Synonymy Amongst the Arbuscular Mycorrhizal Fungi:Glomus claroideum,G. maculosum,G. multisubstenumandG. fistulosum

Ex-type material of Glomus fistulosum was re-established in pot culture and differences from the description in the protologue noted. Type specimens and other cultures from Europe, and North and South America showed the original species description was incorrect. The species is re-described from pot cultured specimens. The holotype of Glomus claroideum was also examined. The two species were morphologically identical. This was confirmed by comparisons with other specimens of G. claroideum. One culture, used in the protologue, but not designated as a paratype, had smaller spores than those from other G. fistulosum or G. claroideum cultures, but could not otherwise be separated. They are therefore synonymized. Type material of Glomus maculosum and specimens of Glomus manihotis from Colombia were studied. The latter came from a heavily parasitized pot culture, and its spores possessed the maculiferous ‘ornamentation’ that supposedly characterized the former. Similar structures were noted in the isotype of G. claroideum. The feature is probably environmentally induced and should not be used as a taxonomic characteristic. The conclusion is drawn that Glomus maculosum should also be synonymized with G. claroideum. Glomus multisubstensum is considered from its protologue, and this too should be synonymized with G. claroideum. An epitype is defined to aid in the circumscription of G. claroideum. Less comprehensive comparisons were also made with other similar species, G. albidum, G. przelewicense, G. lamellosum, G. pustulatum and G. diaphanum. It is concluded that G. lamellosum is inadequately defined, and its validity as a species needs clarification. It is also suggested that Glomus albidum and G. przelewicense may be conspecific.