North American populations of Entoleuca mammata are genetically more variable than populations in Europe

Introduction What is E. mammata? A damaging pathogen in Populus tremuloides, P. grandidentata in North America, and Populus alba, P.trichocarpa, P.tremula and the hybrid aspen in Europe Major cause of aspen death

Locations NA locations: North-east, Great Lakes region, North-western prairies Noticeably absent in Rocky mountains, Alaska (abundance of aspens?) Thought to be restricted to NA EU locations: Noticed in France(1975) Isolated regions in the French Alps 2 races of P. tremula, mountains and plains No serious outbreaks Coexistance? Coevolution?

Objective and Hypothesis Objective: to investigate relationship btw NA and EU Hypothesis: 1) NA and EU are conspecific 2) Fungus was introduced btw continents resulting in both founder and bottleneck effect To prove: 1) should have identical alleles and no phylogenetic grouping according to geographic origin. 2) measure genetic variability btw continents

Materials and Methods Samples from both EU and NA collected 63 samples collected to analyze Wood surface sterilized and incubated Isolates incubated Ascospore isolations Most isolations of hyphae from canker margins

Hypothesis of Conspecificity Alleles determined by sequencing= Several identical alleles Consensus trees, phenograms, bootstrap programs, and calculations= Lack of phlyogenetic grouping of alleles Therefore species conspecific

Direction of Introduction Introduced continent = lower genetic diversity Nei’s, Chao-estimates, rarefaction curves EU lower diversity than NA NA had unique genotypes EU had identical genotypes Therefore, NA→EU

Testing introduction hypothesis Measured genetic differentiation Founder effect→ Fst and Gst calculated High Fst= low gene flow Low Fst= high gene flow (high differentiation) Gst close to 0= variation within population Gst close to = populations different Results Fst=0.193 (low) Gst= (low) Therefore, high differentiation within population

Bottleneck effect? Bottleneck effect Population reduced by atleast 50% New mutations in a small population Should of produced unique alleles Reduce NA and EU identical alleles No unique EU alleles Therefore, no bottleneck effect Introduction effect favoured

Possible introduction events? Wide variety of hosts Carried by humans Long-distance air dispersal Insects and birds woodpecker%20on%20tree%20stump%20180_tcm jpg ecies/insects/agromyzidae.jpg

Summary E. Mammata Conspecific between NA and EU Native to NA Introduced to EU Founder effect