Molecular Identification of Sibling Species of Sclerodermus
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RESEARCH ARTICLE 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 a11111 Yuan Jiang1, Zhongqi Yang1*, Xiaoyi Wang1, Yuxia Hou2 1 Key Laboratory of Forest Protection, China State Forestry Administration, Research Institute of Forest Ecology, Environment and Protection, Chinese Academy of Forestry, Beijing, 100091, China, 2 College of Science, China Agricultural University, Beijing, China * [email protected] OPEN ACCESS Citation: Jiang Y, Yang Z, Wang X, Hou Y (2015) Abstract Molecular Identification of Sibling Species of Sclerodermus (Hymenoptera: Bethylidae) That The species belonging to Sclerodermus (Hymenoptera: Bethylidae) are currently the most Parasitize Buprestid and Cerambycid Beetles by important insect natural enemies of wood borer pests, mainly buprestid and cerambycid Using Partial Sequences of Mitochondrial DNA Cytochrome Oxidase Subunit 1 and 28S Ribosomal beetles, in China. However, some sibling species of this genus are very difficult to distin- RNA Gene. PLoS ONE 10(3): e0119573. guish because of their similar morphological features. To address this issue, we conducted doi:10.1371/journal.pone.0119573 phylogenetic and genetic analyses of cytochrome oxidase subunit I (COI) and 28S RNA Academic Editor: Ulrich Melcher, Oklahoma State gene sequences from eight species of Sclerodermus reared from different wood borer University, UNITED STATES pests. The eight sibling species were as follows: S. guani Xiao et Wu, S. sichuanensis Xiao, Received: September 18, 2014 S. pupariae Yang et Yao, and Sclerodermus spp. (Nos. 1–5). A 594-bp fragment of COI and Accepted: January 15, 2015 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 Published: March 17, 2015 (Kimura-2-parameter distances) between congeneric species averaged to 4.5%, and intra- Copyright: © 2015 Jiang et al. This is an open specific divergences averaged to about 0.09%. Further, the maximum sequence diver- access article distributed under the terms of the Creative Commons Attribution License, which permits gences between congeneric species and Sclerodermus sp. (No. 5) averaged to about unrestricted use, distribution, and reproduction in any 16.5%. All 136 samples analyzed were included in six reciprocally monophyletic clades in medium, provided the original author and source are the COI neighbor-joining (NJ) tree. The NJ tree inferred from the 28S rRNA sequence credited. yielded almost identical results, but the samples from S. guani, S. sichuanensis, S. pupariae, Data Availability Statement: All relevant data are and Sclerodermus spp. (Nos. 1–4) clustered together and only Sclerodermus sp. (No. 5) within the paper. clustered separately. Our findings indicate that the standard barcode region of COI can be Funding: Zhongqi Yang received the State Key efficiently used to distinguish morphologically similar Sclerodermus species. Further, we Program of National Natural Science Foundation of speculate that Sclerodermus sp. (No. 5) might be a new species of Sclerodermus. China (No. 31230015). The funder had an important role in study design. Competing Interests: The authors have declared that no competing interests exist. PLOS ONE | DOI:10.1371/journal.pone.0119573 March 17, 2015 1/15 Molecular Identification of Sclerodermus spp. 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 prov- inces (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 di- rect economic loss was estimated to be approximately above 400 billion Yuan RMB [6]. There- fore, 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 long- horned 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%, respec- tively. 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 (Cole- optera: 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 Saun- ders, 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 par- asitic 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 pro- duces high proportion of females, as well as alate females (advantageous for dispersing after re- leasing 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 impor- tant natural insect enemies against forest wood borer pests, mainly buprestid and cerambycid PLOS ONE | DOI:10.1371/journal.pone.0119573 March 17, 2015 2/15 Molecular Identification of Sclerodermus spp. beetles, in China. Several putative species of Sclerodermus were identified and reared from dif- ferent 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. alterna- tus. These species were artificially reared in large numbers in the laboratory. All these Scleroder- mus 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 se- quences as taxon barcodes. The mitochondrial gene cytochrome c oxidase I (COI) could serve as the core of a global bioidentification