Thaumetopoea wilkinsoni Tams, 1924 occurs in the southeast Mediterranean basin and infests pine and cedar stands. Our objective was to decipher the biogeography of the species and, in particular, to explore its evolutionary history on the island of Crete. We collected 135 individuals from 14 sites on Crete, Turkey, Samos and Rhodes. We sequenced one mitochondrial fragment (cytochrome c subunit I) and used 12 microsatellite loci for population genetic analyses. All results supported the deep divergence of Cretan populations from the neighbouring areas, with the differentiation between Crete and neighbouring regions being similar to the interspecific divergence between T. wilkinsoni and its sibling species, Thaumetopoea pityocampa (Denis and Schiffermüller, 1775). Both mitochondrial and microsatellite markers showed a clear longitudinal (east–west) differentiation of populations within Crete. Our results thus suggest that T. wilkinsoni crossed the Mid-Aegean Trench, became isolated on Crete and differentiated through vicariance after the end of the Messinian Salinity Crisis, favouring the emergence of an endemic lineage. There, Quaternary climatic oscillations coupled with geographical barriers to gene flow have given rise to the currently observed east–west differentiation of Cretan populations.

Contact zones occur at the crossroad between specific dispersal routes and are facilitated by biogeographic discontinuities. Here, we focused on two Lepidoptera sister species that come in contact near the Turkish Straits System (TSS). We aimed to infer their phylogeographic histories in the Eastern Mediterranean and finely analyze their co‐occurrence and hybridization patterns in this biogeographic context.We used molecular mitochondrial and nuclear markers to study 224 individuals from 42 localities. We used discordances between markers and complementary assignment methods to identify and map hybrids and parental individuals.We confirmed the parapatric distribution ofThaumetopoea pityocampa(Lepidoptera: Notodontidae) in the west andThaumetopoea wilkinsoniin the east and identified a narrow contact zone. We identified several glacial refugia ofT. wilkinsoniin southern Turkey with a strong east–west differentiation in this species. Unexpectedly,T. pityocampacrossed the TSS and occur in northern Aegean Turkey and some eastern Greek islands. We found robust evidence of introgression between the two species in a restricted zone in northwestern Turkey, but we did not identify any F₁individuals. The identified hybrid zone was mostly bimodal.The distributions and genetic patterns of the studied species were strongly influenced both by the Quaternary climatic oscillations and the complex geological history of the Aegean region.T. pityocampaandT. wilkinsonisurvived the last glacial maximum in disjoint refugia and met in western Turkey at the edge of the recolonization routes. Expanding population ofT. wilkinsoniconstrainedT. pityocampato the western Turkish shore. Additionally, we found evidence of recurrent introgression byT. wilkinsonimales in severalT. pityocampapopulations. Our results suggest that some prezygotic isolation mechanisms, such as differences in timing of the adult emergences, might be a driver of the isolation between the sister species.

The pine processionary moths Thaumetopoea pityocampa and T. wilkinsoni are among the most important Mediterranean pine defoliators. Although recent studies suggest that the two species may coexist in Turkey, the relevant literature lacks precise information on the occurrence and exact distribution of the two species in this country. In particular, whether the two sister taxa form a contact zone is still unknown. In this study, we aimed to reveal the limits of the ranges of the two species in Turkey by using nuclear (ITS-1, photolyase) and mitochondrial markers (COI). Multilocus molecular characterization of the two species showed for the first time that the two species co-occur in some of the sampling sites. In addition, we determined clear signatures of mitochondrial introgression between the two species, and therefore the existence of a possible hybrid zone within Turkey. These results bring up interesting questions relating to the evolution of the identified hybrid zone