Foto: Bruno Réquillart

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Individual‐based plant‐pollinator networks are structured by phenotypic and microsite plant traits 

Arroyo‐Correa et al., 2021

1. The biotic and abiotic context of individual plants within animal‐pollinated plant populations can influence pollinator foraging behavior. Pollinator movements regulate pollen flow among plant individuals, and ultimately determine individual plant reproductive success. Yet the underlying drivers of this context‐dependency of interactions at the population level and their functional consequences for individuals remain poorly known.
2. Here we used a well‐characterised population of Halimium halimifolium (Cistaceae), a Mediterranean shrub species, in combination with exponential random graph models (ERGMs) to evaluate how the intrapopulation variation in plant attributes configures individual‐based plant‐pollinator networks and determines their reproductive outcomes. Specifically, we assessed (i) how the intrinsic (i.e., phenotype and phenology) and extrinsic (i.e., microsite) plant attributes influenced the emerging configuration of the bipartite plant‐pollinator network and the unipartite plant‐plant network derived from pollinator sharing, and (ii) how these plant attributes combined with the network topological position of individual plants affect their female fitness, measured as the total seed weight per plant.
3. We found that both intrinsic and extrinsic plant attributes contributed substantially to explain the configuration of both the bipartite and the unipartite pollination network. Besides the effects of plant attributes, the functional group to which pollinator species belonged was also important to determine the variance in plant‐pollinator interaction odds, while the probability of plants to share more pollinator species was additionally influenced by the spatial distance between those plants. Further, our results showed that these influences of plant attributes on network structure can be translated into functional outcomes at the plant individual level, with direct consequences for intrapopulation fitness variation.
4. Synthesis. This study builds towards a better understanding of the multiple drivers underlying the context‐dependency of plant‐pollinator interactions and how they mediate the reproductive outputs for individual plants within a population. The application of our analytical framework allows a conceptual shift from descriptive to predictive research on the evolutionary and ecological processes that give rise to complex ecological networks at the population level. 
   

 

https://doi.org/10.1111/1365-2745.13694 

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May Flower

Emily Dickinson 

Pink, small, and punctual,

Aromatic, low,

Covert in April,

Candid in May,



Dear to the moss,

Known by the knoll,

Next to the robin

In every human soul.



Bold little beauty,

Bedecked with thee,

Nature forswears

Antiquity.

 

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Network motifs involving both competition and facilitation predict biodiversity in alpine plant communities 

Losapio et al., 2021

Biological diversity depends on multiple, cooccurring ecological interactions. However, most studies focus on one interaction type at a time, leaving community ecologists unsure of how positive and negative associations among species combine to influence biodiversity patterns. Using surveys of plant populations in alpine communities worldwide, we explore patterns of positive and negative associations among triads of species (modules) and their relationship to local biodiversity. Three modules, each incorporating both positive and negative associations, were overrepresented, thus acting as "network motifs." Furthermore, the overrepresentation of these network motifs is positively linked to species diversity globally. A theoretical model illustrates that these network motifs, based on competition between facilitated species or facilitation between inferior competitors, increase local persistence. Our findings suggest that the interplay of competition and facilitation is crucial for maintaining biodiversity.

 

Global map of alpine plant networks studied here. Red dots on the map indicate the spatial location of the networks, with a few networks plotted for reference. In the networks, green dots represent plant species, and blue and red arrows represent negative- and positive species associations, respectively. Dot size is proportional to species abundance. The four network modules analyzed here are represented at the bottom of the figure, from left to right: intransitive competition, facilitation-driven competition, and competition-driven facilitation 1 and 2.

https://bit.ly/3d2JvAC

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How do plants engage with beneficial microorganisms while at the same time restricting pathogens? 

 Cara Haney and David Thoms

The influence of competing root symbionts on below‐ground plant resource allocation 

Bell et al., 2021.

1. Plants typically interact with multiple above‐ and below‐ground organisms simultaneously, with their symbiotic relationships spanning a continuum ranging from mutualism, such as with arbuscular mycorrhizal fungi (AMF), to parasitism, including symbioses with plant‐parasitic nematodes (PPN).
2. Although research is revealing the patterns of plant resource allocation to mutualistic AMF partners under different host and environmental constraints, the root ecosystem, with multiple competing symbionts, is often ignored. Such competition is likely to heavily influence resource allocation to symbionts.
3. Here, we outline and discuss the competition between AMF and PPN for the finite supply of host plant resources, highlighting the need for a more holistic understanding of the influence of below‐ground interactions on plant resource allocation. Based on recent developments in our understanding of other symbiotic systems such as legume–rhizobia and AMF‐aphid‐plant, we propose hypotheses for the distribution of plant resources between contrasting below‐ground symbionts and how such competition may affect the host.
4. We identify relevant knowledge gaps at the physiological and molecular scales which, if resolved, will improve our understanding of the true ecological significance and potential future exploitation of AMF‐PPN‐plant interactions in order to optimize plant growth. To resolve these outstanding knowledge gaps, we propose the application of well‐established methods in isotope tracing and nutrient budgeting to monitor the movement of nutrients between symbionts. By combining these approaches with novel time of arrival experiments and experimental systems involving multiple plant hosts interlinked by common mycelial networks, it may be possible to reveal the impact of multiple, simultaneous colonizations by competing symbionts on carbon and nutrient flows across ecologically important scales.

 

Alternative scenarios for the allocation of resources in the PPN‐AMF‐plant tripartite symbiosis. (a) Plant‐parasitic nematodes (PPN) acquire the majority of the carbon‐based plant resources (C), and the arbuscular mycorrhizal fungi (AMF) receive a reduced allocation. In turn, this leads to diminished transfer of nutrients from AMF to the host (P/N), whilst the AMF utilize the common mycelial network to translocate nutrients toward other hosts in the system. (b) Identical carbon allocation to symbionts as described in (a), with the majority acquired by the PPN. AMF‐derived nutrients continue to be transferred to the host even though there are reduced resources exchanged. (c) The host plant may distinguish PPN offer no reciprocal benefit and reduce delivery of C. In turn, resources are directed toward more beneficial AMF. In each scenario, the resource allocation to each symbiont may be regulated by the host or through local effector crosstalk within feeding structures (●▲, a). Red arrows—host to symbionts carbon flow; Blue arrows—AMF to host phosphorus/nitrogen flow; width of arrows—the strength of the flow; CMN—common mycelial network. 

https://bit.ly/3tnT4yR

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Kevin Horan 

(https://kevinhoran.com)

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Experimental evidence of microbial inheritance in plants and transmission routes from seed to phyllosphere and root 

Abdelfatta et al., 2021

While the environment is considered the primary origin of the plant microbiome, the potential role of seeds as a source of transmitting microorganisms has not received much attention. Here we tested the hypothesis that the plant microbiome is partially inherited through vertical transmission. An experimental culturing device was constructed to grow oak seedlings in a microbe‐free environment while keeping belowground and aboveground tissues separated. The microbial communities associated with the acorn's embryo and pericarp and the developing seeding's phyllosphere and root systems were analysed using amplicon sequencing of fungal ITS and bacterial 16S rDNA. Results showed that the seed microbiome is diverse and non‐randomly distributed within an acorn. The microbial composition of the phyllosphere was diverse and strongly resembled the composition found in the embryo, whereas the roots and pericarp each had a less diverse and distinct microbial community. Our findings demonstrate a high level of microbial diversity and spatial partitioning of the fungal and bacterial community within both seed and seedling, indicating inheritance, niche differentiation and divergent transmission routes for the establishment of root and phyllosphere communities.

 

Core microbiome distribution and niche differentiation of the vertically transmitted microbiome of the pedunculate oak Quercus robur. Line colours correspond to sample types (pink: embryo, purple: pericarp, brown: roots, green: phyllosphere). The width of the line between each genus and sample type reflects the relative abundance of the genus in that particular sample type. Blue circles represent fungi, red circles represent bacteria.  

https://bit.ly/2OnfSjb

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Complex hysteretic patterns: hidden loops and ecological traps

Theresa Ong

Via: @Dr_Joe_Roberts

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