The Ectomycorrhizal Fungal Community in a Neotropical Forest Dominated by the Endemic Dipterocarp Pakaraimaea dipterocarpacea

Abstract

Ectomycorrhizal (ECM) plants and fungi can be diverse and abundant in certain tropical ecosystems. For example, the primarily paleotropical ECM plant family Dipterocarpaceae is one of the most speciose and ecologically important tree families in Southeast Asia. Pakaraimaea dipterocarpacea is one of two species of dipterocarp known from the Neotropics, and is also the only known member of the monotypic Dipterocarpaceae subfamily Pakaraimoideae. This Guiana Shield endemic is only known from the sandstone highlands of Guyana and Venezuela. Despite its unique phylogenetic position and unusual geographical distribution, the ECM fungal associations of P. dipterocarpacea are understudied throughout the tree’s range. In December 2010 we sampled ECM fungi on roots of P. dipterocarpacea and the co-occurring ECM tree Dicymbe jenmanii (Fabaceae subfamily Caesalpinioideae) in the Upper Mazaruni River Basin of Guyana. Based on ITS rDNA sequencing we documented 52 ECM species from 11 independent fungal lineages. Due to the phylogenetic distance between the two host tree species, we hypothesized that P. dipterocarpacea would harbor unique ECM fungi not found on the roots of D. jenmanii. Although statistical tests suggested that several ECM fungal species did exhibit host preferences for either P. dipterocarpacea or D. jenmanii, most of the ECM fungi were multi-host generalists. We also detected several ECM fungi that have never been found in long-term studies of nearby rainforests dominated by other Dicymbe species. One particular mushroom-forming fungus appears to be unique and may represent a new ECM lineage of Agaricales that is endemic to the Neotropics.

Variation in ectomycorrhizal fungal communities associated with Oreomunnea mexicana (Juglandaceae) in a Neotropical montane forest

“…Ectomycorrhizal tree species that have been studied in detail in the neotropics include Dicymbe corymbosa (Fabaceae), Pakaraimaea dipterocarpacea (Dipterocarpaceae), Quercus crassifolia and Q. laurina (Fagaceae), and Coccoloba spp. (Henkel 2003;Miller et al 2000;Moyersoen 2006;Morris et al 2009; Smith et al 2011Smith et al , 2013. Our study adds new data for a representative of the Juglandaceae in an area of high plant species richness, and dramatic local-scale differences in soil types and rainfall patterns.…”

“…To explore broader patterns of EM fungal diversity, we compiled records from EM fungal inventories of temperate and tropical forests, including studies reviewed by Tedersoo et al (2012) and three more recent studies by Diédhiou et al (2014), Smith et al (2013), and Kennedy et al (2012). We calculated diversity for data presented in each study using Fisher's alpha, which is robust to differences in sample size, and compared temperate versus tropical forests using a oneway ANOVA.…”

Strong coupling of plant and fungal community structure across western Amazonian rainforests

“…These patterns are hypothesized to be driven, at least partly, by the prolific dispersal capabilities of microbial organisms. Recent studies of ectomycorrhizal fungi from the neotropics show similar communities over large geographical areas (Smith et al, 2011(Smith et al, , 2013, indicating limited dispersal barriers at the timescales over which these regional communities assemble. Truly unlimited dispersal, however, would negate the distance-dependent mortality necessary for microbial pathogens to regulate plant coexistence under Janzen-Connell dynamics because host-specific microbes would be ubiquitous.…”

“…For example, negative feedbacks are generally thought to depend on high levels of variability in the strength of plant-fungal interactions and on strong spatial heterogeneity in fungal community composition (Gilbert, 2002). However, theoretical (May, 1991) and empirical Smith et al, 2011Smith et al, , 2013) studies have suggested low levels of fungal host specificity in tropical forests, and many studies have questioned the importance of dispersal limitation in microbes (Finlay, 2002;Queloz et al, 2011). Detailed knowledge on the structure of fungal communities is thus necessary to guide research to answer these critical ecological questions.…”

Influência da profundidade do solo e do manejo de Eucalyptus grandis e Acacia mangium na estrutura das comunidades microbianas do solo

“…Os FMA pertencem a um filo monofilético e isso se deve ao fato de compartilharem uma característica comum, isto é, a formação de "pequenas árvores fúngicas", ou arbúsculos, que se estabelecem no interior de células vegetais do córtex radicular e são locais primários de troca de nutrientes entre os simbiontes (TIBBETT et al, 2002;PERSSON et al, 2003;BANDOU et al, 2006;READ, 2008 (SMITH et al, 2013).…”