title: Multiple introductions from multiple sources: invasion patterns for an important Eucalyptus leaf pathogen.
abstract: Many population studies on invasive plant pathogens are undertaken without knowing the center of origin of the pathogen. Most leaf pathogens of Eucalyptus originate in Australia and consequently with indigenous populations available, and it is possible to study the pathways of invasion. Teratosphaeria suttonii is a commonly occurring leaf pathogen of Eucalyptus species, naturally distributed in tropical and subtropical regions of eastern Australia where it is regarded as a minor pathogen infecting older leaves; however, repeated infections, especially in exotic plantations, can result in severe defoliation and tree deaths. Nine polymorphic microsatellite markers were used to assess the genetic structure of 11 populations of T. suttonii of which four where from within its native range in eastern Australia and the remaining seven from exotic Eucalyptus plantations. Indigenous populations exhibited high allele and haplotype diversity, predominantly clonal reproduction, high population differentiation, and low gene flow. The diversity of the invasive populations varied widely, but in general, the younger the plantation industry in a country or region, the lower the diversity of T. suttonii. Historical gene flow was from Australia, and while self-recruitment was dominant in all populations, there was evidence for contemporary gene flow, with South Africa being the most common source and Uruguay the most common sink population. This points distinctly to human activities underlying long-distance spread of this pathogen, and it highlights lessons to be learned regarding quarantine.
authors.affiliation: Department of Biology National University of Lesotho P. O. 180 Roma Lesotho ; Department of Genetics Forestry and Agriculture Biotechnology Institute (FABI) University of Pretoria Pretoria 0002 South Africa.
authors.forename: Matsepo
authors.initials: M
authors.lastname: Taole
authors.affiliation: Department of Genetics Forestry and Agriculture Biotechnology Institute (FABI) University of Pretoria Pretoria 0002 South Africa ; Agricultural Research Council Vegetable & Ornamental Plant Institute Pretoria South Africa.
authors.forename: Wubetu
authors.initials: W
authors.lastname: Bihon
authors.affiliation: Department of Genetics Forestry and Agriculture Biotechnology Institute (FABI) University of Pretoria Pretoria 0002 South Africa.
authors.forename: Brenda D
authors.initials: BD
authors.lastname: Wingfield
authors.affiliation: Department of Microbiology and Plant Pathology Forestry and Agriculture Biotechnology Institute (FABI) University of Pretoria Pretoria 0002 South Africa ; School of Veterinary and Life Sciences Murdoch University Murdoch WA 6150 Australia.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Wingfield
authors.affiliation: Department of Genetics Forestry and Agriculture Biotechnology Institute (FABI) University of Pretoria Pretoria 0002 South Africa ; School of Veterinary and Life Sciences Murdoch University Murdoch WA 6150 Australia.
authors.forename: Treena I
authors.identifier: 0000-0002-7962-219X
authors.initials: TI
authors.lastname: Burgess
keywords: Forest biosecurity; Teratosphaeria suttonii; gene flow; microsatellite markers; plantation forestry