Genetic Structure in Native Populations of Grape Phylloxera (Homoptera: Phylloxeridae)

Abstract

Random amplified polymorphic DNA (RAPD) markers were used to study genetic structure and diversity in native grape phylloxera populations growing on Vitis arizonica Englemann in central Arizona and on V. riparia Michaux in New York. RAPD data from the Arizona collections were clustered into 3 subpopulations, whereas data from the New York collections were not clustered, which reflected topographic features and the distribution of the sampled vines. Similarity coefficients of the 2 collection areas had similar ranges (0.89–1.0). The similarity coefficient between the Arizona and New York collections was 0.62. Analyses of molecular variance were used to partition the variance in genetic distances, and confirmed the results of the dendrogram clustering. The clustering of the Arizona populations is likely the result of gene flow restriction caused by geographic isolation. Greater diversity was expected among the Arizona populations. That diversity levels were similar suggests that other factors, such as inbreeding or past population history, must play a role in the relatively low level of diversity found in Arizona.