Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
White-sand forests are thought to host many ectomycorrhizal fungi, as demonstrated by the numerous fruiting body collections made by Rolf Singer in the lower Rio Negro in the late 1970s. Despite recognition of the importance of ectomycorrhizal fungi in white-sand forests, there has not yet been a systematic examination of diversity and taxonomic composition across white-sand forests, or more widely across lowland Amazonian forests. In an effort to broaden our view of ectomycorrhizal fungal diversity and distribution on white-sand forests, we collected ectomycorrhizal fruiting bodies in 10 plots of white-sand forests in Brazil and French Guiana between 2012 and 2014. We collected 221 specimens and 62 morphospecies, from the 10 plots, confirming that all studied white-sand forests host ectomycorrhizal fungi. Additionally, we searched for taxa associated with white sands among specimens deposited in Brazilian herbaria. We report 1006 unique ectomycorrhizal specimen records in 18 Brazilian herbaria, of which 137 specimens and 64 species are reported from white-sand forests, mainly in the state of Amazonas, Brazil. Russulaceae and Amanitaceae were frequent in all habitats, and Cortinarius were more frequent on white sands. Our results highlight the high diversity and heterogeneity of ectomycorrhizal communities on white-sand forests, and the wide distribution of ectomycorrhizal fungi throughout Brazil, irrespective of soil type.
Florestas em solos arenosos são consideradas como hospedeiras de muitos fungos ectomicorrízicos (EM), como demonstrado pelas numerosas coletas feitas por Rolf Singer na região do Rio Negro, Amazonas, no final dos anos 70. Apesar do reconhecimento da importância dos fungos ectomicorrízicos em florestas em solos arenosos, não houve nenhum estudo sistemático da diversidade e da composição taxonômica nas florestas em solos arenosos ou mesmo mais amplamente nas terras baixas da Floresta Amazônica. Para ter uma visão global da diversidade e da distribuição de fungos EM em florestas em solos arenosos, foram coletados basidiomas desses fungos em 10 parcelas de florestas em solos arenosos no Brasil e na Guiana Francesa entre 2012 e 2014. Além disso, uma busca foi feita por espécimes depositados em herbários brasileiros que tinham a informação de serem coletas feitas em solo arenoso. Nas 10 parcelas amostradas foram coletados 221 espécimes e 62 morfoespécies, o que confirma que todas as florestas em solos arenosos hospedam fungos EM. Recuperamos 1006 espécimes registrados em 18 herbários brasileiros, dos quais 137 espécimes e 52 espécies são registros de florestas em solos arenosos principalmente no estado do Amazonas, Brasil. Russulaceae e Amanitaceae foram frequentes em todos os habitats e Cortinarius foi o táxon mais frequente em solo arenoso. Os resultados apresentados enfatizam a alta diversidade e heterogeneidade das comunidades de EM em florestas em solos arenosos, assim como a ampla distribuição de fungos em todo o Brasil, não exclusivamente em florestas em solos arenosos.
ISSN: 0006-3606

hal-01278423
https://hal-sde.archives-ouvertes.fr/hal-01278423
DOI : 10.1111/btp.12297

Éditeur(s) : HAL CCSD Royal Society, The
Résumé :  
Plant phenology is concerned with the timing of recurring biological events. Though phenology has traditionally been studied using intensive surveys of a local flora, results from such surveys are difficult to generalize to broader spatial scales. In this study, contrastingly, we assembled a continental-scale dataset of herbarium specimens for the emblematic genus of Neotropical pioneer trees, Cecropia, and applied Fourier spectral and cospectral analyses to investigate the reproductive phenology of 35 species. We detected significant annual, sub-annual and continuous patterns, and discuss the variation in patterns within and among climatic regions. Although previous studies have suggested that pioneer species generally produce flowers continually throughout the year, we found that at least one third of Cecropia species are characterized by clear annual flowering behaviour. We further investigated the relationships between phenology and climate seasonality, showing strong associations between phenology and seasonal variations in precipitation and temperature. We also verified our results against field survey data gathered from the literature. Our findings indicate that herbarium material is a reliable resource for use in the investigation of large-scale patterns in plant phenology, offering a promising complement to local intensive field studies
ISSN: 0962-8452

hal-01032193
https://hal.archives-ouvertes.fr/hal-01032193
DOI : 10.1098/rspb.2010.2259

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
We assessed the extent of recent environmental changes on leaf morphological (stomatal density, stomatal surface, leaf mass per unit area) and physiological traits (carbon isotope composition, δ(13)C(leaf) , and discrimination, Δ(13)C(leaf) , oxygen isotope composition, δ(18)O(leaf) ) of two tropical rainforest species (Dicorynia guianensis; Humiria balsamifera) that are abundant in the Guiana shield (Northern Amazonia). Leaf samples were collected in different international herbariums to cover a 200 year time-period (1790-2004) and the whole Guiana shield. Using models describing carbon and oxygen isotope fractionations during photosynthesis, different scenarios of change in intercellular CO(2) concentrations inside the leaf (C(i)), stomatal conductance (g), and photosynthesis (A) were tested in order to understand leaf physiological response to increasing air CO(2) concentrations (C(a)). Our results confirmed that both species displayed physiological response to changing C(a) . For both species, we observed a decrease of about 1.7‰ in δ(13)C(leaf) since 1950, without significant change in Δ(13)C(leaf) and leaf morphological traits. Furthermore, there was no clear change in δ(18)O(leaf) for Humiria over this period. Our simulation approach revealed that an increase in A, rather than a decrease in g, explained the observed trends for these tropical rainforest species, allowing them to maintain a constant ratio of C(i)/C(a) .
ISSN: 0140-7791

halsde-00675165
https://hal.archives-ouvertes.fr/halsde-00675165
DOI : 10.1111/j.1365-3040.2011.02333.x
PUBMED : 21486302

Éditeur(s) : HAL CCSD
Résumé : National audience
Introduction Une exposition domiciliaire fongique élevée quantifiée par l’index environnemental moléculaire Environmental Relative Moldiness Index (ERMI) est associée au développement de l’asthme dans l’enfance. Dans ce travail, nous avons utilisé cette technique basée sur la quantification moléculaire de 36 champignons dans les poussières pour comparer sa valeur dans l’air à la détection par séquençage haut-débit NGS. Matériels et méthodes Des prélèvements de poussière et d’air ont été collectés dans 20 logements étiquetés « moisis » et 20 logements « non moisis » par les méthodes suivantes : 2 m2 de poussières prélevées à l’aide d’un embout Mitest™ positionné sur un aspirateur ; 3 m3 d’air prélevés par le collecteur cyclonique Coriolis® (Bertin Technologies, France). Tout d’abord, nous avons validé l’ERMI dans l’air versus les poussières, puis comparé dans les prélèvements d’air l’ERMI le séquençage NGS (10 échantillons « moisis » versus 10 échantillons « non moisis »). La cible était le gène 18S séquencé par pyroséquençage à l’aide du système Roche 454. Résultats et discussion Une corrélation entre l’ERMI « poussières » et l’ERMI « air » a été observée avec une valeur significative du test Kendall's tau. Les moisissures intérieures les plus identifiées étaient Aspergillus restrictus, A. fumigatus, A. versicolor, Aureobasidium pullulans Penicillium crustosum, Wallemia sebi, auxquelles s’associaient des moisissures classiquement d’extérieur, Cladosporium cladosporoides, Cladosporium herbarum. L’analyse des séquences obtenues par pyroséquençage était superposable à l’observation par ERMI. Les 3 genres les plus représentés dans l’air intérieur étaient Aspergillus, Penicillium et Cladosporium. Toutefois, quelques genres non inclus dans le panel ont pu être détectés en quantité non négligeable, à l’image des levures notamment du genre Cryptococcus. L’ERMI et le NGS apparaissent donc utiles et corrélés pour la quantification de la charge fongique environnementale dans l’air. L’ERMI a l’avantage d’être une technique rapide, mais sa limite est de cibler a priori 36 genres fongiques (définis initialement aux États-Unis). L’analyse NGS permet d’identifier d’autres genres potentiellement pertinents et donc d’adapter les cibles pour un ERMI « français »
Congrès de la SFMM
Talence-Bordeaux, France

hal-01198651
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01198651
DOI : 10.1016/j.mycmed.2015.06.013