Evaluating the mitochondrial genomic diversity, global distribution and niche overlap of two invasive Phthorimaea species

This study sought to evaluate the genetic diversity of two invasive Phthorimaea species (Phthorimaea operculella Zeller and Phthorimaea absoluta Meyrick), and identify potential niche overlap of both species. The complete mitogenomes of P. operculella and P. absoluta were sequenced and compared. Furthermore, the diversity within the family Gelechiidae was assessed. Subsequently, two species distribution models (MaxEnt and BIOCLIM) were used to identify niche overlaps of both species globally. The complete mitogenomes of both species were similar in size and structure, with a pairwise identity of 92.3%. The models showed a niche overlap of both species and revealed areas of marginal to high suitability for both pests in countries where they have not been reported. Therefore, these results present a compelling case for a deeper genetic and ecological investigation of the Gelechiidae family for taxonomic harmonization, an early warning for surveillance, stricter phytosanitary considerations and preventive management against the spread of the pests.

Evolutionary genomics of three agricultural pest moths reveals rapid evolution of host adaptation and immune-related genes

BACKGROUND

Understanding the genotype of pest species provides an important baseline for designing integrated pest management (IPM) strategies. Recently developed long-read sequence technologies make it possible to compare genomic features of nonmodel pest species to disclose the evolutionary path underlying the pest species profiles. Here we sequenced and assembled genomes for 3 agricultural pest gelechiid moths: Phthorimaea absoluta (tomato leafminer), Keiferia lycopersicella (tomato pinworm), and Scrobipalpa atriplicella (goosefoot groundling moth). We also compared genomes of tomato leafminer and tomato pinworm with published genomes of Phthorimaea operculella and Pectinophora gossypiella to investigate the gene family evolution related to the pest species profiles.

RESULTS

We found that the 3 solanaceous feeding species, P. absoluta, K. lycopersicella, and P. operculella, are clustered together. Gene family evolution analyses with the 4 species show clear gene family expansions on host plant-associated genes for the 3 solanaceous feeding species. These genes are involved in host compound sensing (e.g., gustatory receptors), detoxification (e.g., ABC transporter C family, cytochrome P450, glucose-methanol-choline oxidoreductase, insect cuticle proteins, and UDP-glucuronosyl), and digestion (e.g., serine proteases and peptidase family S1). A gene ontology enrichment analysis of rapid evolving genes also suggests enriched functions in host sensing and immunity.

CONCLUSIONS

Our results of family evolution analyses indicate that host plant adaptation and pathogen defense could be important drivers in species diversification among gelechiid moths.

Complete mitogenome of Phthorimaea operculella (Lepidoptera: Gelechioidea: Gelechiidae)

In this research, the complete mitochondrial genome (mitogenome) of Phthorimaea operculella was sequenced and annotated. The mitogenome of P. operculella is 15,269 bp in length and contains 13 protein-coding genes (PCGs), 22 transfer RNA (tRNA) genes, 2 ribosome RNA (12s and 16srRNA) genes and 1 control region. In addition, we used Endoclita signifier as the outgroup to analyze phylogenetic relationship, and the phylogenetic tree showed the sister relationship between P. operculella and Tuta absoluta.

Revision of the genus Megacraspedus Zeller, 1839, a challenging taxonomic tightrope of species delimitation (Lepidoptera, Gelechiidae)

The taxonomy of the Palearctic genus Megacraspedus Zeller, 1839 (Lepidoptera, Gelechiidae) is revised, based on external morphology, genitalia and DNA barcodes. An integrative taxonomic approach supports the existence of 85 species which are arranged in 24 species groups (disputed taxa from other faunal regions are discussed). Morphology of all species is described and figured in detail. For 35 species both sexes are described; for 46 species only the male sex is reported, in one species the male is unknown, whereas in three species the female adult and/or genitalia morphology could not be analysed due to lack of material.

DNA barcode sequences of the COI barcode fragment with > 500 bp were obtained from 264 specimens representing 62 species or about three-quarters of the species. Species delimitation is particularly difficult in a few widely distributed species with high and allegedly intraspecific DNA barcode divergence of nearly 14%, and with up to 23 BINs in a single species. Deep intraspecific or geographical splits in DNA barcode are frequently not supported by morphology, thus indicating a complex phylogeographic history or other unresolved molecular problems.

The following 44 new species (22 of them from Europe) are described: Megacraspedusbengtssonisp. n. (Spain), M.junnilainenisp. n. (Turkey), M.similellussp. n. (Bulgaria, Romania, Turkey), M.golestanicussp. n. (Iran), M.tokarisp. n. (Croatia), M.nelisp. n. (France, Italy), M.faunierensissp. n. (Italy), M.gredosensissp. n. (Spain), M.bidentatussp. n. (Spain), M.fuscussp. n. (Spain), M.trineaesp. n. (Portugal, Spain), M.skouisp. n. (Spain), M.spinophallussp. n. (Spain), M.occidentellussp. n. (Portugal), M.granadensissp. n. (Spain), M.heckfordisp. n. (Spain), M.tenuiuncussp. n. (France, Spain), M.devoratorsp. n. (Bulgaria, Romania), M.brachypterissp. n. (Albania, Greece, Macedonia, Montenegro), M.barcodiellussp. n. (Macedonia), M.sumpichisp. n. (Spain), M.tabellisp. n. (Morocco), M.gallicussp. n. (France, Spain), M.libycussp. n. (Libya, Morocco), M.latiuncussp. n. (Kazahkstan), M.kazakhstanicussp. n. (Kazahkstan), M.knudlarsenisp. n. (Spain), M.tenuignathossp. n. (Morocco), M.glaberipalpussp. n. (Morocco), M.nupponenisp. n. (Russia), M.pototskiisp. n. (Kyrgyzstan), M.feminensissp. n. (Kazakhstan), M.kirgizicussp. n. (Afghanistan, Kazakhstan, Kyrgyzstan), M.ibericussp. n. (Portugal, Spain), M.steinerisp. n. (Morocco), M.gibeauxisp. n. (Algeria, Tunisia), M.multipunctellussp. n. (Turkey), M.teriolensissp. n. (Croatia, Greece, Italy, Slovenia), M.korabicussp. n. (Macedonia), M.skuleisp. n. (Spain), M.longivalvellussp. n. (Morocco), M.peslierisp. n. (France, Spain), M.pacificussp. n. (Afghanistan), and M.armatophallussp. n. (Afghanistan). Nevadia Caradja, 1920, syn. n. (homonym), Cauloecista Dumont, 1928, syn. n., Reichardtiella Filipjev, 1931, syn. n., and Vadenia Caradja, 1933, syn. n. are treated as junior synonyms of Megacraspedus. Furthermore the following species are synonymised: M.subdolellus Staudinger, 1859, syn. n., M.tutti Walsingham, 1897, syn. n., and M.grossisquammellus Chrétien, 1925, syn. n. of M.lanceolellus (Zeller, 1850); M.culminicola Le Cerf, 1932, syn. n. of M.homochroa Le Cerf, 1932; M.separatellus (Fischer von Röslerstamm, 1843), syn. n. and M.incertellus Rebel, 1930, syn. n. of M.dolosellus (Zeller, 1839); M.mareotidellus Turati, 1924, syn. n. of M.numidellus (Chrétien, 1915); M.litovalvellus Junnilainen, 2010, syn. n. of M.imparellus (Fischer von Röslerstamm, 1843); M.kaszabianus Povolný, 1982, syn. n. of M.leuca (Filipjev, 1929); M.chretienella (Dumont, 1928), syn. n., M.halfella (Dumont, 1928), syn. n., and M.arnaldi (Turati & Krüger, 1936), syn. n. of M.violacellum (Chrétien, 1915); M.escalerellus Schmidt, 1941, syn. n. of M.squalida Meyrick, 1926. Megacraspedusribbeella (Caradja, 1920), comb. n., M.numidellus (Chrétien, 1915), comb. n., M.albella (Amsel, 1935), comb. n., M.violacellum (Chrétien, 1915), comb. n., and M.grisea (Filipjev, 1931), comb. n. are newly combined in Megacraspedus.

Host-plant location by the Guatemalan potato moth Tecia solanivora is assisted by floral volatiles

Insects locate their host plants using mainly visual and olfactory cues, generally of the exploited plant structure. However, when the resource is difficult to access, it could be beneficial to utilise indirect cues, which indicates the presence of reward (e.g., oviposition site or mate). In the present study, we investigated the host-plant location strategy of the monophagous Guatemalan potato moth Tecia solanivora (Lepidoptera: Gelechiidae). The larva of the moth feed exclusively on potato Solanum spp. (Solanaceae) tubers usually hidden below ground. Using electrophysiological and behavioural tests, we characterised the olfactory cues mediating the attraction of the moth towards their host plant. Odour blends were made to represent different potato structures: tubers, foliage, and flowers. Synthetic blends were created by combining potato-emitted compounds that were antennal active which showed positive dose-response. Attraction to these blends of compounds in relation to the mating status of males and females was tested in dual-choice Y-tube assays. Both males and females, virgin and mated, were attracted to a three-compound blend representing flower odour, while foliage and tuber blends attracted neither sexes. Oviposition bioassays indicated additionally that the floral blend enhances oviposition. We show that potato flower odour might indicate the presence of an oviposition site for the female and possibly an increased mating opportunity for both sexes. Our results provide one of the few examples of the use of floral odour as a reliable indicator of host and probably mating possibility for phytophagous insects exploiting a site spatially separated from the flower.

Complete mitochondrial genome of the pink bollworm Pectinophora gossypiella (Lepidoptera: Gelechiidae)

Pectinophora gossypiella (Lepidoptera: Gelechiidae) is a key pest in many cotton-growing countries of the world. In this study, the complete mitochondrial (mt) genome of the pink bollworm P. gossypiella was determined, which is 15,202 bp in length (GenBank accession number: KM225795) containing 37 typical animal mitochondrial gene and an A + T-rich region. The gene order of P. gossypiella mtDNA was different from the insect ancestral gene order in the translocation of trnM, as shared by previously sequenced lepidopteran mtDNAs. The protein-coding genes (PCGs) have typical mitochondrial start codons ATN, with the exception of COI, Nad5, which uses the start codons CGA, GTT. Eight PCGs stop with complete termination codons (TAA), whereas five PCGs use incomplete stop codon T. All of the tRNA genes had typical cloverleaf secondary structures except for trnS1(AGN), in which the dihydrouridine (DHU) arm did not form a stable stem-loop structure. Like other insects, the control region is located between rrnS and trnM with a length of 309 bp and an A + T content of 94.8%, which is the most AT-rich region and comparatively simple, with little evidence of long tandem repeats, but harbors a conserved structure combining the motif ATAGA and a 18-bp poly-T stretch.

DNA barcoding as a screening tool for cryptic diversity: an example from Caryocolum, with description of a new species (Lepidoptera, Gelechiidae)

We explore the potential value of DNA barcode divergence for species delimitation in the genus Caryocolum Gregor & Povolný, 1954 (Lepidoptera, Gelechiidae), based on data from 44 European species (including 4 subspecies). Low intraspecific divergence of the DNA barcodes of the mtCOI (cytochrome c oxidase 1) gene and/or distinct barcode gaps to the nearest neighbor support species status for all examined nominal taxa. However, in 8 taxa we observed deep splits with a maximum intraspecific barcode divergence beyond a threshold of 3%, thus indicating possible cryptic diversity. The taxonomy of these taxa has to be re-assessed in the future. We investigated one such deep split in Caryocolum amaurella (Hering, 1924) and found it in congruence with yet unrecognized diagnostic morphological characters and specific host-plants. The integrative species delineation leads to the description of Caryocolum crypticumsp. n. from northern Italy, Switzerland and Greece. The new species and the hitherto intermixed closest relative C. amaurella are described in detail and adults and genitalia of both species are illustrated and a lectotype of C. amaurella is designated; a diagnostic comparison of the closely related C. iranicum Huemer, 1989, is added.

Karyotypes of parasitic wasps of the family Eulophidae (Hymenoptera) attacking leaf-mining Lepidoptera (Gracillariidae, Gelechiidae)

Karyotypes of eleven parasitoid species of the family Eulophidae were examined, namely, Chrysocharis laomedon (Walker, 1839) (2n = 10), Chrysocharis sp. aff. laomedon (n = 5, 2n = 10), Chrysocharis sp. aff. albipes (Ashmead, 1904) (2n = 12), Mischotetrastichus petiolatus (Erdös, 1961) (n = 6, 2n = 12), Minotetrastichus frontalis (Nees, 1834) (n = 5, 2n = 10), Cirrospilus pictus (Nees, 1834) (2n = 12), Hyssopus geniculatus (Hartig, 1838) (2n = 16), Sympiesis gordius (Walker, 1839) (2n = 12), S. sericeicornis (Nees, 1834) (2n = 12), Pnigalio agraules (Walker, 1839) (2n = 12 + 0-2B) and Pnigalio gyamiensis Myartseva & Kurashev, 1990 (2n = 12 + 0-6B) reared from Phyllonorycter acerifoliella (Zeller, 1839), Ph. apparella (Herrich-Schäffer, 1855), Ph. issikii (Kumata, 1963) (Gracillariidae) and Chrysoesthia sexguttella (Thunberg, 1794) (Gelechiidae). Chromosome sets of all species except P. agraules and P. gyamiensis were studied for the first time. B chromosomes were detected in the two latter species; in P. gyamiensis, the maximum number of B chromosomes represents the highest value known for parasitic wasps to date.