Background The mitochondrial genome (mitogenome) has been extensively used for phylogenetic and evolutionary analysis in Diptera, but the study of mitogenome is still scarce in the family Chironomidae. Methods Here, the first complete mitochondrial genomes of four Chironomid species representing Diamesinae, Orthocladiinae, Prodiamesinae and Tanypodinae are presented. Coupled with published mitogenomes of two, a comparative mitochondrial genomic analysis between six subfamilies of Chironomidae was carried out. Results Mitogenomes of Chironomidae are conserved in structure, each contains 37 typical genes and a control region, and all genes arrange the same gene order as the ancestral insect mitogenome. Nucleotide composition is highly biased, the control region displayed the highest A + T content. All protein coding genes are under purifying selection, and the ATP8 evolves at the fastest rate. In addition, the phylogenetic analysis covering six subfamilies within Chironomidae was conducted. The monophyly of Chironomidae is strongly supported. However, the topology of six subfamilies based on mitogenomes in this study is inconsistent with previous morphological and molecular studies. This may be due to the high mutation rate of the mitochondrial genetic markers within Chironomidae. Our results indicate that mitogenomes showed poor signals in phylogenetic reconstructions at the subfamily level of Chironomidae.

The genus Potamometra Bianchi, 1896 represents big rheophilic semi‐aquatic bugs that typically inhabit middle‐altitude mountainous streams. Here, we integrated molecular and morphological data for delimiting species boundaries and understanding the evolutionary history of the genus Potamometra. Twenty‐seven complete mitochondrial genomes of Potamometra were sequenced, with samples representing most of the known geographically distributed locations around the Sichuan Basin. The results of different species delimitation methods (ABGD, bPTP, GMYC and BPP) based on the monolocus or multilocus data strongly supported the existence of two cryptic new species (Potamometra anderseni Zheng, Ye & Bu, sp. nov. and Potamometra zhengi Zheng, Ye & Bu, sp. nov.) although more entities were found in the tree‐based delimitation methods. The two new species were successfully validated using morphological characters within a detailed taxonomic framework. Phylogenetic analyses supported the reciprocal monophyly of the seven highly node‐supported clades, which were matched with the five known species and two new taxa. A novel gene arrangement pattern that two trnF (trnF1 and trnF2) genes separated by an intergenic spacer (IGS) were found in all the species except the sister group of Potamometra berezowskii Bianchi, 1896 and Potamometra linnavuorii Chen, Nieser & Bu, 2016. This gene rearrangement event could be explained by the tandem duplication and random loss (TDRL) model. Our study emphasized that the combination of molecular sequence data, morphological characters and mitochondrial structural information could improve the accuracy of species delimitation.

Aim: Local environmental selection and lineage admixture have long been accepted as important adaptive mechanisms in adjusting widespread taxa to new environments.We studied a pond skater, Gerris latiabdominis, to explore the relative roles played by these two mechanisms in its process of adaptation to heterogeneous landscapes. Location: East Asia.Taxon: Gerris latiabdominis Miyamoto, 1958.Methods: Mitochondrial (COI, COII) and nuclear (ddRAD-seq) markers were sequenced from 202 individuals. Phylogenetic and phylogeographical analyses were conducted to reveal the population genetic structure. The demographical history was simulated by approximate Bayesian computation (ABC). The single-nucleotide polymorphisms (SNPs) that may have been subjected to natural divergent selection among the populations were assessed, and the recent migration rates were estimated. Finally, shifts in suitable habitat from the last interglacial (LIG) to the present were predicted through ecological niche modelling (ENM). Results:We found population structures inferred from both mitochondrial and nuclear genomes to be almost coincident and to correspond to temporal or spatial heterogeneity. The early Pliocene splitting event between the northern (NO) and southeastern (SE) groups is consistent with the 'arid belt hypothesis', followed by local environmental selection. Approximate Bayesian computation and gene flow estimation strongly suggested that the southwestern (SW) groups originated from a lineage admixture event between the SE and western (WE) groups and subsequently underwent ongoing gene flow from the SE group during the Pleistocene. The mitonuclear discordance pattern in the SW group was probably due to the ancient mitochondrial differentiation. Main conclusion:Our results suggest that both local environmental selection and lineage admixture acted as significant mechanisms of G. latiabdominis adaptation to | 1155 YE Et al. B I OS K E TCHZhen Ye is a researcher at College of Life Sciences, Nankai University. His research interests are phylogeography, speciation and niche model building of aquatic insects.

Holocene climate warming has dramatically altered biological diversity and distributions. Recent human-induced emissions of greenhouse gases will exacerbate global warming and thus induce threats to cold-adapted taxa. However, the impacts of this major climate change on transcontinental temperate species are still poorly understood. Here, we generated extensive genomic datasets for a water strider, Aquarius paludum, which was sampled across its entire distribution in Eurasia and used these datasets in combination with ecological niche modeling (ENM) to elucidate the influence of the Holocene and future climate warming on its population structure and demographic history. We found that A. paludum consisted of two phylogeographic lineages that diverged in the middle Pleistocene, which resulted in a “west–east component” genetic pattern that was probably triggered by Central Asia-Mongoxin aridification and Pleistocene glaciations. The diverged western and eastern lineages had a second contact in the Holocene, which shaped a temporary hybrid zone located at the boundary of the arid–semiarid regions of China. Future predictions detected a potentially novel northern corridor to connect the western and eastern populations, indicating west–east gene flow would possibly continue to intensify under future warming climate conditions. Further integrating phylogeographic and ENM analyses of multiple Eurasian temperate taxa based on published studies reinforced our findings on the “west–east component” genetic pattern and the predicted future northern corridor for A. paludum. Our study provided a detailed paradigm from a phylogeographic perspective of how transcontinental temperate species differ from cold-adapted taxa in their response to climate warming.

Members of the genus Leptocorisa have for long been known as major pests of rice in the East region (China, 2009) and most Leptocorisa species feed on rice, with some species seriously damaged pest in southern China and adjoining countries (Ahmad, 1965;Hsiao et al., 1977;Litsinger et al., 2015). Rice seed bugs are one of the few pests that feed directly on developing rice spikelets in the field (Litsinger et al., 2015). It is reported that adults and nymphs suck out the developing rice grains at the

BACKGROUND Correct identification together with information on distribution range, geographical origin and evolutionary history are the necessary basis for the management and control of invasive species. The bean bug Megacopta cribraria is a crucial agricultural pest of soybean. Recently, M. cribraria has invaded the United States and spread rapidly, causing severe reductions in soybean yields. However, the species boundary and phylogeographical pattern of this invasive bean bug are still unclear. RESULTS The results of different species delimitation methods (Automatic Barcode Gap Discovery, Assemble Species by Automatic Partitioning, Bayesian Poisson Tree Processes and Bayesian Phylogenetics and Phylogeography) strongly demonstrated that M. cribraria and Megacopta punctatissima represent the same species. M. punctatissima should not be considered a distinct species but rather a variety of M. cribraria. Phylogenetic analyses revealed three well‐supported clades (Southeast Asia [SEA], East Asia continent [EAC] and Japan [JA]) with distinct geographical structures in the M. cribraria–M. punctatissima complex. The SEA clade was at the base of the phylogenetic tree, and the sister relationship between the EAC clade and JA clade was strongly supported. The split between the EAC clade and JA clade occurred at approximately 0.71 Ma, corresponding to the submergence period of the East China Sea land bridge. CONCLUSION This study clarified the species boundary between M. cribraria and its closely related species and revealed the phylogeographical pattern and evolutionary history of M. cribraria. The species delimitation and phylogeography results achieved in this study could provide new insights into the monitoring and management of this agricultural pest. © 2022 Society of Chemical Industry.

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