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Studying the evolution of genomic divergence between lineages is a topical issue in evolutionary biology. However, the evolutionary forces that shape the heterogeneous divergence of the genomic landscape are still poorly understood. Here, two wind‐pollinated sister‐species (Ostrya japonica and O. chinensis) are used to explore what these potential forces might be. A total of 40 individuals from 16 populations across their main distribution areas in China were sampled for genome‐wide resequencing. Population demography analyses revealed that these two sister‐species diverged at 3.06–4.43 Mya. Both population contraction and increased gene flow were detected during glacial periods, suggesting secondary contact at those times. All three parameters (DXY, π, and ρ) decreased in those regions showing high levels of differentiation (FST). These findings indicate that linked selection and recombination played a key role in the genomic heterogeneous differentiation between the two Ostrya species. Genotype–environment association analyses showed that precipitation was the most important ecological factor for speciation. Such environmentally related genes and positive selection genes may have contributed to local adaptation and the maintenance of species boundaries. [ABSTRACT FROM AUTHOR]

Species delimitation through which infers species boundaries is emerging as a major work in modern systematics. Hop-hornbeam species in Ostrya (Betulaceae) are well known for their hard and heavy woods. Five species were described in China and their interspecific delimitations remain unclear. In this study, we firstly explored their distributions in all recorded field sites distributed in China. We then selected 110 samples from 22 natural populations of five species from this genus and one type specimen of O. yunnanensis, for molecular barcoding analyses. We sequenced four chloroplast (cp) DNA fragments ( trnH-psbA, trnL-trnF, rps16, and trnG) and the nuclear internal transcribed spacer ( ITS) region for all samples. Sequence variations of Ostrya from four cp DNA fragments identified three groups that showed no correspondence to any morphological delimitation because of the incomplete lineage sorting and/or possible interspecific introgression in the history. However, phylogenetic analyses of ITS sequence variations discerned four species, O. japonica, O. rehderiana, O. trichocarpa, and O. multinervis while O. yunnanensis nested within O. multinervis. Morphological clustering also discerned four species and showed the complete consistency with molecular evidence. Moreover, our phylogenetic analyses-based ITS sequence variations suggested that O. trichocarpa comprised an isolated lineage different from the other Eurasian ones. Based on these results, hop-hornbeams in China should be treated as four separate species. Our results further highlight the importance of ITS sequence variations in delimitating and discerning the closely related species in plants. [ABSTRACT FROM AUTHOR]

This paper provides taxonomic and biological data on one new and one newly recorded species of Coptotriche Walsingham and one new and one newly recorded species of Tischeria Zeller from Japan. Coptotriche symplocosella Kobayashi & Hirowatari, sp. n. (host Symplocos lucida, Symplocaceae), and Tischeria kumatai Sato, Kobayashi & Hirowatari, sp. n. (host Tilia japonica, Malvaceae) are described. The pupal morphology of C. symplocosella is illustrated with scanning electron micrographs. Coptotriche minuta Diškus & Stonis, 2014 and Tischeria relictana Ermolaev, 1986 are newly recorded from Japan. The female, hostplants (Carpinus, Corylus, and Ostrya species), and immature stages of C. minuta and the adult features, female, and hostplants (Betula species) of T. relictana are described with photographs and drawings for the first time. Mine types and characters of Japanese Tischeriidae are reviewed with photographs. [ABSTRACT FROM AUTHOR]

Background: The genus Ostrya (Betulaceae) contains eight species and four of them are distributed in China. However, studies based on limited informative sites of several chloroplast markers failed to resolve interspecific delimitation and relationships among the four Chinese species. In this study, we aimed to use the whole chloroplast genomes to address these two issues. Results: We assembled and annotated 33 complete chloroplast genomes (plastomes) of the four Chinese species, representing 17 populations across most of their geographical distributions. Each species contained samples of several individuals that cover most of geographic distributions of the species. All plastomes are highly conserved in genome structure and gene order, with a total length of 158–159 kb and 122 genes. Phylogenetic analyses of whole plastomes, non-coding regions and protein-coding genes produced almost the same topological relationships. In contrast to the well-delimitated species boundary inferred from the nuclear ITS sequence variations, three of the four species are non-monophyletic in the plastome trees, which is consistent with previous studies based on a few chloroplast markers. Conclusions: The high incongruence between the ITS and plastome trees may suggest the widespread occurrences of hybrid introgression and incomplete lineage sorting during the divergence of these species. In addition, the plastomes with more informative sites compared with a few chloroplast markers still failed to resolve the phylogenetic relationships of the four species, and further studies involving population genomic data may be needed to better understand their evolutionary histories. [ABSTRACT FROM AUTHOR]