Corresponding author: Rimantas Rakauskas (
Academic editor: E. Tasheva
Forty three European population samples of mealy aphids from various winter and summer host plants were attributed to respective species of
Mealy aphids of the genus Hyalopterus Koch are reported to be serious pests of stone fruits all over the World (
The aim of this study was to elaborate morphological identification key of the genus
Forty three population samples of mealy aphids from five European countries were collected from various winter and summer host plants (
Aphid material used in the present study. Samples used for the morphological discrimination analysis with
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Jieznas, Prienai distr., Lithuania, 2012.05.30, 12-24 |
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Daugai, Alytus distr., Lithuania, 2012.05.30, 12-31 |
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Ignalina, Ignalina distr., Lithuania, 2012.06.19, 12-65 |
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Ditrau, Romania, 2012.06.11, z12-52 |
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Gheorheni, Romania, 2012.06.11, z12-53 |
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Blagojevgrad, Bulgaria, 2012.06.25, 12-81 |
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Alytus, Alytus distr., Lithuania, 2012.05.30, 12-28 |
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Eišiškės, Šalčininkai distr., Lithuania, 2012.06.13, 12-41 |
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Costinesti, Romania, 2012.06.13, z12-65 |
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Costinesti, Romania, 2012.06.15, z12-88 |
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Murfatlar, Romania, 2012.06.13, z12-64 |
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Vama Veche, Romania, 2012.06.16, z12-93 |
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Mezopeterd, Hungary, 2012.06.20, z12-120 |
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Kairėnai, Vilnius distr., Lithuania, 2010.07.01, z10-5 |
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Bucuresti, Romania, 2012.06.13, z12-58 |
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Mezopeterd, Hungary, 2012.06.20, z12-119 |
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Pieta Porta Alba, Romania, 2012.06.14, z12-73 |
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Kairėnai, Vilnius distr., Lithuania, 2010.07.01, z10-4 |
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Vama Veche, Romania, 2012.06.16, z12-91 |
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Biharkeresztes, Hungary, 2012.06.20, z12-118 |
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Baltupiai, Vilnius, Lithuania, 2010.06.30, z10-1 |
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Palanga, Klaipėda distr., Lithuania, 2010.07.15, z10-24 |
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For molecular analysis, a single aphid individual from one sampled plant was considered as a unique sample. Total genomic DNA was extracted from a single aphid using the DNeasy Blood & Tissue kit (Qiagen), which involved at least a 2 h digestion of tissue with proteinase K. Partial sequences of mitochondrial COIwere PCR-amplified using previously published primers (
Forty three sequences of three
Samples representing different clades in the molecular trees were used for canonical discrimination analysis: 2 samples from almond (
Based on the earlier references (
– length of antennal segment 2 – width of antennal segment 2 – basal width of antennal segment 3 – length of antennal segment 3 – length of the longest hair on antennal segment 3 – length of antennal segment 4 – length of antennal segment 5 – length of basal part of antennal segment 6 – length of terminal process of antennal segment 6 – length of submedian hair on abdominal tergite 8 – body length (excluding cauda) – length of cauda – length of the second segment of hind tarsus – length of hind femur – length of the frons hair – width of the head across eyes – length of median dorsal head hair – distance between the bases of median dorsal head hairs – length of siphunculus – length of hind tibia – length of ultimate rostral segment – basal width of ultimate rostral segment
Measurements of the slide-mounted apterous viviparous females were performed by means of interactive measurement system Micro-Image (Olympus Optical Co. GmbH). STATISTICA 8 version software (Statsoft 2007) was exploited for data analysis. Pearson’s correlation coefficients were calculated to evaluate the correlation of morphometric characters with body length. Characters with strong (| r | ≥ 0.50) statistically significant (p<0.05) correlation with body length were removed from the further analysis: BL (r=1.00), F3L (r=0.58), T3L (r=0.59), A2L (r=0.57), HW (r=0.51). Remaining seventeen characters were used for forward stepwise discriminant analysis with host plant species as grouping variable followed by canonical analysis. Discriminant analysis was conducted in three steps. The first step was performed to discriminate between the all three mealy aphid species emerged in the COI dendrogram (
Characters that contributed most in canonical discrimination functions were evaluated as having potential for species separation. The eventual species identification key based on these morphological characters and host plant information was constructed. Afterwards, it was applied on mealy aphid samples that were not used for the construction of the identification key (
The maximum parsimony (MP) analysis of partial COI sequences resulted in 425 equally parsimonious trees (length = 152, CI=0.76, RI=0.95). ML tree (T92+G model) showed similar topology, the same as NJ analysis (Kimura 2-parameter distances) and BI (GTR+G model) analyses. NJ, MP and ML bootstrap values over 50 % together with BI posterior probabilities over 0.50 are given at respective nodes of the same tree in
Maximum likelihood (ML) tree showing phylogenetic relationships among three
The scatter plot of the first two canonical variates for samples from 18 different geographical localities representing three mealy aphid species (apterous viviparous females) is shown in
Scatter-plot of the individual canonical scores of the first two canonical variates discriminating 21 samples of
Contribution of eleven morphological characters to the canonical functions discriminating 23 European samples of
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0,05 | 0,66 | 34,70 | 0,00 | 0,71 | 0,29 |
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0,04 | 0,81 | 15,40 | 0,00 | 0,14 | 0,86 |
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0,04 | 0,82 | 14,33 | 0,00 | 0,86 | 0,14 |
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0,04 | 0,89 | 8,37 | 0,00 | 0,81 | 0,19 |
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0,04 | 0,97 | 1,98 | 0,14 | 0,69 | 0,31 |
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0,04 | 0,86 | 11,14 | 0,00 | 0,60 | 0,40 |
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0,06 | 0,58 | 48,13 | 0,00 | 0,12 | 0,88 |
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0,06 | 0,58 | 49,50 | 0,00 | 0,07 | 0,93 |
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0,04 | 0,90 | 7,57 | 0,00 | 0,40 | 0,61 |
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0,04 | 0,92 | 6,30 | 0,00 | 0,75 | 0,25 |
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0,04 | 0,96 | 3,04 | 0,05 | 0,60 | 0,40 |
To discriminate between apterous viviparous females of
To discriminate between apterous viviparous females of
Out of eleven morphological characters included in the canonical function discriminating between sampled apterous viviparous females of mealy aphidspecies complex, the length of median dorsal head hair (MDHSL) enabled separation of 97.3 %
1 | Canonical discrimination function 74,6150*URW - 1,2696*T3L/CL + 1 value exceeding 0. Setae on frons stout. On peaches, nectarines, apricots or reeds |
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– | Canonical discrimination function value less than 0. Setae on frons filiform. On almonds, plums, apricots or reed | 2 |
2 | Length of the median dorsal head hair (MDHSL) 0.026 – 0.039 (average 0.031) mm. Canonical discrimination function -2.2645*SL - 18.6609* MDHSL + 1value exceeds 0. On almond or reeds |
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– | MDHSL 0.036 – 0.067 (0.05) mm. Canonical discrimination function value less than 0. On plums, apricots or reeds |
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Our analysis shows the morphological separation of mealy aphid species complex being a really difficult task which is in accordance with the earlier references (
When performing discriminant analyses, the body length should be eliminated from the data set together with characters that have strong and statistically significant correlation with the body length. In our case, when the entire data set of morphological characters was used for discriminant analysis, samples from reeds appeared the most different (not shown). Contrary, after the body length and correlated characters were removed from analysis, samples from reeds scattered amongst samples from plum and peach.
The results of cluster analysis based on morphological data (
Dendrogram of hierarchical cluster analysis based on 17 morphological characters (squared Mahalanobis distances) using unweighted pair-group average linkage among 29 samples of
This research was funded by a grant (No LEK-04/2012) from the Research Council of Lithuania.