The olive fly, Bactrocera oleae, is the most important pest affecting the olive industry, to
which it is estimated to cause average annual losses in excess of one billion dollars. As with
other insects with a wide distribution, it is generally accepted that the understanding of B.
oleae population structure and dynamics is fundamental for the design and implementation
of effective monitoring and control strategies. However, and despite important advances in
the past decade, a clear picture of B. oleae's population structure is still lacking. In the Mediterranean
basin, where more than 95% of olive production is concentrated, evidence from
several studies suggests the existence of three distinct sub-populations, but the geographical
limits of their distributions, and the level of interpenetration and gene flow among them
remain ill-characterized. Here we use mitochondrial haplotype analysis to show that one of
the Mediterranean mitochondrial lineages displays geographically correlated substructure
and demonstrate that Italic populations, though markedly distinct from their Iberian and Levantine
counterparts are more diverse than previously described. Finally, we show that this
distinction does not result from extant hypothetical geographic limits imposed by the Alps or
the Pyrenees nor, more generally, does it result from any sharp boundary, as intermixing is
observed in a broad area, albeit at variable levels. Instead, Bayesian phylogeographic analysis
suggests the interplay between isolation-mediated differentiation during glacial periods
and bi-directional dispersal and population intermixing in the interglacials has played a
major role in shaping current olive fly population structureFoundation for Science and
Technology (FCT: www.fct.pt) under Strategic Project
PEst-C/AGR/UI0115/2011 and project ALENT-07-
0324-FEDER-001747, as well as by FEDER Funds
through the latter project and Operational Programme
for Competitiveness Factors—COMPETE. BA and
LTC were funded by FCT grants SFRH/BPD/73108/
2010 and Ciência2008- ICAAM, respectively