Genetic structure of an introduced pest, grape phylloxera (Daktulosphaira vitifoliae Fitch), in Europe.

A model for the genetic structure of grape phylloxera populations in Europe was developed using hierarchical sampling techniques and AFLP-PCR (amplified fragment length polymorphism--polymerase chain reaction) methodology. One-hundred three European and 6 North American phylloxera populations were studied. An additional European sampling set comprising 60 samples was analyzed to study regional subdivision. The populations grouped into two clusters loosely correlated with collection site location. Phylloxera populations collected from northern (above lat 43 degrees) geographic regions were significantly different from southern (below 43 degrees) populations. The northern cluster was more heterogeneous than the southern cluster, possibly reflecting holocyclic versus anholocyclic reproduction. Microgeographic scales of phylloxera genetic structure displayed as much variation within as among host plants. The host plant did not affect the genetic structure of European phylloxera as revealed in two independent experiments.