Designing with wild plants for maximizing insect richness in urban areas

Landscape structure, habitat fragmentation, and the ecology of insects

Mustard plants distant from forest fragments receive a lower diversity of flower-visiting insects

Habitat fragmentation strongly affects insect species diversity and community composition, but few studies have examined landscape effects on long term development of insect communities. As mobile consumers, insects should be sensitive to both local plant community and landscape context. We tested this prediction using sweep-net transects to sample insect communities for 8 years at an experimentally fragmented old-field site in northeastern Kansas, USA. The site included habitat patches undergoing secondary succession, surrounded by a low turf matrix. During the first 5 years, plant richness and cover were measured in patches. Insect species richness, total density, and trophic diversity increased over time on all transects. Cover of woody plants and perennial forbs increased each year, adding structural complexity to successional patches and potentially contributing to increased insect diversity. Within years, insect richness was significantly greater on transects through large successional patches (5000 m2) than on transects through fragmented arrays of 6 medium-sized (total area 1728 m2) or 15 small (480 m2) patches. However, plant cover did not differ among patch types and was uncorrelated with insect richness within years. Insect richness was strongly correlated with insect density, but trophic and α diversities did not differ among patch types, indicating that patch insect communities were subsets of a common species pool. We argue that differences in insect richness resulted from landscape effects on the size of these subsets, not patch succession rates. Greater insect richness on large patches can be explained as a community-level consequence of population responses to resource concentration.

Simple SummaryFloral-visiting insects and pollinators play an important role in ecosystem services, and consequently, their identification and study are essential to their adequate preservation and management in crops of agricultural interest. Coffee is a worldwide commodity; however, the diversity of insects that visit its flowers has been little studied. The objective of this research was to quantify the abundance, richness, and functional diversity of coffee floral-visiting insects, especially bees. The results showed that coffee crops host a wide diversity of flower visitors, especially bees, which could be beneficial for productivity and contribute to the maintenance of plant species that accompany coffee cultivation.Despite the important role that flower-visiting insects play in agricultural production, none of the previous studies of coffee pollinators in Colombia have incorporated functional diversity into their analysis. Therefore, this study aimed to quantify the abundance, richness, and functional diversity of insects that visit flowers in coffee crops. Twenty-eight plots were selected among five sites in the north, center, and south of Colombia. In each plot, coffee flower insect visitors were collected and recorded on 90 trees at eight-minute intervals per tree, at three different times over three days. All sampling was carried out during two flowering events per year, over three years, resulting in a total of 1240 h of observations. Subsequently, the insects were taxonomically identified, and the number of individuals and species, as well as the diversity of the order q, were estimated. Functional diversity was also characterized in the bee community. The results: (a) 23,735 individuals belonging to 566 species were recorded; of them, 90 were bees, with the native species being the most abundant during 10:30 and 13:00 h; (b) bees formed five functional groups, with corbiculate and long-tongued non-corbiculate bees being the most abundant and occupying the largest regions of functional space; (c) potential pollinators in coffee crops are Apis mellifera, Nannotrigona gaboi, Tetragonisca angustula, Geotrigona cf. tellurica, and Partamona cf. peckolti. Coffee crops host a wide diversity of flower visitors, especially bees, which could be beneficial for productivity and contribute to the maintenance of plant species that accompany coffee cultivation.

In recent years, the decline of insect biodiversity and the imminent loss of provided ecosystem functions and services has received public attention and raised the demand for political action. The complex, multi-causal contributors to insect decline require a broad interdisciplinary and cross-sectoral approach that addresses ecological and social aspects to find sustainable solutions. The project Diversity of Insects in Nature protected Areas (DINA) assesses insect communities in 21 nature reserves in Germany, and considers interactions with plant diversity, pesticide exposure, spatial and climatic factors. The nature reserves border on agricultural land, to investigate impacts on insect diversity. Part of the project is to obtain scientific data from Malaise traps and their surroundings, while another part involves relevant stakeholders to identify opportunities and obstacles to insect diversity conservation. Our results indicate a positive association between insect richness and biomass. Insect richness was negatively related to the number of stationary pesticides (soil and vegetation), pesticides measured in ethanol, the amount of area in agricultural production, and precipitation. Our qualitative survey along with stakeholder interviews show that there is general support for insect conservation, while at the same time the stakeholders expressed the need for more information and data on insect biodiversity, as well as flexible policy options. We conclude that conservation management for insects in protected areas should consider a wider landscape. Local targets of conservation management will have to integrate different stakeholder perspectives. Scientifically informed stakeholder dialogues can mediate conflicts of interests, knowledge, and values to develop mutual conservation scenarios.

Insects play crucial roles in their specific niches and are vital contributors to various ecosystem processes. They dominate the food webs of both terrestrial and aquatic ecosystems. A study was conducted at Kerala University to evaluate the diversity and abundance of insect species in selected habitats (North and South campus). Sampling was conducted using pitfall traps, sweep nets, beating sheets, Berlese funnels, and hand collection. The collected insects were brought back to the laboratory for identification and counting. A total of 965 insects from 9 Orders and 35 Families were recorded. Indices such as the Shannon index, Simpson index, Margalef index, Evenness index, and Sorenson similarity index were utilized to analyze the diversity of insects. The results indicated that Hymenoptera (30.155%), Orthoptera (25.596%), Lepidoptera (11.192%), and Coleoptera (8.290%) were the most dominant Orders on the campus, comprising 75.233% of the total, whereas the least abundant was Mantodea (0.622%). The South Campus exhibited high species diversity (Margalef index = 8.422), abundance (n = 686), Evenness (E = 0.776), and Shannon diversity (H = 3.124) of insects. It also showed a higher Simpson index (λ = 0.109) compared to the North Campus, which indicated (λ = 0.0610). Moreover, the South Campus recorded a very high number of species, with 56 species (Margalef index = 8.422) compared to 45 species (Margalef index = 7.813) recorded from the North Campus. The higher the index value, the greater the species richness. The high diversity and richness of insects in the southern habitat may be attributed to the large and less disturbed area, the presence of well-distributed ecological niches, more microhabitats, and an abundance of food. Therefore, understanding the factors that influence insect species diversity and abundance at the University of Kerala is important for conservation. This study, thus, highlights the diversity and abundance of insects and the need for sustainable measures to be implemented to conserve these significant species.

Abstract. Wakhid, Rauf A, Krisanti M, Sumertajaya IM, Maryana N. 2020. Species richness and diversity of aquatic insects inhabiting rice fields in Bogor, West Java, Indonesia. Biodiversitas 21: 34-42. Rice fields occupy the largest cultivated area in agricultural landscape in Indonesia and support a variety of living organisms, including aquatic insects. This study was conducted with the objective to determine the species richness and diversity of aquatic insects inhabiting rice fields. Sampling was made in March, May, and July 2017 in rice fields at Situgede, Pandansari, and Kawungluwuk (Bogor region, West Java, Indonesia), and carried out by dragging dip net on the bottom along the edge of the rice plots. A total of 3,306 individuals representing 45 species of aquatic insects belonging to 30 genera, 20 families, and seven orders were recorded. Order Hemiptera was the most abundance comprising 28.89% of the total insects collected, followed by Diptera (24.80%), Coleoptera (24.41%), and Odonata (21.42%). Functional feeding group analysis showed that collectors-gatherers had the highest proportion (40 - 46%), followed by predators (23-44%) and scrapers (10-35%). Rank-abundance curve showed low species evenness with the four most abundant species were Micronecta siva (Kirkaldy) (Hemiptera: Micronectidae), Chironomus sp. (Diptera: Chironomidae), Orthetrum sabina (Drury) (Odonata: Libellulidae), and Helochares sp. (Coleoptera: Hydrophilidae). The Shannon-Wiener index showed the lowest value (H’=1.84) at Situgede and the highest (H’=2.05) at Pandansari. Richness estimate and individual-based rarefaction curve revealed that rice fields at Pandansari have more species richness than the other two sites. This study provides some insights into the aquatic insect community of the human-made ecosystem and suggests that the ecological approach to pest management is necessary for maintaining ecosystem health and promoting biodiversity.

Organic rice is produced from the agricultural production process with the concept of environmentally friendly PTT. One of the technologies that have been applied by organic farmers is Ecological Engineering or called Ecological Engineering (EE). Flowering plants or referred to as refugia plants are a form of ecological service for the restoration of rice agro-ecosystems, so that all control factors can work optimally towards sustainable agriculture. This study aims to determine the diversity, evenness, and richness of useful insects on refugia plants in organic rice fields in Ngompro Village, Ngawi Regency. This study used a survey method using direct observation, insect capture was carried out using a sweep net, a yellow sticky trap, and a pitfall trap. The results showed that natural enemies (useful insects) were insects and spiders. Natural enemies of insects were found in a total of 2796 individuals grouped into six orders, 20 families and 35 genera. Natural enemies of spiders were found in a total of 1107 individuals grouped in one order, 8 families, and 9 genera. The diversity index (H ) of insect species is 3.27 with the medium category. The diversity index for spider species is 2.04 with the medium category. The evenness index (E) of insect species was 0.92 with the stable category. Evenness index for spider species is 0.93 with stable category. The wealth index (R) of insect species is 4.28 with a high index value category. The wealth index for the type of spider is 1.14 with the category of low index value.

Monitoring insects across space and time is challenging, due to their vast taxonomic and functional diversity. This study demonstrates how nets mounted on rooftops of cars (car nets) and DNA metabarcoding can be applied to sample flying insect richness and diversity across large spatial scales within a limited time period. During June 2018, 365 car net samples were collected by 151 volunteers during two daily time intervals on 218 routes in Denmark. Insect bulk samples were processed with a DNA metabarcoding protocol to estimate taxonomic composition, and the results were compared to known flying insect richness and occurrence data. Insect and hoverfly richness and diversity were assessed across biogeographic regions and dominant land cover types. We detected 15 out of 19 flying insect orders present in Denmark, with high proportions of especially Diptera compared to Danish estimates, and lower insect richness and diversity in urbanized areas. We detected 319 species not known for Denmark and 174 species assessed in the Danish Red List. Our results indicate that the methodology can assess the flying insect fauna at large spatial scales to a wide extent, but may be, like other methods, biased towards certain insect orders.

The insect data of 93 national nature reserves in China was used to identify the underlying drivers’ potential for species richness along geographical gradients. We assessed the correlations between predictors (climate and soil) and response variables (insect richness). We found that the following: insect diversity decreased significantly at higher latitudes. The latitudinal variation in insect richness seems to be driven by climate and soil variations and also the diversity of other biota. Among all the tested predictors, plant diversity explained the most latitudinal patterns of insect richness (R2 = 0.498). Insect richness showed a positive correlation with the diversity of other biota and climate factors (mean annual temperature and mean annual precipitation) and was negatively associated with soil pH. Overall, the interspecific relationship between organisms was the main driver of insect diversity’s latitudinal pattern. However, the effects of climate and soil factors cannot be ignored.

This study assesses and compares soil physicochemical properties and insect diversity in mining and non-mining areas of Jharkhand, India. Ten sites (five mining and five non-mining) were sampled to evaluate soil pH, electrical conductivity, organic carbon, macronutrients (N, P, K, S) and micronutrients (Fe, Mn, Zn, Cu, B). Insect diversity and abundance were quantified using quadrat sampling, pitfall traps and sweep netting. Mining areas exhibited pronounced soil degradation characterized by wider pH variation, elevated electrical conductivity, major reductions in soil organic carbon, and nutrient depletion, along with heterogeneous enrichment of certain micronutrients. Insect richness and abundance were significantly lower in mining areas than non-mining sites. Strong positive associations were observed between organic carbon, nutrient status, and insect diversity, indicating that soil deterioration directly influences biological communities. The study highlights the substantial ecological impacts of mining and underscores the need for restoration strategies emphasizing organic matter recovery, salinity and pH management, and habitat rehabilitation to support soil health and biodiversity.

Insect conservation in agricultural landscapes needs both high crop heterogeneity and semi-natural habitats

Continuous urban developments have resulted in increased demand for street furniture, one of which is street light columns. Artificial light at night (ALAN) pose significant impacts on insect diversity in urban and rural areas. The ALAN is a significant driver of decline in insect diversity. This study evaluated the impact of light intensity and sky quality at night on insect diversity in rural and urban areas of the Asir province, Saudi Arabia. Insect traps were installed in both areas during night. Light intensity of nearby road lamps was measured using light meter, while sky quality was measured using sky quality meter. Rural areas exhibited low light intensity (10.33 flux/f.candle) and good sky quality (18.80 magnitude/arcsec2). Urban areas exhibited intense light (89.33 flux/f.candle) and poor sky quality (15.49 magnitude/arcsec2). Higher insect diversity was recorded for rural areas where insects belonging to seven orders (i.e., Diptera, Lepidoptera, Hemiptera, Hymenoptera, Coleoptera, Neuroptera, and Dermaptera) were collected. However, insects of four orders (i.e., Diptera, Lepidoptera, Hemiptera, and Neuroptera) were found in urban areas indicating low diversity. Lepidopteran insects were frequently recorded from rural areas indicating they are attracted to artificial light. It is concluded that excessive ALAN and poor sky quality at night disrupt insect biodiversity. Therefore, ALAN and sky quality must be considered responsible for decline in insect biodiversity along with other known factors.

Continuous urban developments have resulted in increased demand for street furniture, one of which is street light columns. Artificial light at night (ALAN) pose significant impacts on insect diversity in urban and rural areas. The ALAN is a significant driver of decline in insect diversity. This study evaluated the impact of light intensity and sky quality at night on insect diversity in rural and urban areas of the Asir province, Saudi Arabia. Insect traps were installed in both areas during night. Light intensity of nearby road lamps was measured using light meter, while sky quality was measured using sky quality meter. Rural areas exhibited low light intensity (10.33 flux/f.candle) and good sky quality (18.80 magnitude/arcsec2). Urban areas exhibited intense light (89.33 flux/f.candle) and poor sky quality (15.49 magnitude/arcsec2). Higher insect diversity was recorded for rural areas where insects belonging to seven orders (i.e., Diptera, Lepidoptera, Hemiptera, Hymenoptera, Coleoptera, Neuroptera, and Dermaptera) were collected. However, insects of four orders (i.e., Diptera, Lepidoptera, Hemiptera, and Neuroptera) were found in urban areas indicating low diversity. Lepidopteran insects were frequently recorded from rural areas indicating they are attracted to artificial light. It is concluded that excessive ALAN and poor sky quality at night disrupt insect biodiversity. Therefore, ALAN and sky quality must be considered responsible for decline in insect biodiversity along with other known factors.

The aim of the presented study was to estimate the species richness and diversity of insects were investigated in an agro-ecosystem in Bhabar region of Uttarakhand. In total, 992 individuals were collected representing 7 orders (Lepidoptera, Coleoptera, Hemiptera, Hymenoptera, Orthoptera, Diptera and Odonata), 30 families and 91 species that included herbivores, predators, omnivores and saprophages. The most dominant order was Lepidoptera with a relative abundance of (46.15%) and, the least was Diptera (6.59%). The five most abundant families by numbers of individuals were Pieridae (14.8%), Nymphalidae (13.9%), Lycaenidae (6.1%), Papilionidae (5.9%), and Libellulidae (5.4%). The five most diverse families by species were Nymphalidae (13), Pieridae (9), Lycaenidae (8), Papilionidae (7), and Libellulidae (6). The diversity index showed significant Diversity (Hʹ=1.832), Evenness (E=0.9449) and Margalef species richness (d=2.076) of insect fauna. Diversity indices of insect orders showed that Lepidoptera was the most diverse (Hʹ=1.641), Dipterans had highest Evenness (E=0.9449), and Coleopterans had the maximum species richness as per Margalef’s Index (d=2.056). There were 720 individuals of insect pollinators visitors were observed, which belonged to 62 species in 4 orders (Lepidoptera, Coleoptera, Hymenoptera, and Hemiptera).