Pollinator insects on sugar palm (Arenga pinnata Merr.) in South Sumatera, Indonesia

Sugar palm production depends heavily on pollinator insects, including some insects related to A. pinnata. This study aimed to identify pollinating insect species, distribution, and biodiversity in four South Sumatran regions. Sweep nets and yellow sticky traps placed around the flowers of sugar palms were used to catch insects once a week. The trap is set up once every 24 hours. In the Ogan Ilir region, pollinating insect species such as Epuraea aestiva, Mystrops costaricensis, Elaidobius sp., Gabrius sp., and Brachypepluis sp. have been found. Apis meliefera, Apis cerana, Poliba occidentalis, Papilio sp., and Drosophila are found in the Musi Banyuasin of Ogan Komering Ilir (OKI). Drosophila, Graphium agamemnon, Appias libythea, Pothantus lydia, Mycalesis perseus, Vespa affinis, Tetragonula laeviceps, Tabanus sp., Aedes albopictus, Neurothemis fluctuans, Ypthima baldus, Cupha erymanthis, and Apis cerana were found in Muara Enim. Additionally, Muara Enim had the highest pollinator population, while Ogan Ilir had the lowest. Observations showed that the yellow sticky trap technique operated more effectively than the sweep net. The community is anticipated to gain from research by learning more about pollinating insects connected to sugar palms, their role in the surrounding ecosystem, and the bioecology of sugar palms.


Introduction
Indonesian palmae plant Arenga pinnata Wurmb Merr., also called the sugar palm, is omnipresent there [1].The sugar palm plantations covered an area of 529 acres in South Sumatra, producing 192 tons [2].The sugar palm's parts can be utilized for several community needs.Nira is the liquid that is obtained by tapping male flowers and transformed into palm sugar, soft drinks, vinegar, and alcohol, which is the main by-product of the sugar palm plant.The female blooms of the sugar palm plant need to be gathered to produce kolang kaling and sugar palm flour, which are used to make cakes, bread, and biscuits.Brooms and well water filters are made of palm fibers [3,4].According to various studies conducted in the Netherlands, palm trees are frequently planted in parks to reduce CO2 because they are known to produce oxygen, which is beneficial to human health [5].The plant's propagation ability could be jeopardized if the community uses sugar palms for household industries without rejuvenation [6].
The sugar palm plant can thrive in various environments and is simple to cultivate even in sandy and clay soil types, except for acidic soil (very low soil pH) [7,8].According to [9], lowlands up to 1,400 meters above sea level (masl) are among the agroclimates that sugar palms may adapt to.The plant population of sugar palms is decreasing due to many old and unproductive trees.However, population rejuvenation efforts have not been carried out optimally.Based on the study's results, one 1346 (2024) 012025 IOP Publishing doi:10.1088/1755-1315/1346/1/012025 2 factor that affects sugar palm trees' growth is the presence of insects.Insects occupy habitats above the earth's surface, both on land, at sea, and in the air.Various types of habitats, ranging from dry to wet areas and from hot to polar regions, can be occupied by insects [10,11].The most incredible variety of species, a wide range of habitat functions, and ubiquity are all characteristics of insects.In addition, plants can attract insects who need food and a place to reside.[12].The connection between diversity and species interactions warrants special consideration in light of the global reduction in biodiversity [13].
The number of insects associated with plants, such as harmful pest insects, beneficial natural enemies (predators and parasitoids), and those valuable as pollinators, makes insects very important in ecosystems and human life [14,15].Based on research by Withaningsih et al. (2021) [16], insects from the Apidae family (Apis cerana, Apis dorsata, Trigona sp.) and Drosophilidae (Drosophila sp.) were found in sugar palm flowers.These insects act as pollinators.In order to maintain the diversity and vitality of flowering plants, pollination is a crucial ecological activity that also benefits people and other living things [17,18,19,20].A range of ecological concerns, such as the influence of pollinators on floral trait selection and the impact of interspecific plant competition on pollinator visitation and pollination success, require estimates of pollinator visitation.Additionally, about 90% of flowering angiosperms depend on insects or other animals for pollination [21,22].The lack of information and studies on pollinator insects on sugar palm plants and those associated with surrounding vegetation is the reason for the need to research what species of pollinator insects are on sugar palm plants so that methods for growing and developing their population in the wild might be discovered in order to maximize palm production.

Methods
The study was carried out in the districts of Ogan Ilir, Ogan Komering Ilir, Musi Banyuasin, and Muara Enim, utilizing the purposive sampling technique from February until August 2023.Due to the palm trees flowering, the samples of plants that were seen were explicitly chosen.Yellow sticky traps placed close to the palm blossom, multiple traps, and sweep nets with multiple swings were used to establish traps to capture different insect species.Once a week, a morning collection of trapped insects and a sweep net was performed.The number of the sample tree, the type of trap used, and the date of the insect sampling were all written on the labels of the vials containing the trapped insects.

Insect Identification
Insects were photographed from the dorsal position, or a position that clearly shows the morphology of the insect.Insects were photographed using a cellphone camera with the help of macro lenses, a Sinher Xsz 107bn microscope, and Optilab 2.0.Insect identification was done by looking at the morphology of the photographed insects, including the shape of antennae, wings, caput, body color, and limbs.Insect photos were matched to insect identification books, journals, and the "Picture of Insects" application.

Data Analysis
Using the Shannon diversity index (H'), evenness (E), and its dominance species (D), the variety of insect pollinators was examined.R Studio software was used to compare data on the number of captured insect individuals using analysis Kruskal-Wallis to determine whether there is a notable difference in insect species frequencies, Spearman-Rank test to find out if there is a significant difference in the median frequency of occurrence of each insect species.

The study area's description
Four districts made up the study, which was done in five villages.The company manages a sugar palm plantation in the village of Ulak Segung, one of the five observed settlements.The sugar palm plantations in the other four settlements were created organically.Based on morphology, there is a noticeable difference between sugar palm trees that are naturally planted and those that were purposefully planted by companies, with naturally placed sugar palm trees being taller than those maintained by companies.In addition, Ulak Segelung village's sugar palm trees are monocultures rather than naturally grown ones.The differences in the vegetation that grows around the sugar palm trees that were naturally planted are shown in Table 1.The five villages were selected due to their proximity to South Sumatra's palm sugar plantation hub and the sheer volume of plantations there.In addition, safety is a significant consideration because there were multiple locations with deadly palm trees perched atop cliff faces.The other villages are bordered by a variety of vegetation such as duku, paddy, rubber plants, durian, banana trees, and palm trees growing far apart; however, Ulak Segelung village is surrounded by swamp land and sugar palm trees are planted closely, and in great numbers.

Diversity of insect pollinators
This study found that the insect pollinators comprise 39 species, four orders, and thirteen families, totaling 2948 individuals.Eight orders of insect pollinators found were Hymenoptera (family Apidae, and vespidae), Diptera (family Dhrosopilidhae, Teprithidae, Platistomatidae), Lepidoptera (family Pieridae, Hesperidae, Nymphalidae, and Papilionidae), Coleoptera (family Staphylinidae, Curculionidae, Scirtidae, Nitidulidae).The most prevalent animal group (698 individuals, eight species) is the bee (order Hymenoptera), which was followed by hoverflies (order Diptera; 1909 individuals, three species, and three families).Butterflies (order Lepidoptera; 156 individuals, nine species, and four families) were the group with the least amount of them (Table 2 and Fig. 4).Apis cerana is a reasonably common insect in every village.In addition, the most prevalent insect in Sukaraja and East Santapan villages is the Drosophila.Furthermore, Santapan Timur and Sukaraja are the two localities where Apis cerana is primarily found.
According to the amount of insects collected, Sangadesa Musi Banyuasin has the fewest total insects, while the Sukaraja Ogan Komering Ilir village has the most.Additionally, diverse numbers of sugar palm plant observations have been made, including 10 in Sangadesa village and 20 in Sukaraja village.Ulak Segelung village has the highest value compared to other villages, according to the results of the computation of the species diversity study.While sugar palms are naturally grown in neighboring villages, Ulak Segelung village was a company-managed sugar palm farm.According to the statistical analysis, there were noticeable disparities in insects in each village.The statistical analysis revealed considerably varying P values for bug species using various trap kinds in each region.The value of the species dominance index suggests that no species appears to be dominant in Ulak Segelung village, while the diversity index indicates that the village has the maximum insect variety.According to the uniformity index study, the distribution seems normal in each location.Sangadesa, Tanjung Miring, and Santapan Timur communities had the highest diversity index scores after Ulak Segelung.
More insects were caught with a yellow sticky trap than a sweep net, according to the kind of insect trap utilized.Insects were drawn to the trap's yellow color, which is why this was the case.It is because sweep nets involve swinging repeatedly around the sugar palm blossoms, whereas traps were set up nearby and left in place for 24 hours.A sweep net method of insect capture outperformed a yellow sticky trap in Musi Banyuasin district's Sangadesa village, in contrast to where the stunning difference became apparent (Table 3).Heterotrigona itama, Apis cerana, and Drosophila were the most often encountered insects captured with the yellow sticky trap.Although Apis cerana, Scholates ciinctus, and Drosophila are frequently captured insects using sweep nets.

The Frequency Distribution Of Insect Pollinators
The frequency of insect appearance during several weeks of observation reveals that some species occur more frequently than others in Ulak Segelung Ogan Ilir and Sangadesa Musi Banyuasin villages.
Only one species predominated over other species in Sukaraja Ogan Komering Ilir villages, East Santapan Ogan Ilir, and Tanjung Miring Muara Enim.It is also connected to Ulak Segelung village's greater diversity than other villages.On the other hand, in the first, second, and third weeks, a few insect species dominated the appearance of pollinating insects in Ulak Segelung village.Similarly, Apis cerana arrived in Sukaraja village, Ogan Komering Ilir, every week of observation, like the Drosophila in Ogan Komering Ilir, which consistently visits the blossoms during every observation week.
Most flowering plants need animals to pollinate them, an essential ecosystem service in both wild and agricultural systems.However, when pollinator visits are uncommon, quantifying useful visitor frequency estimates cannot be easy.

Relationship between pollinator insect species and frequency
Using a Kruskal-Wallis test and Dunn test in all data sets, accounting for the distribution of pollinator species in relation to sugar palm plants, we find that insect pollinator plants were in every region, and there were distinct pollinating insects.The Ulak Segelung hamlet showed the most noticeable change in the sugar palm trees, although the other four communities were almost comparable in that more Drosophila species were present.The findings of the Spearman-Rank test analysis, which was performed to determine whether there was any correlation between the occurrence of different insect species, show that Epuraea aestiva and Drosophila sp. had a very negative association, with Epuraea aestiva showing up more frequently than Drosophila sp.The appearance of one species with a high population will be accompanied by an increase in the number of other species, according to a positive correlation between Heterotrigona itama and Scirtes sp., Apis cerana and Scirtes sp., Elaeidobius sp., and Epuraea aestiva, and Scirtes flavoguttatus and Epuraea aestiva.However, there was no negative correlation in the Tanjung Miring, Muara Enim, Sukaraja, and Ogan Komering Ilir villages, and practically all species show positive correlations.The villages of Santapan Timur, Ogan Ilir, Sangadesa, and Musi Banyuasin all show negative connections with low values (Figure 3).

Discussion
The village of Ulak Segelung Ogan Ilir has the most diversity, according to the computation results of the diversity index, dominance index, and uniformity index.Many sugar palm trees had been planted there, and many flowers were in bloom at the time of observation.Several pollinator insects approach the flower due to this, which is what attracts them.In comparison, the naturally existing sugar palm trees in the nearby communities were scarcely separated and approximately 3 kilometers apart.Sukaraja Ogan Komering Ilir has modest insect dominance, while other villages have slight insect dominance (no insects rule).The villages with the highest uniformity indices are Ulak Segelung, Ogan Ilir, and Tanjung Miring Muara Enim; a high uniformity indicates a stable society.According to the relationships between these three indices, the dominance value will be low, and the community will be stable when the diversity value is high.Several species, including Gabrius sp., Elaidobius sp., Scirtes sp., Scirtes plavogutattus, Brachypeplus sp., Epuraea aestiva, Drosophila sp., Apis cerana, and Heterotrigona itama, are part of the high diversity in Ulak Segelung village.Various pollinators may visit flowering plants more frequently and in more significant numbers due to their diversity, according to recent research, boosting the pollination process.Even though it was obvious that floral traits were involved in these impacts, it is not yet known whether flower attributes were to blame or, if they were, whether pollinator abundance and visitation frequency were more influenced by mass-ratio effects (mean trait values) or by trait variety.
According to Ewuim's (2011) [23] research on raffia palm plants in Nigeria, Camponotus maculatus, Maycodrosophylla sp., and Lepidoptera larvae were collected more frequently than any other species, with C. acvapimensis and Apis mellifera L. coming from all the sites (villages) in relatively high numbers.This plant, which is related to the sugar palm and was known for producing wine, was a member of that family.One of Malaysia's most frequent pollinators on oil palm trees is Elaidobius sp.Numerous studies have been conducted to boost the prevalence of this pollinator insect in nature because it has been known to improve pollination on certain plants since 1981.The sampling site, distance from natural vegetation, and flower sex impacted the variety and amount of oil palm insect flower visitors.In addition, On Bugala Island (Uganda), plantations were separated into those that were close to natural vegetation (0-15 m) and those that were far away (100-200 m).Collected 162.677 insects in 23 morpho-species, with weevils from the genera Elaeidobius and Metamasius (Family: Curculionidae), beetles from the families Nitidulidae, Staphylinidae and Scarabidae, Diptera from the families Muscidae, Drosophilidae, and Platystomatidae, and honeybee [24].
In a 7-week sampling period, Scirtes sp. and Elaidobius sp., the two species that appeared the most frequently in Ulak Segelung village, Ogan Ilir (Figure a), had medians of 9 and 6, respectively.According to the Z comparison, there was only a significant difference in the appearance of Brachypelpus sp. and Elaidobius sp., whereas, for other insects, there was no significant difference in the frequency of their appearance.Insects that rarely appear have a median of 0, such as Brachypelpus sp.Heterotrigona itama was the most prevalent insect in Tanjung Miring village, Muara Enim (Figure b), within seven weeks of sampling, with a median of 4. Apis cerana and Chupa erymanthis are insects that only occasionally appear, with a median of 0. However, based on the Z comparison, there was a significant difference in the frequency of appearance of Apis cerana -Heterotrigona itama and Chupa erymanthis -Heterotrigona itama, whereas there was no significant difference for the others.On the other hand, Drosophila sp. had the most excellent median of 25.5 at Santapan Timur hamlet, Ogan Ilir (figure c), followed by Apis cerana with a median of 12.5 within seven weeks of sampling as the most prevalent insects.Tetragonula laeviceps, Xylocopa caerulea, and Amathusia phidippus were three insects with a median of 0, yet based on the Z comparison, there was a considerable variation in the incidence of every species without fail.Furthermore, Drosophila sp. was the most prevalent insect in Sukaraja village, Ogan Komering Ilir (Figure d), with a median of 55 within seven weeks of sampling.Apis meliefera and Ropalidia sumatrae were two insects that only sometimes emerged, with a median of 0. According to Z comparison, there was a significant difference between the appearance of the Apis cerana and Apis meliefera, the Apis cerena and Drosophila sp., the Apis meliefera and Papilio sp., and the Apis cerena and Ropalidia sumatrae.In addition, within seven weeks of sampling, Drosopila sp. was the most prevalent bug in Sangadesa village, Musi Banyuasin (Figure e), with a median score of 4.5.Leptosia nina, Potanthus lydia, Mycalesis perseus, and Graphium agamemnon have infrequently seen insects with a median of 0. A considerable difference exists between Drosopila sp and Potanthus lydia, Apis cerana and Potanthus lydia, Drosopila sp and Graphium agamemnon, and Mycalesis perseus and Drosopila sp, according to Z comparison (Figure .2).
The concept of adaptation-based pollination syndromes, in which systematically circumscribed groups of pollinators serve a particular host plant, has been used in relation to palms.Except for those pollinated by beetles, many palms do not exhibit significant anthecological alterations that favor visits from a single taxonomic group of insects.A mixed-species guild of nectar-feeding insects appears to be the most common and reliable pollinator guild, with a comparable guild of generalist-feeding pollinators [25].
The Kruskal-Wallis analysis's findings showed a P-value of <0.01; this value suggests occasional differences in the frequency of appearance of each pollinator species.In all observation regions, significant disparities were discovered.The frequency of insects in sugar palm plants varied throughout many weeks of monitoring (Table 2 and Fig. 1).Pollinator insects can visit other plants when sugar palms are grown naturally because many other plants are growing nearby.Pollinator insects have little choice but to congregate on the sugar palm blossoms in company-planted sugar palm trees because there is no other vegetation in the area.

Conclusion
An increased understanding of the variations in pollinator insects between naturally occurring sugar palm plantations and sugar palm plantations grown by businesses was anticipated as a result of this research.The outcomes in the two locations were, it turns out, remarkably different.Although we initially thought that naturally occurring palm trees would have more pollinators, the data showed that the contrary was true.In five villages and four districts, 2948 insect species belonging to eight orders were discovered.There were considerable differences between species in the pattern of pollinator insect occurrence from week to week.Due to the abundance of various sugar palm trees that flowered simultaneously in Ulak Segelung Ogan Ilir, the village was more diversified than other villages.Since the hamlet lacked any other vegetation, any pollinating insects that came through focused on the sugar palm blossoms.The palm trees that were grown naturally revealed a stronger connection between insect species.

Table 3 .
The number of species and individual insect pollinators based on the type of trap at Ulak Segelung village Ogan Ilir, Tanjung Miring village Muara Enim, Santa pan Timur village Ogan Ilir, Sukaraja village Ogan Komering Ilir, Sangadesa village Musi Banyuasin.