Afrocastellanoa M.E. Smith & Orihara, in Orihara & Smith, Mycologia 109(2): 328 (2017)
Etymology: “Afro-” (i.e., African) refers to the geographical origin of the known members of the genus, and “-castellanoa” is derived from Dr. Michael A. Castellano, a distinguished taxonomist of sequestrate fungi and one of the original nomenclatural authorities of Octaviania ivoryana.
Diagnosis: Basidiomata sequestrate, gasteroid, firm, rubbery, with one or a few rhizomorphs at the base. Similar to Octaviania Vittad. in the morphology of the basidiome and basidiospores, but different from Octaviania in the multilayered peridium and in basidia that are irregularly distributed within the solid gleba, resulting in the absence of a distinct hymenium and subhymenium. Phylogenetically related to the epigeous bolete genus Porphyrellus, but distantly related to the genus Octaviania s.s.. Ectomycorrhizal with Anthonotha (Fabaceae), Uapaca (Uapacaceae), and probably with other caesalpinoid legumes in sub-Saharan Africa.
Index Fungorum number: IF818072
Type species: Afrocastellanoa ivoryana (Castellano, Verbeken & Thoen) M.E. Smith & Orihara 2017, in Orihara & Smith, Mycologia 109(2): 328 (2017)
Notes: Afrocastellanoa is a monotypic genus reported from sub-Saharan Africa. Microscopically, the basidia of Octaviania subg. Parcaea spp. are also irregularly distributed within the gleba, but the gleba of O. subg. Parcaea spp. tends to become glutinous and dark brown to blackish brown at maturity. The peridium of the species in Octaviania subg. Parcaea is also single-layered (Orihara et al. 2012). The monotypic sequestrate genus Heliogaster also superficially resembles Afrocastellanoa. However, Heliogaster differs from Afrocastellanoa in having soft basidiomes with a single-layered peridium and the more or less dendroid columella in the gleba (Orihara et al. 2010). Heliogaster and Afrocastellanoa are phylogenetically distant from each other within the Boletaceae (Figure. 1). Remarkably, our multilocus phylogenetic analysis showed that Heliogaster columellifer was placed close to the epigeous bolete genera Xerocomellus and Nigroboletus (Figure. 1). Durianella echinulata Desjardin, A.W. Wilson and Binder, which was described from Malaysia, also produces a sequestrate, Octaviania-like basidiome that contains basidiospores with conical spines. However, this species differs from Afrocastellanoa in having a peridium covered with dense, pyramidal warts and a peridial context consisting of a single layer of cylindrical, non-gelatinous to weakly gelatinous hyphae (Desjardin et al. 2008). Phylogenetically, Durianella is a member of Boletaceae, but the evolutionary relationships of this taxon are poorly resolved (Desjardin et al. 2008). Desjardin et al. (2008) included Porphyrellus porphyrosporus in their phylogenetic analyses, but this epigeous bolete was not closely related to Durianella. The genus Porphyrellus is polyphyletic and needs systematic reconsideration (Wu et al. 2014). The genus Afrocastellanoa is sister to Porphyrellus s.s., which includes the type species P. porphyrosporus and several allied bolete species.
Figure 1: Bayesian majority-rule consensus tree of the combined 28S and TEF1 data set of the Boletaceae. Bayesian PP and RAxML bootstrap (BS) values (1000 replicates) are indicated above or below branches or at nodes as PP/BS. Values below PP < 0.90 or BS < 50% are not shown. Branches supported by both PP ≥ 0.98 and BS ≥ 70% are depicted as thickened black lines. Branches supported by either PP ≥ 0.98 or BS ≥ 70% are shown as thickened gray lines. Gyrodon lividus was used as the outgroup. Sequences that were newly generated for this study are indicated by asterisks.
Orihara T, Smith ME (2017) Unique phylogenetic position of the African truffle-like fungus, Octaviania ivoryana (Boletaceae, Boletales), and the proposal of a new genus. Afrocastellanoa. Mycologia 109(2):323–332
Orihara T, Smith ME, Shimomura N, Iwase K, Maekawa N. 2012. Diversity and systematics of the sequestrate genus Octaviania in Japan: two new subgenera and eleven new species. Persoonia 28:85–112