My research program uses the techniques of molecular
biology as well as more conventional approaches (culturing,
mating studies, etc.) to answer questions about the
natural history of fungi. Current research is focused
on three areas:
- phylogenetic biology and systematics, especially
of the Agaricales (mushrooms).
- genetics of speciation, including patterns of
morphological vs. genetic divergence, and analysis
of the genetic factors underlying development of
intersterility between related species.
- population biology of fungi, estimation of breeding
systems and measurement of gene flow in natural
populations.
Fungi currently under investigation include the oyster
mushroom (Pleurotus ostreatus) as well as several
species of medically important fungi (Candida albicans
and Cryptococcus neoformans).
The major research effort in our laboratory for
the last 10 years is still aimed at understanding
molecular evolution of ribosomal RNA genes in fungi,
and their use for estimating evolutionary relationships
of the higher Basidiomycotina. We are presently
surveying rDNA sequence variation from various families
of the Agaricales (mushrooms) and related fungi.
Saprobic basidiomycetes offer an excellent system
for studying the meaning of "what is a species"
in fungi. Our research combines the study of morphology,
mating behavior, genetics and molecular systematics
to try and understand how species differ and how
they evolve. Mating compatibility studies have repeatedly
demonstrated strong intersterility barriers among
most species. Our previous studies on DNA-level
variation in the mushroom Collybia dryophila
revealed a surprisingly high degree of genetic divergence
associated with speciation among intersterility
groups. More recently, our studies of speciation
in the oyster mushroom genus Pleurotus have examined
the importance of biogeography as a primary factor
associate with speciation.
At the molecular level, genomes of mushroom species
also appear to 'turn over' more rapidly than other
eukaryotes. We are currently employing molecular
approaches to study genetic mechanisms which may
operate during speciation. These methods include
the use of DNA restriction fragment polymorphisms
(RFLPs) and Amplified Fragment Length Polymorphisms
(AFLP) to estimate genetic diversity and along with
electrophoretic karyotyping, as well as more conventional
methods based on mating compatibility studies. One
of the current objectives of this research will
be to develop a generalized model for genome evolution
in asidiomycotina and its role in the development
of intersterility barriers (speciation).
Population Biology: Unique features of fungal life
history have profound relevance for their population
biology. We have been investigating the significance
of mating systems and life history for determining
genetic structure using molecular markers, both
in wild mushroom species (Pleurotus ostreatus
and Schizophyllum commune) as well as in
several human pathogenic fungi (Candida albicans
and Cryptococcus neoformans,) in collaboration
with Dr. Thomas G. Mitchell of the Duke University
Medical Center). A variety of approaches and markers
are being employed to address questions ranging
from how far do spores disperse, to how much clonality
vs recombination occurs in natural populations.
All of these studies involve graduate students who
define projects within each area.
