Aim Palaeoclimatic and palaeogeological events have been identified as two main factors that influence the genetic structuring of extant organisms. We studied a montane stream‐dwelling insect, Metrocoris sichuanensis, to explore the relative roles played by these two factors in population genetic connectivity. Location Sichuan Basin, China. Methods Mitochondrial (COI, COII, Cytb, 16S) and nuclear (EF‐1α, ITS1) markers were sequenced from 208 individuals. Suitable habitat shifts from the Last Glacial Maximum (LGM) to the present were predicted through fine‐tuned ecological niche modelling (ENM). Phylogenetic and phylogeographical analyses were conducted to reveal the population genetic structure. Intraspecific divergence and expansion times were estimated using beast. Finally, the least cost path (LCP) method coupled with migrate analysis was used to identify possible dispersal corridors and estimate the asymmetric gene flow. Results Our ENM results suggested that population habitat connectivity did not change both in the LGM and current conditions. Whole haplotypes were separated into four highly supported clades/haplogroups that exhibited strong geographical structure. The splitting events between the four lineages likely date back to the Early Pleistocene. Bayesian skyline plot (BSP) indicated a moderate demographic growth from the LGM to the present. A putative dispersal corridor was detected along the Longmen Mountains thrust belt, with unidirectional gene flow from north to south. Main conclusion Our findings support the geographical isolation of the genetic lineages and a deep early Pleistocene split in M. sichuanensis. Landscape connectivity analysis incorporating the genetic data and the ENM prediction revealed that population genetic connectivity was strongly associated with stable climatic habitats shaped by complex topography. The drainage system might have assisted the rapid movement of populations along the Longmen Mountains thrust belt. A strategy for researching the population genetic connectivity of narrow endemics, such as M. sichuanensis, in global biodiversity hotspots is proposed and discussed in this paper.
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.
Riptortus pedestris (Hemiptera: Alydidae) is a major agricultural pest in East Asia that causes considerable economic losses to the soybean crop each year. However, the molecular mechanisms governing the growth and development of R. pedestris have not been fully elucidated. In this study, the Illumina HiSeq6000 platform was employed to perform de novo transcriptome assembly and determine the gene expression profiles of this species across all developmental stages, including eggs, first-, second-, third-, fourth-, and fifth-instar nymphs, and adults. In this study, a total of 60,058 unigenes were assembled from numerous raw reads, exhibiting an N50 length of 2126 bp and an average length of 1199 bp, and the unigenes were annotated and classified with various databases, such as the Kyoto Encyclopedia of Genes and Genomes (KEGG), Clusters of Orthologous Groups (COG), and Gene Ontology (GO). Furthermore, various numbers of differentially expressed genes (DEGs) were calculated through pairwise comparisons of all life stages, and some of these DEGs were associated with immunity, metabolism, and development by GO and KEGG enrichment. In addition, 35,158 simple sequence repeats (SSRs) and 715,604 potential single nucleotide polymorphisms (SNPs) were identified from the seven transcriptome libraries of R. pedestris. Finally, we identified and summarized ten wing formation-related signaling pathways, and the molecular properties and expression levels of five wing development-related genes were analyzed using quantitative real-time PCR for all developmental stages of R. pedestris. Taken together, the results of this study may establish a foundation for future research investigating developmental processes and wing formation in hemimetabolous insects and may provide valuable data for pest control efforts attempting to reduce the economic damage caused by this pest.
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