ARS | Publication request: Ascosphaera subglobosa, a new species from North America associated with the solitary bee Megachile rotundata

Submitted to: Mycologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 15, 2011
Publication Date: January 19, 2012
Citation: Wynns, A.A., Jensen, A.B., Eilenberg, J., James, R.R. 2012. Ascosphaera subglobosa, a new species from North America associated with the solitary bee Megachile rotundata. Mycologia. 104(1): 108-114.

Interpretive Summary: The alfalfa leafcutting bee is used in the U.S. and Canadian for pollinating such crops as alfalfa and hybrid canola seed. Like the honey bee, this bee is susceptible to a disease called chalkbrood. However, the disease in honey bees and in alfalfa leafcutting bee are caused by different fungi that are closely related; both fungi are in the same genus. Several other species of these fungi also occur in bee nesting materials, growing on the pollen, nectar, and other material in the hives. A new species of fungus in this genus, Ascosphaera sublobosa, is described in this publication. This newly found fungus does not appear to be a pathogen and has only been found in North America. It was found in failed nest cells of the alfalfa leafcutting bee. It is unknown at this time whether this fungus is the cause of the failures, or just exploiting that habitat.

Technical Abstract: Ascosphaera is a widespread ascomycetous genus of mostly obligate associates of bees. These fungi have diversified to exploit seemingly every possible substrate available in their bee-associated habitat, occurring as pathogens of the bees, or as saprotrophs on honey, cocoons, nesting materials, pollen, and feces. We describe here a new species, Ascosphaera subglobosa, collected from the pollen provisions and nesting material of the solitary leafcutting bee Megachile rotundata in Canada and the western United States. This new species, closely related to A. atra and A. duoformis, is distinct from other Ascosphaera species by its evanescent spore balls, globose to subglobose spores and unique nuclear ribosomal DNA ITS sequence.