ANALYSIS OF THE ALIEN FLORA OF DNIPROPETROVSK PROVINCE

Plant invasion in the Northern Steppe Dnieper has a long history complicated by excessive anthropogenic transformation of territory. Alien species status, origin areas, life history, and invasive tendency of alien species in Dnipropetrovsk region were investigated. The presence of 286 alien species of 61 families was registered. Some 7 families had the greatest species diversity (156 alien species that was 55% of total species number); 30 families were represented by 2–9 alien species, and 24 families contained only 1 alien species. So, the current proportion of the alien species was almost 17% in the regional flora. Archaeophytes consist of 40% of the total alien species, while neophytes had more than 60%. The proportion of naturalized species amounted 58% from alien species, whereas the share of casual species was 42%. The greatest abundance of alien species was typical for Brassicaceae, Asterasea, and Poaceae (14, 13, and 9% of the total species number). We proved invasive status of 28 species and positive trend regard alien species ratio for last years.


INTRODUCTION
Biological invasions were defined as a fundamental driver of ecosystem degradation (Pyśek & Richardson, 2010;Schindler et al., 2016).Therefore, it is not unusual that spread of alien plants in different regions became the important research topic in recent years (Richardson et al., 2000;Pyśek et al., 2012).Describing the negative effects of plant invasion, Blackburn et al. (2014) emphasize such danger for the native flora as decrease in species extinction probabilities, richness and abundance; significant changes in genetic composition of native populations, phylogenetic and taxonomic diversity, ecosystem productivity, and more.Analysis of alien flora composition and dynamics is an essential element for assessing infestation degree of different taxa (Pyśek, 2003).Blackburn et al. (2011) mentioned the need of integrated model, which could clarify the history and the pattern of invasions, and predict the time and ways to stop them.
In Ukraine, alien species propagation process manifested itself very clearly in areas having a long history of anthropogenic transformation.In Dnipropetrovsk province, located within the geographic area of Northern Steppe Dnieper, the extended anthropogenic impact resulted in overgrazing, quarrying, and pollutants action (Brygadyrenko & Reshetniak, 2014;Tsvetkova et al., 2016).In such circumstances, autochthonous flora undergoes profound destruction, rapid degradation, and loss of typical components replaced on synanthropic species, including aliens (Protopopova, 1991(Protopopova, , 1999)).Unfortunately, for various reasons, the process of alien species intrusion into the regional flora has not been received adequate attention of researchers (Holoborodko et al., 2016).At present, there are no reported complete lists of alien species confined to the Dnipropetrovsk province.At the same time, alien species discovering in regional flora was not a rare event 35 years ago (Tarasov, 1981), as well as during next years (Tarasov, 2012;Baranowski et al., 2012).European researchers (Pyśek et al., 2012) emphasize the research importance of the regional alien flora for better understanding the invasion process.In this paper, we provided the first checklist of alien species founded in the regional flora and assessed the current state of the alien species invasion process.

MATERIALS AND METHODS
The territory of Dnipropetrovsk province covering 31.974km 2 is a plowed steppe (over 80% of territory) with minor forest areas on the river banks (Pakhomov & Brygadyrenko, 2005).Continental climate characterized by the sharp temperature fluctuations, unstable moisture, and seasonal drought periods.Annual evaporation exceeds precipitation by 2-3 times; an average rainfall is 472 mm, while it could fall to 250 mm in the dry years (Furdychko et al., 2006).Regional population density is 103 people per km 2 ; the densities of railways and highways are 49.5 km and 283 km per 1,000 km 2 respectively.Ecological situation is exacerbated by emissions of 587 industrial enterprises, including 57 mining and metallurgical, and 17 chemical plants.In addition, two international airports and two river ports contribute to process of alien species penetration and propagation within the territory of the Dnipropetrovsk province.
Taxa names were given in accordance with Flora Europaea (Moore, 1982) and the modern species nomenclature adopted in Ukraine (Mosyakin & Fedoronchuk, 1999).Alien species have been identified in accordance with generally accepted approach (Pyśek, 1998;Blackburn et al., 2014) as a species appeared due to human activity in regions where previously it does not naturally occur.Definition of invasive status of alien species was made on the basis of the Richardson et al. (2000) criterion, which involves the species classification according to its stage along the introductionnaturalization-invasion continuum (INIC).In line with the approach used by Pyśek et al. (2012) alien plants were classified as naturalized species if they form self-sustaining populations for several life cycles without direct people intervention, or despite it; and plants were named as casual species if they do not form self-sustaining populations in the invaded region.
Following the concept used traditionally in plant invasions studies (Protopopova, 1991(Protopopova, , 1999;;Pyśek, 1998Pyśek, , 2004)), we distinguished archaeophytes (for taxa introduced before 1500 AD) and neophytes (for taxa introduced after that date).Life histories of the species had been classified according to conventional approach (Pergl et al., 2016), namely: annual, over wintering herbaceous plants (biennial or perennial), shrub, and tree.As for the origin areas of the alien species, we stuck to the traditional approach (Pyśek et al., 2012) and identified the following geographical regions as Europe together with the separate Mediterranean region, Asia, Northern and South Americas.

RESULTS AND DISCUSSION
The checklist of regional alien flora consisted of 286 species, which belong to 61 different families and 210 genera.Considering the total number of regional flora includes 1,714 species (Tarasov, 2012), the current proportion of the alien species exceeds 16.7%.Taking into account the Dnipropetrovsk province area, it can be assumed there are 9 alien species per km 2 .This index is much higher than the data shown by Pyśek (2003) for the Czech Republic alien flora (about 4 alien species per square kilometer).High aliens' abundance can be attributed by combination of such regional factors as a complex geomorphologic structure and suitable climatic conditions, as well as an active anthropogenic transformation and transport communications plexus.Results obtained are in accordance with Fuentes et al. (2015) data, that economic activities and climate are substantial factors in alien plants establishment and invasion.
Most of the alien species were presented by herbaceous plants (252 species or 88% of total) with domination of annual species (Table 1).In our study, the distribution of alien species between different families wasn't uniform, and there were only 7 families with large (10 species or more) presence of the aliens (Figure 1).The number of families with the highest diversity of alien species accounted for only 12% of the total number, however it consisted of 156 alien species covering 55% of the total number.Within this group, three families (Brassicaceae, Asteraceae, and Poaceae) were clearly dominant, embracing together more than 36% of total alien species number.
Substantial part of the families (30 or 49% of total) were represented by a smaller number of alien species (2-9 species), and 24 families (39% of total) contained only one alien species (Table 2).Studies allowed establishing the percentage of archaeophytes and neophytes in the total number of alien plants.It was found that archaeophytes make up 40% of the total alien species abundance, while neophytes had 60% of alien plants (Fig. 2).It is obvious that such a ratio indicates an active invasion of alien plants into the flora of Dnipropetrovsk province.Confirming this, Tarasov (1981) has found 51 new alien species in the regional flora in the 70s of the last century; whereas he has reported already about 75 new alien species two decades later (Tarasov, 2005).Overall, over the last 40 years, Tarasov (2012) has discovered and identified a large number of alien species in the regional flora, such as Impatiens parviflora, Artemisia annua, Petrorhagia saxifrage, Hibiscus trionum, Malva mauritiana, Echinocystis lobata, Althaea armeniaca, Solidago serotinoides, Galinsoga parviflora, Galinsoga ciliata, Nicandra physaloides, Bidens frondosa, Solanum cornutum, Zygophyllum fabago, Artemisia tournefortiana, Ambrosia trifida.
In our study, percentage of naturalized species reached 58% of total alien species number.However, index increased to 73% among the archaeophytes, while it reached only 48% among neophytes.Part of the casual species in regional alien flora (42% of total aliens' number) diminished to 27% among the archaeophytes, and covered 52% of the neophyte's number.The results obtained are much higher than data presented by Pyśek (2003), which showed a lower percentage (41% only) of the naturalized alien species in the flora of Czech Republic.
It was established that alien species penetrated into the territory of Dnipropetrovs'k province from the five main areas (Fig. 3).Among them, the greatest contribution to the regional alien flora was made by species originating from the Mediterranean region.At the same time, the definition of the origin areas had not been possible for some alien species; so they were combined into a single group.Using the approach described by Walter et al. ( 2009), we have identified this species as a cryptogenic (i.e, species of unknown origin).Fig. 3. Distribution of alien species according to the origin areas.Proportion of the alien species is given after the origin area title.
In our study, various propagation paths of alien species have been identified (Table 3).In particular, Baranovski (1998Baranovski ( , 2000) ) had shown that alien trees and shrubs distribution was associated with introduction and subsequent naturalization in such habitats as coastal areas, ravines, and natural and planted forests.Currently, the most widespread aliens in arboreal regional flora are Acer negundo, Robinia pseudacacia, Ulmus pumila, Ailanthus altissima, Amorpha fruticosa, and Partenocissus quinquefolia.It was established, that alien species Cenchrus pauciflorus, Zizania latifolia, and Juncellus serotinus (Baranovski, 2000) were first discovered in the Dnieper River surrounding, indicating the waterway penetration.It was shown, that Viola hissarica (Tarasov, 2005) and Thladiantha dubia (Mytsyk & Baranovski, 2006) spread over the region, going beyond the territory of the Dnipropetrovs'k University Botanical Garden.The majority of invasive aliens was typical for such families: Acteraceae (7 alien species), Poaceae (4 species), and Brassicaceae (3 species) with high domination of the annual and biennial herbaceous plants.The woody invasive plants were presented by R. pseudacacia (Khromykh et al., 2015;Holoborodko et al., 2016), and A. negundo (Lykholat et al., 2016b).
Our study revealed the positive invasion trend during recent years.According to Baranovski (1998), A. fruticosa has acquired the invasive status over last 30 years; at present invasion of this species resulted in a significant distortion of natural structure of lowland habitat vegetation.Besides, the young growths of P. serotina and C. occidentalis have been found in the old-year urban plant communities as well as in the natural forests; A. syriaca could spread not only in the ruderal habitats, but also penetrate into the crops of wheat and other cultures.This invasion trend can be caused by the climatic changes typical for last years (Lykholat et al., 2016a;Walter et al., 2009).

CONCLUSION
Nowadays, the alien species occupy almost 17% in the flora of Dnipropetrovsk province, due to a combination of environmental and anthropogenic factors.The uneven alien species distribution between the families together with prevalence of Brassicaceae, Asterasea, and Poaceae was established.Results of our study allowed revealing various patterns and mechanisms of alien species intrusion into the regional flora (purposeful introduction, unintentional entering, and escape from a culture).Number of the neophytes was much higher than the archaeophytes, indicating constant invasion of alien species into the local flora and threats to natural floristic diversity of Dnipropetrovsk province.Invasion positive trend some alien species can be explained by the impact of climatic changes during last years.

Fig. 1 .
Fig. 1.Families with the highest abundance of alien species.Species number is given after the family title Fig. 2. Distribution of alien species according to invasion status (casual or naturalized) among archaeophytes, neophytes, and all aliens.

Table 1 .
Distribution of the alien species according to their life history

Table 2 .
Families with the middle and lower abundance of alien species