Gloniaceae

The family Gloniaceae (Corda) Boehm, Schoch & Spatafora 2009
fam. incertae sedisPleosporomycetidae Schoch et al. 2007

by Eric W.A. Boehm

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In the Gloniaceae (Corda) Boehm, Schoch & Spatafora, the ascomata is a modified hysterothecium, progressively dichotomously branched, laterally anastomosed along their length to form radiating flabelliform or pseudo-stellate composites, seated upon a conspicuous brown felt-like subiculum, sometimes borne in a stroma. In vertical section, hysterothecia globose to obovoid, typically with a thick three-layered peridium, but fragile, unlike the robust peridium of the Hysteriaceae, composed of small pseudoparenchymatous cells, the outer layer heavily encrusted with pigment and often longitudinally striate on the surface, the middle layer lighter in pigmentation and the inner layer distinctly thin-walled, pallid and compressed. The hamathecium is composed of persistent narrow cellular pseudoparaphyses, often borne in a gel matrix, with tips darkened or branched at maturity. Bitunicate asci are borne in a basal layer and at maturity are typically clavate to cylindric, bearing eight ascospores, overlapping biseriate, ranging from hyaline to light yellow, uniseptate, conspicuously constricted at the septum, fusoid in outline, with at least one end, often both, acuminate, and showing bipolar asymmetry. Monotypic family with only one genus, Glonium Muhl. : Fr. previously classified within the Hysteriaceae, but recently transferred to the Gloniaceae, based on a four gene phylogeny (Boehm et al. 2009).

Corda (1842) originally proposed the Gloniaceae Corda as a sub-familial taxonomic rank under the family Hysteriaceae, in which he placed both Hysterographium and Glonium. Boehm et al. (2009) emended and restricted this sub-familial rank and elevated it to family rank. The genus Glonium was retained as circumscribed first by von Höhnel (1918) and then by Petrak (1923a); Hysterographium was retained within the Hysteriaceae (Zogg 1962). We feel justified in reinstating the Gloniaceae and, more importantly, raising it to family rank for a single genus because of the high statistical support the group receives in the four-gene analysis (Boehm et al. 2009). Also, the isolates used to define the group are geographically diverse, from Tasmania and the United States, and, most importantly, include the type species as well.

However, at present we do not include the Gloniaceae within the newly created order Mytilinidiales, because of the highly divergent morphology associated with the genus Glonium, as compared to the current genera within the Mytilinidiaceae. These include character states associated with pseudothecial shape, peridial wall thickness, hamathecial type and ascospore symmetry (Barr 1987; Boehm et al. 2009). Additionally, not enough taxa have been sequenced for the Gloniaceae to establish whether in fact they deserve ordinal status. Thus, for the present, we propose that the family Gloniaceae be considered Pleosporomycetidae incertae sedis. Nevertheless, our four-gene phylogeny does indicate that, despite highly divergent morphologies, especially those related to the hamathecium (i.e., persistent cellular pseudoparaphyses in the Gloniaceae versus narrow trabeculate pseudoparaphyses in the Mytilinidiaceae), the two families are in fact closely related (Boehm et al. 2009).

Zogg (1962) noted four species within the genus Glonium sensu lato that he grouped together in his key. The principle unifying morphological feature was the progressively dichotomously branched, laterally anastomosed hysterothecia that fused along their length to form radiating pseudo-stellate composites, seated upon a conspicuous brown felt-like subiculum, sometimes borne in a stroma. The central taxon was the type for the genus Glonium, namelly G. stellatum, which was included in the analysis by Boehm et al. (2009), in addition to the newly described G. circumserpens from Tasmania.

At present the family is monotypic with one genus, namely Glonium Muhl. : Fr.