Andjeljko Petrović

Lysiphlebus orientalis (Hymenoptera, Braconidae), a new invasive aphid parasitoid in Europe - evidence from molecular markers

We report the occurrence of Lysiphlebus orientalis in Serbia, an aphid parasitoid from the Far East that is new to Europe and has the potential to become invasive. Our finding based on morphological characters is confirmed by analyses of mitochondrial cytochrome oxidase subunit I sequences. An increase in number and an expansion of the host range were observed during field studies over the past two years, and it is determined that the current host range encompasses nine aphid hosts on 12 different host plants, forming 13 tri-trophic associations. A host range determined for European populations of L. orientalis appears wider compared with that in its Far Eastern native habitats where Aphis glycines Mats. is the sole known host. Moreover, it overlaps considerably with the host ranges of European parasitoids that play an important role in the natural control of pest aphids.

Review and Key for the Identification of Parasitoids (Hymenoptera: Braconidae: Aphidiinae) of Aphids Infesting Herbaceous and Shrubby Ornamental Plants in Southeastern Europe

ABSTRACT Original information on aphidiines parasitizing aphids on herbaceous and shrubby ornamental plants in southeastern Europe is presented. In total, 22 species are keyed and illustrated with scanning electron micrographs, stereomicroscope micrographs, and line drawings. The aphidiines presented in this work have been identified from 40 aphid taxa. Two hundred sixty-six aphidiine— aphid—plant associations are presented, out of which 126 are new. The results are discussed in relation to the overall parasitoid—aphid-plant associations in the area.

Identification of Two Cryptic Species within the Praon abjectum Group (Hymenoptera: Braconidae: Aphidiinae) using Molecular Markers and Geometric Morphometrics

ABSTRACT The genus Praon represents a large group of aphid endoparasitoids and is exemplary for the problems encountered in their taxonomy because of a great variability of morphological characters. To investigate the intraspecific variability and to ascertain cryptic speciation within the Praon abjectum Haliday group, biotypes in association with the aphid hosts Aphis sambuci L., Longicaudus trirhodus Walker, and Rhopabsiphum spp. were examined. We combined molecular and geometric morphometric analyses, that is, partial sequences of the mitochondrial cytochrome oxidase subunit I and nuclear 28SD2 genes and the shape of the forewing. Low variation of 28SD2 sequences confirmed the close relatedness of species from the genus Praon. Analysis of the cytochrome oxidase subunit I sequences however identified three separate taxa within the P. abjectum group with substantial genetic divergence. The biotype of P. abjectum associated with L. trirhodus differed from those associated with Rhopabsiphum sp. and A. sambuci by 5.4–6.5% and 7.7% sequence divergence, respectively, while the genetic distance between the latter two biotypes ranged from 9.5 to 10%. The main changes in the forewing shape that discriminate these three biotypes as revealed by geometric morphometrics are related to the stigma shape and the position of the radial nerve. Based on the differences determined in mitochondrial sequences and in the shape of the wing, we describe two new cryptic species within the P. abjectum group as follows: P. sambuci sp. n. in association with A. sambuci/S. nigra and P. longicaudus sp. n. in association with L. trirhodus/T. aquilegifolium.

Review and Key to the World Parasitoids (Hymenoptera: Braconidae: Aphidiinae) of Aphis ruborum (Hemiptera: Aphididae) and Its Role as a Host Reservoir

ABSTRACT A review and illustrated key of the aphidiine parasitoids of Aphis ruborum (Börner and Schilder) are presented including their distribution. The parasitoid spectrum of A. ruborum in the West Palaearctic is rich, composed of Aphidius colemani Viereck, Aphidius matricariae Haliday, Binodoxys acalephae (Marshall), Binodoxys angelicae (Haliday), Ephedrus persicae Froggatt, Lipolexis gracilis Förster, Lysiphlebus confusus Tremblay and Eady, Lysiphlebus fabarum (Marshall), and Praon abjectum (Haliday), and supplemented by the introduction of Lysiphlebus testaceipes (Cresson). In the Americas the parasitoid complex of A. ruborum consists of A. colemani, Aphidius ervi Haliday (South America), and L. testaceipes (South and North America). Furthermore, the reservoir role of A. ruborum in various ecosystems was investigated in Europe (France) and South America (Chile). Faunal peculiarities and relationships of the parasitoid taxa are discussed together with a synopsis of their potential as biocontrol agents.

Genetic and morphological variation in sexual and asexual parasitoids of the genus Lysiphlebus - an apparent link between wing shape and reproductive mode.

BackgroundMorphological divergence often increases with phylogenetic distance, thus making morphology taxonomically informative. However, transitions to asexual reproduction may complicate this relationship because asexual lineages capture and freeze parts of the phenotypic variation of the sexual populations from which they derive. Parasitoid wasps belonging to the genus Lysiphlebus Foerster (Hymenoptera: Braconidae: Aphidiinae) are composed of over 20 species that exploit over a hundred species of aphid hosts, including many important agricultural pests. Within Lysiphlebus, two genetically and morphologically well-defined species groups are recognised: the “fabarum” and the “testaceipes” groups. Yet within each group, sexual as well as asexual lineages occur, and in L. fabarum different morphs of unknown origin and status have been recognised. In this study, we selected a broad sample of specimens from the genus Lysiphlebus to explore the relationship between genetic divergence, reproductive mode and morphological variation in wing size and shape (quantified by geometric morphometrics).ResultsThe analyses of mitochondrial and nuclear gene sequences revealed a clear separation between the “testaceipes” and “fabarum” groups of Lysiphlebus, as well as three well-defined phylogenetic lineages within the “fabarum” species group and two lineages within the “testaceipes” group. Divergence in wing shape was concordant with the deep split between the “testaceipes” and “fabarum” species groups, but within groups no clear association between genetic divergence and wing shape variation was observed. On the other hand, we found significant and consistent differences in the shape of the wing between sexual and asexual lineages, even when they were closely related.ConclusionsMapping wing shape data onto an independently derived molecular phylogeny of Lysiphlebus revealed an association between genetic and morphological divergence only for the deepest phylogenetic split. In more recently diverged taxa, much of the variation in wing shape was explained by differences between sexual and asexual lineages, suggesting a mechanistic link between wing shape and reproductive mode in these parasitoid wasps.

Areopraon chaitophori n. sp. (Hymenoptera: Braconidae: Aphidiinae) associated with Chaitophorus leucomelas Koch on poplars, with a key for European Areopraon Mackauer species.

Abstract Areopraon chaitophori n. sp. associated with Chaitophorus leucomelas Koch on Populus nigra is described and illustrated. The main diagnostic characters of Areopraon species are discussed, and a key for identification of European species is provided. The distal dorsal part of the second metasomal tergite of Areopraon species has a very prominent horizontal longitudinal protuberance which represents a new diagnostic character for Areopraon.

Re-visiting the Aphidius urticae s. str. group: re-description of Aphidius rubi Starý and A. silvaticus Starý (Hymenoptera: Braconidae: Aphidiinae)

Here we tested Aphidius urticae s. str. host-associated lineages from Microlophium carnosum (Buckton), Amphorophora rubi (Kaltenbach), Macrosiphum funestum (Macchiati) and Aulacorthum vaccinii Hille Ris Lambers with the barcoding region of the mitochondrial cytochrome oxidase subunit I gene used to analyse population differences and elucidate phylogenetic relationships between the separated taxa. This molecular marker has been shown to be the most informative molecular marker in resolving species complexes in aphidiine parasitoids. Analyses of the mitochondrial sequences revealed the existence of three clearly separated mitochondrial lineages of A. urticae s. str. group associated with: i) Macrosiphum funestum and Aulacorthum vaccinii aphid hosts, ii) Microlophium carnosum and iii) Amphorophora rubi. This corresponds to the initial descriptions of A. rubi, A. silvaticus and A. urticae and their aphid host associations prior to synonymization of A. rubi and A. silvaticus with A. urticae. On the other hand, significant evolutionary distances ranging from 2.3 to 9.2% between the three mitochondrial lineages were not accompanied by clear morphological differences. Therefore, re-descriptions of A. rubi and A. silvaticus are presented, together with their morphological differentiation in a key, as well as their phylogenetic relationships and genetical differentiation.

Parasitoids (Hymenoptera: Braconidae: Aphidiinae) of Aphids Feeding on Ornamental Trees in Southeastern Europe: Key for Identification and Tritrophic Associations

Abstract Ornamental trees are valuable natural elements which provide several economic, aesthetic, and ecological benefits to humans. They are seriously infested by numerous pests and diseases, among which aphids are of high importance. Here we present a comprehensive list of Aphidiinae parasitoid species that attack aphids on ornamental trees in southeastern Europe, some of which are potential biocontrol agents. Thirty-eight species of Aphidiinae are recorded, keyed, and illustrated. Fifty-six out of 120 recorded tritrophic (parasitoid–aphid–plant) associations were previously unknown. The results are discussed in relation to the overall parasitoid–aphid–tree associations in the target region, as well as potential of parasitoid use in biological control programs.

Sexual Dimorphism in the Parasitoid Wasps Aphidius balcanicus, Aphidius rosae, and Aphidius urticae (Hymenoptera: Braconidae: Aphidiinae)

ABSTRACT In this study, we explored variations in the magnitude and the direction of sexual dimorphism in three parasitoid species from the genus Aphidius Nees (Aphidius balcanicus Tomanović and Petrović, Aphidius rosae Haliday, and Aphidius urticae Haliday). We also explored the variation in sexual dimorphism within one of these species, A. urticae, which parasitizes and develops in three different hosts that belong to three aphid genera. To estimate sexual size dimorphism, we selected two developmentally and functionally unrelated morphological structures: the mesoscutum and the wing. Our results showed that sexual dimorphism in mesoscutum and wing size differ (sexual dimorphism in mesoscutum size appears to be insignificant, whereas the wings are larger in males). We found a high level of variation in sexual dimorphism in wing shape within and between species. We also found that the observed shape changes are not due to size-related, allometric changes in wing shape. These results indicate that sexual dimorphism in wing size and wing shape is highly variable and could be influenced by various factors, including host effects, whereas mesoscutum size appears to be a conserved trait in aphid parasitoids.

Molecular substitution rate increases with latitude in butterflies: evidence for a trans-glacial latitudinal layering of populations?

A well-documented consequence of repeated global ice ages is the negative relationship between latitude and intraspecific genetic diversity. However, little is known about additional effects of such major climatic events on population genetic structure. Here we studied the phylogeographic structure of five lycaenid butterfly species with varied ecological adaptations, sampled across a latitudinal gradient in the Holarctic region. We found a positive correlation between latitude and substitution rate of mitochondrial DNA sequences in all species investigated. We propose that this result is the signal of increased genetic drift and founder effects during post-glacial recolonization of northern populations. Given that phylogenetic branch length is the result of a cumulative process over evolutionary time, we hypothesize that a latitudinal layering of populations has generally been maintained during repeated cycles of glaciation, possibly due to a neutral spatial effect and/or local adaptive advantage. This trans-glacial latitudinal layering could be viewed as a particular case of the more general phenomenon of intraspecific structuring that is created and maintained in a fluctuating environmental gradient.