The analysis of present-day crucians’ settlements in water systems of Eastern Ukraine designated the predominance of the digeneous Goldfish, C. auratus, in the region, the number of which made 78.7 %, from the total number of the examined representatives of the genus. The second group consists of gynogenetic Prussian carps, C. gibelio (14.3 %); it is represented by the clone biotype and recombinant individuals. Crucian carp, C. carassius (3.6 %), turned out to be rare and its number did not exceed the number of the caught hybrids C. auratus × C. carassius (3.4 %). The retrospective analysis of literature data and museum collections gave an opportunity to describe the changes in species composition of the genus which took place during the last 150 years. Within this period the crucian carp, which used to be the single and most common representative of genus Carassius (Jarocki, 1822) in the region, became nearly an extinct species. In the meanwhile the representatives of the group of species of Prussian carps, C. auratus + C. gibelio, which appeared in the region in the late 1960s, rapidly increased their number and became the most numerous fish of the Eastern Ukraine. The discovered tendency is not unique for the researched region; in general it reflects the European tendency for the crucian species. The reasons for that are rivers’ regulation and destruction of bottomland ecosystems. The secondary factors for the elimination of C. carassius are the competitive relations of individuals representing both species and easy hybridization, during which the more numerous species C. auratus absorbs the rare C. carassius.
The main objective of this research was to assess the suitability of the risk assessment methodology developed by Weber & Gut for Central Europe in order to determine the invasive species in the dendroflora of this region's historical parks. In order to do so a region was chosen where the number of old parks is high (Estonia) and then the following characteristics were studied: 1) the distribution of invasive species; 2) the viability of invasive species. Research results showed that the risk assessment for Central Europe developed by Weber & Gut is not suitable for determining invasive tree and shrub species in the historical parks of Estonia. The research viewed 18 species (classified as a high-risk category) and only half of them had characteristics inherent to invasive behaviour (produces reproductive offspring, often in very large numbers, at a considerable distance from parent plants, and thus has the potential to spread over a considerable area). Even in a small territory (45,339 km2), the regional differences in the occurrence of invasive species were substantial. No independent mass reproduction of most of the invasive species was detected during the use of the Weber-Gut risk assessment system. This research showed that the dangers of invasive species cannot be assessed based on one methodology, but each species should be assessed according to their habitat and specifics of the species.
. L. 2007: Wide ecological amplitude of a diversity-reducing invasive grass. BiologicalInvasions 9: 149–160. Gołdyn, H. 2010: Changes in plant species diversity of aquatic ecosystems in the agricultural landscape in West Poland in the last 30 years. Biodiversity and Conservation 19(1): 61–80. Gregor, T., Bönsel, D., Starke-Ottich, I. & Zizka, G. 2012: Drivers of floristic change in large cities – A case study of Frankfurt/Main (Germany). Landscape and Urban Planning 104: 230–237. Hegedüšová, K. 2007: Central database of phytosociological samples (CDF) in Slovakia
invasions, Ecological Applications , 10, 689-710. 10. Occhipinti-Ambrogi A. and Savini D., 2003 - Biologicalinvasions as a component of global change in stressed marine ecosystems, Marine Pollution Bulletin , 46, 542-551. 11. Parker I. M., Simberloff D., Lonsdale W. M., Goodell K., Wonham M., Kareiva P. M., Williamson M. H., Von Holle B., Moyle P. B., Byers J. E. and Goldwasser L., 1999 - Impact Toward a Framework for Understanding the Ecological Effects of Invaders, BiologicalInvasions , 1, 3-19. 12. Purcell J. E., Uye S. I. and Lo W. T., 2007 - Anthropogenic causes
Lower reaches of largest Ukrainian rivers are zones of migrations for exotic euryhaline decapods. During 2000s new records of invasions of three euryhaline exotic decapods, Rhithropanopeus harrisii (Gould, 1841), Eriocheir sinensis Milne-Edwards, 1853 and Macrobrachium nipponense (De Haan, 1849), were made in the channels of Ukrainian rivers. Chinese mitten crab, E. sinensis, spread in the Danube Delta and reservoirs of the Dnieper River; Rh. harrisii - in the channels of the Danube, Dnieper, Southern Bug and small river Gruzskij Yelanchik in the Azov Sea Basin; M. nipponense that was introduced in the Kuchurgan Liman (cooler reservoir of the Moldavian Hydro-power Station) - in the Dniester Delta. The migration zone of the established population can cover significant part of river watershed; it is necessary to take this fact into account at an estimation of biological invasion risk. Main problem in the investigation of exotic decapods in Ukrainian waters is absence of specialized methods used in the standard ecological monitoring. Among euryhaline exotic decapods, only Rh. harrisii is sometimes sampled with the equipment used in the monitoring of macrozoobenthos. A few records of these species at the large extent of their supposed ways of migration are the result of gaps in the study of their distribution in Ukrainian inland waters. Realistic attitude toward this fact is very important for the estimation of invasions in the inland waters of this region.
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