NSF REVSYS
NSF BS&I Award 0918182 (at BSU):
“Collaborative Research: REVSYS: RUI: Phylogenetic and Revisionary Systematics of early-diverging, ecologically unique clades of fungi, Harpellales and Asellariales”
$410,000 9/1/09 to 8/31/12.
Harpellales and Asellariales are two orders of early-diverging fungi that live obligately in the digestive tracts of arthropods worldwide. These micro-fungi have evolved in their very successful symbioses with various morphological and physiological adaptations that have kept them living in harmony with their hosts for millions of years. The Harpellales live primarily in larval aquatic insects (including pests such as mosquitoes, some midges and black flies or certain nymphs modeled by anglers to make fishing “flies”) and Asellariales live in adult isopods (including pill bugs) or springtails. Although they are generally considered to be commensals, their relationships range from lethal or parasitic, on one extreme, to mutualistic for insects that are under nutritional stress. Traditionally, these orders have been placed in the Class Trichomycetes. That morphologically-based classification originally included four orders, but molecular-based phylogenies have shown that the other two orders, the Eccrinales and Amoebidiales, are actually protozoans. In early 2007, published multi-gene phylogenies led to significant changes in the higher level classification of many fungal groups. Dramatic changes were proposed among the basal or early-diverging fungi, including the deconstruction of the Trichomycetes. In fact, the basal fungal tree is a loose aggregation of fragmented clades in desperate need of revision. Many orders and families were with insufficient resolution and taxon sampling to permit subordinal changes. Thus this proposal, which aims to place the members of the Harpellales and Asellariales at various levels amongst the finer twigs of the tree of life and toward a revised classification, is eagerly anticipated, urgently needed, and timely.
This project on early-diverging gut fungi will bring forth molecular-based revisionary syntheses for this ecologically and phylogenetically distinct group of fungi. Over the last several years we have developed techniques for extracting, amplifying and sequencing DNA, including from unculturable specimens dissected from host guts, for phylogenetic reconstructions. We have access to the largest repository of genomic DNA, preserved specimens and axenic cultures in the world; some isolates have been in culture 40+ years while others are newly discovered and described from recent surveys of North American gut fungi. We have assembled an international team of expert collaborators, world leaders in their knowledge and experience with this core group of basal fungi, willing to provide additional specimens, including from the putative closely related Kickxellales and Dimargaritales. The results of the proposed research will have an impact not only in Mycology, but more broadly extending out from this symbiosis, to the various aspects of the biology of these novel fungi that make them so very interesting.
Specific listed objectives are to: 1) revise the two largest genera of Harpellales, Smittium and Stachylina 2) reevaluate the genus Orphella (Harpellales), which may belong in a new order 3) reexamine the families Harpellaceae and Legeriomycetaceae (Harpellales) 4) generate more complete sequence data to establish the phylogenetic placement of the Asellariales, whose genera may represent more than one order and 5) infer a new multi-gene phylogeny and revised taxonomy for monophyletic clade(s) that include the Harpellales and Asellariales. The multiple genes selected for phylogeny reconstruction include the nuclear 18S, 5.8S, and 28S rRNA genes (including also the ITS1 and ITS2 regions) with the protein coding genes RPB1 & RPB2. This suite of genes has demonstrated excellent resolution among fungal lineages for phylogeny reconstruction and the inclusion of more variable domain regions with this study will also address natural relationships at lower levels. This study will generate improved phylogenies that will help to formalize an updated taxonomy and revised classification for these orders and their relationship with their non-symbiotic close relatives.
Additionally, the culmination of the project will bring together websites with video clips and tutorials, interactive keys and searchable databases. Undergraduate and graduate and students will be trained at all levels of the research.
