The evolution of wood-feeding and fungal symbiosis in weevils

Studentships 2009

Detailed project description

The phylogeny of Curculionoidea (weevils) remains poorly understood despite their probably representing the fastest radiation of the Tertiary (62,000 species). They are plant feeding and include many serious crop and forestry pests. Particularly poorly understood is the position of the three main wood-feeding lineages: Scolytinae (bark beetles), Platypodinae (ambrosia beetles) and Cossininae. Although now confirmed as part of the huge family Curculionidae, recent literature has recognised all or some of them as a monophylum, or placed them as three separate lineages within a large polytomy at the base of Curculionidae.

An even greater unknown is the precise mode of wood-feeding. Platypodines and many Scolytines are closely associated with specific xylariaceous ascomycete and basidiomycete fungi and many species carry spores in specialised external structures (mycangia) for inoculation of a new host. Fruiting bodies and mycelium are either consumed directly, contribute indirectly by increasing the nutrient content of decomposing wood, or provide extracellular enzymes which facilitate larval ingestion/burrowing. A phylogenetic understanding of this symbiosis will address the evolution of species richness, novel resource use (wood-feeding) and tritrophic interactions. It is equally important to the ecology of forest turnover, nutrient cycling (decomposition), and applied forestry; ambrosial fungus can cause host plant death, in devastating outbreaks.

The student will test various hypotheses about the host specificity and co-evolution of wood-boring weevils and their associated fungi. We will establish the phylogenetic relationships of the three major wood-feeding weevil lineages, resolve the enigmatic basal relationships of Curculionidae and establish the diversity of fungal associations by testing which fungi are directly associated with the beetles, and what is the degree of specificity of the association (at various hierarchical levels). We will apply a novel method for establishing organismal associations that we originally developed for herbivorous beetles and their host plants (Jurado-Rivera, Vogler et al., Proc. Roy. Soc., 2009, 276, 639–648). Resulting fungal DNA sequences can be compared with existing DNA databases with the aim of identification of the ingested species of fungi, or used directly for phylogenetic reconstruction of fungal lineages. This methodology will be exploited to establish the associated mycota for representatives of the major wood-boring weevil lineages; assess the phylogenetic relationships of major fungal lineages associated with curculionids and test co-evolutionary relationships; test the effect of the host tree species itself (many curculionids feed on a range of trees) on the fungal community associated with a particular beetle species; and test our existing frozen DNA collections for the PCR amplification of fungal DNA for detailed evolutionary analyses.

Training

Exposure to latest methods in taxonomy, combining collection-based and molecular approaches (insect and fungal collections at the NHM and Royal Botanical Gardens, Kew); broad range of ecological and evolutionary theory and phylogenetics. Additional training in transferable skills will be through the highly regarded Graduate School of Imperial College. Applicants should be interested in a combined molecular and collection-based approach and be prepared to learn molecular biology and bioinformatics methods.

Supervisors

Prof A. P. Vogler (A.Vogler@nhm.ac.uk) and Dr C. H. C. Lyal (Dept. of Entomology), in collaboration with Dr M. Bidartondo (Imperial College London/Kew Gardens).