Figures
Abstract
The species belonging to Sclerodermus (Hymenoptera: Bethylidae) are currently the most important insect natural enemies of wood borer pests, mainly buprestid and cerambycid beetles, in China. However, some sibling species of this genus are very difficult to distinguish because of their similar morphological features. To address this issue, we conducted phylogenetic and genetic analyses of cytochrome oxidase subunit I (COI) and 28S RNA gene sequences from eight species of Sclerodermus reared from different wood borer pests. The eight sibling species were as follows: S. guani Xiao et Wu, S. sichuanensis Xiao, S. pupariae Yang et Yao, and Sclerodermus spp. (Nos. 1–5). A 594-bp fragment of COI and 750-bp fragment of 28S were subsequently sequenced. For COI, the G-C content was found to be low in all the species, averaging to about 30.0%. Sequence divergences (Kimura-2-parameter distances) between congeneric species averaged to 4.5%, and intraspecific divergences averaged to about 0.09%. Further, the maximum sequence divergences between congeneric species and Sclerodermus sp. (No. 5) averaged to about 16.5%. All 136 samples analyzed were included in six reciprocally monophyletic clades in the COI neighbor-joining (NJ) tree. The NJ tree inferred from the 28S rRNA sequence yielded almost identical results, but the samples from S. guani, S. sichuanensis, S. pupariae, and Sclerodermus spp. (Nos. 1–4) clustered together and only Sclerodermus sp. (No. 5) clustered separately. Our findings indicate that the standard barcode region of COI can be efficiently used to distinguish morphologically similar Sclerodermus species. Further, we speculate that Sclerodermus sp. (No. 5) might be a new species of Sclerodermus.
Citation: Jiang Y, Yang Z, Wang X, Hou Y (2015) Molecular Identification of Sibling Species of Sclerodermus (Hymenoptera: Bethylidae) That Parasitize Buprestid and Cerambycid Beetles by Using Partial Sequences of Mitochondrial DNA Cytochrome Oxidase Subunit 1 and 28S Ribosomal RNA Gene. PLoS ONE 10(3): e0119573. https://doi.org/10.1371/journal.pone.0119573
Academic Editor: Ulrich Melcher, Oklahoma State University, UNITED STATES
Received: September 18, 2014; Accepted: January 15, 2015; Published: March 17, 2015
Copyright: © 2015 Jiang et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Data Availability: All relevant data are within the paper.
Funding: Zhongqi Yang received the State Key Program of National Natural Science Foundation of China (No. 31230015). The funder had an important role in study design.
Competing interests: The authors have declared that no competing interests exist.
Introduction
Monochamus alternatus Hope (Coleoptera: Cerambycidae), a longhorned pine sawyer beetle, is not only considered the major pest of pine trees but also an important vector of the pinewood nematode, the causal agent of pine wilt disease [1–3]. Since its discovery in 1982 at Nanjing City, Jiangsu Province, China, the pinewood nematode has spread to 179 counties in 15 provinces (and municipalities) of China (China State Forestry Administration 2013) [4]. In the last 20 years, pine wilt disease was reported in 10 provinces of China [5]. Between 1996 and 2001, the stand volume loss caused by the pine wilt disease was more than 1 million m3, and the direct economic loss was estimated to be approximately above 400 billion Yuan RMB [6]. Therefore, a biological control program was initiated in 2000 to control the longhorned beetle [4]. Further, that program surveyed the natural enemies of M. alternatus [4].
Thus far, several Sclerodermus species are used as insect natural enemies to control the longhorned beetle in China, such as S. guani, S. sichuanensis, and S. pupariae. S. guani was used to attack Semanotus bifasciatus Motschulsky (Coleoptera: Cerambycidae) in Miyun, Beijing, China. The average outdoor parasitism of this pest was reduced up to 69.68% after 5 years of releasing S. guani. Further, the percentage of injury to Platycladus orientalis Franco declined from 22.78% to 0.49% [7]. The parasitic ability of S. guani against Anoplophora glabripennis Motschulsky (Coleoptera: Cerambycidae) was tested, and the results showed that the average death rates of the first, second, and third instar larvae were 100%, 92.1%, and 87.29%, respectively. The average parasitism of S. guani toward A. glabripennis in the early-stage larvae was 32.51% in a field experiment. The highest parasitism of 32.51% was noted when the ratio of pest and Bethylidae species was 1: 8–10 [8]. These findings suggest that S. guani is an important parasitic enemy that can be effectively used to prevent M. alternatus larvae; the parasitism was more than 20% in Fujian, China [9]. The parasitic ability of S. sichuanensis for attacking M. alternatus larvae on Pinus massoniana was significantly higher [10].
S. pupariae was described as a new parasitoid species in China by Yang Zhongqi [11]; it has a high potential to be an important natural enemy that can be used for the biological control of stem borer pests. In China, S. pupariae were reared from Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) that attacked velvet ash (Fraxinus velutina Torr.), a tree native to North America. The parasitism rate in the field was 13%. Adult wasps reared from single host pupa or mature larva ranged from 24 to 56 individuals. Laboratory rearing resulted in an emerging adult female to male ratio of 22:1 [11]. Results of the biological characterization showed that many kinds of forest borer pest larvae, such as those of Buprestidae Agrilus auriventris Saunders, A. mali Matsumura, and A. zanthoxylumi Hou, and those of Cerambycidae Stenhomalus complicates Gressitt, A. glabripennis, M. alternatus, and Thyestilla gebleri Faldermann, could be used as hosts by S. pupariae during their feeding and progeny development phases. S. pupariae has a long life and high fecundity and diffusion capacity; therefore, it is a good insect natural enemy for the biocontrol of borer pests [12]. In 2010, Wang indicated that S. pupariae was parasitic to Massicus raddei Blessig (Coleoptera: Cerambycidae) larvae and found that its feeding on the hosts killed great number of pests; therefore, it has a remarkable prospect in biological control [13]. Because S. pupariae has high host-searching and host-attacking abilities and produces high proportion of females, as well as alate females (advantageous for dispersing after releasing in biocontrol programs), it has a high potential to be used as a biocontrol agent against the emerald ash borer [11].
The progress of a biological control program for longhorned beetles has been monitored for more than ten years by our team; we identified many natural insect enemies that could be used to control the longhorned beetle. Several species of Sclerodermus are currently the most important natural insect enemies against forest wood borer pests, mainly buprestid and cerambycid beetles, in China. Several putative species of Sclerodermus were identified and reared from different stem borer pests at our Key Laboratory of Forest Protection, such as Sclerodermus sp. (No. 1) parasitic on the pupae and larvae of Agrilus mali, Sclerodermus sp. (No. 2) parasitic on the larvae of Chalcophora japonica Gory, Sclerodermus sp. (No. 3) parasitic on the larvae of Chrysobothris sp. (Coleoptera: Buprestidae), Sclerodermus sp. (No. 4) parasitic on the larvae of Sphenoptera sp., and Sclerodermus sp. (No. 5) parasitic on the larvae and pupae of M. alternatus. These species were artificially reared in large numbers in the laboratory. All these Sclerodermus putative species were collected from different geographical or climatic environments. Furthermore, they were collected from different host plant species infected by different host pests. Therefore, we speculate that there might be some new species among these Sclerodermus putative species collected from the field. However, distinguishing these Sclerodermus putative species is difficult for many applied entomologists because most scale insects are small, and closely related species might be very similar morphologically.
At present, DNA barcoding is a new approach for species-level identification. Although considerable biological research depends on species diagnoses, taxonomic expertise is lacking. Sustainable identification ability involves the construction of systems that employ DNA sequences as taxon barcodes. The mitochondrial gene cytochrome c oxidase I (COI) could serve as the core of a global bioidentification system for animals. In some cases, this has shown to have a 100% success rate in correctly identifying specimens [14]. Thus, the COI identification system is a reliable, cost-effective, and accessible solution to the current problem of species identification.
The family Bethylidae belongs to the aculeate (stinging) Hymenoptera that includes familiar bees, social wasps, and ants [15]. It is placed in the superfamily Chrysidoidea, members of which are almost exclusively parasitoids [16]. Within the superfamily, the Bethylidae are possibly the most species-rich family, with over 2,000 species that have been described [17]. They are globally distributed and develop as ectoparasitoid on larvae, and occasionally, pupae, of Coleoptera and Lepidoptera species, which they permanently paralyze with a sting (idiobiosis) [18]; a few species are found on other hosts, including Hymenoptera species [19]. Gordh and Móczár [17] published a catalog of the world species of Bethylidae, including Sclerodermus. Evans [20, 21] studied the North American Bethylidae, including Sclerodermus. Lanes and Azevedo [22] listed 71 species of Sclerodermus worldwide when they studied the phylogeny and taxonomy of Sclerodermini. Although the phylogeny of Bethylidae was constructed in 2010 [23], there were only two samples of Sclerodermini; in this study, we further identified several Sclerodermus species and putative species Sclerodermus nos. 1–5 as well as other species of Bethylidae, sequences of which were recently obtained from GenBank. The phylogeny of Bethylidae and taxonomic classification of Sclerodermus were investigated in this study. However, most importantly, we aimed to use molecular methods to identify Sclerodermus putative species that are difficult to distinguish morphologically. Further, we provided reliable evidence for traditional morphological identification.
Material and Methods
Ethics statement
Our study did not involve the use of any non-human primates. Further, we confirm that our field studies did not involve endangered or protected species (i.e., the specimens sampled were Sclerodermus wasps (Hymenoptera: Bethylidae)). The putative species of Sclerodermus spp. (Nos.1–5) were collected from Tongchuan, Ningbo, Kuandian, Bayanhaote, and Kunming, respectively, China. All the fields from where the samples were collected were managed by the local Forest Pest and Disease Control Stations, and the secretaries of the respective stations provided permission to conduct field studies. Finally, no permits were required for the described study, which complied with all the relevant regulations.
Specimen sampling
In total, 136 individuals were collected from different progeny, and 15 individuals of each putative species were reared at the Chinese Academy of Forestry, Beijing, China. Further, S. guani, S. sichuanensis, and S. pupariae were collected from Beijing Xishan Forest Farm. Some S. sichuanensis samples were obtained from Chongqing Academy of Forestry. Table 1 provides an overview of the origin hosts, origin place from where the specimens were collected, and rearing conditions for each putative species, as well as the number of species that have been named and published or are unnamed. In this study, all putative species were reared artificially in the laboratory and were descendants of origin species. For each species, the genomic DNA was extracted from an adult female by using a DNA extraction kit (Tiangen Biotech, Beijing, China). The specimens for phylogenetic analysis of 28S ribosomal RNA gene and thirteen species of other three closely related families were obtained as an outgroup from GenBank; these are listed in Table 2.
DNA extraction, amplification, and sequencing
Total DNA was extracted from fresh individuals by using TIANamp Genomic DNA Kit (Tiangen), following manufacturer’s protocols. Universal primers C1-J-1718 (5′-GGAGGATTTGGAAATTGATTAGTTCC-3′) and C1-N-2329 (5′-ACTGTAAATATATGATGATGAGCTCA-3′) [24] were first used to amplify 600-bp of mitochondrial COI of eight Sclerodermus putative species. PCR conditions were as follows: initial step of 5 min at 95°C, followed by 35 cycles of 45 s at 95°C, 45 s at 50°C, and 30 s at 72°C, and a final extension of 3 min at 72°C; the reactions were conducted using an Eppendorf Mastercycler Pro S (Germany). All 136 samples could be successfully amplified using the universal primers. The 28S ribosomal gene was amplified using primers 28SD2F1 (5′-CGTGTTGCTTGATAGTGCAGC-3′) [25] and 28SD3R (5′-TAGTTCACCATCTTTCGGGTC-3′) [26]. All PCRs were processed in a 25 μL volume containing 1.5 μL DNA template, 3 μL 10× Taq buffer, 2 μL dNTP mixture (2.5 mM), 1 μL primer (10 pmol/μL), and 0.5 μL Taq DNA polymerase (2.5 U/μL) (Tiangen, ET101). PCRs were conducted using TECHNE Techgene thermocycler by using the following profile: an initial denaturation for 2 min at 94°C, followed by 29 cycles of denaturation at 94°C (30 s), annealing at 50°C (45 s), and extension at 72°C (90 s), and final extension for 10 min at 72°C. Products were visualized on 1% agarose gel; photos were obtained using MutiImage Light Cabinet and saved. The PCR products were directly sequenced by SANBO Company. Sequences were aligned using DNAMAN. Sequence divergences were calculated using the K2P distance model. Neighbor-joining (NJ) trees of COI and D2 expansion segments of 28S were reconstructed using MEGA5.1. Cephalonomia gallicola Ashmead, 1887 (Bethylidae: Scleroderminae: Cephalonomia) [27, 28] was chosen as the outgroup for constructing the NJ trees.
All sequences were entered into the GenBank database (COI DNA sequences: GenBank Accessions KM649832-KM649967. 28S DNA sequences: GenBank Accessions KM649696-KM649831).
Results
DNA sequence analyses
In this study, 136 individuals from eight putative species of the genus Sclerodermus were used. The samples per putative species ranged from one to twenty-four, with an average (mode) of fifteen. The sequence of a 594-bp COI fragment was obtained from all Sclerodermus individuals after deleting the terminal ambiguous part of the aligned data. There was 100% sequence identity between S. guani and S. sichuanensis. For COI data, low G-C content was found in all species, averaging to about 30.0%. Sequence divergences (K2P) between congeneric species averaged 4.5%, whereas intraspecific divergences averaged 0.09%. Furthermore, no insertions or deletions were found in DNA sequences, and no stop codons were found when amino acids were translated, implying that all amplified sequences coded for functional COI. The 594-bp nucleotide fragment of COI corresponded to 198 codons. Interestingly, there was 3.0% interspecific divergence between the COI regions of S. guani and S. pupariae, whereas the translated amino acid sequences of the two species were not different. Further, the 1.4% divergence (K2P) between S. guani and Sclerodermus sp. (No. 3) did not lead to a difference in amino acid sequences. Generally, the maximum interspecific divergence between S. guani and Sclerodermus sp. (No. 5) was 16.5%; this translated into a difference of two amino acids.
Comparison of the sequences of five unknown putative species with those of three known species (S. guani, S. sichuanensis, and S. pupariae) revealed that the sequence similarity of Sclerodermus sp. (No. 4) and S. pupariae was 100%. However, the lowest sequence similarity of about 85% was found between Sclerodermus sp. (No. 5) and the three known species (Table 3).
In the COI region, the averaged frequency of adenine (A) and thymine (T) was high (A = 30.9%, C = 18.4%, G = 11.6%, T = 39.1%). The G-C frequency was lower at the third codon position (mean, 14.8% for all individuals) than that at the first and second positions (mean, 36.4% and 38.9%, respectively). The nucleotide frequency of the three codon positions in the eight species is shown in Table 4. The G-C frequency at the third codon position (mean, 18.2% for all individuals) was the highest for Sclerodermus sp. (No. 5), whereas that of S. pupariae and Sclerodermus spp. (Nos. 3 and 4) was 15.1%, which was higher than that of the others (14.1%). Further, the G-C frequency at the first codon position of Sclerodermus sp. (No. 3) was slightly higher than that of the others. The 594-bp region of COI mtDNA was obtained for the 136 individuals; it included 491 conserved sites, 103 variable sites, 102 parsimony-informative sites, one singleton site, 375 zero-fold degenerate sites, 115 two-fold degenerate sites, and 81 four-fold degenerate sites. The COI sequences showed interspecific divergence of 0–17.4%, with a mean divergence of 4.5%. Intraspecific COI sequence divergences were 0–0.1%, with a mean divergence of 0.075% (Fig. 1). The maximum K2P distance was found between Sclerodermus sp. (No. 5) and Sclerodermus sp. (No. 3; 17.4%). Unexpectedly, the minimum distance was between S. guani and S. sichuanensis (0%) and, as expected, Sclerodermus sp. (No. 4) and S. pupariae clusters showed the minimal level of divergence since they might be one species.
Bootstrap values for each haplogroup were calculated using MEGA5.1 with 1,000 replicates. Cephalonomia gallicola (Bethylidae; Epyrinae; Cephalonomia) was chosen as the outgroup.
NJ analysis of the COI sequences revealed that the 136 samples were split into six haplogroups with high bootstrap values (Fig. 1). S. guani and S. sichuanensis were merged into one haplogroup, whereas S. pupariae and Sclerodermus sp. (No. 4) were merged into another haplogroup. S. guani and S. sichuanensis, Sclerodermus sp. (No. 2), and Sclerodermus sp. (No. 1) were separated into three clusters, indicating that they were closely related. The remaining putative species, S. pupariae and Sclerodermus sp. (No. 4), Sclerodermus sp. (No. 5), and Sclerodermus sp. (No. 3) formed three distinct clusters, with interspecific divergence ranging from 3.4% to 17.4%.
The 536-bp sequence of the final alignment of the 28SrDNA gene was obtained for the 136 individuals; this sequence included 523 conserved sites, six variable sites, and six parsimony-informative sites. The NJ tree of the 28S sequence (Fig. 2) almost merged into one cluster, except that the samples of Sclerodermus sp. (No. 5) were clustered together. Further, the 28S gene sequence similarity of S. guani, S. sichuanensis, S. pupariae, and Sclerodermus spp. (Nos. 1–4) was 100%, except for Sclerodermus sp. (No. 5) which had 99.18% sequence similarity with those of others. Further, the K2P distance between Sclerodermus sp. (No. 5) and the other seven species was 1.1%.
Bootstrap values for each haplogroup were calculated using MEGA5.1 with 1,000 replicates. Cephalonomia gallicola (Bethylidae; Epyrinae; Cephalonomia) was chosen as the outgroup.
28S phylogeny of the Bethylidae species
Phylogenetic analysis was performed on a partial 28S ribosomal RNA D2 gene. The maximum likelihood (ML) tree indicated that Bethylidae are strongly monophyletic (90% ML bootstrap percentage (mlBP)). Of the subfamilies, Bethylinae are strongly monophyletic (100% mlBP) and sister to the other commonly recognized subfamilies (Fig. 3). Of the other subfamilies, Pristocerinae were found to be monophyletic (99% mlBP), with Foenobethylus clustering within the group [27, 28], and Pristocerinae was sister to Epyrini [23]. Only Mesitiinae species were strongly included as clusters in a group with Sclerodermini. Sclerodermini and Cephalonomini [23] were strongly supported as monophyletic (98% mlBP). The relationships between the three clades Epyrini, Pristocerinae, and (Sclerodermini + Cephalonomini + Mesitiinae) were equivocal. Species in the same genus clustered together, although they were not always strongly supported to be monophyletic (e.g., Sclerodermus sp. MC-2010 and Sclerodermus in this study; Fig. 3).
The tree was derived using the maximum likelihood method.
Discussion
With the development of modern molecular biological techniques, specific DNA fragments can be used for species identification for determining the general phylogenetic relations and taxonomic status. Gene fragments or site-specific information is the auxiliary tool to distinguish species and has been used in the identification of animal and plant species.
In the present study, COI barcode sequences were used for the identification of several Sclerodermus species for the first time, to our knowledge. Each of the eight Sclerodermus samples had a distinct COI sequence, and hence, they could be distinguished from conspecifics by using the DNA barcode method. The average intraspecies K2P distance was estimated to be only 0.09%, whereas it was about 4.5% among congeneric species. This distance is considerably lesser than that for the six Ceroplastes species (Hemiptera: Coccidae) from China [29]. This could be attributed to the fact that our intraspecies samples were reared in the laboratory and not collected from different locations. However, the sequence divergences between Sclerodermus sp. (No. 5) and any congeneric species was more than 16.0%, whereas the average intraspecies K2P distance for Sclerodermus sp. (No. 5) was only 0.1%. The COI gene marker could be used for phylogenetic analysis and for the identification of cryptic species. Different vertebrate species commonly show a value close to 3% K2P distance for COI, a threshold adopted for Lepidoptera [14]. Thus, more than 16% sequence divergences for Sclerodermus sp. (No. 5) might be strong evidence for a new Sclerodermus species. Similarly, the 594-bp nucleotide fragment of COI corresponding to 198 codons led to a difference of two different amino acids between Sclerodermus sp. (No. 5) and the others. Further, for the 28S gene, although all the other seven species were completely identical with each other, the sequence similarity between Sclerodermus sp. (No. 5) and others was 99.18%. The NJ tree of COI also indicated that the 15 individuals of Sclerodermus sp. (No. 5) were strongly monophyletic (100% (mlBP)). The 28S NJ tree also yielded the same result (99% mlBP). Both the molecular phylogenetic trees suggested that Sclerodermus sp. (No. 5) differentiated the earliest among the species belonging to Sclerodermini. This is also supported by the fact that there was 99.18% sequence similarity between Sclerodermus sp. (No. 5) and the remaining species. However, determining whether Sclerodermus sp. (No. 5) is a new species on the basis of the morphological characteristics identified by Prof. Zhongqi Yang [11] is important in order to develop a biological control method for the newly discovered parasitic natural enemy. Studies on the biological characteristics and behavior of the new species might help in determining whether it is an important parasitoid and a biological agent for the control of larvae and pupae of M. alternatus.
The COI gene sequences for S. guani and S. sichuanensis were exactly the same. Thus, we speculated that the samples for the individuals of the two species had been mixed with each other. Subsequently, we found a laboratory where S. guani and S. sichuanensis species were reared over a long time; S. guani and S. sichuanensis samples were then obtained from the Xishan Forest Farm in Beijing and Chongqing Academy of Forestry Labs, respectively. However, the results of gene sequence analysis were still the same. Further studies might be necessary to explain this phenomenon.
Moreover, there was 100% sequence similarity between S. pupariae and Sclerodermus sp. (No. 4). That might suggest that Sclerodermus sp. (No. 4) was indeed S. pupariae. In 2009, Xiaoyi Wang had used S. pupariae to control Sphenoptera sp. in Bayanhaote, Inner Mongolia. We also collected Sphenoptera sp. from the same location in 2012 and reared Sclerodermus sp. (No. 4) from Sphenoptera sp. in our laboratory. Therefore, we could speculate that they are the same species. However, whether they should be considered as the same species needs further research. Furthermore, Sclerodermus sp. (No. 4) was found in Alashan, Inner Mongolia, suggesting that they could successfully survive and reproduce there. Thus, artificially enlarging their settlement range might contribute substantially to their biological control.
Our results that Bethylidae and Bethylinae as well as Pristocerinae are strongly monophyletic, and that Pristocerinae are clustered with Foenobethylus and Mesitiinae are clustered with Scleroderminae, are consistent with the findings of Martin Carr in 2010 [23]. Further, the relationships between the three clades Epyrini, Pristocerinae, and Mesitiinae + Scleroderminae are close, supporting the fact that they might be monophyletic. However, in our study, Sclerodermus was found to be more closely related to Cephalonomia than to Sclerodermus sp. MC-2010, which thus, was not considered as the sister of Sclerodermus. This discrepancy could be attributed to the geographical difference.
In summary, the Sclerodermus species reared in our laboratory belonged to three well-known species S. guani, S. sichuanensis, and S. pupariae, as well as five unidentified Sclerodermus populations, all of which were small and very similar morphologically. Because distinguishing these Sclerodermus species is difficult for many applied entomologists, we researched the differences between the five unidentified Sclerodermus species and the three well-known species by comparing different gene sequences to verify whether they were in accordance with the existing species-level identification or they were a new species. Firstly, on the basis of traditional morphological identification, which provided reliable evidence and very similar gene sequences Sclerodermus sp. (No. 4) was identified as S. pupariae. Secondly, although S. guani and S. sichuanensis have been published as two different species, our results showed 100% sequence indetity providing reliable evidence for revising the two species as one in the future. Thirdly, this is the first record of Sclerodermus sp. (No. 5) parasitizing M. alternatus larvae and pupae in Pinus massoniana Lamb. Further 95% of the female adults reared from one M. alternatus larvae were alate females, and the sequence data confirmed that this is a new species. Sclerodermus sp. (No. 2) was also first recorded in Pinus massoniana Lamb but parasitizing the larvae of Chalcophora japonica. Further, nearly all reared females were apterous. Thus, although Sclerodermus sp. (No. 2) and (No. 5) were found in Pinus massoniana Lamb, their hosts and morphological features differed; we could not clarify whether they are morphospecies. Sclerodermus sp. (No. 3) was first recorded parasitizing the larvae of Chrysobothris sp., which attacks Larix gmelinii in the north of China. Lastly, the sequences of Sclerodermus sp. (No. 1) were the most similar to those of S. guani, which parasitizes the pupae and larvae of Semanotus sinoauster Gressitt and Saperda populnea L. However, Sclerodermus sp. (No. 1) was first recorded parasitizing the pupae and larvae of Agrilus mali, which mainly attacks Malus pumila Mill and Crataegi cuneatae. Therefore, this species might have a new host. To arrive at the above conclusions, we have considered the host species, the tree species that the host attacks and morphological features to differentiate the unidentified species from the well-known species. A similar method was used for the first record of Meteorus oviedoi (Hymenoptera: Braconidae), a hymenopteran parasitoid of Venadicodia caneti (Lepidoptera: Limacodidae) in Costa Rica [30]. A previous study showed that combining several genetic characters may be the most practical way for efficient species identification [31]. In addition, we used molecular identification to verify our results obtained by traditional morphological identification.
Thus, although the gene sequences prove that Sclerodermus sp. (No. 5) is very likely a new species, and Sclerodermus sp. (No. 1), Sclerodermus sp. (No. 2), and Sclerodermus sp. (No. 3) are similar to the three well-known species, in our parallel research, we have been conducting other molecular analyses, such as ITS-1 and ITS-2, Cytb, and ATP6 to verify whether there are any differences in the results.
Acknowledgments
We particularly thank Prof. Yuxia Hou for allowing us to conduct experiments at the College of Science, China Agricultural University, Beijing, China. We are grateful to all students at Prof. Hou’s laboratory—Sihong Zhou, Xiaowen Ma, Ping Wang, Yun Sun, Nana Liu, and Xiaoning Li—for their technical help. We would also like to thank all the field collectors and feeders in our team: Yanlon Zhang, Maokui Zhan, Zhiyong Wang, Ke Wei, Lina Wang, and Li Wang. Finally, we particularly thank the support received from the Key Laboratory of Forest Protection, China State Forestry Administration and Research Institute of Forest Ecology, Environment and Protection, Chinese Academy of Forestry, Beijing, China.
Author Contributions
Conceived and designed the experiments: ZQY YJ. Performed the experiments: YJ. Analyzed the data: YJ. Contributed reagents/materials/analysis tools: YXH. Wrote the paper: YJ ZQY XYW. Solved the operation problems in experiment: YXH.
References
- 1. Wei JR, Yang ZQ, Therese MP, Du JW. Parasitism and olfactory responses of Dastarcus helophoroides (Coleoptera: Bothrideridae) to different Cerambycid hosts. BioControl. 2009; 54: 733–742.
- 2. Yang H, Wang JJ, Zhao ZM, Yang DM, Tang ZQ. Mating behavior of Monochamus alternatus Hope (Coleoptera: Cerambycidae). Acta Entomologica Sinica. 2007; 50(8): 807–812. (in Chinese)
- 3. Li SQ, Fang YL, Zhang ZN. Effects of volatiles of non-host plants and other chemicals on oviposition of Monochamus alternatus (Coleoptera: Cerambycidae). J Pest Sci. 2007; 80:119–123
- 4. Yang ZQ, Cao LM, Zhang YL, Wang XY, Zhan MK. A new egg parasitoid species (Hymenoptera: Pteromalidae) of Monochamus alternatus (Coleoptera: Cerambycidae), with notes on its biology. Ann Entomol Soc Am. 2014; 107: 402–412
- 5. Shi J, Luo YQ, Yan XS, Chen WP, Jiang P. Response of pine forest to disturbance of pine wood nematode with interpretative structural model. Cultur Divers Ethnic Minor Psychol. 2009; 4(1): 117–122
- 6. Guo XH, Jiang PW, Chang EZ, Sun N. Research on the loss evaluation index system of Bursaphelenchus xylphilus nickle invading China. Journal of Liaoning Forestry Science & Technology. 2008; 5: 5–8 (in Chinese) pmid:25651825
- 7. Wang XJ, Guo GF. Control techniques against Semanotus bifasciatus with Scleroderma guani. Forest Pest and Disease. 2007; 26(4): 28–34
- 8. Yao W, Yang Z. Studies on biological control of Anoplophora glabriennis (Coleoptera: Cerambycidae) with a parasitoid, Sclerodermus guani (Hymenoptera：Bethylidae). Journal of Environmental Entomology. 2008; 30(2): 127–134
- 9. Kang WT, Tang CS, Liang N, Chen S, Huang J, Chen QL et al. Releasing Scleroderma guani to control Monochamus alternatus. Journal of Fujian Agriculture and Forestry University (Natural Science Edition). 2008; 37(6): 575–579
- 10. Zhang X, Zhou Z. Controlling Monochamus alternatus by Domestication of Scleroderma sichuanensi. Journal of Sichuan Forestry Science and Technology. 2007; 28(4): 16–20
- 11. Yang ZQ, Wang XY, Yao YX. A new species of Sclerodermus (Hymenoptera: Bethylidae) parasitizing Agrilus planipennis (Coleoptera: Buprestidae) from China, with a key to Chinese species in the genus. Ann Entomol Soc Am. 2012; 105(5): 619–627
- 12. Wu H, Wang X, Li ML, Yang ZQ, Zeng FX, Wang HY et al. Biology and mass rearing of Sclerodermus pupariae Yang et Yao (Hymenoptera: Bethylidae), an important ectoparasitoid of the emerald ash borer, Agrilus planipennis (Coleoptera: Buprestidae) in China. Acta Entomologica Sinica. 2008; 51(1): 46–54
- 13. Wang XY, Yang ZQ, Tang YL, Jiang J, Gao C, Liu YC et al. Parasitism of Sclerodermus pupariae (Hymenoptera: Bethylidae) on the young larvae of Massicus raddei (Coleoptera: Cerambycidae). Acta Entomologica Sinica. 2010; 53(6): 675–682
- 14. Paul DNH, Alina C, Shelley LB, Jeremy RD. Biological identifications through DNA barcodes. Proc R Soc Lond B. 2003; 270: 313–321
- 15.
Goulet H, Huber J. Hymenoptera of the World: An identification guide to families. Agriculture Canada, Ottawa. 1993. pp. 668.
- 16. Brothers DJ, Carpenter JM. Phylogeny of Aculeata: Chrysidoidea and Vespoidea (Hymenoptera). J Hymenoptera Res. 1993; 2: 227–304
- 17. Gordh G, Móczár L. A catalog of the world Bethylidae (Hymenoptera: Aculeata). Memoirs of the American Entomological Institute. 1990; 46: 1–364
- 18.
Gauld ID, Bolton B. The Hymenoptera. British Museum (Natural History). London: Oxford University Press, Oxford. 1988. pp. 332.
- 19. Melo GAR, Evans HE. Two new Microstigmus species (Hymenoptera, Sphecidae), with description of their parasite, Goniozus microstigmi sp. n. (Hymenoptera, Bethylidae). Proc Entomol Soc Wash, 1993; 92: 258–263
- 20. Evans HE. A synopsis of the American Bethylidae (Hymenoptera: Aculeata). Bull Mus Comp Zool. 1964; 132: 1–222.
- 21. Evans HE. The Bethylidae of America North of Mexico. Mem Am Entomol Soc. 1978; 27: 1–332.
- 22. Lanes GO, Azevedo CO. Phylogeny and taxonomy of Sclerodermini (Hymenoptera, Bethylidae, Epyrinae). Insect Syst Evol. 2008; 39: 55–86.
- 23. Martin CJ, Young PW, Mayhew PJ. Phylogeny of bethylid wasps (Hymenoptera: Bethylidae) inferred from 28S and 16S rRNA genes. Insect Systematics Evolution. 2010; 41: 55–73
- 24. Simon C, Frati F, Beckenbach A, Crespi B, Liu H, Flook P. Evolution, weighting, and phylogenetic utility of mitochondrial gene sequences and a compilation of conserved PCR primers. Ann Entomol Soc Am. 1994; 87: 651–701
- 25. Belshaw R, Quicke DLJ. A molecular phylogeny of the Aphidiinae (Hymenoptera: Braconidae). Mol Phylogenet Evol. 1997; 7: 281–293 pmid:9187088
- 26. Mardulyn P, Whitfield JB. Phylogenetic signal in the COI, 16S and 28S genes for inferring relationships among the genera of Microgastrinae (Hymenoptera; Braconidae): Evidence of a high diversification rate in this group of parasitoids. Mol Phylogenet Evol. 1999; 12: 282–294 pmid:10413623
- 27. Alencar I, Azevedo CO. Reclassification of Epyrini (Hymenoptera: Bethylidae): a tribal approach with comments on their genera. Systematics Entomology. 2013; 38: 45–80
- 28. Lanes GO, Azevedo CO. Phylogeny and Taxonomy of Sclerodermini (Hymenoptera, Bethylidae, Epyrinae). Insect Systematics and Evolution. 2008; 39: 55–86
- 29. Jun D, Fang Y, Tong-Xin Z, Hao-Yuan H, Chao-Dong Z. DNA barcoding of six Ceroplastes species (Hemiptera: Coccoidea: Coccidae) from China. Mol Ecol Resour. 2012; 12: 791–796 pmid:22548741
- 30. Shaw SR, Nishida K. A new species of gregarious Meteorus (Hymenoptera: Braconidae) reared from caterpillars of Venadicodia caneti (Lepidoptera: Limacodidae) in Costa Rica. Zootaxa. 2005; 1028: 49–60
- 31. Banks JC, Whitfield JB. Dissecting the ancient rapid radiation of microgastrine wasp genera using additional nuclear genes. Molecular Phylogenetics and Evolution. 2006; 41: 690–703 pmid:16854601