Fungal Molecular Systematics: Research Results
Origins of lichen associations
Lichen associations arose several times within the fungi, yet until recently the closest relatives to lichens
among non-lichen fungi the were not known. Molecular characters allow the comparison of fungi with diverse
lifestyles and morphologies, and research in collaboration with Paula T. DePriest, has led to the production of
parsimony analyses of SSU rDNA sequences resulting in phylogenetic hypotheses of fungal relationships and predictions
of the origins of the lichen habit. Onto a well-resolved phylogeny for the Eumycota we mapped the character of lichenization
(shown in green on this phylogram). There are at least five separate origins of this symbiosis within the fungi (three lichen
origins within the Basidiomycetes, and two lichen origins within the Ascomycetes). The publication of this phylogenetic tree
with lichens interspersed among the real fungi supported something of a paradigm shift in the general view of lichen-forming fungi.
Rather than viewing lichens as an unusual and separate group one could see clearly that they are just representatives of another fungal
lifestyle.
A resolved phylogeny for the Eumycota
For a larger image of this eumycota phylogeny please see this descriptive page. Or see this related page for popular media coverage of this phylogeny.Evolution of fruiting bodies within the Ascomycetes
There has long been debate over the morphology of the ancestral filamentous ascomycete.
Various mycologists suggested that the first fruiting bodies were cups (as in the discomycetes),
flask-shaped perithecia (as in Neurospora or other Sordariales) or closed spherical cleistothecia (as in Eupenicillium).
As part of doctoral work (with John W. Taylor) I examined phylogenetic relationships of representative apothecial ascomycetes,
commonly known as the cup fungi, based on their nuclear SSU (18S) rDNA nucleotide sequences.
This research led to the first DNA sequences from lichen-forming fungi, and my phylogenetic analyses were the first to resolve the
major questions of fruiting-body evolution within the ascomycetes based on analyses of molecular characters.
I showed that the cup-forming discomycetes were basal, and paraphyletic within the filamentous ascomycetes, as proposed by J. A. Nannfeldt (1932).
The first fruiting body was a simple cup, and this either closed partially (retaining forcible spore ejection from the asci) as in the
perithecial fungi, or closed completely (with the concurrent loss of forcible spore ejection) as in the cleistothecial fungi.
For a closer view of this phylogram please go to this descriptive page.
This research is continuing with the inclusion more taxa, and the determination of phylogenetic hypotheses with parsimony-, distance- and
maximum-likelihood-based methods with statistical support determined from bootstrapping and jackknifing.
Related information
An introduction to AscomycetesThe Lichens of North America
Tree of Life (Arizona) glossary of phylogenetic terms