Impact of urbanization on the ant diversity: a case study on teak plantation in South Sulawesi, Indonesia

Ant communities play an important role in a teak agroecosystem. However, ant diversity is affected by urbanization. The purpose of this study was to determine the diversity and composition of ants in teak plantations in urban and rural areas. This study was conducted in July 2022 at three plantations in two regencies (Gowa and Maros) and one city (Makassar) in South Sulawesi, Indonesia. Gowa and Maros are located in rural areas, while Makassar is located in urban areas. Ants were sampled using a pitfall canopy. At each plantation, 20 trees were sampled randomly for pitfall installation. Ants were identified to the genera level and morphospecies. Ant’s diversity was analyzed using the Shannon Wiener, Simpson, and Evenness index and analysis of dissimilarity (Anosim). Total 273 individual ants samples were collected from 10 species and four subfamilies from three teak plantations in South Sulawesi. Crematogaster sp.1 was the most abundant ant among all the collected samples. Based upon the different indexes, the highest ant diversity was found in Gowa followed by Maros, while the lowest diversity was found in Makassar. The level of ant dominance in Makassar was higher than other two studied areas. The highest species evenness index was also found in Gowa and followed by Maros. The species composition in the three teak plantations was also not similar. Each location had their unique species composition than the other locations. This indicated that urbanization causes negative impacts on ants diversity and evenness as well as increase the dominance of ant species in teak plantations.


Introduction
Multiple modifications of landscapes and ecosystems are the impact of urbanization [1].The effect of urbanization on local species is rarely studied [2].Changes in species composition and shifts from specialist species to generalists are the impacts of urbanization on biodiversity [3,4].In relation to urban areas, a species can be categorized into urban avoiders, suburban adaptable, and urban exploiters [5].Urbanization is also the main cause of biodiversity loss [6].Ant diversity is also affected by urbanization 1230 (2023) 012095 IOP Publishing doi:10.1088/1755-1315/1230/1/012095 2 [7].The major influence caused by urbanization on ants is on their species composition [8].Some ant species have even adapted to the urban environment [9].
The existence of ants is very important in agroecosystems.There are various roles of ants ranging from predators to herbivores [10].One commodity that benefits from the presence of ants is teak plantation.Several predatory ants from the genera Crematogaster, Anoplolepis, and Monomorium are known to act as pest predators that attack teak plants [11].There are important pests that commonly attack teak plants such as the ambrosia beetle [12].The ability of ants to form colonies in tree niches such as trunks, branch cavities, and subcortical cavities of trees and their territorial behaviour can support the process of biological control of teak pests [13].
Up to date, studies on the influence of urbanization and ant communities on teak plants in Indonesia were still not widely studied.Therefore, purpose of this study was to determine the diversity and composition of ants in teak plantations in urban and rural areas.

Study areas
The research was conducted in three teak plantations in South Sulawesi Province during July 2022 (Figure 1).One plot was located in Makassar City and two plots were located in Maros and Gowa Regencies.Makassar City represents urban areas, while Maros and Gowa Regencies represent rural areas.Based on [14], the population in Makassar City is 1.5 million people (8500 people/km 2 ), while in Maros Regency there are only 0.36 millions people (222 people/km 2 ) and Gowa Regency with 0.79 millions people (419 people/km 2 ).

Sampling method
Each plot consists of 20 sample trees.Each plot was made of two rows with 10 trees in each row (Figure 2).The distance between rows and trees were maintained approximately 4 × 4 m.While the distance between trees was also as far as 4 m.Ant sampling was carried out using the canopy pitfall method [15].Pitfall traps were installed for each tree at a height of 1 m from the ground.The trap was filled with 70% ethanol.Traps were set 8.00 AM and collected it for one and two weeks.Trapped insects were collected and stored in vials.

Sortation and identification
The insects obtained during the survey were first sorted at the Plant Pest Laboratory, Department of Plant Pests and Diseases, Faculty of Agriculture, Hasanuddin University.Furthermore, the obtained ants were identified and counted.Identification was carried out down to the genera and morphospecies level [16] based on the identification key in Nazaretta et al. [17].

Data analysis
Ant diversity was analyzed using the Shannon-Wiener, Simpson, and Evenness index [18].The level of ant diversity was analyzed using the Shannon-Wiener index.Dominance level was analyzed by Inverse Simpson index.While the level of evenness was measured using the Evenness index.Species composition was analyzed using ANOSIM (Analysis of Dissimilarity) analysis with the Bray-Curtis index.All analyzes were performed using R-statistic v.4.2.0 [19].

Ant diversity
A total of 273 individuals and 10 morphospecies of ants from nine genera and four subfamilies were identified from all locations (Table 1).Myrmicinae became the subfamily with the most species (4 species) followed by Formicinae (3 sp.), Dolichoderinae (2 sp.), and Pseudomyrmicinae (1 sp.).Crematogaster sp.1 was the most common species with a total of 170 individuals followed by Pheidole sp.1 and Paratrechina longicornis (Figure 3).Ant species found in teak plantations have the potential to become natural enemies of pests that can attack teak plants.Crematogaster and Monomorium are genera of ants which are predators of teak pests [11].Eight of the 10 ant species found were generalized foragers.Only Pheidole sp.1 and Tetraponera sp.1 that are not classified as generalized foragers [20].
Based on the index results, there were differences in the level of diversity at each location based on the index.On the Shannon-Wiener index, ant diversity in Makassar City as an urban area was very low compared to Gowa and Maros as rural areas.Based upon their dominance, the level of dominance in Makassar City is very high based on the low value of the Inverse Simpson index.Meanwhile, the level of evenness of species in Makassar City was also lower than Gowa and Maros.
The number of ant species found in urban areas was lower than in rural areas (Figure 4).In Makassar, as an urban area, there were only four species.This number was lower than in Gowa (7 species) and Maros (5 species).While the opposite results obtained in the abundance of ants.The number of individual ants in Makassar (170 individuals) was higher than that of Maros (76 individuals) and Gowa (27 individuals).

Ant species composition
The species composition at each location showed differences (R-Anosim = 0.341; P = 0.001).When compared between locations, the difference in composition between Gowa and Maros was lower than Gowa-Makassar and Maros-Makassar (Table 2).In addition, there were unique ant species in each location (Figure 5).In Gowa, there were three unique ant species.On Maros there were two unique species.Meanwhile, in Makassar there was only one unique species.There were two ants found in two locations, P. longicornis which was found in Gowa and Maros and Monomorium sp.1 which was found in Gowa and Makassar.Meanwhile, two species that were found in all locations, Crematogaster sp.1 and Camponotus sp.1.Miguelena and Baker [8] explain that urbanization has more effect on the composition of ant species.Two of 10 species were known as invasive and tramp species, they were Tapinoma melanocephalum and Paratrechina longicornis.However both of them cannot be found in the same location.Liu et al. [21] explain that the two ants could compete if found in the same location.The P. longicornis was also known as the "True Crazy Ant" due to its tramp nature [22].
The high population of Crematogaster sp.1 ants was similar to the results of a study by Stukalyuk et al. [23].Crematogaster sp.1 ants could adopt invasive traits in urban environments.Cordonnier et al. [9] also stated that several taxa including ants can change their behavior to become invasive or cryptic invasive in urban environments.In addition, in oil palm plantations, Pfeiffer et al. [24] categorized Crematogaster sp.1 as the dominant ant based on criteria such as a high number of worker castes, polydomous nests, and dominance in bait trap tuna.

Conclusion
A total of 10 ant species from nine genera and four families were recorded from three teak plantations in South Sulawesi.The number of ant species in the Makassar area as an urban area was lower, however their abundance was higher.The composition of ant species in urban and rural areas also shows differences.This proves that ants can be adapted to both urban and rural environments.

Table 1 .
List of ants recorded from all studied plots

Table 2 .
ANOSIM analysis results comparison of the composition of each location.Below the diagonal shows the value of R ANOSIM.