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opencc-zeroNov 2021View details →

Global synthesis of effects of plant species diversity on trophic groups and interactions

Numerous studies have demonstrated that plant species diversity enhances ecosystem functioning in terrestrial ecosystems, including diversity effects on insects (herbivores, predators and parasitoids) and plants. However, the effects of increased plant diversity across trophic levels in different ecosystems and biomes have not yet been explored on a global scale. Through a global meta-analysis of 2,914 observations from 351 studies, we found that increased plant species richness reduced herbivore abundance and damage but increased predator and parasitoid abundance, predation, parasitism and overall plant performance. Moreover, increased predator/parasitoid performance was correlated with reduced herbivore abundance and enhanced plant performance. We conclude that increasing plant species diversity promotes beneficial trophic interactions between insects and plants, ultimately contributing to increased ecosystem services.

opencc-by-4.0Jul 2024View details →

Scripts and data for: Increased host diversity limits bacterial generalism but may promote microbe-microbe interactions

Research Overview: In this project, we compared cloacal microbiome communities from reptiles from six localities that spanned a gradient in host taxonomic diversity. We found that diversity of the bacterial communities was relatively stable across locations, but that host-specific taxa were overrepresented in high host diversity communities. ASVs in high host diversity communities were more likely to have strong interactions with other bacterial lineages across multiple hosts. Host generalist bacteria were more likely to be from a generalist phylum. Methodology: We used a 16S rRNA metabarcoding approach to quantify bacterial community diversity. We processed the output fastq files using qiime2, and processed the output files using the qiime2R package. We performed our analyses in R. Processed input files and scripts are described below.

Figure 1a from: Eisenhauer N (2018) Aboveground-belowground interactions drive the relationship between plant diversity and ecosystem function. Research Ideas and Outcomes 4: e23688. https://doi.org/10.3897/rio.4.e23688

Figure 1a - Importance of the duration of the experiment for its outcome. The effect of plant diversity on plant productivity and on the performance of decomposers increases over time. Regression between the R² of the relationship between plant diversity and plant productivity and the R² of the relationship between plant diversity and decomposer biomass/density. Data from the Jena Experiment from different years [plant productivity in 2003 – 2009; microbial biomass in 2003 – 2009 (white circles); meso- (gray circles) and macroinvertebrate densities (black circles) in 2004, 2006 and 2008].

Figure 3 from: Eisenhauer N (2018) Aboveground-belowground interactions drive the relationship between plant diversity and ecosystem function. Research Ideas and Outcomes 4: e23688. https://doi.org/10.3897/rio.4.e23688

Figure 3 - Plant diversity effects on soil microbes more pronounced at elevated [CO2]. Microbial biomass (µg Cmic g-1 soil dry mass) and basal respiration (BR; µl O2 h-1 g-1 soil dry mass) as affected by plant species richness (SR) and CO2 concentrations. Dashed lines indicate ambient CO2 levels, solid lines elevated CO2 levels (+180 ppm). SR x CO2 for Cmic: p=0.007; SR x CO2 for BR: p=0.03). Data from August 2010. Means with SE. Redrawn after Eisenhauer et al. (2013).

Figure 4 from: Eisenhauer N (2018) Aboveground-belowground interactions drive the relationship between plant diversity and ecosystem function. Research Ideas and Outcomes 4: e23688. https://doi.org/10.3897/rio.4.e23688

Figure 4 - Conceptual figure showing how global change drivers like temperature increase and drought may increase plant diversity–ecosystem function relationships.

Figure 2 from: Eisenhauer N (2018) Aboveground-belowground interactions drive the relationship between plant diversity and ecosystem function. Research Ideas and Outcomes 4: e23688. https://doi.org/10.3897/rio.4.e23688

Figure 2 - Conceptual scheme of how aboveground–belowground interactions may influence the positive relationship between plant diversity and ecosystem functioning. The left part of the scheme illustrates how lower quantity and quality of plant inputs to the soil in species-poor plant communities (being low in resource use complementarity) may induce negative soil feedback effects. The right part of the scheme shows that higher quantity and quality of plant inputs in species-rich plant communities (being high in resource use complementarity) may cause the dominance of positive soil feedback effects. Mutualists will decrease (Wurst et al. 2008, Latz et al. 2012) and/or superimpose (Eisenhauer et al. 2012a) detrimental effects of antagonists on plants. The four proposed projects complement each other to explore the underlying mechanisms of this scheme across different experimental contexts.

Figure 1b from: Eisenhauer N (2018) Aboveground-belowground interactions drive the relationship between plant diversity and ecosystem function. Research Ideas and Outcomes 4: e23688. https://doi.org/10.3897/rio.4.e23688

Figure 1b - Importance of the duration of the experiment for its outcome. Long-term plant diversity studies on soil biota are rare. Relationship between sampling time since the establishment of the biodiversity experiment, number of studies investigating soil biota and percentage of significant plant diversity effects on soil biota (Eisenhauer et al. 2012a). Size of the bubbles and respective numbers indicate percentage of significant plant diversity effects (regression between number of studies and time: R²=0.56, p=0.033, between time and significant plant diversity effects: R²=0.66, p=0.014, n=20 studies).

opencc-zeroDec 2014View details →

Data from: Diversity increases indirect interactions, attenuates the intensity of competition, and promotes coexistence

A fundamental assumption of coexistence theory is that competition inevitably decreases species diversity. Consequently, in the quest to understand the ecological regulators of diversity, there has been a great deal of focus on processes with the potential to reduce competitive exclusion. However, the notion that competition must decrease diversity is largely based on the outcome of two-species interaction experiments and models, despite the fact that species rarely interact only in pairs in natural systems. In a field experiment, we found that competition among native perennial plants in multispecies assemblages was far weaker than competition between those same species in pairwise arrangements and that indirect interactions appeared to weaken direct competitive effects. These results suggest that community assembly theory based on pairwise approaches may overestimate the strength of competition and likelihood of competitive exclusion in species-rich communities. We also found that Centaurea stoebe, a North American invader, retained strong competitive effects when competing against North American natives in both pairwise and multispecies assemblages. Our experimental results support an emerging body of theory suggesting that complex networks of competing species may generate strong indirect interactions that can maintain diversity and that ecological differentiation may not be necessary to attenuate competition.

opencc-zeroSep 2021View details →

Pollen transport networks reveal highly diverse and temporally stable plant-pollinator interactions in an Appalachian floral community

Floral visitation alone has been typically used to characterize plant-pollinator interaction networks even though it ignores differences in the quality of floral visits (e.g. transport of pollen) and thus may overestimate the number and functional importance of pollinating interactions. However, how network structural properties differ between floral visitation and pollen transport networks is not well understood. Furthermore, the strength and frequency of plant-pollinator interactions may vary across fine temporal scales (within a single season) further limiting our predictive understanding of the drivers and consequences of plant-pollinator network structure. Thus, evaluating the structure of pollen transport networks and how they change within a flowering season may help increase our predictive understanding of the ecological consequences of plant-pollinator network structure. Here we compare plant-pollinator network structure using floral visitation and pollen transport data and evaluate within-season variation in pollen transport network structure in a diverse plant-pollinator community. Our results show that pollen transport networks provide a more accurate representation of the diversity of plant-pollinator interactions in a community but that floral visitation and pollen transport networks do not differ in overall network structure. Pollen transport network structure was relatively stable throughout the flowering season despite changes in plan and pollinator species composition. Overall, our study highlights the need to improve our understanding of the drivers of plant-pollinator network structure in order to more fully understand the process that govern the assembly of these interactions in nature.

opencc-zeroJan 2023View details →

Edge disturbance shapes liana diversity and abundance but not liana-tree interaction network patterns in moist semi-deciduous forests, Ghana

Edge disturbance can drive liana community changes and alter liana-tree interaction networks, with ramifications for forest functioning. Understanding edge effects on liana community structure and liana-tree interactions is therefore essential for forest management and conservation. We evaluated the response of liana community structure and the patterns of liana-tree interaction structure to forest edge in two moist semi-deciduous forests in Ghana (Asenanyo and Suhuma Forest Reserves: AFR and SFR, respectively). Liana community structure and liana-tree interactions were assessed in 24 50 × 50 m randomly located plots in three forest sites in each forest: edge, interior and deep-interior established at 0-50 m, 200 m and 400 m from edge. Edge effects positively and negatively influenced liana diversity in forest edges of AFR and SFR, respectively. There was a positive influence of edge disturbance on liana abundance in both forests. We observed anti-nested structure in all the liana-tree networks in AFR, while no nestedness was observed in the networks in SFR. The networks in both forests were less connected, and thus more modular and specialised than their null models. Many liana and tree species were specialised, with specialisation tending to be symmetrical. The plant species played different roles in relation to modularity. Most of the species acted as peripherals (specialists), with only a few species having structural importance to the networks. The latter species group consisted of connectors (generalists) and hubs (highly connected generalists). Some of the species showed consistency in their roles across the sites, while the roles of other species changed. Generally, liana species co-occurred randomly on tree species in all the forest sites, except edge site in AFR where lianas showed positive co-occurrence. Our findings deepen our understanding of the response of liana communities and liana-tree interactions to forest edge disturbance, which are useful for managing forest edge.