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Article: Mutualistic interactions between ants and fungi: A review.

Dejean, Alain / Azémar, Frédéric / Naskrecki, Piotr / Tindo, Maurice / Rossi, Vivien / Faucher, Christian / Gryta, Hervé

Ecology and evolution

2023 Volume 13, Issue 8, Page(s) e10386

Abstract: The large amount of dead plant biomass caused by the final extinction events triggered a fungi proliferation that mostly differentiated into saprophytes degrading organic matter; others became parasites, predators, likely commensals, and mutualists. ... ...

Abstract	The large amount of dead plant biomass caused by the final extinction events triggered a fungi proliferation that mostly differentiated into saprophytes degrading organic matter; others became parasites, predators, likely commensals, and mutualists. Among the last, many have relationships with ants, the most emblematic seen in the Neotropical myrmicine Attina that cultivate Basidiomycota for food. Among them, leaf-cutting, fungus-growing species illustrate an ecological innovation because they grow fungal gardens from fresh plant material rather than arthropod frass and plant debris. Myrmecophytes shelter "plant-ants" in hollow structures, the domatia, whose inner walls are lined with thin-walled Ascomycota hyphae that, in certain cases, are eaten by the ants, showing a form of convergence. Typically, these Ascomycota have antibacterial properties illustrating cases of farming for protection. Ant gardens, or mutualistic associations between certain ant species and epiphytes, shelter endophytic fungi that promote the growth of the epiphytes. Because the cell walls of certain Ascomycota hyphae remain sturdy after the death of the mycelium, they form resistant fibers used by ants to reinforce their constructions (e.g., galleries, shelters for tended hemipterans, and carton nests). Thus, we saw cases of "true" fungal agriculture involving planting, cultivating, and harvesting Basidiomycota for food with Attina. A convergence with "plant-ants" feeding on Ascomycota whose antibacterial activity is generally exploited (i.e., farming for protection). The growth of epiphytes was promoted by endophytic fungi in ant gardens. Finally, farming for structural materials occurred with, in one case, a leaf-cutting, fungus-growing ant using Ascomycota fibers to reinforce its nests.
Language	English
Publishing date	2023-07-28
Publishing country	England
Document type	Journal Article ; Review
ZDB-ID	2635675-2
ISSN	2045-7758
ISSN	2045-7758
DOI	10.1002/ece3.10386
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article ; Online: Host-tree selection by the ant garden-initiating arboreal ponerine Neoponera goeldii.

Dejean, Alain / Rossi, Vivien / Azémar, Frédéric / Compin, Arthur / Petitclerc, Frédéric / Talaga, Stanislas / Corbara, Bruno

Ecology

2022 Volume 104, Issue 1, Page(s) e3843

MeSH term(s)	Animals ; Ants ; Trees ; Gardens ; Behavior, Animal
Language	English
Publishing date	2022-09-25
Publishing country	United States
Document type	Journal Article
ZDB-ID	2010140-5
ISSN	1939-9170 ; 0012-9658
ISSN (online)	1939-9170
ISSN	0012-9658
DOI	10.1002/ecy.3843
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Article ; Online: Temperature rising would slow down tropical forest dynamic in the Guiana Shield.

Aubry-Kientz, Mélaine / Rossi, Vivien / Cornu, Guillaume / Wagner, Fabien / Hérault, Bruno

Scientific reports

2019 Volume 9, Issue 1, Page(s) 10235

Abstract: Increasing evidence shows that the functioning of the tropical forest biome is intimately related to the climate variability with some variables such as annual precipitation, temperature or seasonal water stress identified as key drivers of ecosystem ... ...

Abstract	Increasing evidence shows that the functioning of the tropical forest biome is intimately related to the climate variability with some variables such as annual precipitation, temperature or seasonal water stress identified as key drivers of ecosystem dynamics. How tropical tree communities will respond to the future climate change is hard to predict primarily because several demographic processes act together to shape the forest ecosystem general behavior. To overcome this limitation, we used a joint individual-based model to simulate, over the next century, a tropical forest community experiencing the climate change expected in the Guiana Shield. The model is climate dependent: temperature, precipitation and water stress are used as predictors of the joint growth and mortality rates. We ran simulations for the next century using predictions of the IPCC 5AR, building three different climate scenarios (optimistic RCP2.6, intermediate, pessimistic RCP8.5) and a control (current climate). The basal area, above-ground fresh biomass, quadratic diameter, tree growth and mortality rates were then computed as summary statistics to characterize the resulting forest ecosystem. Whatever the scenario, all ecosystem process and structure variables exhibited decreasing values as compared to the control. A sensitivity analysis identified the temperature as the strongest climate driver of this behavior, highlighting a possible temperature-driven drop of 40% in average forest growth. This conclusion is alarming, as temperature rises have been consensually predicted by all climate scenarios of the IPCC 5AR. Our study highlights the potential slow-down danger that tropical forests will face in the Guiana Shield during the next century.
MeSH term(s)	Biomass ; Climate Change ; Ecosystem ; Forests ; Guyana ; Hot Temperature/adverse effects ; Models, Biological ; Rainforest ; South America ; Temperature ; Trees ; Tropical Climate/adverse effects
Language	English
Publishing date	2019-07-15
Publishing country	England
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	2615211-3
ISSN	2045-2322 ; 2045-2322
ISSN (online)	2045-2322
ISSN	2045-2322
DOI	10.1038/s41598-019-46597-8
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Article: Tree growth and mortality of 42 timber species in central Africa

Ligot, Gauthier / Gourlet-Fleury, Sylvie / Dainou, Kasso / Gillet, Jean-François / Rossi, Vivien / Mazengué, Mathurin / Ekome, Stevy Nna / Nkoulou, Yanick Serge / Zombo, Isaac / Forni, Eric / Doucet, Jean-Louis

Forest ecology and management. 2022 Feb. 01, v. 505

2022

Abstract: Tree growth and mortality are two central processes in mixed and structurally complex moist tropical forests, yet accurate estimates of the variables needed to model them remain sparse and scattered. It is thus still difficult to predict forest evolution ...

Abstract	Tree growth and mortality are two central processes in mixed and structurally complex moist tropical forests, yet accurate estimates of the variables needed to model them remain sparse and scattered. It is thus still difficult to predict forest evolution at a local scale and build reliable management plans. To help fill this gap, for 1–7 years we annually monitored 21,180 trees belonging to 42 species exploited for timber production in Central Africa. We made new species-specific estimates of diameter increments and mortality rates, and investigated how tree growth varied with tree size and logging history. We compared our results with the legal values of diameter increments, mortality rates, and minimum cutting diameters used to build forest management plans in Cameroon. Diameter increment was found to vary with tree size for most of the species studied. The relationships between diameter increment and tree size were mostly humpback-shaped. The trees with diameters close to or lower than the reference minimum cutting diameter generally grew faster than the average. We also found that tree growth could slow for 1–2 years after timber exploitation and was then spurred for at least 5 years. The tree growth response to logging was nevertheless species-specific. This study provides new estimates of tree diameter increments and mortality rates that could help make more accurate forest projections and draw up sustainable management plans in Africa.
Keywords	administrative management ; evolution ; forest ecology ; mortality ; timber production ; tree and stand measurements ; tree growth ; trees ; Cameroon
Language	English
Dates of publication	2022-0201
Publishing place	Elsevier B.V.
Document type	Article
ZDB-ID	751138-3
ISSN	0378-1127
ISSN	0378-1127
DOI	10.1016/j.foreco.2021.119889
Database	NAL-Catalogue (AGRICOLA)

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Article ; Online: Competition and site weakly explain tree growth variability in undisturbed Central African moist forests

Gourlet‐Fleury, Sylvie / Rossi, Vivien / Forni, Eric / Fayolle, Adeline / Ligot, Gauthier / Allah‐Barem, Félix / Baya, Fidèle / Bénédet, Fabrice / Boyemba, Faustin / Cornu, Guillaume / Doucet, Jean‐Louis / Gillet, Jean‐François / Mazengue, Mathurin / Mbasi Mbula, Michel / Van Hoef, Yorick / Zombo, Isaac / Freycon, Vincent

Journal of Ecology. 2023 Sept., v. 111, no. 9 p.1950-1967

2023

Abstract: Identifying and quantifying factors that influence tree growth are crucial issues to ensure sustainable forest management, particularly in moist tropical forests. Tree growth depends on several factors comprising ontogenic stage, competition by ... ...

Abstract	Identifying and quantifying factors that influence tree growth are crucial issues to ensure sustainable forest management, particularly in moist tropical forests. Tree growth depends on several factors comprising ontogenic stage, competition by neighbours and environmental conditions. Several studies have focused on one or two of them, but very few have considered all three, especially in Central Africa. We investigated the effects of diameter and competition on tree growth, in four Central African sites characterized by their soil physicochemical properties, at both tree community and population levels. We calibrated growth models using diameter data collected on 29,741 trees between 2015 and 2018, on twelve 4 or 9‐ha plots spread over the four sites. These models included diameter, wood density, competition indices and site effect as explainable variables at the community level and excluded wood density at the population level. At the community level, the best models explained 11% of growth variability with a decreasing effect of species wood density, diameter, site and competition. Our results show that even if low, site effect can result from different soil nutrients depending on both tree size and species wood density. We observed higher tree growth on sites with (i) high exchangeable K, organic C, total N and total P for low wood density species; (ii) high available P and C:N for small trees, high exchangeable Ca and Mg for medium to large trees, all belonging to medium and hard wood density species. At the population level, the best models explained between 0 to 43% of growth variability, with significant competition effect (resp. site effect) for 21 (resp. 9) of the 43 species studied. Site ranking varied greatly between the 9 species concerned, probably reflecting different sensitivities to the scarcity of particular soil nutrients. Synthesis. Our study provides original results on the factors influencing tree growth in Central Africa, showing that the potential effect of soil nutrients depends on tree size and species wood density. Remaining highly unpredictable at the population level, this effect makes it essential to increase the number of dynamics monitoring systems in logging concessions.
Keywords	ecology ; exchangeable calcium ; exchangeable potassium ; soil ; sustainable forestry ; total nitrogen ; tree growth ; trees ; wood density ; Central Africa
Language	English
Dates of publication	2023-09
Size	p. 1950-1967.
Publishing place	John Wiley & Sons, Ltd
Document type	Article ; Online
Note	JOURNAL ARTICLE
ZDB-ID	3023-5
ISSN	0022-0477
ISSN	0022-0477
DOI	10.1111/1365-2745.14152
Database	NAL-Catalogue (AGRICOLA)

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Article: A joint individual-based model coupling growth and mortality reveals that tree vigor is a key component of tropical forest dynamics.

Aubry-Kientz, Mélaine / Rossi, Vivien / Boreux, Jean-Jacques / Hérault, Bruno

Ecology and evolution

2015 Volume 5, Issue 12, Page(s) 2457–2465

Abstract: Tree vigor is often used as a covariate when tree mortality is predicted from tree growth in tropical forest dynamic models, but it is rarely explicitly accounted for in a coherent modeling framework. We quantify tree vigor at the individual tree level, ... ...

Abstract	Tree vigor is often used as a covariate when tree mortality is predicted from tree growth in tropical forest dynamic models, but it is rarely explicitly accounted for in a coherent modeling framework. We quantify tree vigor at the individual tree level, based on the difference between expected and observed growth. The available methods to join nonlinear tree growth and mortality processes are not commonly used by forest ecologists so that we develop an inference methodology based on an MCMC approach, allowing us to sample the parameters of the growth and mortality model according to their posterior distribution using the joint model likelihood. We apply our framework to a set of data on the 20-year dynamics of a forest in Paracou, French Guiana, taking advantage of functional trait-based growth and mortality models already developed independently. Our results showed that growth and mortality are intimately linked and that the vigor estimator is an essential predictor of mortality, highlighting that trees growing more than expected have a far lower probability of dying. Our joint model methodology is sufficiently generic to be used to join two longitudinal and punctual linked processes and thus may be applied to a wide range of growth and mortality models. In the context of global changes, such joint models are urgently needed in tropical forests to analyze, and then predict, the effects of the ongoing changes on the tree dynamics in hyperdiverse tropical forests.
Language	English
Publishing date	2015-05-29
Publishing country	England
Document type	Journal Article
ISSN	2045-7758
ISSN	2045-7758
DOI	10.1002/ece3.1532
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Article: Tropical tree allometry and crown allocation, and their relationship with species traits in central Africa

Mankou, Géraud Sidoine / Ligot, Gauthier / Loubota Panzou, Grace Jopaul / Boyemba, Faustin / Loumeto, Jean Joël / Ngomanda, Alfred / Obiang, Diosdado / Rossi, Vivien / Sonke, Bonaventure / Yongo, Olga Diane / Fayolle, Adeline

Forest ecology and management. 2021 Aug. 01, v. 493

2021

Abstract: Common allometric patterns have been reported across the tropics and good performance on independent data was retrieved for the most recent pantropical model predicting tree aboveground biomass (AGB) from stem diameter, wood density and total height. ... ...

Abstract	Common allometric patterns have been reported across the tropics and good performance on independent data was retrieved for the most recent pantropical model predicting tree aboveground biomass (AGB) from stem diameter, wood density and total height. General models are undoubtedly useful for the estimation and monitoring of biomass and carbon stocks in tropical forests, however specific allometry, allocation, and traits, are at the core of many models of vegetation dynamics, and there is lack of such information for some regions and species. In this study, we specifically evaluated how size-dependent changes in above-ground biomass and biomass allocation to crown relate to other allometric and life-history traits for tropical tree species. We gathered destructive data available in eight terra firme forest sites across central Africa and the combined dataset consisted of 1,023 trees belonging to 54 tropical tree species phylogenetically dispersed, with only two congeneric species. A huge body of field and laboratory measurements was used for computing AGB and crown mass ratio (CMR) at the tree level, and to derive key allometric traits at the species level. For the latter, species-specific relationships between tree diameter and total height, crown exposure to light, wood density, and bark thickness were fitted for 50 species. Our results show interspecific variation in the relationships relating tree diameter to both AGB and CMR, and including species traits in a multi-specific AGB model confirmed that interspecific variation in biomass allometry is primarily determined by species wood density. We also showed that the allocation of biomass to crown increases linearly with tree diameter for most species, and that interspecific variation in the CMR model is associated with the species dispersal mode and maximum height. Trait covariations among our set of tropical tree species widespread and/or locally abundant in central Africa, revealed a continuum between large-statured species, which tended to be light-demanding, deciduous and wind-dispersed, and species with opposite attributes. Information on allometry, allocation, and traits provided here could further be used in comparative ecology and for parameterizing dynamic and succession models. Also importantly, the species-specific AGB models fitted for major tree species, including most timber species of central Africa, will help improve biomass estimates.
Keywords	aboveground biomass ; administrative management ; allometry ; bark ; carbon ; data collection ; dry matter partitioning ; forest ecology ; interspecific variation ; life history ; models ; phylogeny ; species dispersal ; tree and stand measurements ; trees ; tropical plants ; wood density ; Central Africa
Language	English
Dates of publication	2021-0801
Publishing place	Elsevier B.V.
Document type	Article
Note	NAL-AP-2-clean
ZDB-ID	751138-3
ISSN	0378-1127
ISSN	0378-1127
DOI	10.1016/j.foreco.2021.119262
Database	NAL-Catalogue (AGRICOLA)

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Article ; Online: Generalization of the partitioning of shannon diversity.

Marcon, Eric / Scotti, Ivan / Hérault, Bruno / Rossi, Vivien / Lang, Gabriel

PloS one

2014 Volume 9, Issue 3, Page(s) e90289

Abstract: Traditional measures of diversity, namely the number of species as well as Simpson's and Shannon's indices, are particular cases of Tsallis entropy. Entropy decomposition, i.e. decomposing gamma entropy into alpha and beta components, has been previously ...

Abstract	Traditional measures of diversity, namely the number of species as well as Simpson's and Shannon's indices, are particular cases of Tsallis entropy. Entropy decomposition, i.e. decomposing gamma entropy into alpha and beta components, has been previously derived in the literature. We propose a generalization of the additive decomposition of Shannon entropy applied to Tsallis entropy. We obtain a self-contained definition of beta entropy as the information gain brought by the knowledge of each community composition. We propose a correction of the estimation bias allowing to estimate alpha, beta and gamma entropy from the data and eventually convert them into true diversity. We advocate additive decomposition in complement of multiplicative partitioning to allow robust estimation of biodiversity.
MeSH term(s)	Algorithms ; Animals ; Biodiversity ; Ecosystem ; Entropy ; Environment ; Models, Biological ; Population Density ; Population Dynamics ; Species Specificity
Language	English
Publishing date	2014-03-06
Publishing country	United States
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ISSN	1932-6203
ISSN (online)	1932-6203
DOI	10.1371/journal.pone.0090289
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Article ; Online: Spatial validation reveals poor predictive performance of large-scale ecological mapping models.

Ploton, Pierre / Mortier, Frédéric / Réjou-Méchain, Maxime / Barbier, Nicolas / Picard, Nicolas / Rossi, Vivien / Dormann, Carsten / Cornu, Guillaume / Viennois, Gaëlle / Bayol, Nicolas / Lyapustin, Alexei / Gourlet-Fleury, Sylvie / Pélissier, Raphaël

Nature communications

2020 Volume 11, Issue 1, Page(s) 4540

Abstract: Mapping aboveground forest biomass is central for assessing the global carbon balance. However, current large-scale maps show strong disparities, despite good validation statistics of their underlying models. Here, we attribute this contradiction to a ... ...

Abstract	Mapping aboveground forest biomass is central for assessing the global carbon balance. However, current large-scale maps show strong disparities, despite good validation statistics of their underlying models. Here, we attribute this contradiction to a flaw in the validation methods, which ignore spatial autocorrelation (SAC) in data, leading to overoptimistic assessment of model predictive power. To illustrate this issue, we reproduce the approach of large-scale mapping studies using a massive forest inventory dataset of 11.8 million trees in central Africa to train and validate a random forest model based on multispectral and environmental variables. A standard nonspatial validation method suggests that the model predicts more than half of the forest biomass variation, while spatial validation methods accounting for SAC reveal quasi-null predictive power. This study underscores how a common practice in big data mapping studies shows an apparent high predictive power, even when predictors have poor relationships with the ecological variable of interest, thus possibly leading to erroneous maps and interpretations.
Language	English
Publishing date	2020-09-11
Publishing country	England
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	2553671-0
ISSN	2041-1723 ; 2041-1723
ISSN (online)	2041-1723
ISSN	2041-1723
DOI	10.1038/s41467-020-18321-y
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Article: Bayesian multioutput feedforward neural networks comparison: a conjugate prior approach.

Rossi, Vivien / Vila, Jean-Pierre

IEEE transactions on neural networks

2006 Volume 17, Issue 1, Page(s) 35–47

Abstract: A Bayesian method for the comparison and selection of multioutput feedforward neural network topology, based on the predictive capability, is proposed. As a measure of the prediction fitness potential, an expected utility criterion is considered which is ...

Abstract	A Bayesian method for the comparison and selection of multioutput feedforward neural network topology, based on the predictive capability, is proposed. As a measure of the prediction fitness potential, an expected utility criterion is considered which is consistently estimated by a sample-reuse computation. As opposed to classic point-prediction-based cross-validation methods, this expected utility is defined from the logarithmic score of the neural model predictive probability density. It is shown how the advocated choice of a conjugate probability distribution as prior for the parameters of a competing network, allows a consistent approximation of the network posterior predictive density. A comparison of the performances of the proposed method with the performances of usual selection procedures based on classic cross-validation and information-theoretic criteria, is performed first on a simulated case study, and then on a well known food analysis dataset.
Language	English
Publishing date	2006-01
Publishing country	United States
Document type	Journal Article
ZDB-ID	1021767-8
ISSN	1941-0093 ; 1045-9227
ISSN (online)	1941-0093
ISSN	1045-9227
DOI	10.1109/TNN.2005.860883
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