New species of Ophiocordyceps unilateralis, an ubiquitous pathogen of ants from Thailand

• Two new species of Ophiocordyceps unilateralis were discovered and described in Thailand.
• The new species are distinct on both morphological and molecular basis.
• The relations between species cannot be inferred with confidence but the two new species seemed to be basal.
• Ophiocordyceps pulvinata is strongly supported as outgroup to O. unilateralis complex.

Ophiocordyceps unilateralis is an ubiquitous pathogen of ants with hidden phylogenetic diversity associated with host specificity. In this study, we describe two new species to this species complex: Ophiocordyceps septa and Ophiocordyceps rami. Both were found on unidentified ants of the genus Camponotus (C. sp.1 and C. sp2 respectively). Ophiocordyceps septa is very similar to Ophiocordyceps polyrhachis-furcata, Ophiocordyceps camponoti-leonardi, and Ophiocordyceps camponoti-saundersi (found respectively on the ants Polyrhachis furcata, Camponotus leonardi, and Camponotus saundersi) but differs in the size, the shape and the septation of the ascospores, while O. rami is clearly identifiable with macro-morphological features including multiple stromata similar to Ophiocordyceps halabalaensis on Camponotus gigas. A thorough morphological examination was also provided for O. polyrhachis-furcata, O. camponoti-leonardi, and O. camponoti saundersi, showing that the first was apparently distinguishable from the others by the absence of septation of the ascospores. A combined molecular phylogeny also supports O. septa and O. rami as distinct new species.