Xylaria furcata reconsidered and nine resembling species

Xylaria collections from termite nests with dichotomously branched stromata have been identified as X. furcata. However, Léveillé's original material is no longer available, and the modern interpretation of X. furcata is based on a 1908 collection made by von Höhnel from termite nests at Buitenzorg Botanical Garden in Java. A packet of this von Höhnel material at FH was designated as the neotype by Rogers et al. in 2005.

We reexamined the neotype from FH and its duplicates from various herbaria and found that three different species were mixed in these specimens. Despite that all of them have dichotomously branched stromata and tiny ascospores, only one fits the 2005 neotypification of X. furcata, where exposed perithecial mounds on the stromatal surface were unambiguously indicated. This portion of material is redesignated as the neotype, while the other two species with immersed perithecia are described as new: X. hoehnelii and X. robustifurcata. The ITS sequence obtained from the neotype helped us designate a specimen with cultures obtained from it as the epitype. From specimens identifiable as X. furcata, we describe four new species: X. brevifurcata, X. furcatula, X. insignifurcata, and X. tenellifurcata. Additionally, we recognize X. furcata var. hirsuta at the species level as X. hirsuta and consider X. scoparia a distinct species rather than a synonym of X. furcata. Molecular phylogenetic analyses based on three protein-coding loci showed that X. furcata and resembling species were grouped into two clusters: the X. furcata cluster with half-exposed to fully exposed perithecial mounds and the X. hoehnelii cluster with largely immersed perithecial mounds.

Ten species are recognized for X. furcata and resembling species, all of which could have been identified as X. furcata in the past. Its diversity has been overlooked primarily due to the small and similar stromata. Several additional species have been confirmed to be related to X. furcata by DNA sequences but are yet to be described due to the lack of mature stromata. While the species diversity of macrotermitine termites is equally high in Africa as in Asia, all of the species are primarily found in Asia, with X. hirsuta as the only exception. This suggests that there may be many more undiscovered species for this fungal group.