Microbial Reproductive Modes Fungal Reproduction Week 12, PMB 220 J. Taylor
The cost of sex is two-fold. Clonal progeny have twice as many parental genes.
The Value of Sex? The Red Queen Hypothesis. "Now, here, you see, it takes all the running you can do, to keep in the same place." Lewis Carroll John Tenniel (illus) 1872.
The Value of Sex? Muller’s Ratchet H. Muller, 1964
Goddard, Godfray Burt. 2005 Nature 434:636-640
Goddard, Godfray Burt Nature 434:636-40 2005
Harsh environment Goddard, Godfray Burt Nature 434:636-40 2005 Benign environment
Sex is nearly ubiquitous. Only the bdelloid rotifers have been claimed to be an old asexual group. Aydin Örstan http://users.unimi.it/ricci/html/bdelloid.htm
Numbers of Species of Fungi Ascomycota 32,267 46.0% Lichenized fungi 13,500 18.7% Basidiomycota 22,244 32.0% Chytridiomycota 793 1.0% Zygomycota 1,056 1.5% Mitosporic fungi 14,104 19.6% Dictionary of the Fungi, Hawksworth et al. 1996
What is a species? How do they reproduce?
Determining thereproductive mode of Microbes: Recombination v. clonality
Clonal: Association of Alleles.
Compter sex: Resampling without replacement.
Tree Length Test
Gene Genealogy Concordance
Computer sex: Shuffling variable nucleotides among genes.
You have to know the species before you can study reproductive mode.
Example: Coccidioides immitis Vasso Koufopanou Austin Burt Mat Fisher
Distribution of Coccidioides immitis Rippon, 1988
Finding Single Nucleotide Polymorphisms Agarose and SSCP gels of PCR products
Coccidioides immitis: multilocus genotypes as single nucleotide polymorphisms (SNPs)
Parsimony analysis: Consensus of 62 most parsimonious trees.
California Coccidioides Fisher et al. 2000
Likelihood ratio tests Kishino-Hasegawa Two different topologies Shimodaira-Hasagawa Multiple topologies
Lichens Scott Kroken Trebouxia and Letharia
Letharia columbiana Question: Are there two species of Letharia, one sexual and the other not? Letharia vulpina
Letharia vulpina • always produces soredia • apothecia are rare • Letharia columbiana • always produces apothecia • sometimes produces isidia • Are they a “species pair” and how do they reproduce?
Distribution of Letharia species Xerox PARC map
Asexual Sexual www.lichen.com Thomas Nash Apothecia, filled with meiotic ascospores Soredia, algal cells wrapped in hyphae
6 species suggested Kroken and Taylor. 2000. Mycologia 93:38-53
Fertilization Spermagonium-- produces spermatia Trichogyne-- fuses with spermatium Paternity analysis of lichen apothecia
Letharia “lupina” paternity analysis ‘lupina’ locus CS EarI ‘lupina’ ITS 1F/ 2 SacI Mom1 and 7 kids Mom2 and 6 kids Mom1 and 7 kids Mom2 and 6 kids All 36 apothecia in both species are the result of outcrossing Kroken and Taylor 2001 Fungal Genetics & Biology 34:83-92
Dispersal of Letharia vulpina with its alga Xerox PARC map Högberg et al. 2002. Molecular Ecology 11:1191-1196
Recombining and Clonal in Letharia Recombining: North American sorediate Recombining: North American apotheciate Clonal: European and North African sorediate Letharia species