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 (amplifi ed fragment length polymorphism - polymerase chain reaction) methodology. O ne-hundred three European and 6 North American phylloxera populations were studied. An additional European sampling set comprising 60 samples was anal yzed to study regional subdivision. The populations grouped into two cluste rs loosely correlated with collection site location. Phylloxera populations collected from northern (above lat 43 degrees) geographic regions were sig nificantly different from southern (below 43 degrees) populations. The nort hern cluster was more heterogeneous than the southern cluster, possibly ref lecting holocyclic versus anholocyclic reproduction. Microgeographic scales of phylloxera genetic structure displayed as much variation within as amon g host plants. The host plant did not affect the genetic structure of Europ ean phylloxera as revealed in two independent experiments.