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Doctoral thesis, 2000

Ecology of Daldinia spp. with special emphasis on Daldinia loculata

Johannesson, Hanna

Abstract

This thesis comprises studies on the xerophytic ascomycete genus Daldinia. By studying ecological, morphological and molecular characters of herbarium specimens, five distinct Daldinia species were identified from northern Europe: D. concentrica, D. fissa, D. grandis, D. loculata and D. petriniae. The last two mentioned have previously been referred to as D. concentrica in the literature. The distinct stromatal host-specificity of the three species: D. concentrica, D. loculata and D. petriniae was studied in an inoculation experiment. The results indicate that the observed substrate-specificity is not a result of enhanced wood-decaying capability in the substrate on which stromata are usually found. Reproducible PCR-based molecular markers were developed for the postfire species D. loculata by using available sequence data of nuclear genes from species closely related to D. loculata. Each marker spans over one or several introns and showed relatively high intraspecific variability. The genetic variation of D. loculata was studied both within and among forest sites. In a local population structure study of D. loculata in burned birches, we found that it can establish endophytically in sound-looking wood of living trees, most probably by sexual ascospores. In birches killed by forest fire, each haploid genet occupied an extensive volume of wood. Multilocus genotyping of vegetative mycelia and offspring of the attached stromata indicated multiple matings of the relatively large vegetative mycelia in wood by several other, very small, genets. The genetic structure of six Fennoscandian and one Kamchatkan D. loculata subpopulation was studied in order to reveal any differentiation on a continental scale. Low levels of genetic differentiation among the Eurasian subpopulations of D. loculata were found, and the differentiation did not increase with distance; the Kamchatkan subpopulation, sampled more than 7000 km from the Fennoscandian subpopulations, was only moderately differentiated from the others. These results suggest that D. loculata consists of a large, coherent Eurasian population of latent mycelia in unburned forests, established by ascospores dispersed from scattered burned forest sites. A tentative life cycle of D. loculata is presente

Keywords

Xylariaceae; host-specificity; forest fire; postfire fungi; molecular markers

Published in

Acta Universitatis Agriculturae Sueciae. Silvestria
2000, number: 168
ISBN: 91-576-6052-2
Publisher: Swedish University of Agricultural Sciences