35Likelihood ratio tests Kishino-Hasegawa Two different topologies Shimodaira-HasagawaMultiple topologies
36Trebouxia and Letharia LichensScott KrokenTrebouxia and Letharia
37Letharia columbianaQuestion: Are there two species of Letharia, one sexual and the other not?Letharia vulpina
38Letharia vulpina Letharia columbiana always produces soredia apothecia are rareLetharia columbianaalways produces apotheciasometimes produces isidiaAre they a “species pair” and how do they reproduce?
45Kroken and Taylor 2001 Fungal Genetics & Biology 34:83-92 Letharia “lupina” paternity analysis‘lupina’ locus CS EarI‘lupina’ ITS 1F/ 2 SacIMom1 and 7 kidsMom2 and 6 kidsMom1 and 7 kidsMom2 and 6 kidsAll 36 apothecia in both speciesare the result of outcrossingKroken and Taylor 2001 Fungal Genetics & Biology 34:83-92
51More polymorphism?Microsatellites orShort Tandem Repeats
52Molecular markers- Microsatellites Dinucleotide repeats randomly dispersed through the genomectgcgtgtgacatACACACACACACACActgtatgtgatcHighly polymorphic and multialleleic due to polymeraseslippage during strand replicationCocci_1 ctgcgtgtgacatACACACACACACACA ctgtatgtCocci_2 ctgcgtgtgacatACACACACACACACACA------ctgtatgtCocci_3 ctgcgtgtgacatACACACACACACACACACA----ctgtatgtCocci_4 ctgcgtgtgacatACACACACACACACACACACACActgtatgt
59North America/ Mexico C. immitis ( ) and C. posadasii ( ) show isolation by distance...r = 0.694**r = 0.905
60...but NOT if South American isolates (all C. posadasii) are included…r = 0.023r = 0.694**
61S. American isolates contain 6% of the variation found in N. America 28% of loci are in linkage disequlibrium (7% in N. America)This is a bottlenecked population…and is descended fromthe TEXAS population ofCoccidioides posadasii
62Genetic dating show that South American populations were founded from those inNorth America between 9, ,000 BP(the Pleistocene)
63Migration of Homo sapiens into South America by 10,000 BC Jared Diamond ‘Guns, Germs and Steel’, 1997
64How did non-CA C. immitis arrive in South America? Host-pathogen dispersal:9,000 year old bones of Bison antiquus from Nebraskacontain C. immitis spherules. Demonstrates potential forlong-distance dispersal with a hostHuman infections are viable for more than 12 yearsAncient Amerindian middens contain high concentrations ofC. immitisDocumented invasion of South America by the Amerindians12,500 yrs bp.
65Does the present distribution of C. posadasii reflect the co-dispersal of a host and its pathogen?
66Recombining and Clonal in Coccidioides Clonal (C. posadasii in Latin Amer?)