Appl. Entomol. Zool. 41 (1): 63–71 (2006) http://odokon.ac.affrc.go.jp/

Morphological and genetic indiscrimination of the grain , avenae complex (: )

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 -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 (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 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 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 phunculus database. The sequence for the North American x. RA/SIPH: relative portion of reticulated samples of S. avenae was supplied by Prof. Carol area on siphunculus D. von Dohlen at Utah State University (USU). To compare the morphological similarity of each All sequences were identified as the mt COII individual, principle component analysis (PCA) through alignments with other retrieved sequences was performed using SAS version 8.01. from the same regions using Megalign (DNA- DNA extraction, PCR, sequencing, alignment star™). The pair-wise distances between sequences and genetic analysis. Genomic DNA was ex- were calculated under a general time-reversible tracted using DNAzol® according to the manufac- model by PAUP* 4.0b10 (Swofford, 2003). Phylo- turer’s protocol. The partial fragments of mt COII, genetic analyses were performed using PAUP* one of the representative molecular markers for the 4.0b10. For maximum parsimony analysis, heuris- identification of species in subfamily Aphidinae tic searches were employed with 1,000 random (Moran et al., 1999; von Dohlen and Moran, 2000; additions of sequences, 10 trees held at each von Dohlen et al., 2002; von Dohlen and Teulon, pseudoreplicate and TBR branch swapping. The 2003), were obtained from the various populations 50% majority rule consensus tree bootstrap analy- in the Sitobion avenae-complex by PCR using the sis was performed using a full heuristic method, primers of 2993 (CAT TCA TAT TCA GAA with 1,000 replicates and 1,000 random additions TTA CC) and A3772 (GAG ACC ATT ACT TGC of sequences in 10 holds of trees for each step. For TTT CAG TCA TCT) (von Dohlen and Moran, maximum likelihood analysis, the best-fit nu- 2000). PCRs were performed using Advantage cleotide substitution model was explored by hierar- PCR II Taq polymerase (BD Advantage™) and the chical likelihood-ratio tests using Modeltest Ver- reaction mixture (20 ml contained 10 mM each sion 3.06 (Posada and Crandall, 1998). The substi- primer, 200 mM dNTPs, 2.5 mM MgCl2 and 0.04 mg tution ratios, expected nucleotide frequencies, in- genomic DNA template. The thermal program was variable site ratios and gamma shape parameters 35 cycles of 94°C/30 s, 58°C/30 s and 68°C/1 min, were also calculated. For both the maximum parsi- followed by a final extension at 68°C/10 min. The mony analysis and the maximum likelihood analy- PCR products were cleaned using Microcon YM- sis, the heuristic search strategy was performed 100 (Millipore), and directly sequenced in the with 100 random additions of sequences and a tree NICEM (The National Instrumentation Center for bisection recognition method. Heuristic search Environment Management, Seoul National Univer- strategies were performed with 100 random addi-

Table3. Geographical and ecological sources of samples used in nucleotide sequence comparisons

Species/Samples Locality Host plants Genbank Accession #

Sitobion akebiae Korea Rubus sp. AY935629 Sitobion akebiae (Red colony) Korea Hordeum sativum AY935630 Sitobion akebiae (Green colony) Korea Hordeum sativum AY935631 Sitobion akebiae Korea Oryza sativa AY935632 Sitobion akebiae Korea Poa sp. AY935633 Sitobion akebiae Korea Zea mays AY935634 Sitobion avenae England unknown U41116 Sitobion avenae North America unknown USU Sitobion miscanthi Australia Paspalum dilatatum U41125 Sitobion fragariae England unknown U41120 Sitobion near fragariae Australia unknown U41124 Sitobion ibarae Korea Rosa sp. AY935635 Macrosiphum mordvilkoi Korea Rosa sp. AY935628 Macrosiphum rosae Australia Cultivated rose U41117 New Synonymy of Sitobion avenae Complex 67 tions of sequences, 10 trees held at each pseudoreplicate and TBR branch swapping. Three 0.45) 0.054) 0.031) species were selected as out-groups: one species in 0.040) the genus Sitobion and two species in neighboring genus, Macrosiphum. The complete list of species in this study is summarized in Table 3. 0.199) (0.25 0.142) (0.29 0.195) (0.25 0.128) (0.18 SD) RESULTS AND DISCUSSION Indiscrimination of the quantitative morpholog- ical characteristics for three grain aphids, S. 0.074) (1.65 0.071) (1.34 0.092) (1.54 akebiae, S. miscanthi and S. avenae 0.053) (2.14 Based on measurements, three species in the S. (means complex avenae complex cannot be justified by the morpho- logical characteristics examined in this study 0.155) (0.75 0.101) (0.60 1.118) (0.67 (Table 4). For example, the ranges of the relative 0.061) (0.83 length of the antennal segment III to the processus Sitobion avenae terminalis (Ant.III/PT) and the relative length of the base of the antennal segment VI to the proces- sus terminalis (Ant.VIb/PT) of S. akebiae encom- 0.123) (0.94 0.083) (0.79 0.058) (0.92 0.068) (1.08 pass those of S. avenae and S. miscanthi. The length of the longest hairs on the antennal segment III (LH) in S. miscanthi is variable, encompassing the entire range of length found for the three other species. Also, the relative length of the second seg- 0.0078) (1.32 0.0042) (1.40 0.0029) (1.33 0.0029) (1.25 ment of hind tarsus to the ultimate rostral segment of S. miscanthi is more variable than those of S. avenae and S. akebiae. These morphological characteristics, which have been used in the identification of members of the S. 0.118) (0.023 0.103) (0.020 0.079) (0.020 0.062) (0.019 avenae complex, are therefore revealed to be of no use for the identification of these three species (Table 4). For example, the relative length of SIPH to the cauda of S. avenae (1.08–1.65) exceeds the 0.052) (0.44 0.019) (0.47 0.032) (0.47 criteria of the species (1.5) (Blackman and 0.028) (0.43 Eastop, 2000) and overlaps with the criteria for S. akebiae (1.18–1.93) and S. miscanthi (1.46– 1.99). The range of 2HT/URS in the S. avenae complex is also too variable for use in identifying 0.179) (0.19 0.081) (0.19 0.094) (0.20 0.092) (0.23 the four species. Predominant abdominal pigmen-

tation and longer hairs on heads and antennae, by morphological characters of the Comparison of measurement ranges 10 quantitative

which S. miscanthi have been distinguished (Taka- .

hashi, 1921; Blackman and Eastop, 2000), are also e4 bl 0.399) (0.90 0.507) (0.97 0.367) (0.92 variable. Abdominal pigmentations are not always 0.416) (0.99 Ta (mm) /PT /PT /Ant. III BD (mm) /URS /Ant.III /HF /Cauda /SIPH 2.07–3.57 0.79–1.18 0.17–0.28 0.32–0.56 0.014–0.024 1.06–1.39 1.00–1.27 0.73–0.94 1.83–2.36 0.10–0.29 1.80–3.12 0.70–1.37 0.15–0.33 0.25–0.59 0.010–0.034 1.11–1.50 0.75–1.17 0.64–0.84 1.46–1.99 0.18–0.34 1.99–3.63 0.77–1.13 0.15–0.25 0.25–0.80 0.010–0.028 1.18–1.55 0.45–0.94 0.37–0.71 1.08–1.65 0.23–0.35 found solely on S. miscanthi, they are also found 2.18–3.40 0.75–1.18 0.16–0.34 0.20–0.60 0.010–0.026 1.17–1.44 0.70–1.15 0.51–0.89 1.18–1.93 0.16–0.33 on the specimens of S. akebiae on the Miscanthus Body length Ant.III Ant.VIb LH LH 2HT SIPH SIPH SIPH RA species. Hair lengths of S. miscanthi are not signifi- 8) (2.57 24) (2.96 28) (2.79 21) (2.80 cantly longer than those of other species. n n n n ( ( ( ( Species S. avenae

However, S. fragariae may be distinguished from S. akebiae S. fragariae S. avenae by the relatively long siphunculi to the S. miscanthi 68 H. J. CHOE et al.

S. akebiae and S. miscanthi are genetically similar (0.17–1.56% differences in mt COII sequences). The sequences of mt COII for S. avenae and S. akebiae differed by less than 1.38% and were iden- tical between some samples: S. akebiae (sample #4, 6: on Oryza sativae and Zea mays) in Korea and S. avenae from England (sample #8); and S. akebiae (#1, 2: on Rubus sp. and Hordeum sativum) in Korea and the North American sample (#9) of S. avenae. The genetic distances between the three species (0.00–1.56%) were not larger than the intra-specific differences in S. akebiae (0.00– 1.38% in mt COII sequences), whereas the three outgroup species differed by more than 2.94– Fig. 1. Plot of principle components I and II showing 5.19%. Consequently, the three grain aphids (S. similarity of members of the Sitobion avenae complex (S. ave- nae: pink square, S. akebiae: blue diamond, S. miscanthi: red akebiae, S. avenae and S. miscanthi) cannot be dis- circle, S. fragariae: green triangle) based on 10 common mor- tinguished by mt COII, whereas S. fragariae is well phological characteristics. distinguished (1.39–3.27%) from the other three species (Table 5). hind femur, cauda and antennal segment III (SIPH/HF, SIPH/Cauda, SIPH/Ant.III) (Table 4). Molecular phylogenetic relationships of S. ave- Concurrently, S. fragariae is distinguishable from nae complex S. akebiae and S. miscanthi by its longer PT (small The parsimony analysis generated 12 most-par- mean value of Ant.VIb/PT), longer SIPH (high simonious trees (CI0.7945; without uninforma- mean values of SIPH/Ant.III and SIPH/HF) and tive characters, CI0.7059). The topologies of shorter cauda (high mean value of SIPH/cauda). trees are nearly equal and varied only in the rela- The PCA results also imply that morphological tionships among the four S. akebiae sequences characteristics used in the identifications are not (sample #1, 2, 4, 6) and the two S. avenae se- sufficient to distinguish S. akebiae from S. avenae quences (sample #8, 9). The 50% majority rule and S. miscanthi. However, S. fragariae is distinc- consensus tree shows the groupings of the popula- tive from other species in the S. avenae complex tions of the three species S. akebiae, S. avenae and (Fig. 1). S. miscanthi (Fig. 2). The best-fit model for the maximum likelihood Molecular variations on the partial sequences of analyses was GTRGI, following the Modeltest. mt COII among S. avenae complex The parameters under the best-fit model are as fol- An alignment of 582 nucleotide sequences of mt lows: the rate matrices are R(A-C)1.5e08, COII gene was compared for the four S. avenae R(A-G)6.4e08, R(A-T)2.7e+08, R(C-G) complex species and the three outgroup species, 4.385430, and R(C-T)6.6e09. The estimated Sitobion ibarae, Macrosiphum mordvilkoi and base compositions are A0.40569, C0.10711, Macrosiphum rosae, which are monoecious holo- G0.07394, and T0.41326. The assumed pro- cyclic on Rosa spp. (Rosaceae). These outgroups portion of invariable sites is 0.8172. were chosen because of their assumed close rela- MP and ML analyses generated clades mixed tions with S. avenae-complex and feeding on simi- among the three similar species of grain aphids; S. lar host plants, with Rosa spp. (Rosaceae) as the akebiae, S. avenae and S. miscanthi (Fig. 2). The primary hosts (Blackman and Eastop, 2000). three species were not clustered as individually dis- Corresponding to the previous results demon- tinct clades based on the results of the mt COII. strating that ‘mt COI-II and EF1a sequences are not distinguishable between S. akebiae and S. mis- Novel synonymy of Sitobion akebiae and Sitobion canthi’ (Sunnucks and Hales, 1996; Sunnucks et miscanthi with Sitobion avenae al., 1996), our results for mt COII also showed that Three grain aphids, S. avenae, S. akebiae syn. n. New Synonymy of Sitobion avenae Complex 69

and S. miscanthi syn. n., were revealed to be indis- tinguishable by the morphological characteristics used in their identifications, whereas Sitobion fra- gariae was shown to be a distinct species separated from the other three species, based on their rela- tively long siphunculi. Those three species were also shown to have close genetic relationships based on the sequences of mt COII and their phylo- genetic relationships as shown by maximum parsi- mony (MP) and maximum likelihood (ML) analy- ses (Fig. 2). Currently, it is accepted that the heteroecious holocyclic lifecycle of S. akebiae from various pri- mary host plants to grasses is one of the reasons for its separation as a distinctive species from S.

complex and three outgroupcomplex species, avenae (Shinji, 1935; Takahashi, 1964; Miyazaki, 1971). However, it has been observed in S. akebiae that both monoecious and heteroecious populations

S. avenae exist, and that monoecious populations appear to be predominant. In Korea, monoecious populations of grain aphids were found on wheat, rice, barley and other grasses in both the field and in green- Macrosiphum rosae Macrosiphum houses. During the early spring in Korea, popula- and tion densities of S. akebiae on primary host plants (Akebia and Rubus) are normally very low while the colonization and propagation of grain aphids (S. akebiae syn. n.) on secondary hosts (Poaceae) are prevalent, similar to the populations of S. ave- nae in other regions (personal observation). Mo- noecious holocyclic lifecycles of S. akebiae syn. n. Macrosiphum mordvilkoi Macrosiphum

, in Japan were inferred by the results of phenologi- cal studies (Yano et al., 1983; Kanehira et al., 1988). S. ibarae Significant relationships between host plants and the morphology of S. akebiae populations have been found. The populations of S. akebiae syn. n. 0.0000 0.0070 0.0103 0.0053 0.0138 0.0138 0.00530.0087 0.0138 0.0120 0.0138 0.0017 0.0000 0.0156 0.0070 0.0052 0.0156 on Rubus spp. tend to have long siphunculi like S. ) ) ) fragariae, which also alternates between Rubus and

) grasses. However, the population is genetically ) sp.) 0.0365 0.0430closer 0.0361 0.0413 0.0379to 0.0413S. 0.0361 avenae 0.0348 0.0430 0.0383, S. 0.0361 akebiae 0.0464 syn. n. and S. mis- sp.) dilatatum P. air-wise uncorrectedair-wise genetic distances of mt COII among the populations canthi syn. n., than the populations of S. fragariae sp.) 0.0017 0.0035 0.0035 0.0070 sp.) 0.0435 0.0516 0.0447 0.0430 0.0450 0.0430 0.0447 0.0386 0.0516 0.0421 0.0430 Rosa or S. near fragariae (Table 5). No evidence was .P Rubus sativum Hordeum Hordeum sativum Hordeum Oryza sativa Poa Zea mays Rosa (Australia) 0.0244 0.0327 0.0258discovered 0.0241 0.0276 0.0241 0.0258 for 0.0192 0.0327the 0.0069 sympatric speciation among the e5 (Korea, (Korea, bl

(Australia, populations with different lifecycles in S. akebiae (England) 0.0177 0.0266 0.0228 0.0139 0.0211 0.0139 0.0210 0.0141 0.0266 Ta Samples (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (Korea, (Korea, (Korea, (Korea, (Korea, (Korea, (Korea, (Korea, (Korea, (Korea, (England) 0.0035 0.0036 0.0052 0.0000 0.0018 0.0000 0.0070 (North America) 0.0000 0.0000 0.0103 0.0138 0.0035 0.0138 0.0120 0.0036 (Korea, (Korea, (Australia, rose)syn. 0.0454 n. 0.0519 0.0450 0.0503 0.0469 0.0503 0.0467 0.0421 0.0519 0.0455 0.0484 0.0519 0.0294 fragariae In conclusion, current results do not justify the

near separation of the grain aphids into three separate S. akebiae S. akebiae M. rosae M. rosae S. akebiae S. akebiae S. akebiae S. akebiae S. miscanthi S. avenae S. avenae M. mordvilkoi S. fragariae S. ibarae S. species, S. avenae, S. akebiae syn. n. and S. mis- (2) (1) (14) (3) (4) (5) (6) (7) (8) (9) (13) (12) (10) (11) canthi syn. n. Therefore, it is suggested that the three species be synonymized as a single species 70 H. J. CHOE et al.

Fig. 2. Phylogenetic relationships among members of the S. avenae-complex. A: A phylogram among the 12 trees generated by maximum parsimony analysis (numbers above branches indicate the bootstrapping index on the 50% majority-rule consensus tree), B: The phylogram generated by maximum likelihood analysis.

(i.e., S. avenae (F.)) with diverse morphological ACKNOWLEDGEMENTS and lifecycle variations (monoecious holocyclic, heteroecious holocyclic and even anholocyclic in We sincerely appreciate the assistance of the institutes and greenhouses and warmer climates). colleagues who provided the slide specimens used in this study: Gwan-Seok Lee (Insect Museum, National Institute of Agricultural Science and Technology, Rural Development of Sitobion (Sitobion) avenae (Fabricius, 1775) Administration, Republic of Korea), Carol D. von Dohlen (In- Aphis avenae Fabricius, 1775, Systema Entomolo- sect Museum, Utah State University, USA), Jung-Wook Kim giae: 736. (Department of Entomology, University of California, CA, Aphis granaria Kirby, 1798, Trans. Linn. Soc. USA), Gary Miller (Systematic Entomology Lab., USDA, Lond. 2: 238. USA) and Robert G. Foottit (Canadian National Collection, Canada). Our gratitude extends again to Carol D. von Dohlen Macrosiphum akebiae Shinji, 1935, Kontyu 9(5): for sharing the molecular sequence of the Nearctic sample for 243. New Synonymy this study. This study was supported by the Brain Korea 21 Macrosiphum miscanthi Takahashii, 1921, Agr. program and Seoul National University. Exp. St., Govt. Formosa Rept. 20: 1–97. New REFERENCES Synonymy Blackman, R. L. and V. F. Eastop (2000) Aphids on the World’s Crops: An Identification and Information Guide. New Synonymy of Sitobion avenae Complex 71

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