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Estimating levels of gene flow between natural populations of cereal aphids (Homoptera: Aphididae)

Published online by Cambridge University Press:  10 July 2009

Hugh D. Loxdale
Affiliation:
Entomology and Nematology Department, Rothamsted Experimental Station, Harpenden, UK.

Abstract

Gene flow between field populations of the cereal aphids Sitobion avenae (Fabricius), Sitobion fragariae (Walker) and Rhopalosiphum padi (Linnaeus) is examined using statistical analyses of allozyme frequency data (both Slatkin's and F statistics). Analysis using Slatkin's method confirms the conclusions previously drawn from earlier analyses. Thus there is found to be high gene flow between subpopulations of S. avenae and R. padi, and a more restricted level between local S. fragariae subpopulations, especially when infesting the secondary host (cocksfoot grass, Dactylis glomerata). The value of Nm (number of immigrants per generation) calculated for S. avenae was approximately 2 and is indicative of high gene flow i.e. Nm>1.0. Also, as previously found by x2 genetic contingency testing, the F statistical analysis confirms that S. fragariae subpopulations infesting D. glomerata are genetically more heterogeneous than those infesting the primary host, blackberry, Rubus fruticosus agg. Hence, there may be less gene flow between populations on the secondary host compared with that on the primary. The results obtained are compared with the flight behaviour of these particular aphid species and to their respective host plant abundances. The advantages and disadvantages of both Slatkin's method and F statistics for analysing insect population genetic structure are noted.

Information

Type
Research Paper
Copyright
Copyright © Cambridge University Press 1990

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