Xylaria karyophthora: a new seed-inhabiting fungus of Greenheart from Guyana

Abstract

In 2010-2011, a Xylaria sp. was documented growing from seeds of both Chlorocardium rodiei and Chlorocardium venenosum, a commercially valuable timber in Guyana. We conducted extensive surveys in 2015-2016, where this Xylaria sp. was observed fruiting from ca. 80% of dispersed seeds in both natural and logged forests in the Upper Demerara-Berbice, Potaro-Siparuni, and the Cuyuni-Mazaruni districts of central Guyana. Species of Xylaria are ascomycetous fungi generally characterized by black, carbonaceous, multiperitheciate ascoma commonly found growing on dead wood. Combined teleomorphic and molecular data indicate that the fungus represents a novel species, described here as Xylaria karyophthora.

Emerging Forest Diseases: A Case Study of Greenheart (Chlorocardium spp., Lauraceae) and the Newly Described Fungus, Xylaria karyophthora

“…The almost sudden emergence of this fungus is consistent with several plausible explanations including that of a novel species introduced from a different geographic location or an endemic that became parasitic as a result of anthropogenic disturbance/changes in habitat and climate [65][66][67]. Further, we conducted multilocus phylogenetic analysis based on PRB2 and α-actin and found X. karyophthora to be derived from within a clade of wood-inhabiting species [11], suggesting a possible shift from woody to seed substrata. We therefore surmise two plausible hypotheses for the ecology of this fungus.…”

“…Second, X. karyophthora could represent an emerging infectious organism due to a new host-pathogen interaction that resulted from a recent host jump to Greenheart from another unidentified host or introduced from a different geographic region [65]. From all indications, the preliminary distribution of X. karyophthora also shows a highly effective seed parasite passing a series of filters that correspond to successful invasion, i.e., transport, establishment, and spread [11]. Another fascinating observation is that Greenheart is found mainly in mixed stands or forming reefs (clumps) [28], however, X. karyophthora has only been observed in association with Greenheart seeds and not the seeds of other species in the stand.…”

“…At that time, the authors also made note of a xylariaceous fungus on the fruits of Greenheart, which they identified as a Nodulisporium species. This record is, to our knowledge, the first record of a xylariaceous fungus on Greenheart seeds, and may represent X. karyophthora [11].…”

“…However, in 2011 we observed numerous black fungal fruiting bodies emerging directly from dead Greenheart seeds in logged and unlogged forest of central Guyana (Figure 1). This fungus was subsequently described as Xylaria karyophthora [11]. Extensive field studies undertaken in 2011 and 2015-2016 indicated this new species of Xylaria was aggressively colonizing and producing fruiting structures on the cotyledons of ca.…”

“…However, the very recent discovery and documentation of Xylaria karyophthora Husbands, Urbina & Aime, a putative pathogen of the seeds of Chlorocardium spp., may present a new and emerging threat to the Greenheart industry in Guyana [11].…”