Vol 9, No 3 (2018)

The results of the studies on the occurrence of the North American species Robinia pseudoacacia L. (Fabaceae Lindl.), an alien one in the south of the Russian Far East, are shown. In the period of 2014–2018, this species was registered in landscaping in 27 inhabited localities of Primorskii krai. It is absent in natural phytocoenosis, but inhabits anthropogenic landscapes. Places of intense vegetative reproduction of R. pseudoacacia were detected. The investigations showed the potential possibilities for a wider distribution of the species.

The influence of nickel and copper salts on seed germination of the native species Bidens tripartita L. and the alien species B. frondosa L. growing in geographically remote populations was studied in the laboratory conditions. It was shown that the seeds of the alien species were more resistant to the action of heavy metals than the native seeds. Perhaps, this was due to the higher biomass of B. frondosa seedlings, which, along with other indices, indicated a high adaptability of the species to extreme conditions, ensuring its successful expansion. We observed differences in germination of B. tripartita seeds from the Upper and Middle Volga populations influenced by nickel and copper salts at concentrations of 50 mg/L and 1, 50, and 100 mg/L, respectively. Copper was found to have the greatest toxic effect on seed germination at concentrations of 50–100 mg/L.

Bruchidius terrenus (Sharp, 1886) (Coleoptera: Chrysomelidae: Bruchinae) is a new invasive East Palearctic species of seed beetles to the fauna of the Crimea and Russia was emerged in November 2017 from the seeds of Albizia julibrissin Durazzini, 1772 and A. kalkora (Roxburgh) Prain, 1897, that were collected in the Nikitsky Botanical Garden. B. terrenus is a monophagous species: larvae develop in the seeds of silk trees (Albizia Durazzini, 1772). The infestation levels of the seeds of A. julibrissin and A. kalkora were 45 and 78%, respectively. The species is monovoltine; emergence of imagoes was observed in November–December. The overwintering stage is imago.

The emergence of the ascomycete Fusarium circinatum Nirenberg & O’Donnell (teleomorph Gibberella circinata), the causal agent of pitch canker of pine in Europe, is an alarming signal to Russia. This review briefly summarizes the analyses of biology of F. circinatum and its vectors of dissemination. Open wounds on the bark of the trunk and branches can be the gates for the droplet and airborne infection caused by the Fusarium phytopathogens. The infection is followed by the formation of cankers caused by the related phytopathogens, the occurrence of severe resin bleeding, and the death of the crown. In Russia, this pathogen can emerge and spread in the Black Sea coastal area (most likely toward the southeast of Krasnodar) in pine nurseries and plantations. However, it is not clear yet whether the regional climate conditions will be optimal for F. circinatum and how competitive it will be in new environments. The insect species associated with the pine trees are considered as an important factor for dissemination of F. circinatum, since they can be both the direct carriers of the fungal propagules (i.e., act as the vectors for transmitting the causal agents) and the cause of the physical damage to the pine shoots, branches, and trunk, becoming a gates for infection. After completing the life cycle on the tree infected with F. circinatum, the mature insect migrates to another possibly healthy tree, carrying the sticky fungal spores adhering to the surface of its body and leaving them attached to the new host tree. The study describes the insect species associated with the pines (Pinus). In addition, it is concerned with analyzing their role in dissemination of F. circinatum. It has been proved that, in Russia, there are many insects potentially capable of rapidly spreading the pitch canker of pines if F. circinatum invades the country.

Results of application of different approaches to the data visualization during the study of alien plant species have been analyzed and summarized, and the prospects of their use for different purposes have been evaluated. The existing experience in the study of alien plant species shows that traditional methods used to analyze their composition and distribution patterns in different regions are informative only for determining the main tendencies reflecting global processes of a phytobiota synanthropization. At the same time, new state-of-art methods are required to reveal the latent patterns of plant migration and the processes of their naturalization. The most promising approaches to analyzing large volumes of data are multivariate statistical methods. The potential of these methods is determined by their capability to identify relationships between a wide range of floristic and biological data and environmental characteristics, which can be visualized. These methods allow us to present different data in the form of diagrams reflecting interactions between individual species or whole groups of alien plants and climatic or environmental variables. They make it possible to create models of expansion of invasive species. They reflect the current statistical distances and relationships between different objects of study, which makes it possible to identify features of the group strategy of colonization of various natural and/or technogenic habitats by alien species. These strategies depend mainly on the biological characteristics of species, level of anthropogenic transformation of a regional flora, and environmental parameters.

For the first time on the territory of the big Siberian city of Novosibirsk in the arboretums, gardens, parks, and residential areas, 91 species of woody plants of different geographical origin, which naturally produce seed and vegetative progeny, have been recorded. It has been found that 44% of species in the city also grow in the natural conditions of the Russian Far East and countries of Southeast Asia, 33% are of North American origin, and 23% are European and Eurasian range types. Most of the alien species (45%) have vegetative regeneration, 34% of species are self-seeding, and 21% of species have seed and vegetative regeneration. By the character of natural regeneration in the urban environment, there are three groups of alien species: species that actively regenerate by seed and also have vegetative regeneration and spread over landscape objects and outside of them (Acer negundo, Amelanchier spicata, A. alnifolia, Elaeagnus commutata, Euonymus europea, Fraxinus pennsylvanica, Prunus pensylvanica, Physocarpus opulifolius, Ulmus laevis, and others), species that have vegetative regeneration and increase the area of growth through formation of clump-clones (Amorpha fruticosa, Menispermum dauricum, Parthenocissus quenquefolia, P. inserta, Rosa rugosa, Rubus odoratus, Symphorycarpos albus, Syringa vulgaris, Swida sericea, Vitis amurensis), and those that regenerate and remain for a long time in the sites of planting without increase in the area (Acer platanoides, Eleutherococcus senticosus, E. sessiliflorus, Deutzia parviflora, Syringa josikaea, S. wolfii).

In the current study laboratory experiments were conducted to elucidate the allelopathic and autotoxic effects of Parthenium hysterophorus, Senna uniflora and Hyptis suaveolens. The seed germination experiments were conducted using the leachates obtained from different organs of the three species. Ten grams, each of the plant materials were homogenized in 100 mL of quartz-distilled water for 24 hours, filtered and used as a stock solution of 100% concentration. From the stock solution, 25, 50 and 75% concentrations were prepared by diluting with quartz-distilled water. Three replicates with 30 seeds each for each plant species were maintained. Observations were made at regular intervals of 24 hours. The emergence of radicle was taken as the indicator of germination. Germination, root and shoot elongation was monitored for eight days. The study revealed inhibition of germination in both the species by the leaf leachates of P. hysterophorus of all concentrations. There was a strong and positive relationship between the concentration of the shoot and root leachates of H. suaveolens and their inhibitory effect on P. hysterophorus. The leachates of H. suaveolens, inhibited seed germination totally in P. hysterophorus in all concentrations. Allelopathic effect of leaf leachates of H. suaveolens on S. uniflora lasted longer than a week, inhibiting seed germination. The autotoxic effects of P.hysterophorus were much stronger than that of other two species. It is concluded that among the three species, H. suaveolens leaf leachates had the strongest inhibitory effect both on P. hysterophorus and S. uniflora and can be recommended as bio-herbicide.