Integrated Taxonomic Revision of Afrotropical Xyleborinus (Curculionidae: Scolytinae) Reveals High Diversity After Recent Colonization of Madagascar

The ambrosia beetle genus Xyleborinus Reitter, 1913 is particularly species rich in Madagascar where the genus exhibits extraordinary morphological variation not seen elsewhere. This study provides the first detailed molecular phylogeny of the genus based on COI, 28S, and CAD gene fragments. Biogeographical and taxonomic hypotheses were tested for the Afrotropical fauna with a particular focus on the Malagasy radiation. Analyses revealed a single colonization of Madagascar no earlier than 8.5–11.0 Ma, indicating an extraordinary recent radiation on the island which has given rise to at least 32 species. Two recolonization events of the African mainland were strongly supported by the molecular data, with several other intraspecific dispersals to the mainland inferred from species distributions. A taxonomic re-evaluation of all Afrotropical Xyleborinus resulted in several taxonomic changes. We found that morphological differences associated with COI divergence higher than 7% indicated different species. Twelve new species are described: Xyleborinus castriformis Eliassen & Jordal, sp. nov., Xyleborinus clivus Eliassen & Jordal, sp. nov., Xyleborinus concavus Eliassen & Jordal, sp. nov., Xyleborinus coronatus Eliassen & Jordal, sp. nov., Xyleborinus diadematus Eliassen & Jordal, sp. nov., Xyleborinus laevipennis Eliassen & Jordal, sp. nov., Xyleborinus magnispinosus Eliassen & Jordal, sp. nov., Xyleborinus margo Eliassen & Jordal, sp. nov., Xyleborinus ntsoui Eliassen & Jordal, sp. nov., Xyleborinus singularis Eliassen & Jordal, sp. nov., Xyleborinus tuberculatus Eliassen & Jordal, sp. nov., and Xyleborinus turritus Eliassen & Jordal, sp. nov., all from Madagascar. New synonyms are proposed for Xyleborinus aemulus (Wollaston, 1869) [=Xyleborinus spinifer (Eggers, 1920)], Xyleborinus andrewesi (Blandford, 1896) [=Xyleborinus mimosae (Schedl, 1957)], Xyleborinus dentellus (Schedl, 1953) [=Xyleborinus forcipatus (Schedl, 1957)], Xyleborinus octospinosus (Eggers, 1920) [=Xyleborinus mitosomipennis (Schedl, 1953)], and Xyleborinus similans (Eggers, 1940) [=Xyleborinus sclerocaryae (Schedl, 1962)]. Two species were given new status: Xyleborinus profundus (Schedl, 1961) is elevated from subspecies of Xyleborinus aduncus (Schedl, 1961), and Xyleborinus mitosomus (Schedl, 1965) is reinstated from its previous synonymy with Xyleborinus spinosus (Schaufuss, 1891). Xyleborus gracilipennis Schedl 1957 is reverted to its original genus, and a similar status is confirmed for Xyleborus collarti Eggers 1932. The number of taxonomically valid Xyleborinus species in the Afrotropical region is now 47, which includes 3 adventive species. Revised diagnoses for all species and a key for species identification are provided.

The Cadherin Protein Is Not Involved in Susceptibility to Bacillus thuringiensis Cry1Ab or Cry1Fa Toxins in Spodoptera frugiperda

It is well known that insect larval midgut cadherin protein serves as a receptor of Bacillus thuringiensis (Bt) crystal Cry1Ac or Cry1Ab toxins, since structural mutations and downregulation of cad gene expression are linked with resistance to Cry1Ac toxin in several lepidopteran insects. However, the role of Spodoptera frugiperda cadherin protein (SfCad) in the mode of action of Bt toxins remains elusive. Here, we investigated whether SfCad is involved in susceptibility to Cry1Ab or Cry1Fa toxins. In vivo, knockout of the SfCad gene by CRISPR/Cas 9 did not increase tolerance to either of these toxins in S. frugiperda larvae. In vitro cytotoxicity assays demonstrated that cultured insect TnHi5 cells expressing GFP-tagged SfCad did not increase susceptibility to activated Cry1Ab or Cry1Fa toxins. In contrast, expression of another well recognized Cry1A receptor in this cell line, the ABCC2 transporter, increased the toxicity of both Cry1Ab and Cry1Fa toxins, suggesting that SfABCC2 functions as a receptor of these toxins. Finally, we showed that the toxin-binding region of SfCad did not bind to activated Cry1Ab, Cry1Ac, nor Cry1Fa. All these results support that SfCad is not involved in the mode of action of Cry1Ab or Cry1Fa toxins in S. frugiperda.

Epirrita pulchraria (Taylor, 1907) transferred to Malacodea, with notes on the phylogeny and ecology of the tribe Operophterini (Lepidoptera: Geometridae: Larentiinae)

The Nearctic Epirrita pulchraria (Taylor, 1907) was revealed as a sister taxon of the Palaearctic Malacodea regelaria Tengström,1869 in a molecular phylogenetic analysis of the tribe Operophterini. DNA sequence variation in one mitochondrial (COI) and eight nuclear (28S, EF-1α, WGL, GAPDH, RPS5, IDH, MDH, CAD) gene fragments was used in the analysis. Bayesian inference resulted in a well-resolved phylogenetic hypothesis. According to the recovered phylogeny a new combination is proposed: Rachela pulchraria Taylor, 1907 is transferred from Epirrita Hübner, 1808 to Malacodea Tengström, 1869 as Malacodea pulchraria (Taylor, 1907) comb. nov. Larvae of both M. pulchraria and M. regelaria feed on coniferous trees, which distinguishes them from other members of the tribe. Close relatedness of M. pulchraria and M. regelaria is also supported by our study of male genital morphology. Ambiguous phylogenetic affinities of Epirrita viridipurpurescens (Prout, 1937) are discussed.