Identification of winter moth (Operophtera brumata) refugia in North Africa and the Italian Peninsula during the last glacial maximum

Abstract

Numerous studies have shown that the genetic diversity of species inhabiting temperate regions has been shaped by changes in their distributions during the Quaternary climatic oscillations. For some species, the genetic distinctness of isolated populations is maintained during secondary contact, while for others, admixture is frequently observed. For the winter moth (Operophtera brumata), an important defoliator of oak forests across Europe and northern Africa, we previously determined that contemporary populations correspond to genetic diversity obtained during the last glacial maximum (LGM) through the use of refugia in the Iberian and Aegean peninsulas, and to a lesser extent the Caucasus region. Missing from this sampling were populations from the Italian peninsula and from North Africa, both regions known to have played important roles as glacial refugia for other species. Therefore, we genotyped field‐collected winter moth individuals from southern Italy and northwestern Tunisia—the latter a region where severe oak forest defoliation by winter moth has recently been reported—using polymorphic microsatellite. We reconstructed the genetic relationships of these populations in comparison to moths previously sampled from the Iberian and Aegean peninsulas, the Caucasus region, and western Europe using genetic distance, Bayesian clustering, and approximate Bayesian computation (ABC) methods. Our results indicate that both the southern Italian and the Tunisian populations are genetically distinct from other sampled populations, and likely originated in their respective refugium during the LGM after diverging from a population that eventually settled in the Iberian refugium. These suggest that winter moth populations persisted in at least five Mediterranean LGM refugia. Finally, we comment that outbreaks by winter moth in northwestern Tunisia are not the result of a recent introduction of a nonnative species, but rather are most likely due to land use or environmental changes.

Predicting the invasion range for a highly polyphagous and widespread forest herbivore

“…However, the lack of predicted presence in these areas could have arisen simply from inadequate sampling in that region. Winter moth was recently reported from Tunisia (Mannai et al 2015), and genetic analyses suggest this population is native to the region (Andersen et al 2019b). Andersen et al (2019b) also reported winter moth occurrence in southern Spain and Italy.…”

“…Winter moth was recently reported from Tunisia (Mannai et al 2015), and genetic analyses suggest this population is native to the region (Andersen et al 2019b). Andersen et al (2019b) also reported winter moth occurrence in southern Spain and Italy. Because dates of these observations fall outside of the range of dates that were used for the climate data (1970-2010), they were not used in our analysis, though their inclusion could further change the predicted distribution of winter moth to include additional Mediterranean locations.…”

Northern Fennoscandia via the British Isles: evidence for a novel post-glacial recolonization route by winter moth (Operophtera brumata)

“…Five-hundred and fifty-two individual winter moths were included after removing individuals from which fewer than 20 of 24 polymorphic microsatellites were amplified as part of this study. To that dataset, 249 individuals genotyped in Andersen et al (2017Andersen et al ( , 2019 were added to increase the geographic sampling of winter moth populations.…”

“…Under this approach, dataset(s) are simulated based on scenarios that include several likely regions of origin, and summary statistics from the sample dataset are compared to those from the simulated datasets to determine the most likely scenario. The approach can be used to examine the evolutionary histories of native organisms that have become pests by exploring whether outbreaks are the result of natural range expansion or introductions of novel (and potentially more virulent) populations (e.g., Wei et al 2015, Andersen et al 2019. However, this approach is not without its limitations.…”

“…Previous studies have determined that the genetic structure of winter moth populations in Continental Europe was largely shaped by their use of glacial refugia during the last glacial maximum (LGM) (Andersen et al 2017(Andersen et al , 2019. One of these studies (Andersen et al 2019) determined that outbreaking populations of winter moth in North Africa represented a native population that had likely been present in the region since at least the LGM. As such, the authors proposed that contemporary human-mediated disturbances and/or climate change might be responsible for the recent outbreak.…”