Abstract:
Glycaspis brimblecombei is an invasive insect pest of Eucalyptus that has spread
rapidly around the world since its first report in California in 1998. The pest now
occurs on at least four continents where Eucalyptus is grown as a non-native plantation
species. To characterize global routes of invasion for this insect, we characterized the
sequences of a portion of the Cytochrome Oxidase 1 (COI) gene from 105 individuals
from the invasive and native range, including from Australia, Brazil, Chile, La Réunion,
Mauritius, South Africa and the United States. In addition, we developed 13 polymorphic
microsatellite markers, of which we used 11 to characterize the diversity in the same
105 specimens. Our results suggest that there have been two independent introduction
events from Australia, which is assumed to be the origin, to distinct parts of the adventive
range. The first introduction was into the United States, from where it appears to have
spread to South America and eventually to South Africa. This finding highlights the
threat of bridgehead populations to accelerate pest invasions in Eucalyptus, even if
those populations are on widespread non-commercial populations of Eucalyptus (as in
California). A second introduction appears to have occurred on the islands of Mauritius
and La Réunion and provides another example of the establishment of independent
lineages of invasive global insect pests. This complex invasion pattern mirrors that found
in other Eucalyptus pests.
