Reproductive Patterns Drive the Gene Flow and Spatial Dispersal of Euschistus heros (Hemiptera: Pentatomidae)

Ecological zoning of Euschistus heros in Brazil based on the net reproductive rate at different temperatures and relative-humidity levels

The Neotropical brown stink bug, Euschistus heros (Fabricius, 1798) (Hemiptera: Pentatomidae), is one of the major insect pests in soybean crops, causing severe damage; however, some aspects of its biology that are essential for management remain unknown. To aid in the management of E. heros, the present study investigated the fertility life table of this species at 7 temperatures (18, 20, 22, 25, 28, 30, and 32 ± 1 °C) and 4 relative-humidity levels (30, 50, 70, and 90 ± 10%). Based on the net reproductive rate, R0, we developed an ecological zoning for this pest in Brazil, to identify climatically favorable areas for population growth. Our results indicated that the most favorable range is between 25 and 28 °C and above 70% RH. The ecological zoning indicated that farmers should be more concerned in the northern and Midwest regions, which include the state of Mato Grosso, the largest soybean and corn producer in Brazil. These results provide valuable information, indicating the hotspots most likely to be attacked by the Neotropical brown stink bug.

The genome sequence of the Neotropical brown stink bug, Euschistus heros provides insights into population structure, demographic history and signatures of adaptation

The Neotropical brown stink bug, Euschistus heros, is a major pest of soybean in South America. The importance of E. heros as a pest has grown significantly in recent times due to increases in its abundance and range, and the evolution of insecticide resistance. Recent work has begun to examine the genetic diversity, population structure, and genetic mechanisms of insecticide resistance in E. heros. However, to date, investigation of these topics has been hampered by a lack of genomic resources for this species. Here we address this need by assembling a high-quality draft genome for E. heros. We used a combination of short and long read sequencing to assemble an E. heros genome of 1.4 Gb comprising 906 contigs with a contig N50 of 3.5 MB. We leveraged this new genomic resource, in combination with genotyping by sequencing, to explore genetic diversity in populations of this species in Brazil and identify genetic loci in the genome which are under selection. Our genome-wide analyses, confirm that there are two populations of E. heros co-occurring in different geographical regions in Brazil, and that, in certain regions of the country these populations are hybridizing. We identify several regions of the genome as under selection, including markers associated with putative insecticide resistance genes. Taken together, the new genomic resources generated in this study will accelerate research into fundamental aspects of stinkbug biology and applied aspects relating to the sustainable control of a highly damaging crop pest.

Revisiting Stål's thoughts: formalizing the ictericus group in Euschistus (Euschistus) (Hemiptera: Heteroptera: Pentatomidae)

Euschistus Dallas is distributed throughout the Western Hemisphere and is composed of 67 species in three subgenera: Euschistomorphus Jensen-Haarup, Lycipta Stål, and the nominate subgenus. Euschistus (Euschistus) includes several economically important species. Due to the lack of a phylogenetic analysis for the subgenus Euschistus, its groupings are based primarily on male genitalia. In this paper, the following Nearctic taxa that were first grouped together by Stål (1872), namely E. ictericus (Linnaeus), E. variolarius (Palisot de Beauvois), E. servus servus (Say), E. servus euschistoides (Vollenhoven), and E. tristigmus tristigmus (Say), are reviewed and redescribed. Several other similar, and probably related, taxa are also included in this study: E. tristigmus luridus (Dallas), E. inflatus Van Duzee, and E. latimarginatus Zimmer. Morphological patterns pertaining to the internal and external male and female genitalia allowed us to formalize the ictericus group to include the above-mentioned species (except E. tristigmus). The morphological overlap between the subspecies and sympatric areas of distribution have led us to consider E. servus euschistoides as a junior synonym of E. servus servus, and to corroborate the synonymy first proposed by Uhler (1861) of E. tristigmus luridus under E. tristigmus tristigmus.