Importance of ascospore ornamentation in the taxonomy of Daldinia

Abstract

Representative specimens of fifteen Daldinia spp. were studied for ultrastructural characteristics of their ascospores by scanning electron microscopy (SEM). The ornamentation of their outermost spore layers was found to be species-consistent, confirming the results of concurrent studies on the morphology of their teleomorphs and anamorphs, secondary metabolite profiles and PCR-based genetic fingerprints. Daldinia spp. may either show smooth or transversally striated ascospores. The spores of the species within the latter group are always ellipsoid-equilateral to ellipsoid-inequilateral with narrowly rounded ends. Smooth, broadly ellipsoid to cylindrical ascospores were observed in all species (D. caldariorum, D. fissa and D. loculata) that are known to produce their stromata on substrates damaged by fire. The ascospores of D. concentrica differed from those of D. childiae (i.e., the cosmopolitan taxon previously regarded as D. concentrica ss. auct.) and other Daldinia spp. in showing a very faint ornamentation, which only became visible at 10000x magnification by SEM. A specimen collected on the isle of Jersey (Channel Islands, UK) showed morphological similarities to the pantropical D. eschscholzii, but its ascospores appeared smooth by SEM, and it may therefore represent a previously undescribed species.

A polyphasic taxonomy of Daldinia (Xylariaceae)1

“…Consequently, a polythetic approach, relying on morphological studies and HPLC profiling in conjunction with PCR fingerprinting and scanning electron microscopy (SEM) (Stadler et al 2001c , d , 2002 ) supported the status of D. childiae , revealed that D. concentrica sensu Rogers et al ( 1999 ) and D. eschscholtzii contain similar secondary metabolites in their stromata, and confirmed previous results by Van der Gucht ( 1993 , 1994 ) on their anamorphic and ultrastructural characteristics. Stadler et al ( 2004a ) described five additional “cryptic” species from the Canary Islands, the Channel Islands, and Sicily.…”

Theissenia reconsidered, including molecular phylogeny of the type species T. pyrenocrata and a new genus Durotheca (Xylariaceae, Ascomycota)

“…Scanning electron microscopy (SEM) was carried out using a conventional procedure as described in Stadler et al (2002). Analytical HPLC of stromatal methanol extracts was performed using the standardized method, comprising diode array detection as described by Hellwig et al (2005) and mass spectrometric detection in the positive and negative electrospray mode, using a comprehensive library of reference compounds (Bitzer et al .…”

Ascus apical apparatus and ascospore characters in Xylariaceae

“…1987), striations in H. californicum (Ju & Rogers 1996), and pleated folds in H. rectangulosporum (Rogers et al 1992) and H. thouarsianum (Miller 1961). Transverse striations are also apparent in some Daldinia species (van der Gucht 1993, Stadler et al . 2002).…”

“…have ascospores with faint transverse striations perpendicular to the long axis of the spore (Rogers & Candoussau 1982, Rogers 1985, van der Gucht & van der Veken 1992, Ju & Rogers 1996). Van der Gucht (1993) and Stadler et al . (2002) emphasized the significance of transverse striations of the ascospores in certain species of Daldinia .…”