Data from: Contrasted invasion processes imprint the genetic structure of an invasive scale insect across southern Europe

Deciphering the colonization processes by which introduced pests invade
new areas is essential to limit the risk of further expansion and/or
multiple introductions. We here studied the invasion history of the
maritime pine bast scale Matsucoccus feytaudi. This host-specific insect
does not cause any damage in its native area, but it devastated maritime
pine forests of South-Eastern France where it was detected in the 1960s,
and since then reached Italy and Corsica. We used population genetic
approaches to infer the populations’ recent evolutionary history from
microsatellite markers and Approximate Bayesian Computation. Consistent
with previous mitochondrial data, we showed that the native range is
geographically strongly structured, which is probably due to the patchy
distribution of the obligate host and the limited dispersal capacity of
the scale. Our results show that the invasion history can be described in
three successive steps involving different colonization and dispersal
processes. During the mid-XXth century, massive introductions occurred
from the Landes planted forest to South-Eastern France, probably due to
transportation of infested wood material after World War II.
Stepping-stone expansion, consistent with natural dispersal, then allowed
M. feytaudi to reach the maritime pine forests of Liguria and Tuscany in
Italy. The island of Corsica was accidentally colonized in the 1990s, and
the most plausible scenario involves the introduction of a limited number
of migrants from the forests of South-Eastern France and Liguria, which is
consistent with an aerial dispersal due to the dominant winds that blow in
spring in this region.