Sharing resources for mutual benefit: crosstalk between disciplines deepens the understanding of mycorrhizal symbioses across scales

Mycorrhizal scientists from 53 countries gathered in the city of Prague from 30 July until 4 August 2017 for the 9th International Conference on Mycorrhiza (ICOM9). They came to discuss an ancient symbiosis based on the exchange of resources between plant and fungal partners, with many impacts on plant health (van der Heijden et al., 2015). Much like this mutualistic interaction, delegates from disparate disciplines united with a strong focus on integration and sharing of resources for mutual benefit. By exchanging knowledge among researchers from the fields of molecular biology, physiology and ecology, the participants of ICOM9 made a leap forward in our understanding of symbiotic structure and function at multiple scales

Multi-scale temporal dynamics and spatial structuration of Mediterranean communities : the case of orchids and fungi as contrasted and dépendent models of interactions

Face au constat alarmant de l'érosion de la biodiversité, il est indispensable de quantifier les impacts des changements globaux sur les espèces. Centrée sur deux modèles biologiques, les orchidées et les champignons, cette thèse a visé à (i) quantifier les réponses au niveau de la phénologie des espèces, de la composition des communautés et des interactions biotiques, aux changements globaux et (ii) d'analyser les patrons observés au regard des conditions environnementales et de l'écologie des espèces. Ces travaux ont été réalisés en combinant des approches diachroniques (échelles temporelles multiples, avec un délai de 30 ans pour les orchidées et 170 ans pour les champignons) et synchroniques (échelles spatiales multiples avec des contextes d'usages de sols différents). Les résultats indiquent des réponses marquées (décalage phénologique, changement de composition des communautés, effet sur les stratégies écologiques) des deux modèles biologiques aux changements climatiques et usages de sols. Les traits écologiques et biologiques modulent fortement les réponses des espèces à ces changements. Ces études contribuent à la fois à une meilleure compréhension des mécanismes de structuration des communautés et à la définition de conseils opérationnels des organismes étudiés dans une perspective de conservation en région méditerranéenne.In regard to the alarming rate of biodiversity erosion, it is essential to quantify the impact of global changes on species. Using two biological models, orchids and fungi, this study aimed at (i) quantifying the responses of species' phenology, community composition and biotic interactions to global changes and (ii) analyzing the observed patterns in regard to the environmental conditions and the species' ecology. These studies were based on multiple temporal (with a 30 year-delay in case of orchids and 170 year-delay in case of fungi) and spatial scales (different land-uses). The results indicate a marked response (phenological delay, change in community composition, effect on ecological strategies) of both models to climate and land-use changes. Both the ecological and biological traits of species strongly influence species' responses to global changes. This study allows a better understanding of the mechanisms underlying orchids and fungal assemblies and provides practical and applied guidelines for the conservation of these organisms in the Mediterranean region

Recent declines and range changes of orchids in Western Europe (France, Belgium and Luxembourg)

International audienceIn recent decades, many studies have documented local declines of orchid species due to environmental changes. However, few data are available about the changes of orchid species distributions at large spatial and temporal scales. We aimed to characterize the recent dynamics of orchid distributions in Western Europe, in regard to (i) climate and land use changes and (ii) species’ ecology (i.e. biogeographic and open/closed habitat preferences). We analyzed data from a large-scale survey of 134 orchid species over 20 years in France, Belgium and Luxembourg. We designed null models to assess the nature and significance of recorded changes within each administrative unit and for each orchid species. We found sharp decline of most orchids in the northern part of the study area (i.e. northern France, Belgium and Luxembourg) resulting in an overall shift to the Mediterranean area in the south. We found more frequent decline of heliophilous species than of sciaphilous species, possibly due to the open habitat loss in relation to strong urbanization and changes in agricultural practices in the northern part of the study area. No significant differences in appearance or disappearance were detected between Mediterranean and Euro-Siberian species, thus suggesting that climate change is not a primary constraint of distribution changes over the period considered. Conversely, land use changes seem to affect in a higher extent the distribution of western European orchids. Observed distribution reduction of orchid species in the southern Mediterranean area will exacerbate the already existing contrast in species richness and related conservation priorities between the north and south of the study are

Inter-annual variability in flowering of orchids: lessons learned from 8 years of monitoring in a Mediterranean region of France

It is important to evaluate the loss of biodiversity caused by global changes. In the case of orchids, it is still unclear how long the monitoring duration should be chosen in order to achieve a good compromise between the reliability of the orchid dynamics recorded and sampling duration (e.g. years of monitoring). This study aims to propose a method of monitoring orchids. Using a large database, we investigated the inter-annual variability in flowering of orchids in a French Mediterranean region. The database includes an 8-year-long study (2006–2013) of 47 species at 26 locations in three different types of habitats. The number of individual plants that flowered per species varied significantly between years, but not the number of species. Depending on habitat, two to four years were needed to observe the total number of species per location. Therefore, in Mediterranean regions a one-year-study seems to be insufficient to produce reliable results

Contrasted population dynamics in orchids between insular and continental situations

24-28 octoberInternational audienc

Contrasted responses of orchid occurrence between community and species level to the vegetation dynamics in Mediterranean region: first lessons from a 30 year long sampling interval using a Site-Occupancy Model

2-6 décembre 2013International audienceThere is an increasing interest in understanding and evaluating shifts in biodiversity induced by the ongoing global change. Orchids are particularly relevant organisms to investigate diachronic variations because they respond to anthropic pressure (land-use change, habitat fragmentation, etc.). Here we used a Site-Occupancy Model in order to describe the dynamics of orchid occurrence in Corsica at community and species level, and evaluate the influence of land-use change on orchid occurrence. We compared the occurrence of 45 orchid species at 62 locations in Corsica between 1982?1984 and 2009?2011. Data were collected by the same observer during the two sampling periods applying the same protocol of species inventories. We considered environmental factors and species biological traits as co-factors in the Site-Occupancy Model to estimate the probability of species detection. At community level, we found no significant difference in orchid occurrence between the two sampling periods, in contrast to the species level. Species responded differently to the increase of vegetation cover. We concluded that (i) conservation strategies should be species-dependent, as we observed contrasted responses to the land-use change between species, and (ii) that the use of Site-Occupancy Models is an appropriate way to analyze temporal dynamics of orchids and to investigate the ecological processes underlying these dynamics

Trends in Mediterranean orchid populations : a case study with a 30 year long sampling interval based on a Site-Occupancy Model

17-19 may 2013International audienc

Diversity of Mycorrhizal Fungi in Temperate Orchid Species: Comparison of Culture-Dependent and Culture-Independent Methods

Many orchid species are endangered due to anthropogenic pressures such as habitat destruction and overharvesting, meanwhile, all orchids rely on orchid mycorrhizal fungi (OMF) for seed germination and seedling growth. Therefore, a better understanding of this intimate association is crucial for orchid conservation. Isolation and identification of OMF remain challenging as many fungi are unculturable. In our study, we tested the efficiency of both culture-dependent and culture-independent methods to describe OMF diversity in multiple temperate orchids and assessed any phylogenetic patterns in cultivability. The culture-dependent method involved the cultivation and identification of single pelotons (intracellular hyphal coils), while the culture-independent method used next-generation sequencing (NGS) to identify root-associated fungal communities. We found that most orchid species were associated with multiple fungi, and the orchid host had a greater impact than locality on the variability in fungal communities. The culture-independent method revealed greater fungal diversity than the culture-dependent one, but despite the lower detection, the isolated fungal strains were the most abundant OMF in adult roots. Additionally, the abundance of NGS reads of cultured OTUs was correlated with the extent of mycorrhizal root colonization in orchid plants. Finally, this limited-scale study tentatively suggests that the cultivability character of OMF may be randomly distributed along the phylogenetic trees of the rhizoctonian families

Responses of orchids to habitat change in Corsica over 27 years

International audienc