North American populations of
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North American populations of Entoleuca mammata are genetically more variable than populations in Europe. Introduction. What is E. mammata ?

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Introduction 4149041

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


Introduction

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

http://www.glfc.cfs.nrcan.gc.ca/treedisease/photos/Pg%2052-c.JPG


Locations

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 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

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

http://www.na.fs.fed.us/spfo/pubs/fidls/hypoxylon/hypox_fig1.jpg

http://www.forestpathology.org/hypoxylo.gif


Hypothesis of conspecificity

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

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

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= 0.160 (low)

  • Therefore, high differentiation within population

http://www.umbc.edu/bioclass/biol100/powerpoints/lecture10/img032.jpg


Bottleneck effect

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

http://www.uri.edu/artsci/bio/twombly/BIO113/images/drift2a.jpg


Possible introduction events

Possible introduction events?

  • Wide variety of hosts

  • Carried by humans

  • Long-distance air dispersal

  • Insects and birds

http://www.rspb.org.uk/Images/great%20spotted%20woodpecker%20on%20tree%20stump%20180_tcm3-27242.jpg

http://www.canadianbiodiversity.mcgill.ca/english/species/insects/agromyzidae.jpg


Summary

Summary

  • E. Mammata

  • Conspecific between NA and EU

  • Native to NA

  • Introduced to EU

  • Founder effect


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