Origin and taxonomic status of the Palearctic population of the stem borer Sesamia nonagrioides (Lefèbvre) (Lepidoptera: Noctuidae)

Abstract

The major pest of maize in Mediterranean Europe, the stem borer Sesamia nonagrioides (Lefèbvre) (Lepidoptera: Noctuidae), has a fragmented distribution, north and south of the Sahara. The present study aimed: (1) to clarify the uncertain taxonomic status of the Palearctic and sub-Saharan populations which were first considered as different species and later on as subspecies (Sesamia nonagrioides nonagrioides and Sesamia nonagrioides botanephaga) and (2) to investigate the origin of the Palearctic population which extends from Spain to Iran, outside what is considered typical for this mainly tropical genus. We reconstructed the evolutionary history of both populations using one nuclear and two mitochondrial genes. The sub-Saharan taxon was fragmented in two isolated populations (West and East) whose mitochondrial genes were distant by 2.3%. The Palearctic population was included in the East African clade and its genes were close or identical to those of a population from Central Ethiopia, where the species was discovered for the first time. Similarly, in Africa, the alleles of the nuclear gene were distributed mainly in two West and East clades, whereas some Palearctic alleles belonged to the West clade. The Palearctic population originated therefore from East and West Africa and is the progeny of the cross between these two African populations. The main species concepts were in agreement, leading to the conclusion that the three populations are still conspecific. In the surveyed regions, the species therefore does not include two subspecies but three isolated populations. The Palearctic population suffered from severe bottlenecks that resulted in the fixation of one East African mitochondrial genome and the large reduction in its genetic diversity compared to the African populations. The data suggest that natural colonization of the Palearctic region was more plausible than human introduction. The allelic distribution of the Palearctic population was similar to that of species that survived the last glaciation. It is concluded that the African populations expanded during the last interglacial, crossed the Sahara and mixed in North Africa where fixation of the East mitochondrial genome occurred. The species then colonized Europe westward through only one eastern entrance. The coalescent-based estimate of the time to the ancestor of the Palearctic population was 108 000 years, which is consistent with this scenario.

Systematics and biology of Cotesia typhae sp. n. (Hymenoptera, Braconidae, Microgastrinae), a potential biological control agent against the noctuid Mediterranean corn borer, Sesamia nonagrioides

“…The parasitism success of C. typhae in European host populations, assessed in the present work, was initially questioned because European S. nonagrioides are genetically well differentiated from African populations (Moyal et al 2011), and they may have evolved immune responses adapted to European parasitoids and pathogens. However, the variation of reproductive success of C. typhae in the different host populations did not depend on the continental origin of the host, because C. typhae performed globally better in the Italian population than in the French and the Kenyan ones.…”

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

“…For example, in Europe, many studies have shown how the persistence of populations in separate glacial refugia (e.g., the Iberian, Italian, and Balkan peninsulas, the Caucasus region, North Africa, and microrefugia in the Alps) during the Quaternary climatic oscillations promoted genetic diversity in contemporary populations (Andersen, Havill, Caccone, & Elkinton, ; Habel, Lens, Rodder, & Schmitt, ; Huck, Buedel, & Schmitt, ; Niedzialkowska et al, ; von Reumont, Struwe, Schwarzer, & Misof, ; Rofes et al, ; Schmitt, ; Schmitt & Müller, ; Sim, Hall, Jex, Hegel, & Coltman, ; Stolting et al, ; Torroni et al, ). For outbreaking species, reconstructing the biogeographical history of the species can help to determine the factors that might be promoting their outbreak (e.g., Moyal et al, ; Song et al, ; Zhu et al, ).…”

Phylogeography of Sesamia nonagrioides (Lepidoptera: Noctuidae) in Iran inferred from mitochondrial DNA

“…This analysis separated the sequences into a network of closely related haplotype groups (with connected branches with less than 95% probability). Population diversity indices including haplotype diversity (h), nucleotide diversity (π) (Nei & Miller 1990) and F st for each population of S. nonagrioides were calculated using Arlequin 3.5.1.2 (Excoffier & Lischer 2010). The results of analyses of molecular variation (AMOVA) were visualized using a script of R statistic program integrated in the Arlequin.…”