n African Entomology - Evidence for multiple origins of grape phylloxera ( Fitch) (Hemiptera : Phylloxeridae) in South African vineyards




The ancestry of introduced populations can be inferred from gene genealogies if an adequate sample can be obtained, and population structure can be elucidated, from the native range. Grape phylloxera was introduced to South Africa in the late 19th century and has caused considerable damage in this country, as elsewhere. A previous study suggested a single introduction to South Africa, independent of those in other viticultural regions of the globe. Here, a more extensive sampling of South African vineyards was obtained to test the hypothesis of a single introduction and infer the geographic and host plant source, or sources, of introductions. Genetic diversity was low, though in 36 samples 10 mitochondrial haplotypes were observed, seven unique and only two common. Some differentiation between grape phylloxera among the three populations was observed. Two clades were found, differing by a number of substitutions. Both these haplotype clades are closely related to grape phylloxera collected from the native grapevine, , from the northern United States of America and Canada. The results suggest at least two introductions, and the differentiation of one of the South African haplotype clades from other introduced populations around the world suggests a direct introduction from the native range.


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