Evolution of host-shifts within the Clavicipitaceae

Cordyceps tuberculata

Clavicipitaceae is a large family of obligate biotrophs and necrotrophs of plants, arthropods and fungi. Most are antagonistic parasites, although a few of the grass endophytes are reported as beneficial to their hosts and are considered mutualists (Clay , 1988). As part of my earlier research on the systematics of unitunicate perithecial ascomycetes (Spatafora and Blackwell, 1993), I determined SSU rDNA sequences for multiple taxa in the family and performed a series of phylogenetic analyses. The ordin al placement of the Clavicipitaceae had been unclear for sometime; rival hypotheses had placed the family in the Xylariales, the Hypocreales or ranked as an order. Phylogenetic analysis of the SSU rDNA nucleotide sequences clearly placed the Clavicipitac eae in the Hypocreales (Spatafora and Blackwell, 1993), a finding that is further supported by the analysis of LSU rDNA as well (Spatafora, unpublished).

For the past couple of years I have been investigating relationships within the Clavicipitaceae with the goal of developing hypotheses for the evolution host-shifts within the family. The greatest number of species in the family are parasites of nine ord ers of arthropods and are classified in the genera Cordyceps, Torrubiella and Hypocrella. A few species of Cordyceps are also parasites of Elaphomyces , a genus of ascomycetous truffles. The remaining taxa are symbi onts of the grass family (Poaceae) and include fungi in the genera Claviceps,Balansia as well as others. I am in the process of constructing molecular (LSU rDNA) and morphological datasets for the Clavicipitaceae with an emphasis on the ent omopathogenic species. Through phylogenetic analysis of both data sets, I am developing hypotheses on the primitive character state of host association and the patterns of host-shifts among the major lineages of Clavicipitaceae.

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