Evidence of potential hybridization in the Thaumetopoea pityocampa‐wilkinsoni complex

Abstract

1 The winter pine processionary moth complex includes some major defoliating insects of Pinus and Cedrus forests in southern Europe and the Mediterranean Basin, where they also cause health problems to humans and animals. 2 The complex includes at least two species that were separated recently based on molecular and morphological evidence: Thaumetopoea pityocampa in the west and Thaumetopoea wilkinsoni in the east of the Mediterranean Basin. 3 Individuals from two populations, selected as representative of Th. pityocampa and Th. wilkinsoni, were used to test whether hybridization is possible under controlled conditions. 4 The hybrid offspring showed intermediate morphological and performance traits, whereas heterosis for pupal weight was detected in one of the hybrid lines. The genetic analysis confirmed the crosses. 5 Both species have large phenological plasticity and may come into contact at the edge of their range, where they could hybridize. 6 Based on the evidence accumulated so far, it is recommended that the current species designations are maintained, although a deeper study of the trait variability is required, especially in the contact zones.

Winter temperature predicts prolonged diapause in pine processionary moth species across their geographic range

“…Such a difference in duration has been interpreted as a way to optimize the larval development in the next generation (Démolin, 1969; Robinet, Laparie & Rousselet, 2015). The duration of this pupal diapause appears genetically determined, as populations from different elevations or latitudes reared under the same conditions over a few generations maintain their typical phenology (Petrucco-Toffolo et al, 2018). Moths generally emerge in summer, but a variable fraction of the individuals may postpone their emergence and enter a prolonged pupal diapause that may last, as far as we know, up to 9 years in Th.…”

Role of Egg Parasitoids in Controlling the Pine Processionary Moth in the Cedar Forests of Chréa National Park (Algeria)

“…As for the activity of T. embryophagum, it is more important after the host population's peak where its regulatory effect is significant, although the number of parasitized egg masses remains low. Petrucco-Toffolo et al [59] attribute this constraint to the protective scales that hinder the parasitic success. However, the results of Daniel et al [60] have reported an abundance of this species in Italy.…”

Response of the egg parasitoids of the pine processionary moth to host density and forest cover at the southern edge of the range

“…First, mean realized fecundity of the host is also lower at the southern edge of the range than at higher latitudes, likely because lower plant quality for larvae associated with hot and dry conditions (Pimentel et al ., 2010); this results in a reduced availability of eggs per egg batch, which may limit the access of the parasitoids to the resources (Mills & Getz, 1996). Second, egg batches from the southern populations of the pine processionary moth are characterized by a different type of scales covering the eggs (Petrucco‐Toffolo et al ., 2018), which may negatively affect the activity of the egg parasitoids that are known to respond to the quality of the eggs (Zovi et al ., 2008; Uemura et al ., 2019). Third, the climate at the southern edge of the range can make it difficult for parasitoids to exploit the resources, because of a bad synchronization between parasitoid emergence and moth oviposition (Auger‐Rozenberg et al ., 2015) or because of a higher probability to be exposed to excessively high temperatures.…”