Biology subjects

Bidartondo, M. I.

Publications and source records attributed to Bidartondo, M. I..

7 recordsLinked to original sources

bioRxiv2026

Host identity and fungal source pools shape mycorrhizal assembly under carbon removal interventions in large-scale afforestation

1. Large-scale afforestation is central to global carbon dioxide removal (CDR) commitments. Soil inoculation and enhanced rock weathering (ERW) may increase tree biomass carbon stocks during woodland establishment. Both can alter soil fungal communities, but whether they change the root-colonising mycorrhizal fungi that support tree nutrition and growth is largely unknown. 2. In a fully-factorial field trial on former upland pasture in Wales (11.5 ha; ~25,000 saplings), we tested the effects of soil inoculation (addition of soil from nearby mature, donor forests) and ERW (basalt amendment) on root-associated ectomycorrhizal (EcM) and arbuscular mycorrhizal (AM) fungi, and tree growth in mixed-broadleaf and conifer plantations, two and four years after planting. To identify key colonisation sources, we also characterised mycorrhizal fungi in roots and soils of surrounding hedgerows, source tree nursery, non-forested control plots, donor woodlands and soil inoculum. 3. Soil inoculation caused a subtle shift in conifer EcM community composition (3% of variation) but had no detectable effect in broadleaves. Basalt amendment raised soil pH but did not change mycorrhizal composition, diversity, or colonisation. 4. Root-associated EcM communities were distinct from those detected in plantation soils and shared far more taxa with the tree nursery than with the donor inoculum (41-48% vs. 2-9% of plantation EcM taxa) whereas AM communities largely reflected fungi present in pre-existing pasture. 5. Host identity was the dominant factor structuring mycorrhizal communities, overshadowing both treatments, and was the strongest predictor of aboveground biomass. 6. Synthesis and applications: This field-scale evaluation shows early mycorrhizal assembly during woodland establishment is strongly structured by tree species identity and pre-existing fungal source pools, limiting the effect of inoculation at planting. Mycorrhizal management should therefore target the nursery stage and be tailored to individual tree species. Basalt amendment for ERW is unlikely to harm mycorrhizal communities during establishment. Because soil fungal communities did not reflect root symbiosis, our findings also stress that monitoring of belowground outcomes in CDR-focused planting should include root sampling rather than relying on soil DNA alone.

ecology↗

bioRxiv2026

High nitrogen deposition is associated with phosphorus-efficient ectomycorrhizas in Europe's Scots pine forests

Atmospheric inorganic nitrogen (N) deposition has been linked to increased tree phosphorus (P) deficiency and shifts in ectomycorrhizal (ECM) fungal community composition across Europe, but the underlying mechanisms remain poorly understood due to the scarcity of species-level studies of fungal physiology at large spatial scales. Here, we characterized ECM communities in nine Scots pine (Pinus sylvestris L.) stands across Europes largest N deposition gradient to gain mechanistic insight into N-driven ECM community shifts, by assessing morpho-physiological traits (i.e. soil exploration types and ECM root-tip level exoenzyme activities involved in organic N and P acquisition) on individual ectomycorrhizas. Our data revealed high functional variation in foraging strategies across species and sites, including within dominant ECM genera (Cortinarius, Elaphomyces, Lactarius, Piloderma, Russula). Shifts in community-level exoenzyme activities along the N deposition gradient were consistent with increasing P limitation, with a buffering effect of phosphomonoesterase activity on host nutritional status (i.e. reduced foliar N:P). These trends were mainly driven by interspecific differences in enzymatic profiles and species turnover along the gradient, rather than intraspecific variation within widespread species. Dominant low-biomass species in high N sites (e.g. E. citrinopapillatus, L. subdulcis, R. ochroleuca) were efficient P-foragers, with some displaying high oxidative activity, potentially hampering soil carbon storage under elevated N loads. These findings highlight the role of ECM species-specific traits in mediating ecosystem processes and can help understand the future of pine forests under chronic N pollution, with potential implications for applied forestry.

ecology↗

bioRxiv2026

MycorrhizaFinder: an efficient machine learning tool to quantify endomycorrhizal colonisation of real-world roots

AbstractO_ST_ABSBackground and aimsC_ST_ABSRoot colonisation by endomycorrhizal fungi has long been one of the most widely used metrics in mycorrhizal studies. However, due to the significant time required to assess colonisation using traditional microscope techniques, studies of colonisation at large scales are impractical. AI-powered approaches may increase output and facilitate ecosystem assessments. MethodsWe trained an AI-powered tool (MycorrhizaFinder) on field roots from diverse grasslands and heathlands hosting common Northern European plants with a range of arbuscular (AM) and ericoid mycorrhizal (ErM) fungal structures, and dark septate endophytes (DSE), also common in field-sourced roots. We incorporated a user-customized confidence threshold to encourage the user to engage with inevitable morphological ambiguities, in e.g. ErM and DSE. A Macro F1 statistic was used to assess the tools development. ResultsWe provide a sample workflow from root processing and microscope slide scanning to semi-automated model training and performance evaluation. Without human supervision, our automated baseline Macro F1 is 66% for arbuscular and at 57% for ericoid mycorrhizal colonisation assessment. ConclusionMycorrhizaFinder is user friendly, requires no programming skills and offers flexibility for advanced agronomists or ecologists who wish to train the tool using their own labelled mycorrhizal root datasets, including images acquired from different instruments or staining protocols. This adaptability allows users to customize the model for specific ecosystems or experimental designs. Leveraged with molecular identification and/or functional assessment of fungi, MycorrhizaFinder could support scalable and repeatable monitoring across ecosystems to assess mycorrhizal status and track land-use changes over time.

ecology↗

bioRxiv2024

Ectomycorrhizal fungi are influenced by ecoregion boundaries across Europe

AimEcoregions and the distance decay in community similarity are fundamental concepts in biogeography and conservation biology that are well supported across plants and animals, but not fungi. Here we test the relevance of these concepts for ectomycorrhizal (ECM) fungi in temperate and boreal regions. LocationEurope. Time period2008 - 2015. Major taxa studiedEctomycorrhizal fungi. MethodsWe used a large dataset of [~] 24,000 ectomycorrhizas, assigned to 1,350 operational taxonomic units, collected from 129 forest plots via a standardised protocol. We investigated the relevance of ecoregion delimitations for ECM fungi through complementary methodological approaches based on distance decay models, multivariate analyses, and indicator species analyses. We then evaluated the effects of host tree and climate on the observed biogeographical distributions. ResultsEcoregions predict large-scale ECM fungal biodiversity patterns. This is partly explained by climate differences between ecoregions but independent from host tree distribution. Basidiomycetes in the orders Russulales and Atheliales and producing epigeous fruiting bodies, with potentially short-distance dispersal, show the best agreement with ecoregion boundaries. Host tree distribution and fungal abundance (as opposed to presence/absence only) are important to uncover biogeographical patterns in mycorrhizas. Main conclusionsEcoregions are useful units to investigate eco-evolutionary processes in mycorrhizal fungal communities and for conservation decision-making that includes fungi.

ecology↗

bioRxiv2020

Carbon for nutrient exchange between the lycophyte, Lycopodiella inundata and Mucoromycotina fine root endophytes is unresponsive to high atmospheric CO2 concentration

Background and AimsNon-vascular plants associating with arbuscular mycorrhizal (AMF) and Mucoromycotina fine root endophyte (MFRE) fungi derive greater benefits from their fungal associates under higher atmospheric [CO2] than ambient, however nothing is known about how changes in [CO2] affects MFRE function in vascular plants. MethodsWe measured movement of phosphorus (P), nitrogen (N) and carbon (C) between the lycophyte, Lycopodiella inundata and Mucoromycotina fine root endophyte fungi using 33P-orthophosphate, 15N-ammonium chloride and 14CO2 isotope tracers under ambient and elevated atmospheric [CO2] concentrations of 440 and 800 ppm, respectively. Key ResultsTransfer of 33P and 15N from MFRE to plant were unaffected by changes in [CO2]. There was a slight increase in C transfer from plant to MFRE under elevated [CO2]. ConclusionsOur results demonstrate that the exchange of C-for-nutrients between a vascular plant and Mucoromycotina FRE is largely unaffected by changes in atmospheric [CO2]. Unravelling the role of MFRE in host plant nutrition and potential C-for-N trade changes between symbionts under varying abiotic conditions is imperative to further our understanding of the past, present and future roles of diverse plant-fungal symbioses in global ecosystems.

plant biology↗

bioRxiv2020

Phenology and function in lycopod-Mucoromycotina symbiosis

Lycopodiella inundata is a lycophyte with a complex life cycle. The gametophytes and the juvenile, mature and retreating sporophytes form associations with Mucoromycotina fine root endophyte (MFRE) fungi, being mycoheterotrophic as gametophytes and mutualistic as mature sporophytes. However, the function of the symbiosis across juvenile and retreating sporophyte life stages remains unknown. We measured carbon-for-nutrient exchanges between L. inundata and MFRE across the transition from newly emerging sporophytes to mature sporophytes and in retreating adult sporophytes. We show MFRE fungi play distinct functional roles at each plant life stage, with evidence of bidirectional exchange of plant C for fungal acquired nutrients (N and P) between mature adult and retreating adult sporophytes and fungi, but no transfer of plant C to fungi and little fungal-acquired nutrient gain in juvenile sporophytes. Furthermore, we show that these functional stages correspond with different cytologies of colonisation. Our results show that MFRE have considerable plasticity in their interactions with the host plant which is related to the developmental stage of the host. This highlights the need for further research into symbiotic fungal function across plant life histories.

plant biology↗

bioRxiv2019

Mucoromycotina fine root endophyte fungi form nutritional mutualisms with vascular plants.

Fungi and plants have engaged in intimate symbioses that are globally widespread and have driven terrestrial biogeochemical processes since plant terrestrialisation >500 Mya. Recently, hitherto unknown nutritional mutualisms involving ancient lineages of fungi and non-vascular plants have been discovered. However, their extent and functional significance in vascular plants remains uncertain. Here, we provide first evidence of abundant carbon-for-nitrogen exchange between an early-diverging vascular plant (Lycopodiaceae) and Mucoromycotina (Endogonales) fine root endophyte regardless of changes in atmospheric CO2 concentration. Furthermore, we provide evidence that the same fungi also colonize neighbouring non-vascular and flowering plants. These findings fundamentally change our understanding of the evolution, physiology, interrelationships and ecology of underground plant-fungal symbioses in terrestrial ecosystems by revealing an unprecedented nutritional role of Mucoromycotina fungal symbionts in vascular plants.

plant biology↗