by a complex of vector-borne virus species in the family Closteroviridae. GLD is present in all grape-growing regions of the world, primarily affecting wine grape varieties. The disease has emerged in the last two decades as one of the major factors affecting grape fruit quality, leading to research efforts aimed at reducing its economic impact. Most research has focused on the pathogens themselves, such as improved detection protocols, with limited work directed toward disease ecology and the development of management practices. Here we discuss the ecology and management of GLD, focusing primarily on Grapevine leafroll-associated virus 3, the most important virus species within the complex. We contextualize research done on this system within an ecological framework that forms the backbone of the discussion regarding current and potential GLD management strategies. To reach this goal, we introduce various aspects of GLD biology and ecology, followed by disease management case studies from four different countries and continents (South Africa, New Zealand, California-USA, and France). We review ongoing regional efforts that serve as models for improved strategies to control this economically important and worldwide disease, highlighting scientific gaps that must be filled for the development of knowledge-based sustainable GLD management practices

Appendix B. Influence of enemy exclusion on arbuscular mycorrhizal infection.

Influence of enemy exclusion on arbuscular mycorrhizal infection

Appendix E. Demographic details by site and census.

Demographic details by site and census