Published online December 19, 2023
https://doi.org/10.5141/jee.23.050
Journal of Ecology and Environment (2023) 47:24
Jeong Ho Hwang* and Jong-Hak Yun
Wetland Center, National Institute of Ecology, Changnyeong 50303, Republic of Korea
Correspondence to:Jeong Ho Hwang
E-mail chsh123@naver.com
This article is licensed under a Creative Commons Attribution (CC BY) 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/ The publisher of this article is The Ecological Society of Korea in collaboration with The Korean Society of Limnology
Background: Crabgrass (Digitaria ciliaris, Poaceae) is a globally distributed weed, including in Afro-Eurasia, America, and Australia. As a highly gregarious plant, crabgrass is an important habitat for a diverse array of insects, and a potential habitat for agricultural pests. To compare the insect communities associated with the crabgrass community, insects were sampled using sweep sampling (100 sweeps per sample) at five sites, including Daejeon (Daejeon and Gap rivers), Anseong, Namhae, and Inje, with a focus on the Daejeon River.
Results: A total of 5,888 individual insects belonging to eight orders, 42 families, and 115 species were collected from the five sites. Both the number of species and individuals of Hemiptera were the highest at all of the sites. In the present study, 73% of the insect population fed on D. ciliaris as a host plant. The dominant species in the D. ciliaris community was Laodelphax striatellus (Delphacidae), being ubiquitous at all the sites which showed a high abundance of rice pests in the communities and the suitability of D. ciliaris as an alternative host plant for them. The Shannon–Wiener diversity index was highest in Inje on 17 September (2.88), and the Chao1-bc diversity index was highest in the Gap River on 5 September (80). The sampling efficiency of 100 sweep samples (sample coverage) was calculated to be as high as 90%. The results of the samples taken from September to November in the Daejeon River showed that the number of species and individuals decreased gradually over time, and the number of dominant species decreased sharply between September and October. Similarity analysis indicated that sampling dates that were closer together yielded sampled assemblages with higher faunal similarity. In addition, in each sampling, the difference in the minimum temperature during the two-week period prior to sampling and faunal similarities were negatively correlated.
Conclusions: This study provides foundational data that could enhance our understanding of insect diversity in D. ciliaris. The data can facilitate ecological conservation and management of Korean grasslands generally, as well as identification of potential pests that may disperse from D. ciliaris communities to nearby farmland.
Keywords: assemblages, grassland, insect diversity, sampling, seasonality, similarity, sweep-netting
Crabgrass (
Insects using plants as their main habitat or food source often form a distinct association with a specific dominant plant community, so plant communities with a single dominant plant species generally have similar association trends with insects under the same climatic conditions (Farrell et al. 1992; Hwang et al. 2022). Recent studies on insect communities associated with a specific plant community have mainly been related to cultivated plants, whereas studies on insect communities in a specific wild plant community have been rather limited (Frenzel and Brandl 2003; Hwang et al. 2022; Lee et al. 2022).
Because of its ecological and agricultural importance, many studies on vegetation associated with
Insect community samplings in
Terrestrial insect communities associated with the
The quantitative sweep sampling method reflects the reality that it is not possible to collect all the species in a studied area. Therefore, it has been used as an effective method for rapidly sampling large numbers of insects to effectively compare the biodiversity of different regions (Spafford and Lortie 2013; Yi et al. 2012). Furthermore, the efficiency of sweep sampling in various habitats has been evaluated (Doxon et al. 2011; Hwang et al. 2022; Spafford and Lortie 2013; Swart et al. 2017).
For quantitative statistics at each site, 100 sweeps (50 m transects) were performed in each investigated date (Fig. 1). Insect nets with a total length of 1,200 mm, net depth of 700 mm, and diameter of approximately 300 mm were used. Before sorting, the terrestrial insects collected with 100 sweeps were shaken off into a zipper bag (25 × 30 cm). Afterward, sampled insects were placed in 94% ethanol and sorted in the laboratory before being classified under a stereomicroscope (Olympus SZ1145; Olympus, Tokyo, Japan). Various faunal atlases and papers were referred to for identification (Ahn et al. 2018; An 2011; An and Kim 2020; Hong et al. 2011, 2012; Park et al. 2012; Takizawa 2005), and experts were consulted for species that were difficult to classify. In addition, host plants were searched with various encyclopedias and papers to confirm insect species, and by implication, the percentage of sampled insects, that fed on Poaceae (including
For the diversity index, the Shannon–Wiener function (H’) derived from the information theory of Margalef (1958) and modified by Lloyd and Ghelardi (Pielou 1966) was used. The dominance index was calculated using McNaughton’s dominance index (DI) (McNaughton 1967), the abundance index was calculated using Margalef’s (1958) index, and the evenness index was calculated using Pielou’s (1975) formula. The Chao1 bias-corrected index (Chao1-bc), which is widely used together with the diversity index and evaluated to have excellent performance, was calculated using the SPADE program (Chao and Shen 2010; Głowacki 2011).
Sørensen’s similarity index, an incidence-based similarity measure, and the Bray–Curtis similarity index, an abundance-based measure, which are both generally used to assess community composition and are resistant to sampling errors, were calculated using species prediction and diversity estimation (SPADE) (Beals 1984; Chao and Shen 2010; Giovas 2021; Schroeder and Jenkins 2018; Sørensen 1948). The calculated similarity indices were used to create a hierarchical clustering dendrogram using the unweighted pair group method with arithmetic means using SPSS version 21 (IBM Co., Armonk, NY, USA). Furthermore, to determine the relationship between insect communities and temperature, the minimum temperature during the two-week period prior to the sampling date and the Bray–Curtis similarity index were analyzed using Spearman’s correlation analysis, calculated in SPSS. In addition, on three sampling dates (Daejeon River on 9 September and 9 October, and Gap River on 5 September) the species richness estimation curves and sample coverage were built based on 10 sweep sampling units of 10 sweeps each using the R software package iNEXT in R version 3.6.0 (Hsieh et al. 2016). We assumed that sample coverage values in same dominant species are similar compared to different dominant species. Interpolation and extrapolation of the species richness estimation curves were extended to only twice the sampling units to maintain a reliability of 95% using the default setting.
In total, eight orders, 42 families, 115 species, and 5,888 individuals of insects were collected. In the samples from Daejeon River, the number of species and individuals were the highest in early September. In the present study, approximately 73% of the insect population fed on
Table 1 . Summary of the result on insect communities associated with
Sampling site and date | Abbreviation | Orders | Families | Species | Individuals | Percentage of individuals that feed on |
---|---|---|---|---|---|---|
Daejeon River 9 September | A-ES (early September) | 5 | 18 | 42 | 1,829 | 90.3 |
Daejeon River 9 October | A-EO (early October) | 4 | 16 | 36 | 427 | 56.7 |
Daejeon River 18 October | A-MO (mid-October) | 5 | 15 | 23 | 270 | 65.9 |
Daejeon River 24 October | A-LO (late October) | 4 | 7 | 11 | 87 | 79.3 |
Daejeon River 7 November | A-EN (early November) | 2 | 8 | 14 | 59 | 47.5 |
Daejeon River 21 November | A-LN (late November) | 1 | 3 | 4 | 20 | 90.0 |
Gap River 5 September | B-ES (early September) | 6 | 24 | 45 | 1,693 | 58.1 |
Gap River 8 October | B-EO (early October) | 6 | 11 | 18 | 400 | 87.3 |
Anseong 11 October | C-MO (mid-October) | 5 | 15 | 26 | 160 | 55.0 |
Anseong 30 October | C-LO (late October) | 4 | 7 | 9 | 22 | 22.7 |
Namhae 10 October | D-MO (mid-October) | 5 | 17 | 33 | 704 | 79.1 |
Inje 17 September | E-MS (mid-September) | 6 | 20 | 41 | 217 | 58.5 |
Total | 8 | 42 | 115 | 5,888 | 73.0 |
Site abbreviations refer to localities in Fig. 1.
Table 2 . Species richness and abundance (in parenthesis) by insect orders sampled by sweep-netting in
Order | Species richness (abundance) | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
Sampling sites | ||||||||||||
A-ES | A-EO | A-MO | A-LO | A-EN | A-LN | B-ES | B-EO | C-MO | C-LO | D-MO | E-MS | |
Hemiptera | 24 (1,711) | 23 (382) | 15 (242) | 7 (78) | 10 (55) | 4 (20) | 21 (1,214) | 8 (350) | 17 (134) | 5 (16) | 22 (643) | 24 (171) |
Coleoptera | 7 (49) | 6 (25) | 2 (3) | 4 (4) | 12 (396) | 4 (29) | 1 (1) | 2 (4) | 10 (15) | |||
Diptera | 8 (60) | 5 (10) | 4 (9) | 2 (2) | 6 (63) | 3 (18) | 4 (13) | 2 (4) | 4 (33) | 2 (7) | ||
Orthoptera | 2 (8) | 2 (10) | 1 (2) | 3 (13) | 1 (1) | 3 (11) | 1 (1) | 3 (13) | 1 (2) | |||
Hymenoptera | 1 (1) | 1 (14) | 1 (6) | 2 (6) | 1 (1) | 2 (11) | 3 (21) | |||||
Odonata | 1 (1) | 1 (1) | 1 (1) | 1 (1) | ||||||||
Lepidoptera | 1 (1) | |||||||||||
Mantodea | 1 (1) |
Abbreviations of sampling sites were given in Table 1.
In this study, there were three cases of sampling (Gap River on early September, Daejeon River on early September and early October) where the 100 sweep samples were comprised of ten subsamples of ten sweeps each, to make it possible to estimate the number of species per ten sweeps. The numbers of species were similar between the Daejeon and Gap rivers in September, but when estimating the richness based on 200 sweeps (two extrapolations), the number of species in Dajeon River on early September tended to converge with that of the Daejeon River on early October. All sample coverages were calculated to be as high as 90% (Fig. 2).
In the Daejeon River samples, community analysis showed that the Shannon–Wiener diversity index was the highest in early October (2.71), and the Chao1-bc diversity index was the highest in early September (57.6). The most frequently dominant and sub-dominant species at each site were
Table 3 . Community structure of insects associated with
Abbreviation of sampling sites | Community analysis indices | Dominant (subdominant) species | |||||
---|---|---|---|---|---|---|---|
H’ | DI | RI | EI | Chao1-bc | |||
Daejeon River 9 September | A-ES | 2.16 | 0.55 | 5.46 | 0.40 | 57.60 | |
Daejeon River 9 October | A-EO | 2.71 | 0.40 | 5.78 | 0.52 | 54.33 | |
Daejeon River 18 October | A-MO | 2.00 | 0.60 | 3.93 | 0.44 | 25.50 | |
Daejeon River 24 October | A-LO | 1.37 | 0.72 | 2.24 | 0.40 | 26.00 | |
Daejeon River 7 November | A-EN | 1.88 | 0.64 | 3.19 | 0.49 | 32.00 | |
Daejeon River 21 November | A-LN | 0.59 | 0.90 | 1.00 | 0.29 | 7.00 | |
Gap River 5 September | B-ES | 2.71 | 0.38 | 5.92 | 0.49 | 80.00 | |
Gap River 8 October | B-EO | 1.90 | 0.53 | 2.84 | 0.46 | 25.00 | |
Anseong 11 October | C-MO | 2.36 | 0.54 | 4.93 | 0.50 | 35.00 | |
Anseong 30 October | C-LO | 1.68 | 0.64 | 2.59 | 0.53 | 16.50 | |
Namhae 10 October | D-MO | 2.27 | 0.49 | 4.88 | 0.45 | 6.40 | |
Inje 17 September | E-MS | 2.88 | 0.37 | 7.44 | 0.54 | 60.00 | |
Total | 2.99 | 0.31 | 13.13 | 0.44 | 164.40 |
Abbreviations of sampling sites were given in Table 1. H’: diversity index; DI: dominance index; RI: richness index; EI: evenness index.
The results of the Sørensen/Bray–Curtis similarity analysis by sampling dates in the Daejeon River
Table 4 . Comparison of the index of Sørensen and Bray–Curtis (in parenthesis) on insect communities sampled in different sampling times in the Daejeon River.
A-ES | A-EO | A-MO | A-LO | A-EN | |
---|---|---|---|---|---|
A-EO | 0.74 (0.28) | ||||
A-MO | 0.43 (0.21) | 0.51 (0.55) | |||
A-LO | 0.26 (0.08) | 0.30 (0.30) | 0.41 (0.47) | ||
A-EN | 0.29 (0.05) | 0.32 (0.22) | 0.38 (0.24) | 0.24 (0.27) | |
A-LN | 0.13 (0.02) | 0.15 (0.09) | 0.22 (0.10) | 0.13 (0.15) | 0.33 (0.48) |
Abbreviations of sampling sites were given in Table 1.
The Sørensen/Bray–Curtis similarity analysis results for all samples, including Daejeon and Gap River, Inje, and Namhae, also showed that regardless of the inter-site distance, the similarities between the samples with a large temporal difference between them were conspicuously low (Table 5, Fig. 4). Furthermore, Bray–Curtis similarities were more indicative of the dominant species in samples, showing high similarity between the samples with the same dominant species.
Table 5 . Comparison of the index of Sørensen and Bray–Curtis (in parenthesis) on insect communities from all sites.
A-ES | A-EO | A-MO | A-LO | A-EN | A-LN | B-ES | B-EO | C-MO | C-LO | D-MO | |
---|---|---|---|---|---|---|---|---|---|---|---|
A-EO | 0.74 (0.28) | ||||||||||
A-MO | 0.43 (0.21) | 0.51 (0.55) | |||||||||
A-LO | 0.26 (0.08) | 0.30 (0.30) | 0.41 (0.47) | ||||||||
A-EN | 0.29 (0.05) | 0.32 (0.22) | 0.38 (0.24) | 0.24 (0.27) | |||||||
A-LN | 0.13 (0.02) | 0.15 (0.09) | 0.22 (0.10) | 0.13 (0.15) | 0.33 (0.48) | ||||||
B-ES | 0.53 (0.53) | 0.54 (0.18) | 0.38 (0.09) | 0.21 (0.03) | 0.20 (0.04) | 0.12 (0.02) | |||||
B-EO | 0.40 (0.33) | 0.41 (0.44) | 0.44 (0.36) | 0.48 (0.30) | 0.31 (0.14) | 0.18 (0.09) | 0.41 (0.27) | ||||
C-MO | 0.38 (0.10) | 0.42 (0.32) | 0.49 (0.27) | 0.43 (0.24) | 0.15 (0.14) | 0.13 (0.11) | 0.31 (0.09) | 0.41 (0.29) | |||
C-LO | 0.20 (0.01) | 0.22 (0.03) | 0.38 (0.05) | 0.30 (0.07) | 0.17 (0.05) | 0.15 (0.05) | 0.11 (0) | 0.30 (0.02) | 0.46 (0.23) | ||
D-MO | 0.40 (0.29) | 0.41 (0.31) | 0.39 (0.39) | 0.18 (0.17) | 0.17 (0.04) | 0.16 (0.03) | 0.38 (0.14) | 0.27 (0.24) | 0.37 (0.19) | 0.19 (0.01) | |
E-MS | 0.46 (0.15) | 0.49 (0.30) | 0.44 (0.21) | 0.19 (0.11) | 0.29 (0.25) | 0.13 (0.16) | 0.47 (0.16) | 0.31 (0.34) | 0.33 (0.18) | 0.08 (0.02) | 0.43 (0.16) |
Abbreviations of sampling sites were given in Table 1.
The population trends at Daejeon River showed that the abundance of most of the dominant species (
Spearman’s correlation between the difference in minimum temperature during the two weeks before sampling and the Bray–Curtis similarity was significant for all the comparisons (
The results of the insect community sampling of the
Sample coverage was calculated to evaluate the sampling efficiency of 100 sweeps in collecting insects in the
The dominant species in the
In addition, in the community analysis related to temperature, the Bray–Curtis similarity tended to be high among the samples with similar minimum temperatures for the 2 weeks prior to sampling, which was clearly confirmed by Spearman’s correlation analysis. This is because the minimum temperature is related to the survival rate of insects and greatly affects the community, especially the abundance of the dominant species, such as Delphacidae and Cicadellidae (Park et al. 2011).
In the Daejeon River, the closer the sampling dates, the higher the insect community similarity (Fig. 3). This is assumed to reflect the characteristics of insects with short life cycles and high minimum temperatures required for survival. Also, when comparing the similarities of all samples, there is a tendency for the similarities to be high if the sampling dates are similar, even if the sites are different. In the case of the Sørensen’s similarity values, samples were divided into one group belonging to samples mainly collected in September, and another group mainly collected in October. Similarly, in the case of Bray–Curtis similarity, there was a tendency for similarities to be higher between samples with proximate sampling dates, except for Angeong, which had a dominant species (
Sweeping is a collecting method that targets insects living on plants, and the sampling results can vary greatly depending on which vegetation is swept. However, if sampling is performed in a specific dominant plant community, it is possible to reduce the variability attributable to vegetation composition and obtain basic data to identify the insect community trends in a specific dominant plant community (Hwang et al. 2022). The insect community data for
As
Supplementary information accompanies this paper at https://doi.org/10.5141/jee.23.050.
Table S1. Annual temperature and precipitation in the sites. Table S2. Insect inventory in the
We thank Mean-Young Yim for supporting the identification of host plants and also appreciate Dong Hee Kim for receiving research grant.
Not applicable.
JHH did conceptualization, data curation, investigation, and writing the original draft. JHY did methodology, supervision, writing the review and editing. All the authors approved the manuscript.
This work was supported by the National Research Foundation of Korea (grant numbers 2022M3H9A109717911).
All data generated or analyzed during this study are included in this published article and its supplementary information files.
Not applicable.
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The authors declare that they have no competing interests.
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