Ant Communities (hymenoptera: Formicidae) in an Urban Ecosystem near the Atlantic Rainforest 3. Data Analysis 4. Results and Discussion

The relationships between an urban ecosystem located near the Atlantic Rainforest in southeastern Brazil and ant communities were studied with the objective of quantifying the ant richness and abundance in the household environment and its surroundings. Eighty residences were sampled, where 58 species and 28 genera pertaining to 7 sub-families were found to be present. Inside the residences, the species richness was found to be lower (26), although the abundance was greater (10,670), with the wash area and kitchen being the locales that contributed with the greatest number of hits. The opposite was true in the areas outside the residences, where 54 species and 3,747 ants were observed. Inside houses, the species known as Tramp ants were found, in the following order of importance: Solenopsis saevissima, Tapinoma melanocephalum, Linepithema humile, Paratrechina fulva, Wasmannia auropunctata, P. longicornis, Pheidole megacephala, Monomorium pharaonis and M. floricola. Externally, mainly in the yards and gardens, species such as Octostruma rugifera, Heteroponera dolo, Hypoponera sp.1 and sp.6, Gnamptogenys sp. 4, G. striatula, Odontomachus meinerti, Pachycondyla constricta and P. striata were found. In general, a greater number of species and lower abundance of individuals were observed in the neighborhoods nearer the mountains than in those closer to the urban center. The collection was conducted in 16 neighborhoods in the city, with the northernmost neighborhoods being close to the Serra do Itapety (23° 29' 22 " S and 46° 11' 55 " W; 800 m above the sea level), and those in the south approximating the Serra do Mar (23° 45' 02 " S and 46° 07' 63 " W; 720 m above the sea level) (Figure 1). In each neighborhood, 5 houses were randomly sampled. The collections were conducted every two months for a period of 12 months, always in the same houses. The bait was made from dehydrated beef liver, honey, pineapple cake, and peanut oil, according to the recipe and following the methodology proposed by Bueno and Campos-Farinha (1999). Small amounts of fresh bait were placed inside beverage straws 0.5 cm in diameter and 2 cm long. In the interiors of the houses (household environment), 8 baits were placed: 3 in the kitchen, 2 in the bathroom, and 3 in the wash area. The baits were removed after 24 hours and placed in plastic bags. Manual collections were also conducted around the outside of the houses (walls, gardens, garage, and yard). The material was initially …

The collection was conducted in 16 neighborhoods in the city, with the northernmost neighborhoods being close to the Serra do Itapety (23° 29' 22" S and 46° 11' 55" W; 800 m above the sea level), and those in the south approximating the Serra do Mar (23° 45' 02" S and 46° 07' 63" W; 720 m above the sea level) (Figure 1).

Ant collection
In each neighborhood, 5 houses were randomly sampled.The collections were conducted every two months for a period of 12 months, always in the same houses.The bait was made from dehydrated beef liver, honey, pineapple cake, and peanut oil, according to the recipe and following the methodology proposed by Bueno and Campos-Farinha (1999).Small amounts of fresh bait were placed inside beverage straws 0.5 cm in diameter and 2 cm long.In the interiors of the houses (household environment), 8 baits were placed: 3 in the kitchen, 2 in the bathroom, and 3 in the wash area.The baits were removed after 24 hours and placed in plastic bags.Manual collections were also conducted around the outside of the houses (walls, gardens, garage, and yard).
The material was initially identified according to morpho-species within genera.The identification of the species was carried out by comparison with the ant collections at the Museu de Zoologia of Universidade de São Paulo and the Coleção Entomológica Adolph Hempel (Instituto Biológico), as well as with the pertinent literature.Classification follows Bolton (2003).Vouchers were deposited at the University of Mogi das Cruzes (SP).

Data Analysis
Species richness was defined as the number of ant species occurring in each house, and abundance as the number of individuals collected of each species.The Wilcoxon test, using GraphPad Prism 3.0 software, was applied to test for significant differences between species richness, as well as between the number of individuals inside and outside the houses.Similarity between the interior and exterior of the houses was calculated using the Jaccard index (Magurran, 1988).The relative frequency was calculated based on presence or absence date, and the matrix of association between species with more than 3% frequency was done using the Spearman correlation test (Siegel, 1975).

Results and Discussion
In 80 samples, 14,417 specimens were collected, distributed among 58 species and 28 genera pertaining to

Introduction
Urban ecosystems are generally recognized as being areas undergoing profound and constant local human activity, composed of high-density human habitation, industrial and commercial centers (McIntyre et al., 2001).The environmental modifications that occur during the process of urbanization can affect the distribution of organisms in diverse ways.For example, in this environment, many species achieve high densities, and assume dominant positions due to the existence of unoccupied niches, absence of competitors, and few natural enemies (Luck and Dahsten, 1974); or the intentional and unintentional introduction of exotic species can cause the dislocation of native species (Suarez et al., 1998;Crooks and Soulé, 1999).Yamaguchi (2004Yamaguchi ( , 2005)), studying the influence of urbanization on ant distribution in parks, suggested that these insects would become the bio-indicators of variation in urban environments.
Some ant species have successfully occupied urban environments, achieving wide distribution and abundance.This success is probably related to their feeding habits, as the majority of ants is omnivorous, and also because they exploit small spaces for nesting, such as crevices and holes.Human contact with ants in the urban environment can be observed in residences, commercial establishments, and even in hospitals.In houses, ants cause discomfort, whereas in hospitals, they can carry pathogenic organisms (Eichler, 1978;Bueno and Campos-Farinha, 1999).
In Brazil, the process of urbanization is occurring at an accelerated pace, and often advancing on areas that are considered to be priorities for conservation.This is the case of the city of Mogi das Cruzes, located in southeastern Brazil, where the urban network is centered around the ciliary plants of the Tietê River, and is expanding in the direction of the Itapety and Serra do Mar mountains, which belong to the Atlantic Rainforest biome.To maintain urban biodiversity for inhabitants, and because of it intrinsic value in the face of increasing population and urban growth, knowledge regarding the ecology of the species in these locales is needed.
Thus, the present study seeks to quantify the richness and abundance of ants in the household environment and its surroundings, with the objective of determining the communities that occur in an urban ecosystem characterized by its proximity to the Atlantic Rainforest, to compare this ecosystem with other urban areas.

Study site
The city of Mogi das Cruzes, São Paulo, is the largest city in the Tietê-cabeceiras hydrological basin, of 731 km 2 and with 330,000 inhabitants.It has the second largest forest covering in the Atlantic Rainforest, 17,100 ha, located mainly in the proximity of the Serra do Itapety and Serra do Mar mountains, along the Tietê River.internal areas of the houses (Figure 4a) and also between the number of individuals collected within each species (p < 0.05) (Figure 4b).The similarity between species richness in the two areas, calculated using the Jaccard index, was low (0.38).There was a predominance of species known as tramp ants in the interior of the houses, possibly contributing to a higher number of individuals collected, as they are characterized by the recruitment of a large number of worker ants for foraging activities (Bueno and Campos-Farinha, 1999).Tramp ants are species that are intimately associated with human activities, and generally nest in structures built in urban environments (Schultz and McGlynn, 2000).They share characteristics that facilitate their introduction into new environments, such as generalist feeding habits, polygamy, reduced intra-specific aggression, small size, and high recruitment, as well as having a high rate of migration, uni-colonial population, abolition of nuptial flight, and very small workers and queens (Passera, 1994;Holway et al., 2002).
In the internal areas of the residences, the species Tapinoma melanocephalum Fabricius, 1793, The number of ant species collected in the urban area studied demonstrates, together with the studies of Fowler et al. (1993), Bueno and Fowler (1994), Delabie et al. (1995), Silva andLoeck (1999) and Piva and Campos-Farinha (1999), that tropical urban ecosystems are richer in ant species compared to those in temperate climates.In tropical regions, the availability of food and nesting sites, which are important conditions for the maintenance of the species in a specific locale (Hölldobler and Wilson, 1990), are abundant and generate environments which are propitious for a greater number of species.
Comparing the internal and external areas of the residences, lower species richness (26) was observed inside houses, but the highest abundance (10,670), with the wash area and kitchen being the locales that contributed with the greater number of hits (Figure 3).The inverse was found in the external areas of the houses, with 54 species and 3,747 ants being recorded (Figure 3), of which close to 57% were collected foraging in the soil and/or vegetation of the gardens and yards of the residences.The Wilcoxon test showed significant differences (p < 0.05) between species richness in the external and   1).
One can see that the most frequent and the most abundant species were practically the same inside and outside the residences, being the species with the widest geographical distribution (Schultz and McGlynn, 2000), and that they are on the list of the most significant urban ants in southeastern Brazil and southern Bahia proposed by Campos-Farinha et al. (2002).Since all the ants on this list were collected in different neighborhoods of Mogi das Cruzes, they can be placed in order of importance for this urban area, based on the relative frequency of each one: S. saevissima, T. melanocephalum, L. humile Mayr, 1868, P. fulva, W. auropunctata Roger, 1863, P. longicornis (Latreille, 1802), Ph. megacephala, M. pharaonis and M. floricola Jerdon, 1851.Of these, Ph. megacephala was almost the unique species collected in Vila dos Remédios and Vila Industrial, which are the oldest neighborhoods of the city.
Due to their behavioral characteristics, the presence of Ph. megacephala may be responsible for the death of native invertebrates, ants in particular (Fowler et al., 1994;Vanderwoude et al., 2000), and they indicate that they are dominant in houses and other environments intensively impacted by humans (Fowler et al., 1994;Delabie et al., 1995).Their negative association with P. longicornis and S. saevissima (Figure 5) has already been reported by Delabie et al. (1995), however their antagonism with L. humile as described by Haskins and Haskins (1965), Crowell (1968) and Delabie et al. (1995), could not be verified, as this native species appeared in Thus, the presence of native vegetation in the yards and gardens of the houses, or of the forest near the neighborhoods, may possibly be allowing the existence in an urban area of some taxa which are characteristic of the forest area, which over time, can generate a positive impact on the maintenance of the biodiversity of this ecosystem.

Figure 4 .Figure 5 .
Figure 4. Comparison of species richness a) and the number of individuals per species; and b) in the household environment and around the outside of the houses in an urban ecosystem located near the Atlantic Rainforest.