Molecular Ecology (2010) 19, 1122-1133

Michelle T. Franklin, Carol E. Ritland and Judith H. Myers (2010)
Spatial and temporal changes in genetic structure of greenhouse and field populations of cabbage looper, Trichoplusia ni
Molecular Ecology 19 (6), 1122-1133
Abstract: Trichoplusia ni is a subtropical moth that migrates annually from southern California to southern British Columbia, Canada where it invades vegetable greenhouses and field crops. The heated greenhouse environment has altered the natural extinction-recolonization dynamics of T. ni populations, and allows year-round persistence in some locations. In addition, the extensive use of the biopesticide, Bacillus thuringiensis subspecies kurstaki (Bt) in some greenhouses has selected for resistance. Here we investigated the genetic structure of T. ni populations in British Columbia greenhouses and in field populations in California and British Columbia using amplified fragment length polymorphisms (AFLP) as related to patterns of Bt resistance. The majority of British Columbia field populations were similar to the California field populations, the potential source of migrants. However populations in two geographic areas with high concentrations of greenhouses showed local genetic differentiation. Some of these populations experienced severe bottlenecks over-winter and following Bt sprays. Greenhouse populations showed a pattern of isolation by distance and a strong positive relationship between genetic differentiation and levels of Bt resistance. These patterns indicate that greenhouses that sometimes support year-round populations of T. ni and the ensuing strong bottlenecking effects following winter cleanups and Bt application cause genetic differentiation of T. ni populations. Long distance migrants to field populations contribute to genetic homogeneity of these.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Judith H. Myers, Michelle T. Franklin

Research topic(s) for pests/diseases/weeds:
molecular biology - genes
population dynamics/ epidemiology
Research topic(s) for beneficials or antagonists:
resistance/tolerance/defence of host

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Trichoplusia ni		U.S.A. (SW)
	Trichoplusia ni		Canada (west)
Bacillus thuringiensis var. kurstaki (entomopathogen)	Trichoplusia ni		U.S.A. (SW)
Bacillus thuringiensis var. kurstaki (entomopathogen)	Trichoplusia ni		Canada (west)