Biodiversity Data Journal :
Taxonomy & Inventories
|
Corresponding author: Zhongping Xiong (xzping_0@126.com)
Academic editor: Miles Zhang
Received: 01 Mar 2023 | Accepted: 06 Apr 2023 | Published: 11 Apr 2023
© 2023 Xiaoxiao Chen, Jingge Kuang, Wenjing Tao, Zhongping Xiong, Kangshan Mao
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Chen X, Kuang J, Tao W, Xiong Z, Mao K (2023) A new species of Megastigmus (Hymenoptera, Megastigmidae) from China. Biodiversity Data Journal 11: e102828. https://doi.org/10.3897/BDJ.11.e102828
|
Most species of Megastigmus are considered important economic pests that grow in seeds, especially of conifers. Accurate identification of species is a crucial step for the biological research of parasitic pests and the further application of biological control. However, their large variety, small size, similar morphology and different growth and development stages have brought great challenges to taxonomic research. Traditional morphological identification often takes a long time and this requires us to seek a new method for rapid and accurate identification. Therefore, the better identification of Megastigmus urgently needs to be combined with molecular methods to help taxonomic development.
Here, Megastigmus daduheensis sp. n. (Chalcidoidea: Megastigmidae) was identified, based on morphology and molecular markers, such as COI and Cytb. M. daduheensis sp. n. is distinct from other known species of the same genus in the morphology. The results of the molecular phylogenetic tree, similarity alignment and genetic distance indicate that the COI and Cytb sequences of M. daduheensis sp. n. are highly similar to M. sobinae and M. duclouxiana, but there are some genetic differences. The genetic distances of M. daduheensis sp. nov. with M. duclouxiana and M. sabinae were 0.34 and 0.33 and the percentages of shared base pairs were 76.3% and 76.8%, respectively. Both morphological and molecular data classified M. daduheensis sp. n. as a new species. The obtained COI and Cytb sequences of M. daduheensis sp. n. can be used as DNA barcodes, providing molecular data for rapid and accurate identification of this species in the future.
morphology, DNA barcoding, phylogenetic relationships, genetic distance
Megastigmidae comprises over 200 species currently classified into 12 valid genera which are generally considered to have a worldwide distribution and Megastigmus is the only cosmopolitan genus of the family (
Megastigmus is a diverse group with 144 valid species described in the Universal Chalcidoidea Database (
DNA barcoding is a method for species identification, based on a relatively short DNA gene fragment with sufficient variation and easy amplification (
The infested cones of C. chengiana were collected from Ri’er Township (102°35′ E, 30°59′ N), Xiaojin County, Aba Autonomous Prefecture of Tibetan and Qiang (Ngawa), Sichuan Province, China. The cones were kept in mesh bags, where the spawning adult insects were collected and immediately frozen in liquid nitrogen and preserved at -80°C until DNA extraction. All type specimens are deposited in the Natural History Museum of Sichuan University, Chengdu (NHMSU) with an accession number NHMSU-20201015-XJ.
Terminology of morphological structures in this study mostly follows
We used Mitoz 3.5.0 software (
Family/ Genus |
Species |
GenBank No. (COI) |
GenBank No. (Cytb) |
Megastigmus |
M. daduheensis sp. n. |
||
M. aculeatus |
|||
M. amicorum |
|||
M. atedius |
|||
M. atlanticus |
|||
M. bipunctatus |
|||
M. borriesi |
|||
M. cryptomeriae |
|||
M. dorsalis |
|||
M. duclouxiana |
|||
M. hoffmeyeri |
|||
M. lasiocarpae |
|||
M. milleri |
|||
M. pictus |
|||
M. pinsapinis |
|||
M. pinus |
|||
M. rafni |
|||
M. rosae |
|||
M. sabinae |
|||
M. schimitscheki |
|||
M. spermotrophus |
|||
M. stigmatizans |
|||
M. strobilobius |
|||
M. suspectus |
|||
M. synophri |
|||
M. thyoides |
|||
M. tsugae |
|||
M. zebrinus |
|||
Torymidae |
Torymus geranii |
Female. Length (body + ovipositor): 2.81 ~ 3.05 + 3.09 ~ 3.17 mm. Colour: body (Fig.
Head. Head about 1.6× as wide as long in dorsal view; whole face with pale, dense setae; frons with many obvious striated sculptures; ocellus arranged in a blunt triangle, POL about twice as long as OOL and OCL; several short setae between ocelli, the rest on other parts of head (Fig.
Mesosoma. Pronotum and mesoscutum with irregular sculpture and orientation of rugae, notauli brown and sparse setae scattered on both sides (Fig.
Metasoma. Gaster not compressed laterally, 1.21 mm long, with sparse bristles scattered with four black horizontal bands and the spacing between the horizontal bands decreasing successively (Fig.
Male. Body black, 2.4 ~ 2.6 mm long (Fig.
The key from China distinguished the females of Megastigmus daduheensis sp. n. by their body length less than 5 mm, ovipositor exceeding body length, stigma neck less than 0.5 times the width of the stigma and scultellum dark yellow. (Fig.
The new species is named after its type locality, Daduhe, Sichuan Province.
The eggs are laid in the cones of Cupressus chengiana S.Y. Hu, feeding on the nuts and the adults fly out of the cones from October to November every year.
Key to species of Megastigmus from China (females) |
||
1 | Body length greater than 5 mm | M. sinensis Sheng, 1989 |
– | Body length less than 5 mm | 2 |
2 | Ovipositor equals or exceeds body length | 3 |
– | Ovipositor shorter than body length | 8 |
3 | Stigma neck more than 0.5 times the width of the stigma | M. aculeatus Swederus, 1975 |
– | Stigma neck less than 0.5 times the width of the stigma | 4 |
4 | Marginal vein shorter than postmarginal vein length | 5 |
– | Marginal vein equals or exceeds postmarginal vein length | 6 |
5 | Scultellum dark brown | M. duclouxianae Xu & He, 1995 |
– | Scultellum dark yellow | M. daduheensis sp. n. |
6 | Width of head about 1.17 times the length in the ventral view | M. carinus Xu & He, 1995 |
– | Head about twice as wide as long in the ventral view | 7 |
7 | Pronotum with two yellow spots | M. likiangensis Roques & Sun, 1995 |
– | Pronotum without spots | M. sp. (Host:Tsuga forresttii) |
8 | Mid-lobe of mesoscutum with short longitudinal ridge | M. ezomatsuanus Hussey & Kamijo, 1958 |
– | Mid-lobe of mesoscutum with transverse costulae | 9 |
9 | Ovipositor longer than gaster length | M. cellus Xu & He, 1995 |
– | Ovipositor equal to or shorter than gaster length | 10 |
10 | Scultellum black | 11 |
– | Scultellum yellow or brown | 13 |
11 | Pedicel of antennae longer than F1 length | M. lasiocarpae Crosby, 1913 |
– | Pedicel of antennae equal to or shorter than F1 length | 12 |
12 | Marginal vein equal to postmarginal vein length | M. sp. (Host: Sabina recurva var.coxii) |
– | Marginal vein shorter than postmarginal vein length | M. pictus Foerster, 1841 |
13 | Stigma neck length equal to the width of the stigma | M. pseuclotsugaphilus Xu & He, 1995 |
– | Stigma neck length shorter than the width of the stigma | 14 |
14 | Body orange yellow | 15 |
– | Body yellowish-brown or light yellow | 16 |
15 | Head with dark spots | M. sabinae Xu & He, 1989 |
– | Head without dark spots | M. formosana Roques & Pan, 2005 |
16 | Transscutal articulation of scutellum with irregular reticulate sculpture | M. pseuclomali Xu & He, 1995 |
– | Transscutal articulation of scutelluma with striped or smooth sculpture | 17 |
17 | F7 more than twice as long as wide | M. pingii Roques & Sun, 1995 |
– | F7 less than twice as long as wide | 18 |
18 | Pronotum 1.9 times longer than width | M. rigidae Xu & He, 1998 |
– | Pronotum 1.1-1.3 times longer than width | M. cryptomeriae Yano, 1918 |
Megastigmus is sometimes difficult to classify accurately because of its small size and similar morphological characteristics. Therefore, the phylogenetic relationships are important to resolve species boundaries. Here, the existing mitochondrial data (COI + Cytb) was used to construct a molecular phylogenetic tree of Megastigmus, so as to verify the taxonomic status of the new species described above (Fig.
In recent years, genetic distance has been regarded as one of the main characteristics of Hymenoptera species classification (
Pairwise genetic distances of COI and Cytb amongst 28 species of Megastigmus.
(COI/ Cytb) |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
2 |
0.09/0.11 |
|||||||||
3 |
0.56/0.55 |
0.54/0.57 |
||||||||
4 |
0.60/0.17 |
0.59/0.14 |
0.12/0.56 |
|||||||
5 |
0.56/0.11 |
0.54/0.09 |
0.10/0.57 |
0.12/0.17 |
||||||
6 |
0.57/0.05 |
0.56/0.10 |
0.10/0.55 |
0.13/0.17 |
0.10/0.10 |
|||||
7 |
0.55/0.05 |
0.53/0.09 |
0.10/0.54 |
0.14/0.16 |
0.10/0.09 |
0.06/0.04 |
||||
8 |
0.56/0.10 |
0.54/0.08 |
0.11/0.56 |
0.13/0.14 |
0.10/0.09 |
0.12/0.10 |
0.12/0.08 |
|||
9 |
0.56/0.11 |
0.55/0.07 |
0.10/0.56 |
0.12/0.15 |
0.11/0.09 |
0.11/0.10 |
0.12/0.10 |
0.10/0.06 |
||
10 |
0.56/0.10 |
0.55/0.07 |
0.11/0.55 |
0.11/0.14 |
0.09/0.07 |
0.11/0.09 |
0.11/0.08 |
0.08/0.04 |
0.06/0.04 |
|
11 |
0.58/0.12 |
0.57/0.14 |
0.09/0.56 |
0.11/0.14 |
0.11/0.13 |
0.10/0.12 |
0.10/0.12 |
0.10/0.13 |
0.10/0.12 |
0.08/0.12 |
12 |
0.55/0.11 |
0.54/0.10 |
0.10/0.55 |
0.11/0.17 |
0.07/0.08 |
0.10/0.10 |
0.10/0.10 |
0.06/0.06 |
0.07/0.07 |
0.06/0.05 |
13 |
0.59/0.11 |
0.58/0.09 |
0.22/0.57 |
0.25/0.17 |
0.21/0.09 |
0.23/0.10 |
0.22/0.09 |
0.23/0.07 |
0.25/0.08 |
0.22/0.06 |
14 |
0.56/0.15 |
0.54/0.12 |
0.12/0.58 |
0.11/0.17 |
0.11/0.15 |
0.12/0.14 |
0.12/0.14 |
0.12/0.15 |
0.14/0.14 |
0.12/0.14 |
15 |
0.57/0.15 |
0.55/0.13 |
0.10/0.57 |
0.12/0.13 |
0.10/0.17 |
0.13/0.17 |
0.13/0.16 |
0.10/0.15 |
0.12/0.14 |
0.10/0.15 |
16 |
0.57/0.10 |
0.54/0.09 |
0.10/0.56 |
0.11/0.16 |
0.09/0.09 |
0.11/0.11 |
0.12/0.10 |
0.07/0.07 |
0.06/0.07 |
0.06/0.05 |
17 |
0.56/0.10 |
0.54/0.08 |
0.09/0.56 |
0.11/0.15 |
0.09/0.08 |
0.12/0.09 |
0.10/0.09 |
0.07/0.05 |
0.07/0.05 |
0.02/0.04 |
18 |
0.57/0.11 |
0.55/0.09 |
0.10/0.56 |
0.12/0.17 |
0.09/0.09 |
0.11/0.11 |
0.12/0.10 |
0.07/0.07 |
0.07/0.07 |
0.06/0.05 |
19 |
0.57/0.10 |
0.55/0.09 |
0.11/0.56 |
0.12/0.16 |
0.09/0.09 |
0.12/0.10 |
0.12/0.09 |
0.09/0.06 |
0.08/0.07 |
0.06/0.05 |
20 |
0.56/0.10 |
0.55/0.08 |
0.10/0.55 |
0.10/0.14 |
0.09/0.08 |
0.10/0.08 |
0.12/0.08 |
0.08/0.05 |
0.07/0.05 |
0.07/0.04 |
21 |
0.56/0.12 |
0.54/0.11 |
0.09/0.56 |
0.10/0.17 |
0.09/0.11 |
0.10/0.10 |
0.09/0.10 |
0.09/0.10 |
0.10/0.08 |
0.08/0.09 |
22 |
0.57/0.10 |
0.54/0.09 |
0.09/0.55 |
0.12/0.13 |
0.08/0.10 |
0.11/0.09 |
0.11/0.08 |
0.07/0.06 |
0.09/0.06 |
0.07/0.05 |
23 |
0.58/0.07 |
0.56/0.11 |
0.12/0.56 |
0.14/0.20 |
0.11/0.11 |
0.07/0.06 |
0.06/0.06 |
0.13/0.09 |
0.12/0.11 |
0.10/0.09 |
24 |
0.55/0.10 |
0.53/0.07 |
0.08/0.55 |
0.11/0.14 |
0.09/0.08 |
0.10/0.08 |
0.10/0.07 |
0.07/0.04 |
0.07/0.03 |
0.06/0.03 |
25 |
0.56/0.13 |
0.54/0.12 |
0.10/0.57 |
0.11/0.17 |
0.12/0.13 |
0.11/0.11 |
0.13/0.12 |
0.09/0.11 |
0.10/0.11 |
0.09/0.11 |
26 |
0.56/0.12 |
0.54/0.10 |
0.10/0.55 |
0.10/0.16 |
0.09/0.11 |
0.12/0.11 |
0.13/0.09 |
0.06/0.06 |
0.07/0.07 |
0.07/0.05 |
27 |
0.56/0.09 |
0.54/0.07 |
0.09/0.56 |
0.10/0.14 |
0.09/0.09 |
0.11/0.09 |
0.11/0.08 |
0.05/0.03 |
0.07/0.05 |
0.06/0.04 |
28 |
0.56/0.11 |
0.54/0.08 |
0.09/0.56 |
0.11/0.15 |
0.07/0.08 |
0.09/0.09 |
0.09/0.08 |
0.07/0.05 |
0.07/0.06 |
0.05/0.04 |
(COI/ Cytb) |
11 |
12 |
13 |
14 |
15 |
16 |
17 |
18 |
19 |
20 |
12 |
0.10/0.13 |
|||||||||
13 |
0.25/0.13 |
0.21/0.06 |
||||||||
14 |
0.11/0.15 |
0.10/0.16 |
0.24/0.15 |
|||||||
15 |
0.10/0.15 |
0.09/0.15 |
0.21/0.18 |
0.09/0.13 |
||||||
16 |
0.10/0.13 |
0.03/0.04 |
0.22/0.07 |
0.12/0.15 |
0.090.15 |
|||||
17 |
0.08/0.12 |
0.05/0.06 |
0.22/0.07 |
0.11/0.15 |
0.10/0.15 |
0.06/0.07 |
||||
18 |
0.10/0.13 |
0.03/0.04 |
0.22/0.07 |
0.12/0.15 |
0.09/0.14 |
0.01/0.02 |
0.06/0.07 |
|||
19 |
0.11/0.13 |
0.06/0.07 |
0.24/0.09 |
0.11/0.15 |
0.10/0.17 |
0.07/0.08 |
0.05/0.06 |
0.07/0.07 |
||
20 |
0.09/0.12 |
0.05/0.06 |
0.23/0.07 |
0.1/0.15 |
0.11/0.16 |
0.06/0.07 |
0.06/0.05 |
0.06/0.08 |
0.07/0.06 |
|
21 |
0.08/0.14 |
0.07/0.11 |
0.23/0.12 |
0.09/0.15 |
0.09/0.17 |
0.09/0.10 |
0.08/0.09 |
0.09/0.10 |
0.09/0.10 |
0.08/0.10 |
22 |
0.09/0.11 |
0.06/0.08 |
0.22/0.09 |
0.11/0.10 |
0.09/0.12 |
0.07/0.08 |
0.07/0.07 |
0.07/0.07 |
0.07/0.07 |
0.07/0.06 |
23 |
0.11/0.13 |
0.11/0.10 |
0.24/0.11 |
0.13/0.16 |
0.12/0.18 |
0.12/0.11 |
0.10/0.11 |
0.13/0.11 |
0.12/0.10 |
0.12/0.10 |
24 |
0.09/0.11 |
0.05/0.05 |
0.23/0.05 |
0.12/0.14 |
0.10/0.14 |
0.06/0.06 |
0.05/0.04 |
0.06/0.06 |
0.08/0.05 |
0.05/0.03 |
25 |
0.09/0.13 |
0.09/0.12 |
0.23/0.11 |
0.13/0.14 |
0.10/0.14 |
0.09/0.12 |
0.09/0.11 |
0.09/0.12 |
0.10/0.13 |
0.09/0.11 |
26 |
0.10/0.15 |
0.05/0.07 |
0.23/0.08 |
0.10/0.17 |
0.09/0.18 |
0.06/0.08 |
0.06/0.07 |
0.06/0.07 |
0.07/0.07 |
0.06/0.06 |
27 |
0.09/0.13 |
0.04/0.06 |
0.23/0.06 |
0.11/0.15 |
0.09/0.16 |
0.05/0.07 |
0.05/0.05 |
0.06/0.07 |
0.06/0.05 |
0.06/0.05 |
28 |
0.09/0.12 |
0.04/0.06 |
0.23/0.07 |
0.09/0.15 |
0.10/0.15 |
0.06/0.07 |
0.04/0.05 |
0.06/0.07 |
0.06/0.05 |
0.06/0.04 |
(COI/ Cytb) |
21 |
22 |
23 |
24 |
25 |
26 |
27 |
|||
22 |
0.07/0.09 |
|||||||||
23 |
0.10/0.11 |
0.11/0.10 |
||||||||
24 |
0.07/0.08 |
0.07/0.05 |
0.11/0.09 |
|||||||
25 |
0.09/0.11 |
0.10/0.10 |
0.12/0.13 |
0.10/0.10 |
||||||
26 |
0.08/0.11 |
0.07/0.08 |
0.12/0.12 |
0.06/0.05 |
0.08/0.12 |
|||||
27 |
0.08/0.10 |
0.07/0.07 |
0.11/0.09 |
0.06/0.03 |
0.08/0.11 |
0.04/0.06 |
||||
28 |
0.06/0.09 |
0.05/0.06 |
0.10/0.10 |
0.06/0.03 |
0.08/0.10 |
0.06/0.05 |
0.05/0.05 |
Note: COI fragment before backslash (/) and Cytb fragment after backslash. 1 M. Sabinae; 2 M. duclouxiana; 3 M. daduheensis sp. nov.; 4 M. dorsalis; 5 M. aculeatus; 6 M. amicorum; 7 M. bipunctatus; 8 M. pinus; 9 M. spermotrophus; 10 M. tsugae; 11 M. zebrinu; 12 M. schimitscheki; 13 M. strobilobius; 14 M. synophri; 15 M. stigmatizans; 16 M. pinsapinis; 17 M. atedius; 18 M. suspectus; 19 M. rafni; 20 M. pictus; 21 M. cryptomeriae; 22 M. thyoides; 23 M. atlanticus; 24 M. hoffmeyeri; 25 M. rosae; 26 M. lasiocarpae; 27 M. milleri; 28 M. borriesi.
The identification of species based on morphological differences is essential to insect taxonomy. Nevertheless, the traditional classification method has drawbacks when it comes to tiny and similar-looking species, while molecular data can make up for the shortcomings of this method. Currently, many studies have stated explicitly the appropriateness of mtDNA in resolving the relationships amongst subspecies or closely-related species (
In this paper, morphological characters and molecular data (COI and Cytb) were used to classify parasitic wasps from Cupressus chengiana S.Y. Hu. Both methods confirm that M. daduheensis sp. nov. is a separate species, which is clearly different from other species in the genus and has a certain degree of diversification. Although M. daduheensis sp. n. was similar to M. sobinae and M. duclouxiana in morphology, it can be distinguished from other species, based on characters on the mesoscutum, stigma and ovipositor. M. daduheensis sp. nov. and M. sabinae were sister species, based on the phylogenetic relationship and genetic distance and, together, they constituted one clade with M. duclouxiana. This result is consistent with previous studies and supports Megastigmus on Cupressaceae plants formed a distinct clade (
This study not only increased the species diversity of Megastigmus, but also provided the genetic information of M. daduheensis sp. nov. and enriched the genetic database. However, our study only obtained COI and Cytb genes of this genus, which contained incomplete genetic information. Therefore, it can be combined with other mitochondrial or nuclear genes for a comprehensive analysis and verification in the future. In addition, there are a large number of species within this genus, but most of them are studied, based on morphology, ecology and physiology, while molecular data is very scarce. Hopefully, we will be able to collect more samples and obtain molecular data to make up for the shortfall.
We thank Wentao Wang and Xue Li for their help with sample collection. This study is financially supported by National Natural Science Foundation of China (grant No. U20A2080), Sichuan Science and Technology Program (2023NSFSC0186), and Sichuan University (Fundamental Research Funds for the Central Universities, SCU2021D006, SCU2020D003; Institutional Research Fund from Sichuan University, 2021SCUNL102).