URBAN GREENERY APHIDS ( HEMIPTERA , APHIDIDAE )

In 2010-2011, a study of the occurrence of aphids was carried out in three parks in Bydgoszcz, the Balaton Park, the Jan Kochanowski Park and the Park by Unii Lubelskiej. Observations were made every ten days by monitoring trees and shrubs as soon as aphids appeared, i.e. from the end of April to the beginning of August. The counts of aphids were replicated three times, on each plant species where the insects were observed. Based on the collected material, 14 aphid species were found on 16 plant species in the Jan Kochanowski Park, 16 species of aphids on 14 plant species in the Balaton Park and in the Park by Unii Lubelskiej, only 12 species feeding on 16 plant species. In both years of the study, of aphid species feeding on trees and shrubs, Aphis fabae, Aphis sambuci, Aphis spiraephaga and Hyalopterus pruni, occurred most frequently. The Balaton Park was characterized by the largest number of aphids colonizing plants; in contrast, the number of tree and bush species on which they fed was the lowest.


INTRODUCTION
Urban environments create specific conditions for entomofauna, since human activity has caused the degradation of the primary ecosystems in them.The most numerous group colonizing the urban green areas are insects with piercing-sucking mouthparts, including aphids (Lubiarz et al. 2011;Trojan and Winiarska, 2001;Barczak, 2004).
The first Polish studies of urban entomofauna and its changes under the influence of urbanization pressure were published in the seventies of the last century (Lubiarz et al., 2011).They gave the grounds for learning processes determining the development and reproduction of insects in cities.The studies indicated that the factors that determine the numbers of their populations and survival rates in cities are abundance of food sources and various aspects of human activity.A study was conducted in Poland, proving that there is a different response of different trophic groups of insects to the effect of factors connected with urbanization pressure (Trojan and Winiarska, 2001).They are characterized by an aptitude for adapting to constantly changing urban conditions.Insects with piercing-sucking mouthparts constitute the most numerous group of these arthropods, being at the same time the largest threat to urban greenery (Trojan and Winiarska, 2001;Barczak, 2004).
The number of sucking insects is particularly high on trees growing along the streets, even several hundred times higher than on trees in parks or in suburban areas (Bennewicz et al., 2011;Lubiarz et al., 2011).
From the available literature sources, it is known that the results of studies of aphidofauna in urban agglomerations in Poland are still insufficient, since they have been conducted irregularly and are not completely documented.A better examination of the aphidofauna in cities during its occurrence on host plants can help to select species of trees and shrubs with little sensitivity to aphids and improve programs of ornamental plant protection.Moreover, it will be possible to monitor pollution in cities indirectly through observations of the changes in the numbers and degree of plant infestation by these phytophages (Lubiarz et al., 2011).
Bydgoszcz has very good natural conditions for the development and life cycle of many animal species, both due to the large stretches of urban greenery and the vicinity of extensive forest areas and water reservoirs, as well as a system connecting the Brda River, the Vistula and the Bydgoszcz Canal (Banaszak and Izdebska, 1995).
Occasional observations of the occurrence of aphids in the area of Bydgoszcz and its vicinity were only carried out by Szelegiewicz (1968) in the 1960s.In 2010, a study of the species composition of those hemipterans on the shrubs and trees constituting the basic part of urban green in Bydgoszcz was initiated (Bennewicz et al., 2011).
The aim of this study was to characterize the aphid communities, their species composition and domination structure on trees and shrubs in three different city parks in Bydgoszcz.

MATERIALS AND METHODS
Observations were conducted in 2010-2011 in three parks situated in the central part of Bydgoszcz.They differ in period of establishment and the proportion of high greenery.Water reservoirs occur within all the research areas or in the neighborhood.The Jan Kochanowski Park is surrounded by high-density city center housing, the Park in Unii Lubelskiej street borders railway areas and the Brda river.The community park Balaton is located in an area of widely distributed blocks of flats of Bartodzieje.
The Jan Kochanowski Park was established in 1909-1910 in the style of an English landscape park.It is one of the most elegant green areas in the center of Bydgoszcz, and occupies an area of 2.8 ha.The greenery in Unii Lubelskiej street encompasses 4.08 ha and belongs to the oldest park areas in Bydgoszcz.Its current shape is a result of planting made after World War II.The Balaton Park, in turn, was established in the 1970s together with the surrounding housing estate.It has 5.16 ha together with a water reservoir with an area of almost 2 ha (80 x 225 m) (Badtke, 2007).
Currently in the Jan Kochanowski Park, mainly magnificent trees of local species occur, such as Acer pseudoplatanus, Acer platanoides, Carpinus betulus, Fagus sylvatica, Tilia cordata Quercus robur, and foreign species, such as Aesculus hippocastanum, Acer saccharinum.Among shrubs, Berberis vulgaris, Philadelphus coronarius, Sambucus nigra and Viburnum opulus occur in large numbers.
Aphids of the family Aphididae collected in the individual research areas from various plant species were presented in Tables 2, 3 and 4. Plants were sur-veyed every ten days, from the moment the aphids appeared, i.e. from the end of April to the end of July.Aphids in colonies were counted in three replications on each species of a tree or shrub where the insects were observed.
Analysis of the collected material was carried out based on the determination of the aphid species feeding on plants in the studied parks of Bydgoszcz, using keys and catalogues (Szelegiewicz, 1968;Blackman andEastop, 1984, 1994).The number of aphids was determined, as well as the structure of their domination and similarity of their communities between the studied areas (parks).
To determine individual domination for the aphid species, according to Klimaszewski et al. (1980) the following domination classes were adopted: D4very numerous species -dominant, accounting for more than 20% of the collected material in the given habitat; D3 -numerous species -subdominant, represented by 10.1-20% of the total number of indi- viduals; D2 -quite numerous species -recedent, ranging from 3-10% of the collected material; D1rare species, subrecedent -represented by less than 3% of the total number of individuals in the community.
Quantitative comparison of the insect communities (similarity of domination structure) was carried out using the Renkonen index (Re).It was assumed that communities are similar for values of Re from about 50% (e.g.Pawlikowski, 1985).For a qualitative and quantitative comparison of aphid communities, the Hutchison (1970) test was used, where the total species diversity index (H') (Shannon and Weaver, 1963) was applied for the assessment of significance of differences between compared communities of insects.

RESULTS, DISCUSSION AND CONCLUSIONS
In 2010-2011, 27 species of aphids of the family Aphididae in some parks in Bydgoszcz were determined on 23 species of trees and shrubs.This includes 20 species of aphids of the subfamily Aphidinae, 2 species from each of the subfamilies Chaitophorinae, Myzocallidinae and Drepanosiphinae, and 1 species from each of the subfamilies Anoeciinae and Pemphiginae.Among the aphid species caught, Aphis fabae, Aphis sambuci, Myzus lythri, Eucallipterus tiliae and Periphylus testudinaceus (Tables 1, 2, 3, 4) occurred in all the parks studied.The most numerous species were A. fabae, A. sambuci, Aphis spiraephaga and Hyalopterus pruni (Table 1).
In both years of the study, 14 species of aphids were recorded on 16 plant species in Jan Kochanowski Park (JK).On Prunus cerasifera, 2 species were feeding (Myzus lythri and Rhopalosiphum nymphaeae).The other species of aphids were feeding on one plant species (Table 2).
In the Balaton Park (B), 16 aphid species were feeding on 14 species of trees and shrubs (Table 3).One species of aphids was feeding on the majority of plants.Only on Prunus cerasifera and Ribes aureum were three aphid species observed (respectively, Brachycaudus prunicola, H. pruni and M. lythri, as well as Cryptomyzus ribis, Hyperomyzus lactucae and Nasonovia ribisnigri).On trees Cerasus mahaleb two species of aphids occurred, Myzus ceraci and M. lythri (Table 3).
In both years of the study, in the Park by Unii Lubelskiej (UL), 12 aphid species occurred on each of the 16 plant species; only on P. cerasifera only two aphid species were recorded: B. prunicola and M. lythri (Table 4).
In the first year of the study, a similar number of aphids was observed in the parks JK and B; on average about 1200 and 1500 individuals in colonies, respectively (Table 5).In UL there were on average 820 individuals in colonies.In the second year of the study, a slightly higher infestation of plants by aphids was observed and their numbers in colonies were on average from less than 1800 in Balaton Park, 1600 in JK, to about 1500 in the park UL.
In both years of the study, in the Jan Kochanowski Park (JK) the aphid species Aphis fabae, feeding on Philadelphus coronarius, reached the highest numbers (in 2010 more than 600 individuals of this species were observed in colonies, and in 2011 about 650 individuals) (Table 1 and Table 2).Similarly in the Park by Unii Lubelskiej (UL), the most numerous species was A. fabae recorded on Euonymus europaea, P. coronarius and Viburnum opulus (in 2010 about 370 individuals were found, and in 2011 there were almost 850) (Table 1 and Table 4).In the Balaton Park (B), two aphid species, A. fabae and A. sambuci, reached similar numbers in both years.Black bean aphids were feeding on P. coronarius (in 2010 its colonies consisted of about 470 specimens of aphids, and in 2011 about 560 individuals).Elder aphid (A.sambuci) occurring on Sambucus nigra did not exceed the number of 300 individuals in 2010, whereas in 2011 there were more than 820 specimens of this species on the studied shrubs in the colonies (Tables 1 and 3).
Moreover, in both years of the study, in the Jan Kochanowski Park (JK) and in the Park by Unii Lubelskiej (UL), among the studied aphid species, Aphis spiraephaga feeding on Spiraea x vanhouttei reached large numbers (Tables 1, 2, 4).In 2010, in JK on average about 230 individuals of A. spiraephaga were found, and in UL there were almost 200 aphids of this species in colonies.The following year the colonies were, on average, more than 170 and 200 individuals of A. spiraephaga, respectively (Table 1).In addition, the species Hyalopterus pruni, which occurred only in Balaton Park, mainly on Phragmites australis, Prunus cerasifera and Populus nigra, is notable.Colonies of this aphid in 2010 consisted of about 430 individuals and in 2011 around 170 individuals (Table 1, Table 3).
From this data, it follows that Balaton Park was characterized by the largest infestation of plants by aphids on the least number of species of trees and shrubs on which those hemipterans were feeding (Tables 1, 2, 3, 4).
In both years, Aphis fabae predominated among the caught aphid species (Table 5).This species was recorded on three species of plants, mainly Philadelphus coronarius (Table 2, Table 3, Table 4).In the Park Balaton, A. sambuci and H. pruni predominated in both years.In the parks Jan Kochanowski and in Unii Lubelskiej, on Spiraea x vanhouttei the species Aphis spiraephaga also predominated (Table 5).
The quantitative comparison of aphid communities in the studied parks carried out in 2010-2011 using the Renkonen index (Re) showed a similar structure of domination between aphid communities in Jan Kochanowski Park and the Park in Unii Lubelskiej (Table 6).In 2010 the value of Re was from 79.09%, and in 2011 58.17%.Moreover, in 2011 a similarity of domination structure was also observed between aphid communities in the parks JK and B (Re = 63.43%)(Table 6).
In both years of the study, the aphid community in the Balaton Park in 2010 showed the highest species diversity (H'=2.54), in comparison with the communities of these insects in the Jan Kochanowski and Unii Lubelskiej parks (Table 6).However, the assessment of species diversity value (H') for compared aphid communities made with the Hutchison test did not show statistically significant differences.This may result from the fact that the value of the Shannon-Weaver index (H') calculated for the studied aphid communities in all the parks was rather low (Table 6).
In 2010-2011, the study of the aphid species occurring in selected parks of Bydgoszcz included all the species of trees and shrubs on which aphids were feeding (Bennewicz et al., 2011).Similar studies were conducted only in Poznań in the Dendrological gardens and in the central area of Poznań (Wilkaniec, 2001;Wilkaniec and Sztukowska, 2008;Wilkaniec et al., 2012).Other studies carried out in Warsaw, Lublin, Krakow or gdańsk referred to single species of groups of trees or shrubs (Jaśkiewicz, 1999;Tykarska, 2001;Budzińska and goszczyński, 2010;Wojciechowicz-Żytko and Jankowska, 2011).
This study begun in Bydgoszcz had a complex character and its first stage was the faunistic-ecological analysis of the material.The data will then be compared with ecotoxicological aspects of the studied material and area.
Taking into consideration all the results discussed in the present study, the dominant species was Aphis fabae feeding mainly on Philadelphus coronarius and on V. opulus and E. europaea shrubs.Similarly, in the Park 'On Wzgórze Dąbrowskiego' in Bydgoszcz this species was a dominant on P. inodorum; and in the Dendrological gardens in Poznań it was also recorded in great numbers on Philadelphus spp.(Bennewicz et al., 2011;Wilkaniec, 2001).From the available literature, it is known that the species Periphylus testudinaceus occurring numerously on trees of Acer spp., in the present study predominated in the Park in Unii Lubelskiej.It was commonly found in different parks of Bydgoszcz and other cities of Poland (Wilkaniec, 2001;Starżyński, 2006;Bennewicz et al., 2011;Lubiarz et al., 2011).Shrubs of S. nigra, particularly in 2011 in the Jan Kochanowski Park and Balaton Park, were numerously infested by Aphis sambuci.From the study by goszczyński and Osek (2007) it can be concluded that a more numerous occurrence of this species was observed on shrubs growing in concentration.This was not confirmed in the study in urbanized areas in Bydgoszcz, where both the single shrub and the whole complex of shrubs were colonized in the same amounts (Bennewicz et al., 2011).
The occurrence and domination of the aphid Hyalopterus pruni in Balaton Park was probably affected by Phragmites australis, being the secondary host of this aphid, growing abundantly around the water reservoir.In early spring, H. pruni was recorded in large numbers on single trees of Prunus cerasifera, the primary host of this aphid.A similar situation occurred in other parks of Bydgoszcz, where water reservoirs of different sizes were overgrown with P. australis, and P. domestica and P. cerasifera are found in the remains of house gardens (Bennewicz et al., 2011).
The study of aphids colonizing plums (Prunus spp.) conducted on the coast of the Baltic Sea in the area of Lithuania, Latvia, Estonia and Poland showed both species present currently in the whole area of this study and those characteristic only of Poland (Rakauskas and Cichocka, 2005).Aphid species H. pruni and Rhopalosiphum nymphaeae were recorded along the entire coast of the Baltic.They were also found in the studied parks of Bydgoszcz on P. cerasifera, just as in other areas of urban greenery in Bydgoszcz (Bennewicz et al., 2011).The aphid Brachycaudus prunicola recorded only in Poland in the study by Rakauskas and Cichocka (2005), was also observed in the studied parks of Bydgoszcz (Bennewicz et al., 2011).In the area of parks in Bydgoszcz, the aphid Myzus lythri was also feeding on P. cerasifera, observed by Bennewicz et al. (2011) on P. domestica.This aphid species was not recorded by Rakauskas and Cichocka (2005), but it is considered to be a species occurring in a substantial area of Poland (Szelegiewicz, 1968).
To conclude, the low species diversity of aphids in the studied parks could be affected by the small number of host plant species, as is the case in the Park 'On the Canal' and the Park 'On Wzgórze Dąbrowskiego' (Bennewicz et al., 2011).Those parks are some of the oldest green areas in Bydgoszcz and new plantings are carried out in them only occasionally.In consequence, no statistically significant differences were observed between the H' values for the compared communities in the studied parks of Bydgoszcz.
Moreover, in both years of the study, the dominant species was A. fabae, which is a rich source of food, mainly for spiders and many species of insects, including the predatory larvae of Cecidomyiidae, Chamaemyiidae and Syrphidae as well as parasitoids (Barczak, 1994;Winiarska, 1998;Kean and Müller, 2004;Wojciechowicz-Żytko and Jankowska, 2011).These aphidophages can reduce aphid colonies and modify the fluctuations of their numbers in the season.This is going to be the next stage of the faunisticecological analysis of the planned study.

Table 1 .
Mean number of aphid species in parks in Bydgoszcz in 2010-2011.

Table 2 .
Aphid species occurring on trees and bushes in Jan Kochanowski Park in 2010-2011.

Table 3 .
Aphid species occurring on trees and bushes in Balaton Park in 2010-2011.

Table 4 .
Aphid species occurring on trees and bushes in the park by Unii Lubelskiej in 2010-2011.

Table 6 .
Characteristic of aphid communities in the parks of Bydgoszcz in 2010-2011.