Appl. Entomol. Zool. 41 (1): 63–71 (2006) http://odokon.ac.affrc.go.jp/ Morphological and genetic indiscrimination of the grain aphids, Sitobion avenae complex (Hemiptera: Aphididae) Hyun Jung CHOE, Si Hyeock LEE and Seungwhan LEE* Entomology Program, School of Agricultural Biotechnology, Seoul National University; Seoul 151–742, Korea (Received 14 June 2005; Accepted 20 September 2005) Abstract Four grain aphids, Sitobion spp. [S. avenae (F.), S. akebiae (Shinji), S. miscanthi (Takahashi) and S. fragariae (Walker)] on various grasses (Poaceae), nominated as Sitobion avenae-complex in this paper, were compared for their morphological and genetic characteristics. For morphological comparison, ten characters frequently used in the identi- fication of S. avenae-complex were compared among samples from various global locations. The results from these comparisons demonstrated that the ranges of specific characteristics overlap considerably. The means of most charac- teristics were very similar among S. avenae, S. miscanthi and S. akebiae, indicating that the characteristics are not useful for the individual identification of these three grain aphids. Also, the intra-specific variations of the Far Eastern S. akebiae were as large as the inter-specific differences between S. miscanthi and S. avenae. In the nucleotide se- quence comparison of the mitochondrial cytochrome oxidase subunit II (mt COII) gene, the pair-wise genetic dis- tances among the populations of the three species ranged from 0.00 to 1.56%, almost equal to the intra-specific dis- tances of Far Eastern S. akebiae (0.00–1.38%). In this context, it is suggested that S. akebiae (Shinji) syn. n. and S. miscanthi (Takahashi) syn. n. be synonymized under the senior name, S. avenae (F.). Key words: Grain aphids; Sitobion; morphological indiscrimination; mitochondrial cytochrome oxidase; genetic simi- larity (Walker, 1848) in Europe, North America and Aus- INTRODUCTION tralia (Vickerman and Wratten, 1979). The genus Sitobion Mordvilko, with 91 species Previous authors have disagreed regarding the in the world, is one of the largest genera of the sub- morphological identification of species in the S. family Aphidinae (Hemiptera: Aphididae). Among avenae complex. After Shinji (1935) described S. these species, about half are reported to be found akebiae with the population migrating from Akebia on monocotyledons, mainly on the family Poaceae (Lardizabalaceae) to grasses (Poaceae), the grain (Remaudière and Remaudière, 1997; Blackman aphid in Far East Asia had been treated as a sub- and Eastop, 2000). There are four known species species of S. avenae (S. avenae akebiae), or am- of grain aphids in the world, important due to their biguously as the nominal subspecies of S. avenae economic impact on Poaceae crops (Table 1): Sito- (Takahashi, 1964; Paik, 1965). Later, S. akebiae bion akebiae (Shinji, 1935) in the Far East (Taka- was recorded on other primary winter host plants hashi, 1964; Miyazaki, 1971; Yano et al., 1983; including Rubus spp. (Rosaceae), Stellaria spp. Kanehira et al., 1988; Lee et al., 2002); Sitobion (Callitrichaceae) and Platanus spp. (Platanaceae) avenae (Fabricius, 1775) in North, Central and in Korea and Japan, and resumed its classification South America and the Paleoarctic, excluding parts as a separate species (Miyazaki, 1971; Lee et al., of the Far East (Müller, 1977; Vickerman and 2002). S. miscanthi, another grain aphid, was iden- Wratten, 1979); S. miscanthi (Takahashi, 1921) in tified on Miscanthus spp. in Taiwan according to South Asia, New Zealand, Australia and Hawaii three characteristics morphologically different (Eastop, 1966; David, 1976), and S. fragariae from S. avenae: slightly longer body hair, promi- *To whom correspondence should be addressed at: E-mail: [email protected] DOI: 10.1303/aez.2006.63 63 64 H. J. CHOE et al. Table1. Biological characters of the Sitobion avenae complex (revised from Blackman and Eastop, 2000; Lee et al., 2002) Species Life cycles Distribution (Records) Sitobion akebiae (Shinji) Heteroecious Holocyclic Far East (Korea, Japan) (1st hosts: Akebia, Stellaria aquatica, Platanus acerifolius, Rubus crataegifolius 2nd host: grasses) Sitobion avenae (F.) Monoecious Holocyclic Europe, the Mediterranean, (host: grasses) the Middle East, Central Asia, India, Nepal, Pakistan, Africa, North, Central and South America Sitobion fragariae (Walker) Heteroecious Holocyclic Europe, the Mediterranean, (1st hosts: Rubus spp. the Middle East, Pakistan, Nepal, 2nd host: grasses) S. Africa, western N. America, S. America, Australia, New Zealand Sitobion miscanthi (Takahashi) Monoecious Holocyclic India, Pakistan, Bangladesh, Nepal, (host: grasses) Sri Lanka, Vietnam, China, Taiwan, Borneo, Malaya, Australia, New Zealand, Fiji, Tahiti, Tonga, Cook Islands, Hawaii nent dark pigmentation on the abdomen and longer grain aphids in the Sitobion avenae complex from siphunculi (Takahashi, 1921). Recently, synonymy various global localities. The primary objective of with S. akebiae was suspected by Blackman and this study is clarification of the identity of the four Eastop (2000). Often misidentified, S. avenae and grain aphid species. S. fragariae are easily distinguished by the relative length of the siphunculi, though they occur in the MATERIALS AND METHODS same geographical regions, Nearctic and Western Paleoarctic (Stoetzel, 1987). The four grain aphids Specimens for morphological measurement. mentioned above are nominated as Sitobion avenae The samples of Sitobion akebiae were collected complex, in this study. from various plants in Korea and mounted on mi- The close relationship between the three species croscopic slides in Canada Balsam (see Blackman in the S. avenae complex has also been suspected and Eastop, 2000). All macroscopic specimens by the comparison of DNA sequences. Comparison were deposited in the insect collections of Seoul of EF1a and mitochondrial cytochrome oxidase National University (SNU, Seoul) and the National subunits I and II (mt COI-II) sequences from the Institute of Agricultural Sciences and Technology three species showed no variations for EF1a or mt (NIAST, Suwon) in Korea. The specimens of S. COI-II between S. akebiae and S. miscanthi, and avenae, S. fragariae and S. miscanthi were bor- only small variations on mt COI-II between S. mis- rowed from the aphid collections of various re- canthi and S. avenae, even though the same gene gions: the Canadian National Insect Collection sequences typically distinguish other Sitobion (CNC) in Ottawa, Canada; the Systematic Ento- species (Sunnucks and Hales, 1996; Sunnucks et mology Laboratory (SEL), USDA, Beltsville, al., 1996). However, S. miscanthi, S. near fragariae Maryland, USA; the Insect Museum of University and S. fragariae were well distinguished by differ- of California, Riverside (UCR), USA; the Insect ences in chromosomal numbers and microsatellites Museum of Utah State University, Logan (USU), (Hales et al., 1998). USA; and the Institute of Entomology, Czech In this study, both morphological and molecular Academy of Sciences, Ceske Budejovice, Czech characteristics were compared among the four Republic (IECAS). Details of the specimens are New Synonymy of Sitobion avenae Complex 65 Table2. Slide specimens of Sitobion species used in measurements No. of No. of Depository Species Host plants collection Localities specimens institutes sites Sitobion akebiae Avena sativa (Poaceae) 2 1 Korea (28) SNU Akebia sp. 1 1 NIAST Hordeum vulgarae 83 Miscanthus sp. 4 2 Secale cereale 31 Stellaria sp. 1 1 Triticum spp. (Poaceae) 1 1 Rubus spp. (Rosaceae) 3 2 Zea mays (Poaceae) 5 1 Sub total 28 13 Sitobion avenae Agropyron latiglume 31Canada (18) CNC Avena sativa (Poaceae) 7 7 USA (3) SEL Bromus sp. (Poaceae) 1 1 German (1) UCR Holcus lanatus 11Switzerland (1) USU Polygonum 11India (1) IECAS Triticum spp. (Poaceae) 4 4 Iris sp. (Iridaceae) 1 1 Unidentified Poaceae 6 6 Sub total 24 22 Sitobion miscanthi Unidentified Poaceae 8 4 India (5) SEL Sub total 8 4 New Zealand (2) Sitobion fragariae Dactylis glomerata 21Canada (10) CNC Bromus sp. (Poaceae) 3 1 USA (4) SEL Holcus lantanus 11Slovakia (3) UCR Poa sp. (Poaceae) 1 1 England (4) USU Rubus alleghemiensis 11 Rubus discolor 44 Rubus friticosus 31 Unidentified Poaceae 4 1 Unknown 2 2 Sub total 21 13 Total 81 52 listed in Table 2. ment III to processus terminalis Morphological characters and principal com- iii. Ant.VIb/PT: relative length of antennal seg- ponent analysis. The following 10 characters were ment VI basal length to processus terminalis selected according to characteristics frequently ap- iv LH: length of longest hair on antennal seg- plied in the identification of grain aphids (Taka- ment III hashi, 1921; Stoetzel, 1987; Blackman and Eastop, v. LH/Ant.III BD: relative length of longest 2000). The characters consist of the measurements hair on antennal segment III to the basal of six body parts and four relative lengths between width of antennal segment III appendages (such as the length of each segment of vi. URS/2HT: relative length of ultimate rostral antennae, legs, siphunculi and cauda). segment to second hind tarsus i. Body length vii. SIPH/Ant.III: relative length of siphunculus ii. Ant.III/PT: relative length of antennal seg- to antennal segment III 66 H. J. CHOE et al. viii. SIPH/HF: relative length of siphunculus to sity, Republic of Korea). Sequences of S. avenae, hind femur S. fragariae, S. miscanthi and Macrosiphum rosae ix. Cauda/SIPH: relative length of cauda to si- (Linnaeus, 1758) were retrieved from the GenBank