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Regiocrella, a new entomopathogenic genus with a pycnidial anamorph and its phylogenetic placement in the Clavicipitaceae

     Department of Plant Pathology, Cornell University, 334 Plant Science Building, Ithaca, New York 14853

Joseph F. Bischoff

     National Center for Biotechnology Information, National Institutes of Health, Bethesda, Maryland 20894

Harry C. Evans

     CABI Bioscience UK Centre (Ascot), Silwood Park, Buckhurst Road, Ascot, BERKS. SL5 7TA, U. K.

Kathie T. Hodge

     Department of Plant Pathology, Cornell University, 334 Plant Science Building, Ithaca, New York 14853

A new genus, Regiocrella, is described with two species, R. camerunensis and R. sinensis, based on specimens collected in Cameroon and China. Both species are parasitic on scale insects (Coccidae, Homoptera). Morphological and molecular evidence place the new genus in the Clavicipitaceae (Hypocreales), despite its combination of characters that are atypical of that family; Regiocrella is characterized by having perithecia partly immersed in a subiculum, noncapitate asci, unicellular fusiform ascospores and pycnidial-acervular conidiomata. The two new species, R. camerunensis and R. sinensis, are distinguished based on ascospore and perithecium size. Morphological characters were evaluated and compared to other genera in the Clavicipitaceae, especially those parasitic on scale insects or with pycnidial-acervular anamorphs or synanamorphs (i.e. Aschersonia, Ephelis or Sphacelia): Atkinsonella, Balansia, Claviceps, Epichlöe, Hypocrella, Myriogenospora and Neoclaviceps. The phylogenetic relationships of Regiocrella were examined with three gene loci: large subunit nuclear ribosomal DNA (LSU), translation elongation factor 1- (TEF), and RNA polymerase II subunit 1 (RPB1). The results of this study confirm that Regiocrella is distinct from other genera in the Clavicipitaceae and that its two species form a monophyletic group. Regiocrella is shown to be closely related to the scale insect pathogen Hypocrella and the plant-associated genera Balansia, Claviceps, Epichlöe, Myriogenospora and Neoclaviceps. This study also provides insights into the evolution of pycnidial-acervular conidiomata and scale insect parasitism within the Clavicipitaceae. Plant-associated genera form a monophyletic group correlated with Clavicipitaceae subfamily Clavicipitoideae sensu Diehl. We also demonstrate that scale insect parasites have multiple evolutionary origins within the family and genera with pycnidial-acervular anamorphs or synanamorphs have a single origin.

Key words: Ascomycota, evolution, Hypocreales, molecular phylogenetics, systematics