Late Pliocene vegetation and climate of Zhangcun region,Shanxi, North China

To understand the Neogene climatic changes in eastern Asia and evaluate the intercontinental climatic differences, we have quantitatively reconstructed the vegetation successions and climatic changes in the late Pliocene Zhangcun area based on the palynological data and explored the regional climatic differences between central Europe and eastern Asia. The late Pliocene palynological assemblage of Zhangcun, Shanxi was composed of 63 palynomorphs, belonging to 50 families, covering angiosperms (90.2%), gymnosperms (9.7%), ferns (0.09%), and other elements (0.02%). Four periods of vegetation succession over time were recognized. In period 1, a needle‐ and broad‐leaved mixed forest prevailed with a cool and dry climate. Period 2 was characterized by an expansion of forest with a warmer and wetter climate. The number of conifers increased and that of herbs decreased in period 3, and the climate became cool and dry. In period 4, the forest was dominated by conifers and reflecting a cooler climate. The data of seven climatic parameters in general and four periods estimated by the Coexistence Approach suggested that (1) The late Pliocene temperatures and precipitations were higher than today. (2) The Neogene climate of both Central Europe and North China exhibited a general cooling and drying trend although the mean annual temperature dropped by ca. 1 °C in North China, vs. ca. 7 °C in Central Europe from the middle Miocene to the late Pliocene. (3) The decline of the mean maximum monthly precipitation might signal a weakening of the summer monsoon. (4) The decline of both the mean coldest monthly temperature and the mean minimum monthly precipitation might be linked to the strengthening of the winter monsoon in eastern Asia. (5) The rapid uplift of the Tibetan Plateau strengthened the climatic cooling and drying during the late Pliocene of the Zhangcun region.     

An ultrastructural investigation of the testes and spermiogenesis in Myobia murismusculi (Schrank) (Acari,Actinedida: Myobiidae)

Summary

The stages of spermiogenesis in Myobia murismusculi were investigated on the basis of ultrastructural analysis of both the testes and the female organs: receptaculum seminis and seminal duct. The walls of the testes consist of a thin epithelial layer. Germ and secretory cells lie free in the lumen of the testes. In the early stages of differentiation, both cell types represent clusters of sister cells joined by intercellular bridges. Each secretory cell contains prominent RER and Golgi complex, which produce single dense granule. Growing gradually the granule fills the whole volume of the cell's cytoplasm. Mature secretory cells disintegrate and the secretory product discharges into the testicular lumen. The germ cells are represented by the early, the intermediate and the late spermatids as well as the immature sperm (prospermia). Neither spermatogonia nor meiotic figures were observed in adult males. As spermiogenesis starts, numerous narrow invaginations of the outer membrane (peripheral channels) develop on the cell surface. They form a wide circumferential network connected to pinocytotic vesicles. Owing to the secretory activity of the Golgi complex, a large acrosomal granule is formed in the early spermatids. A long acrosomal filament runs along the intranuclear canal. Nuclear material condenses and forms two spherical bodies of different electron density. The lighter one can be observed until the stage of the late spermatids, when the nuclear envelope almost completely disappears. The electron-dense nuclear body transforms into a definite chromatin body, which is observed in the mature sperm as a cup-shaped structure. The late spermatids are characterized by the presence of a large electronlucent vacuole, which seems to be unique for the process of spermiogenesis in Actinedida. After the spermia enter the female genital tract, the peripheral channels disappear as well as the vacuole. The cells form long amoeboid arms with a special microtubular layer underneath the plasma membrane. The chromatin body is encircled by a large acrosomal granule of complex shape provided by long extensions running deep into the cytoplasm. The cytoplasm contains no organelles except for a group of unmodified mitochondria in the post-nuclear region. The main characteristics of the Myobia spermiogenesis are discussed with regard to other actinedid mites.     

Morphological and embryological characters of three middle Asian Allium L. species (Alliaceae)

Morphological and embryological characters of the xerophilous species Allium crystallinum Vved., A. filidens Regel, and A. fritschii Khassanov et Yengalycheva (Allium subg. Allium) were compared. The morphology of flowers, the rate of development of male and female embryonic structures and correlations with bud dimensions were studied. The overall similarity of the embryonic processes and structures underlines the close taxonomic relationship of the species investigated as concluded from morphological and anatomical characters. However, several differences in embryological characters between A. filidens and A. fritschii confirm the separation of the latter species at species level.     

Effects of the insecticide pyrethroid ii in the ames test,and onhordeum vulgare andvicia faba

The insecticide pyrethroid II, representing synthetic pyrethroids of the second generation, was not found to be mutagenic inSalmonella typhimurium strains TA1535, TA100, TA1538, TA98 and TA97. High concentrations of the tested insecticide inhibited the germination and length of roots of germinating seeds, the height of plants cultivatedin vitro, and slightly increased the frequency of aberrant anaphases and telophase in root-tips ofVicia faba andHordeum vulgare.     

Effects of temperature and salinity on the larvae of two species of rhizocephalan (Crustacea: Cirripedia)

Summary

Responses of larvae of two rhizocephalan species to changes in seawater temperature and salinity were studied under laboratory conditions. Peltogasterella gracilis parasitizes the hermit crab Pagurus pectinatus, which occurs at stable salinity and gradually changing temperature in summer. Sacculina polygenea is a parasite of the crab Hemigrapsus sanguineus, which lives in the intertidal zone in summer where salinity and temperature can fluctuate during the day. The development of both species is comprised of five naupliar stages and the cyprid stage, and it was considered successful if more than 50% of the nauplii attained the cyprid stage. P. gracilis nauplii successfully developed at 12–20°C and 30–34‰, but at 22°C successful development occurred in a narrower salinity range (32–34‰). All nauplii died both at 25°C and in 26‰. S. polygenea nauplii successfully reached the cyprid stage at higher temperatures (18–25°C) and a wider salinity range (18–34‰) than P. gracilis nauplii, but at 12°C and 16‰ larval development of S. polygenea was suppressed. Under favorable conditions, naupliar development lasted 3.5 days in P. gracilis and 2–3 days in S. polygenea. The cyprids of both rhizocephalan species demonstrated a greater resistance to temperature and salinity changes than nauplii. However, P. gracilis cyprids were active in a narrower salinity range (16–34‰), as compared to S. polygenea cyprids (8–34‰). Under favorable conditions the cyprids of both species survived for 6 to 10 days.     

Shift in birch leaf metabolome and carbon allocation during long-term open-field ozone exposure

Current and future ozone concentrations have the potential to reduce plant growth and increase carbon demand for defence and repair processes, which may result in reduced carbon sink strength of forest trees in long‐term. Still, there is limited understanding regarding the alterations in plant metabolism and variation in ozone tolerance among tree species and genotypes. Therefore, this paper aims to study changes in birch leaf metabolome due to long‐term realistic ozone stress and to relate these shifts in the metabolism with growth responses. Two European white birch (Betula pendula Roth) genotypes showing different ozone sensitivity were growing under 1.4–1.7 × ambient ozone in open‐field conditions in Central Finland. After seven growing seasons, the trees were analysed for changes in leaf metabolite profiling, based on 339 low molecular weight compounds (including phenolics, polar and lipophilic compounds, and pigments) and related whole‐tree growth responses. Genotype caused most of the variance of metabolite concentrations, while ozone concentration was the second principal component explaining the metabolome profiling. The main ozone caused changes included increases in quercetin‐phenolic compounds and compounds related to leaf cuticular wax layer, whereas several compounds related to carbohydrate metabolism and function of chloroplast membranes and pigments (such as chlorophyll‐related phytol derivatives) were decreasing. Some candidate compounds such as surface wax‐related squalene, 1‐dotriacontanol, and dotriacontane, providing growth‐related tolerance against ozone were demonstrated. This study indicated that current growth‐based ozone risk assessment methods are inadequate, because they ignore ecophysiological impacts due to alterations in leaf chemistry.     

The pathogenicity determinant of Citrus tristeza virus causing the seedling yellows syndrome maps at the 3'-terminal region of the viral genome

Citrus tristeza virus (CTV) (genus Closterovirus , family Closteroviridae ) causes some of the more important viral diseases of citrus worldwide. The ability to map disease-inducing determinants of CTV is needed to develop better diagnostic and disease control procedures. A distinctive phenotype of some isolates of CTV is the ability to induce seedling yellows (SY) in sour orange, lemon and grapefruit seedlings. In Florida, the decline isolate of CTV, T36, induces SY, whereas a widely distributed mild isolate, T30, does not. To delimit the viral sequences associated with the SY syndrome, we created a number of T36/T30 hybrids by substituting T30 sequences into different regions of the 3' half of the genome of an infectious cDNA of T36. Eleven T36/T30 hybrids replicated in Nicotiana benthamiana protoplasts. Five of these hybrids formed viable virions that were mechanically transmitted to Citrus macrophylla , a permissive host for CTV. All induced systemic infections, similar to that of the parental T36 clone. Tissues from these C. macrophylla source plants were then used to graft inoculate sour orange and grapefruit seedlings. Inoculation with three of the T30/T36 hybrid constructs induced SY symptoms identical to those of T36; however, two hybrids with T30 substitutions in the p23-3' nontranslated region (NTR) (nucleotides 18 394–19 296) failed to induce SY. Sour orange seedlings infected with a recombinant non-SY p23-3' NTR hybrid also remained symptomless when challenged with the parental virus (T36), demonstrating the potential feasibility of using engineered constructs of CTV to mitigate disease.     

Sibling species in the Chrysis ignita complex: molecular,morphological and trophic differentiation of Baltic species,with a description of two new cryptic species (Hymenoptera: Chrysididae)

Cryptic species complexes cause major challenges for taxonomists and alter understanding of species diversity. In Northern Europe, the Chrysis ignita species group is one such complex with numerous sympatric sibling species. The objective of this paper is to assess the taxonomy of 15 species from this group using three different approaches: molecular, morphological and trophic differentiation. The analysed set of molecular markers included a 7400‐bp‐long sequence of the mitochondrial genome covering complete sequences of CO1, CO2, ATP8, ATP6, CO3, ND3, 16S and 12S rRNA, nine tRNAs and a partial sequence of CytB, as well as a 3880‐bp‐long sequence of the nuclear DNA covering a part of 18S rRNA, the ITS1, 5.8S rRNA, ITS2 and a part of 28S rRNA. Discrete diagnostic characters of each species sequence were retrieved using the Characteristic Attribute Organisation System algorithm and a molecular identification key was compiled. The study revealed a higher evolutionary rate of the genes ATP8, ATP6, CO3, ND3 and CytB compared to that of CO1, CO2 and 16S; the studied nuclear markers demonstrated a lower evolutionary rate than the mitochondrial markers. A consensus tree compiled based on the combined mtDNA and nuclear markers with a strongly supported topology resolved the position of the C. schencki – C. parietis sp.n. clade as sister to the C. ignita – C. impressa clade and supported the monophyly of the C. angustula – C. longula clade. We compiled a morphometric species identification key applying linear discriminant equations. The trophic differentiation was assessed using data on host preferences of ten Chrysis species reared from trap‐nests; the analysis demonstrated that most of them are specialists exploiting a single or a few taxonomically related host species. In most cases, all three approaches supported the distinct status of the included species. Moreover, two previously undescribed species were consistently supported by the molecular methods. Therefore, we describe these as new, namely C. horridula sp.n. and C. parietis sp.n. Only C. mediata and C. solida were not clearly distinguished using the molecular phylogeny reconstruction methods. However, based on distinctive niche divergence, the presence of molecular characters and morphometric differences, we consider them as phylogenetically young but distinct species. In view of the weak morphological and molecular differentiation, the widely overlapping distribution areas and often similar habitat preferences and the trophic specialization, the C. ignita complex presents a possible model for studies of sympatric cryptic speciation. This published work has been registered in ZooBank, http://zoobank.org/urn:lsid:zoobank.org:pub:1EBAF0E1‐5FB7‐4CF4‐A595‐C11982448360 .