Metabarcoding malaise trap plant components enables monitoring the diversity of plant-insect interactions

The declines observed in insect abundance and diversity in the past decades has also been observed in plants, and these events are most certainly correlated. Rapid largescale biomonitoring of both plants and insects can help monitor these changes and inform decisions for land management and species protection. Malaise traps have been used for nearly 80 years for passive insect sampling of primarily flying insects, and when they enter these traps, they carry the fragments of the plants they have visited, either as plant fragments and pollen on the body surface, or as digested food material in gut contents. DNA metabarcoding is a potential method to identify these plant traces in the ethanol of the malaise bottles, which is not possible with traditional microscopy. Metabarcoding could offer more insight into what plants insects are directly interacting with at a given time, and allow for the detection of rare plants, and neophyte species visited by insects. This study, to our knowledge, is the first examination of DNA metabarcoding plant traces from Malaise trap samples, we examine 105 samples from 21 sites throughout Germany collected in a 2-week period in May of 2020. Here we report on the feasibility of sequencing these sample types, analysis of the resulting taxa, the usage of cultivated plants by insects near nature conservancy areas, and the detection of rare and neophyte species.

High species richness of tachinid parasitoids (Diptera: Calyptratae) sampled with a Malaise trap in Baihua Mountain Reserve, Beijing, China

Tachinidae are one of the most speciose families of Diptera and the largest group of non-hymenopteran parasitoids. Little is known about their diversity, distribution patterns, and seasonal variation in most ecosystems. This study reports on tachinid flies collected by a Malaise trap over 73 weeks in Baihua Mountain Reserve, northern China, and investigates the patterns of local species richness and its temporal distribution. The most species-rich season was summer, but the majority of specimens were recovered in spring. A total of 755 tachinid specimens were collected, consisting of 144 species in 85 genera, comprising 26.5% of the species and 49.7% of the genera recorded from northern China. A total species richness of 243 was estimated, indicating that only a portion of the community of tachinid flies was collected at this location and suggesting that the diversity of tachinids might be underestimated across Beijing and northern China. This work is a first step in assessing patterns of tachinid diversity in China using quantitative sampling and establishes a baseline for comprehending the temporal and spatial diversity of these ecologically significant parasitoids.

Pooling size sorted Malaise trap fractions to maximize taxon recovery with metabarcoding

Background Small and rare specimens can remain undetected when metabarcoding is applied on bulk samples with a high specimen size heterogeneity. This is especially critical for Malaise trap samples, where most of the biodiversity is contributed by small taxa with low biomass. The separation of samples in different size fractions for downstream analysis is one possibility to increase detection of small and rare taxa. However, experiments systematically testing different size sorting approaches and subsequent proportional pooling of fractions are lacking, but would provide important information for the optimization of metabarcoding protocols. We set out to find a size sorting strategy for Malaise trap samples that maximizes taxonomic recovery but remains scalable and time efficient. Methods Three Malaise trap samples were sorted into four size classes using dry sieving. Each fraction was homogenized and lysed. The corresponding lysates were pooled to simulate unsorted samples. Pooling was additionally conducted in equal proportions and in four different proportions enriching the small size fraction of samples. DNA from the individual size classes as well as the pooled fractions was extracted and metabarcoded using the FwhF2 and Fol-degen-rev primer set. Additionally, alternative wet sieving strategies were explored. Results The small size fractions harboured the highest diversity and were best represented when pooling in favour of small specimens. Metabarcoding of unsorted samples decreases taxon recovery compared to size sorted samples. A size separation into only two fractions (below 4 mm and above) can double taxon recovery compared to not size sorting. However, increasing the sequencing depth 3- to 4-fold can also increase taxon recovery to levels comparable with size sorting, but remains biased towards biomass rich taxa in the sample. Conclusion We demonstrate that size fractionation of Malaise trap bulk samples can increase taxon recovery. While results show distinct patterns, the lack of statistical support due to the limited number of samples processed is a limitation. Due to increased speed and lower risk of cross-contamination as well as specimen damage we recommend wet sieving and proportional pooling of the lysates in favour of the small size fraction (80–90% volume). However, for large-scale projects with time constraints, increasing sequencing depth is an alternative solution.

Population Abundance of Flies Collected in Different Traps in Small Ruminants in Ladang Pasir Akar, Besut, Terengganu

Flies are common ectoparasites to livestock. Some species of flies are important to small ruminants because they can spread disease and cause disturbance to animals, thus lowering their productivity. Considering the impact of flies to the productivity of small ruminants, it is important to identify the species of flies that occur in an area for early control actions. The study was aimed to determine the species of flies in Diptera family that occur in Ladang UniSZA Pasir Akar and their population abundance. The flies were collected using three types of traps: Malaise trap, yellow pan trap and yellow sticky trap for three consecutive weeks. The traps were set up in three different locations in small ruminants rearing area in the farm. Nine Diptera families significant to livestock were identified: Calliphoridae, Ceratopogonidae, Culicidae, Muscidae, Psychodidae, Rhiniidae, Sarcophagidae, Simuliidae and Tabanidae. The family Sarcophagidae recorded the highest abundance in the farm (26.57%), while the lowest of flies count was from the family Tabanidae (0.82%). The most diverse family of Diptera was collected by Malaise trap and the lowest diversity was recorded from yellow pan trap. The results from this study had provided the first insight of the flies important to small ruminants occurred in this farm.

Aleiodes (Hymenoptera, Braconidae, Rogadinae) diversity in Washington U.S.A. including three new species

Aleiodes Wesmael is a large cosmopolitan genus of endoparasitoid wasps that is evidently especially speciose in the Western Hemisphere based on numbers of described species. As with most diverse insect groups, relatively little is known about Aleiodes species diversity and biology. Here I summarize what is known about Aleiodes diversity in Washington State and contiguous Inland Northwest states and province, and I report three new species recently collected by malaise trap sampling for Aleiodes in Okanogan County, WA: Aleiodes khalafi, Aleiodes okanoganensis, and Aleiodes quasiburrus. Given the number of new species (three) and first records of previously described species (two) in Washington elucidated by this study, there is evidently much work to do to reach a fair estimate of Aleiodes species diversity in the Inland Pacific Northwest.

Remarkable Species Diversity of the Leafhopper Genus Xestocephalus (Hemiptera: Cicadellidae: Aphrodinae) in Thailand

Xestocephalus Van Duzee is among the most common and widespread genera of Cicadellidae in the temperate and tropical regions of the world. In the present study, 205 specimens of the genus Xestocephalus were collected in Thailand, whereas only a single species of the genus was recorded previously using Malaise trap field sampling, studied by comparative morphology. Seventeen species were recognized, including twelve new species: X. binarius sp. nov., X. chrysanthemum sp. nov., X. cowboyocreus sp. nov., X. densprint sp. nov., X. dimiprocessus sp. nov., X. exproiecturus sp. nov., X. gracilus sp. nov., X. limpidissimus sp. nov., X. malleus sp. nov., X. nonattribus sp. nov., X. recipinams sp. nov., and X. tenusis Liang sp. nov. Four species were recorded in Thailand for the first time: Xestocephalus abyssinicus Heller and Linnavuori, Xestocephalus asper Linnavuori, Xestocephalus ishidae Matsumura, and Xestocephalus toroensis Matsumura. Detailed morphological descriptions of all 17 species are given; photographs of external habitus and male genitalia of the species from Thailand are provided. A checklist of species of the genus is also given, and a key to all Thailand Xestocephalus species is also provided.

Effectiveness of sweep net, yellow pan trap and malaise trap for sampling parasitic hymenoptera on tidal swamp rice

The presence of the parasitic Hymenoptera plays a vital role in pest management for sustainable agriculture. So, it is crucial to know the parasitoid species that exist in an agroecosystem. Sweep Net, Yellow Pan Trap, and Malaise Trap are often used to study the diversity of Hymenoptera parasitic in agroecosystems. This study aims to see the effectiveness of Sweep Net, Yellow Pan Trap, and Malaise Trap in trapping Parasitic Hymenoptera. The study was carried out at four sub-districts, namely are Batang Tuaka, Keritang, Reteh, and Tembilahan Hulu sub-district. The research was carried out by sampling with the transect line method. Sweep net, Yellow pan trap, and Malaise trap have trapped 5,732 individuals of Parasitic Hymenoptera on tidal swamp rice in Indragiri Hilir Regency. The Parasitic Hymenoptera consists of 10 superfamilies, 30 families, and 320 morphospecies. Malaise traps are the best for trapping parasitic Hymenoptera on tidal swamp rice. Malaise traps have been able to trap up to 62% of morphospecies and 81% of the abundance of individual Parasitic Hymenoptera on tidal swamp rice. Yellow pan traps trap 28% of morphospecies and 15% of the abundance of individual Parasitic Hymenoptera. The sweep net can trap 10% of morphospecies and 4% of the abundance of individual Parasitic Hymenoptera.Keywords: Parasitic Hymenoptera; trap; tidal swamp rice.

Effects of Malaise trap spacing on species richness and composition of terrestrial arthropod bulk samples

The Malaise trap is a popular device for assessing diverse terrestrial arthropod communities because it collects large samples with modest effort. A number of factors influence its collection efficiency, placement being one of them. For instance, when designing larger biotic surveys using arrays of Malaise traps we need to know the optimal distance between individual traps that maximises observable species richness and community composition. We examined the influence of spacing between Malaise traps by metabarcoding samples from two field experiments at a site in Waterloo, Ontario, Canada. For one experiment, we used two trap pairs deployed at weekly increasing distances (3 m increments from 3 to 30 m). The second experiment involved a total of 10 traps set up in a row at 3 m distance intervals for three consecutive weeks. Results show that community similarity of samples decreases over distance between traps. The amount of species shared between trap pairs drops considerably at about 18 m trap-to-trap distance. This change can be observed across all major taxonomic groups and for two different habitat types (grassland and forest). Large numbers of OTUs found only once within samples cause rather large dissimilarity between distance pairs even at close proximity. This could be caused by a large number of transient species from adjacent habitats which arrive at the trap through passive transport, as well as capture of rare taxa, which end up in different traps by chance.