Flora oF the city oF Podgorica, Montenegro – chorologic structure and coMParison with the Floras oF roMe, Patras, and salonika

Research on the geographical structure of the flora of Podgorica revealed that 85.9% of the species are native, while 14.1% are non-native. This ratio is typical of Mediterranean settlements, where even the most urbanized region reflects the overall character of the surrounding flora. In terms of chorologic groups, the three largest are: euryMediterranean (18.2%), cosmopolitan (12.6%), and steno-Mediterranean (8.3%). The percentage of endemic and subendemic plants is also significant (6.8%). Within the group of aliens, species of Asian origin prevail. Comparative analysis of the chorologic spectra of Podgorica, Rome, Patras, and Salonika revealed some similarities.


INTRODUCTION
In comparison to natural environments, cities represent a relatively young habitat type.Their floras consist of a combination of both native and non-native (alien) components.Plants from surrounding natural ecosystems that can adapt to ystems that can adapt to newly human-created environments are native, while species originating from geographically distant areas and introduced intentionally or unintentionally by man generally belong to the alien flora.In the geobotanical literature, all plants that become part of the flora through the direct or indirect impact of man are defined as anthropophytes.The first classification of anthropophytes was given by Thellung (1922).He distinguished two main categories based on the origin of species: apophytes, or elements of the native flora; and anthropochores, or elements of some alien flora.According to Schroeder (1969), anthropochores can be classified on the basis of three criteria: i) by their degree of naturalization (idiochorophytes, agriophytes, epecophytes, ephemerophytes, and argasiophytes); ii) by the time of immigration (idiochorophytes, archaeophytes, and neophytes); and iii) and by the manner in which man supported their immigration (idiochorophytes, acolutophytes, xenophytes, and ergasiophytes).On the other hand, Trinajstić (1975) combined three criteria (chronological, anthropological, and ecological) and distinguished four main categories: archaeophytes, paleophytes, neophytes, and neotophytes.Each of these categories are then divided into four subcategories: ergasiophytes, ergasiophygophytes, epekophytes, and ephemerophytes.Further, Trinajstić (1975) distinguished a unique category of helenopalophytes category of helenopalophytes from the Adriatic Coast of Yugoslavia.
It is often very difficult to determine the exact date of introduction of a species.Archaeophytes are particularly difficult to distinguish from original species, since original and secondary areas of distribution continuously overlap.The differentiation of such taxa is further complicated by the time that has elapsed since the original introduction.Indeed, it is not always clear whether a species is native or introduced (Sykora and Westhoff, 1997).In addition, we wanted to demonstrate the to demonstrate the importance of the native component of the flora and the inherent need to protect it by preserving remnants of both natural and seminatural habitats.just as importantly, we call attention to alien plants and the threat they bring to diversity of the native flora.

Besides the aforementioned categories, the
Some general information about the selected cities is given in Table 1, while their geographical locations are shown on Fig. 1.

MATERIAlS AND METHODS
The flora within the city of Podgorica currently consists of 1227 taxa (Stešević and jovanović, 2008), four of which are excluded from our analysis: Fraxinus excelsior, Asphodelus albus, and Myricaria germanica (uncertain data taken from the literature); and the hybrid taxon Carex acuta × elata.
Pignatti's classification system was chosen instead of the more generally accepted one of Stevanović (1992) owing to compatibility with owing to compatibility with urban flora also includes anekophytes or obligate weeds (Scholz, 1991).These plants have coexisted with humans since prehistoric time, which has resulted in a high level of uncertainty regarding their native ranges.This group includes: Bromus hordeaceus, Capsella bursa-pastoris, Chenopodium album, Cynodon dactylion, Hordeum leporinum, Poa annua, Senecio vulgaris, and Stellaria media (Sukopp and Scholz, 1997).
The two main objectives of this paper were: i) to present the general chorologic spectrum of the flora of Podgorica; and ii) to compare the chorologic spectra of Podgorica, Rome, Patras, and Salonika, with special reference to structure of the alien flora.the chorologic data reported for the other three selected (sub)Mediterranean settlements: Rome (Celesti-Grapow, 1995); Patras (Chronopoulos andChristodoulakis, 1996, 2000); and Salonika (Krigas andKokkini, 2004, 2005).
We use the term alien (sensu Richardson et al., 2000) to embrace the following related terms: naturalized, invasive, casual ephemeral, introductioned, occasional escaped plants, and cultivation relics.
In a few cases, it was necessary to harmonize the data according to Pyšek et al. (2002Pyšek et al. ( ) due to šek et al. (2002) ) due to inconsistent information about the origin of some information about the origin of some alien taxa.
Because of the lack of information about time of introduction, structure of the alien flora is given only in respect to its origin.If a species distribution covered more than one continent, it was considered as a representative of each of them.The general information about the compared cities presented in Table 1 was gathered from the following sources: Podgorica (Stešević and jovanović, 2008); Rome (Celesti-Grapow, 1995); Patras (Chronopoulos and Christodoulakis, 1996); and Salonika (Krigas andKokkini, 2004, 2005; Hellenic National Meteorological Service: www.hnms.gr).
Additionally, the role of apophytes was emphasized.
In contrast to the Mediterranean, it has been found that Central European cities have a more uniform flora with a higher abundance of aliens, which comprise 20-60% (average 35-40%) (Brandes, 1989;Pyšek, 1998).
Due to the abundance of natural and seminatural habitats within the city of Podgorica, numerous endemic and subendemic taxa are recorded in the central zone.However, rapid urbanization and  insufficient preservation of remaining fragments of natural habitat put serious pressure on the native flora.
The majority of endemic and subendemic species are recorded from areas near the courses of the rivers Morača and Cijevna, which are well known as floristically rich and diverse (Bulić, 1993(Bulić, , 1998(Bulić, , 2008;;Bulić et al., 2008).Part of this floristic diversity is included in the flora of the city of Podgorica.
With respect to participation of the Eurasian element in the broad sense, Podgorica surpasses the other cities by 26.5%.Within this chorologic type, the Eurasian (7.7%) and paleotemporal (5.1%) groups dominate.The South European-South Siberian group (which includes the Pontic element and the majority of its subelements) contributes 4.7% and the European-Caucasian group 4%.
In the boreal chorologic type (5.2%), the circumboreal and Euro-Siberian groups show about the same percentage (2.6 and 2.5%, respectively).Atlantic elements participate in the spectrum with 2.2%.
The contribution of alien taxa to the chorologic spectrum of Podgorica is 14.1%, which can be considered a relatively low value.Saarisalo-Taubert (1963) pointed out the relationship between age of a settlement and structure of its flora.Following this, we consider the main reason for the small number of aliens to be an artifact of the old age of Podgorica.According to Sukopp et al. (1979), Sukopp andWerner (1983), Pyšek (1989a), and Kowarik (1990), development of a transportation system and intensive trade open better options for the introduction and spread of new species and contribute to their increasing numbers.We maintain that poorly developed trade and transportation networks are a possible second reason for the low numbers of aliens.
Table 3 shows structure of the alien flora in the urban area of Podgorica.
Among alien plants in the urban area of Podgorica, species of Asian and North American distribution are prevalent.In addition, the majority of taxa are considered to be escaped from cultivation.In many countries, deliberate introduction of plant species is considered to be the main road of introduction (Groves, 1998;Reinhard and White, 2001;Mack, 2003).New trends in horticulture contribute a lot.Almost as a rule biological characteristics that make species attractive for breeding contribute to their successful expansion.According to Kowarik (2003), the naturalization rate of deliberately introduced species is considerably higher than the rate of accidentally introduced ones.
For example, Broussonetia papyrifera, an ornamental species found within the city of Podgorica, has spread rapidly due to vegetative reproduction and has started to outcompete Ailanthus altissima.Recently, pampas grass (Cortaderia selloana), a species on the EPPO list of invasive alien plant species (http://www.eppo.org/QUARANTINE/ias_plants.htm),has been used in landscaping of city lawns and parks.Consequently, we expect this species to join the list of other alien species escaped from cultivation within Podgorica.
The comparative spectra of the alien floras of Rome, Patras, Podgorica, and Salonika are given in Fig. 3.
With the exception of Patras, where South American taxa dominate, a common feature of the alien floras of the compared cities is the prevalence of taxa having Asian origin.The majority of these taxa were introduced as ornamentals.In all spectra, species of Australian origin have very low participation or are completely missing (Patras, Salonika).values of the S�rensen index show the greatest �rensen index show the greatest rensen index show the greatest similarity between the alien floras of Podgorica and Rome (52.7%, see Table 4).In view of the similarity in taxonomic structure of these two floras (Stešević and jovanović, 2008) and similar climatic conditions, such a result was expected.
Observing the trends in floristic composition over the past two centuries, many authors noted an obvious decrease in the number of native species.According to Sukopp (1973), during the period from 1850 to 1950, some European cities faced extinction rates between 4 and 16%.The example of Warsaw (Sudnik-Wojcikovska, 1987) shows that over a period of 150 years, 15% of native species became extinct, while for Zürich the rate for the last 160 years was only 5.7% (landolt, 2001).For the Czech industrial city of Plzeň, the decrease of native species was 11.5% over the past 120 years (Chocholouškova and Pyšek, 2003).
One of the most drastic examples of general floristic loss is the case of Turnhout, Belgium, where nearly 25% of the flora became extinct between 1888 and 1990 (van der veken et al., 2004).
The loss of native flora due to spreading of alien species is a phenomenon known as biotic homogenization (McKinney andlockwood, 1999, 2006;Olden et al., 2004;la Sorte and McKinney, 2006).
The aforementioned unplanned rapid urbanization causes on the one hand a loss of native species and on the other creates space for expansion of already established and newly introduced alien species.We expect that the effects of biotic homogenization will be evident soon.

Fig. 2 .
Fig. 2. Structure of the alien flora of Podgorica with respect to origin.If a species distribution covers more than one continent, it is considered as a representative of each of them.

Table 1 .
General information about the cities of Patras, Podgorica, Rome, and Salonika: area, number of inhabitants, climate type, average annual temperature, and average annual rainfall.

Table 3 .
Structure of the alien flora of Podgorica with respect to origin.If a species distribution covers more than one continent, it is considered as a representative of each of them.

Table 4 .
Values of the Sørensen similarity index for the alien flora of Podgorica compared to those of Rome, Patras, and Salonika.