Fungal phylogenies and plant functional traits structure root associated fungal networks in a subtropical forest

Rhizosphere fungi are essential for plant survival and ecosystem functioning, but the processes structuring plant-fungal interactions remain largely unknown. We constructed association networks between 43 plant species and two groups of root-associated fungi (mycorrhizal and pathogenic) using sequence data. We revealed modularity within the association networks using network analysis, and correlated this modular structure with functional traits and phylogenetic history driving plant-fungal interactions. We observed strong modularity in both plant-mycorrhizal fungal and plant-pathogenic fungal association networks. Plant functional traits and fungal phylogeny clustered within modules. Host plants of mycorrhizal fungi differed significantly between modules in terms of their leaf dry matter content, photosynthetic traits and root tissue density. Host plants of pathogenic fungi differed significantly between modules in terms of their dark respiration rate, light compensation point and root morphology. Modularity within fungi was a product of fungal phylogeny, whereas host plant modularity was a product of functional traits (leaf morphology, photosynthetic rate and root morphology). Our study illustrates the link between plant functional traits and fungal assembly, and highlights the importance of niche-based processes in shaping plant-fungus association networks. Our results suggest that plant traits may be instrumental in managing the composition of belowground fungal communities.

Analysis of morphogenesis in hyphomycetes: new characters derived from considering some conidiophores and conidia as condensed hyphal systems

Hyphomycetes (ascomycetous and basidiomycetous anamorphs) comprise numerous genera and species that have been difficult to place in fungal phylogeny. In this commentary, autobiographical notes preface a new analysis of reproductive structures in many hyphomycetes. This adopts the premise that many of the more complex examples of conidiophores and conidia represent condensed hyphal systems. Many new and potentially useful taxonomic characters are described, which are particularly applicable to computer-based synoptic keys or databases, but should also be considered by those describing new taxa or redescribing existing ones.Key words: moulds, taxonomy, conidia, conidiophores, morphogenesis, branching.

Molecular phylogenetics of the Chytridiomycota supports the utility of ultrastructural data in chytrid systematics

The chytrids (Chytridiomycota) are morphologically simple aquatic fungi that are unified by their possession of zoospores that typically have a single, posteriorly directed flagellum. This study addresses the systematics of the chytrids by generating a phylogeny of ribosomal DNA sequences coding for the small subunit gene of 54 chytrids, with emphasis on sampling the largest order, the Chytridiales. Selected chytrid sequences were also compared with sequences from Zygomycota, Ascomycota, and Basidiomycota to derive an overall fungal phylogeny. These analyses show that the Chytridiomycota is probably not a monophyletic group; the Blastocladiales cluster with the Zygomycota. Analyses did not resolve relationships among chytrid orders, or among clades within the Chytridiales, which suggests that the divergence times of these groups may be ancient. Four clades were well supported within the Chytridiales, and each of these clades was coincident with a group previously identified by possession of a common subtype of zoospore ultrastructure. In contrast, the analyses revealed homoplasy in several developmental and zoosporangial characters.Key words: zoospore ultrastructure, Chytridiales, molecular phylogeny, Chytridiomycota, operculum.