Estimating ancestral geographical distributions: a Gondwanan origin for aphid parasitoids?

We tested the published hypothesis of a Gondwanan origin for the overwhelmingly northern hemisphere aphid parasitoids (Aphidiinae) as follows: (i) finding their sister group by a phylogenetic analysis of the entire Braconidae (Insecta: Hymenopterai using sequence data from approximately 500 bp fragments of both the nuclear 28S (D2 region) and mitochondrial 16S rDNA genes, (ii) using this sister-group relationship and the more informative 28S D2 gene to estimate the phylogeny of the Aphidiinae and (iii) estimating the ancestral distribution for the Aphidiinae using maximum-likelihood and maximum-parsimony methods. Both methods indicated a Gondwanan origin.

Mushroom bodies of vespid wasps

Mushroom bodies are higher centers in the brains of insects. Studies on honey bees and species of ants suggest that these centers are particularly prominent in social insects. The present study confirms the presence of large mushroom bodies in five subfamilies of vespid wasps, while at the same time showing significant departures from the mushroom body organization that typifies bees and ants. Although the basic organizational plan of the insect mushroom body into calyces, peduncle, and lobes is maintained, as is the arrangement of axons of intrinsic neurons, the size and arrangements of the vespid mushroom body lobes differ markedly from those known from other Hymenoptera. Furthermore, considerable variation is found both between and within vespid subfamilies. The present results are discussed with respect to current hypotheses about functional attributes of mushroom bodies and the phylogeny of the Vespidae.

Phylogenetic signal in the COI, 16S, and 28S genes for inferring relationships among genera of Microgastrinae (Hymenoptera; Braconidae): evidence of a high diversification rate in this group of parasitoids

The subfamily Microgastrinae is a highly diversified group of parasitoid wasps that attacks all of the different groups of Lepidoptera. We explore here the phylogenetic signal in three gene (mitochondrial COI and 16S, and nuclear 28S) fragments as an assessment of their utility in resolving generic relationships within this species-rich insect group. These genes were chosen because their level of sequence divergence is thought to be appropriate for this study and because they have resolved relationships among other braconid wasps at similar taxonomic levels. True phylogenetic signal, as opposed to random signal or noise, was detected in the 16S and 28S data sets. Phylogenetic analyses conducted on each microgastrine data set, however, have all resulted in poorly resolved trees, with most clades being supported by low bootstrap values. The phylogenetic signal, if present, is therefore concentrated on a few well-supported clades. Some rapidly evolving sites may be too saturated to be phylogenetically useful. Nonetheless, the sequence data (nearly 2300 nucleotides) used here appear to exhibit the appropriate level of variation, theoretically, to resolve the relationships studied. Moreover, the clades that are well supported by the data are usually supported by more than one data set and represent different levels of sequence divergence. We suggest that the lack of phylogenetic signal observed is an indication of the presence of many short internal branches on the phylogeny being estimated, which in turn might be the result of a rapid diversification of the taxa examined. Relative specialization of diet, which is typically associated with parasitic behavior, is believed to result in high radiation rates, which may have been especially high in microgastrine wasps because of the great diversity of their lepidopteran hosts. This hypothesis of a rapid diversification caused by an abundance of host species remains speculative and more data will be needed to test it further.

Hierarchical analysis of variation in the mitochondrial 16S rRNA gene among Hymenoptera

Nucleotide sequences from a 434-bp region of the 16S rRNA gene were analyzed for 65 taxa of Hymenoptera (ants, bees, wasps, parasitoid wasps, sawflies) to examine the patterns of variation within the gene fragment and the taxonomic levels for which it shows maximum utility in phylogeny estimation. A hierarchical approach was adopted in the study through comparison of levels of sequence variation among taxa at different taxonomic levels. As previously reported for many holometabolous insects, the 16S data reported here for Hymenoptera are highly AT-rich and exhibit strong site-to-site variation in substitution rate. More precise estimates of the shape parameter (alpha) of the gamma distribution and the proportion of invariant sites were obtained in this study by employing a reference phylogeny and utilizing maximum-likelihood estimation. The effectiveness of this approach to recovering expected phylogenies of selected hymenopteran taxa has been tested against the use of maximum parsimony. This study finds that the 16S gene is most informative for phylogenetic analysis at two different levels: among closely related species or populations, and among tribes, subfamilies, and families. Maximization of the phylogenetic signal extracted from the 16S gene at higher taxonomic levels may require consideration of the base composition bias and the site-to-site rate variation in a maximum-likelihood framework.

Evolutionary relationships among the Braconidae (Hymenoptera: Ichneumonoidea) inferred from partial 16S rDNA gene sequences

Phylogenetic relationships among the Braconidae were examined using homologous 16S rDNA gene sequence data. Analyses recovered the few well-supported relationships evident in this family from morphological analyses, viz the monophyly of the microgastroid complex of subfamilies, the monophyly of the cyclostome complex of subfamilies (= braconoids), a sister-group relationship between the Alysiinae and Opiinae, and a close relationship between the Helconinae and Blacinae. With respect to the braconoid complex of subfamilies, a sister-group relationship was recovered between Aphidiinae and Mesostoinae, and a clade composed of Gnamptodontinae + Histeromerinae + Rhyssalinae + Aphidiinae + Mesostoinae was also recovered. The Doryctinae and Rogadinae sensu lato (s.l.) were generally not resolved as monophyletic. With respect to the helconoid complex of subfamilies, a sister-group relationship was recovered between Sigalphinae and Agathidinae, whereas Neoneurinae fell out among other helconoid subfamilies. Other relationships among the helconoid subfamilies were unclear from these analyses. With respect to the microgastroid complex of subfamilies, our data conform to morphological estimates, recovering ((Microgastrinae + Miracinae) + Cardiochilinae) + Cheloninae. The topology of our trees suggests that the cyclostome subfamilies are a natural derived group, inferring that endoparasitism (not ectoparasitism) is the ancestral state for the Braconidae, unless all of the ectoparasitic ancestors of the helconoid + microgastroid subfamilies are now extinct.

A molecular phylogeny of the Aphidiinae (Hymenoptera: Braconidae)

Phylogenetic relationships within the Aphidiinae, and between this and other subfamilies of Braconidae (Hymenoptera), were investigated using sequence data from three genes: elongation factor-1alpha, cytochrome b, and the second expansion segment of the 28S ribosomal subunit. Variation in both protein-coding genes was characterized by a high level of homoplasy, but analysis of the expansion segment--robust over a range of alignment methods and parameters-resolved some of the older divergences. Parsimony analysis of the combined data suggests the following tribal relationships: (Ephedrini + (Praini + (Aphidiini + Trioxini))). In addition, the cyclostome subfamilies were found to form a clade separate from the Aphidiinae, but relationships between the Aphidiinae and the noncyclostome braconids could not be resolved. The inferred phylogeny also supported a secondary loss of internal pupation within the Praini and a polyphyletic origin of endoparasitism within the Braconidae.

Evidence for AT-transversion bias in wasp (Hymenoptera: Symphyta) mitochondrial genes and its implications for the origin of parasitism

We inferred the incidence of nucleotide conversions in the COI and 16S rRNA mitochondrial genes of members of the Symphyta and basal Apocrita (Hymenoptera). Character-state reconstructions in both genes suggested that conversions between A and T (AT transversions) occurred much more frequently than any other type of change, although we cannot wholly discount an underlying transition bias. Parsimony analysis of COI nucleotide characters did not recover phylogeny; e.g., neither the Tenthredinoidea nor Apocrita were recovered as monophyletic. However, analysis of COI amino acid characters did recover these relationships, as well as others based on fossil and morphological evidence. Analysis of 16S rRNA characters also recovered these relationships providing conversions between A and T were down-weighted. Analysis of the combined data sets gave relatively strong support for various relationships, suggesting that both data sets supported similar topographies. These data sets, both separately and combined, suggested that the phytophagous Siricidae were more closely related to the predominantly parasitic Apocrita than were the ectoparasitic Orussoidea. This suggests that the wasp parasitic lifestyle did not have a single origin, unless the Siricidae have more recently reverted to phytophagy. Alternatively, parasitism evolved twice independently, once in the Orussoidea and again in the Apocrita. The latter scenario is supported by the observation that the evolution of parasitism was accompanied by a tendency for the larvae to develop inside plant tissues. Adaptations that accompanied the movement of wasps into a confined, wood-boring habitat may have preadapted them to becoming ectoparasitic.

Phylogenetic analysis of a retrotransposon with implications for strong evolutionary constraints on reverse transcriptase

This study examines the evolutionary dynamics of a retrotransposon in a group of parasitoid wasps. A region containing the reverse transcriptase (RT) domain was sequenced for 43 elements from the genomes of nine different wasp species. Phylogenetic analysis of the elements revealed concordance with taxonomic classification of the host species, and the pattern was consistent with that expected for vertical transmission of a multicopy element during differentiation of the species. Twenty-three of the 43 elements had comparable intact open reading frames in the amplified region, and these were used in an analysis of evolutionary constraint on the amino acid sequence. As previously documented for retroelements, closely related elements exhibited nearly equal substitution rates at nonsynonymous and synonymous sites, but relative nonsynonymous substitution rates decreased as increasingly divergent elements were compared. A statistical test indicated that the decrease was not due to saturation of weakly selected sites. The pattern is most likely caused by a "pseudogene effect." Individual elements are not subject to purifying selection, and therefore, synonymous and nonsynonymous substitutions accumulate at equal rates. Comparisons among closely related elements are influenced strongly by this pseudogene evolution, whereas comparisons among distantly related elements reveal selection on the actively replicating lineages connecting the elements. These distant comparisons more accurately reflect the constraints on the amino acid sequence, and the comparisons among elements in this study indicated strong constraints on RT.

[Claves ilustradas para las subfamilias, tribus y géneros de esfécidos neotropicales (Apoidea: Sphecidae) [Illustrated clues for subfamilies, tribes, and genera of neotropical Spheciade (Apoidea:Sphecidae)]

141 genera of Sphecidae, representing 1,628 species, are known from the Neotropical Region. Illustrated keys to genera, tribes, and subfamilies are presented in Spanish and English. These have been modified and updated from those in Bohart & Menke's 1976 book, Sphecid Wasps of the World. The validity of a few genera recognized by Bohart & Menke is now in question and the keys are annotated to alert users to these problems. A list of neotropical genera and higher taxa is included. Names in the list are appended with significant literature published since 1976. The history and current status of subfamilies are reviewed. Ten subfamilies are recognized. Family characters and biology are summarized. Morphological terms are illustrated and a glossary provided.

Parthenogenesis-inducing microorganisms in Aphytis (Hymenoptera: Aphelinidae)

Production of males in uniparental lines of two species in the parasitic wasp genus Aphytis was induced by rifampicin, and male sexual functioning was determined. Wolbachia-specific 16S rDNA primers were used in a PCR in order to: (1) assess correlation between thelytokous reproduction and the presence of Wolbachia; (2) detect the loss of Wolbachia DNA in uniparental A. lingnanensis following antibiotic treatments, with or without the presence of a host; and (3) clone and sequence part of the Wolbachia 16S rDNA from the uniparental Aphytis species for phylogenetic studies. Males produced viable sperm that was transferred to the female spermatheca following mating. However, sperm failure to effect egg fertilization resulted in all-male progeny. Wolbachia were found in the two uniparental (A. lingnanensis and A. diaspidis) but not in the two biparental (A. lingnanensis and A. melinus) Aphytis lines tested. They can be detected in wasps up to 7 days following antibiotic treatments, regardless of the presence of host. The 16S rDNA for the symbionts in the two Aphytis species is virtually identical, and is most closely related to the Wolbachia found in Muscidifurax uniraptor (Pteromalidae).

Sequence analysis of the D1 and D2 regions of 28S rDNA in the hornet (Vespa crabro) (Hymenoptera, Vespinae)

The two variable domains D1 and D2 near the 5' end of the 28S ribosomal RNA gene (large subunit rRNA) have been sequenced for Vespa crabro. The sequence was aligned to corresponding rDNA regions of the wasp species Nasonia vitripennis, Melittobia digitata and the fruit fly Drosophila melanogaster. We analysed the nucleotide composition and sequence similarity for the different regions of the investigated sequences and present the inferred secondary structure of Vespa crabro.

Molecular identification and phylogeny of parasitic wasp species (Hymenoptera: Trichogrammatidae) by mitochondrial DNA RFLP and RAPD markers

Mitochondrial DNA (mtDNA) restriction fragment length polymorphism (RFLP) and random amplified polymorphic DNA (RAPD) were tested for their ability to discriminate between seven species of minute parasitic wasps belonging to the genus Trichogramma. They proved to be reliable species-diagnostic molecular markers. Pairwise comparisons of the mtDNA restriction maps revealed considerable differentiation among the seven species. Percentage of common restriction sites ranged from 30% to 83%. Phylogenetic analyses performed either on the mtDNA nucleotide distance matrix or on the matrix of the restriction site-state generated a tree congruent with those based on allozymes and morphology. RAPD procedures also revealed species-specific banding patterns and seem promising for a rapid and easy identification of Trichogramma species. Moreover, for some Trichogramma species, RAPD banding patterns might be informative of the phylogenetic relatedness.

Comparison of Vespula germanica venoms obtained from different sources

This study was carried out to compare the allergenic potency of Vespula germanica (VG) venoms extracted by different methods and commercially available venoms from Vespula species currently used for in vivo and in vitro studies including immunotherapy. Pure VG venom was used as the reference material. Protein content and enzymatic and allergenic properties of all venoms studied were determined by dye stain reagent, hyaluronidase and phospholipase A1B enzyme activities, and radioallergosorbent test inhibition studies, respectively. Radioallergosorbent test discs sensitized with commercial and pure VG venom were compared using specific IgE antibodies from subjects allergic to VG venom. The data obtained indicate that there were important differences in the allergenic potency between the Vespula species venoms employed for in vivo and/or in vitro assays, VG venom obtained by sac dissection, and pure VG venom. These results indicate that venoms from Vespula species used for in vitro and in vivo tests have a lower concentration of allergens and contain nonvenom proteins. These data should be taken into account when these vespid venoms are used for diagnostic purposes and also when evaluating immunotherapy studies.

Description and biology of Trichopria painteri n.sp. (Hymenoptera: Diapriidae), a solitary parasitoid of Stomoxys calcitrans (Diptera: Muscidae) from Harare, Zimbabwe

Taxonomic description and life history are given of Trichopria painteri n.sp. (Hymenoptera: Diapriidae), a solitary endoparasitoid that emerged from Stomoxys calcitrans (L.) (Diptera: Muscidae) pupae collected at an agricultural installation near Harare, Zimbabwe, Africa. Although its low level of parasitism. high immature mortality and short adult life span would require augmentative releases of T.painteri, this parasitoid could reduce isolated field populations of S.calcitrans to an acceptable level within several weeks.

DNA insertions as a component of the evolution of unique satellite DNA families in two genera of parasitoid wasps: Diadromus and Eupelmus (Hymenoptera)

In the two parasitoid wasps, Diadromus collaris and Eupelmus orientalis, the satellite DNAs were each found to consist wholly or largely of a single family (5%-7% of the genome). Several clones of each family were obtained and sequenced. The repeat unit in each species is characterized by both the repetition of a basic motif and the presence of an inserted sequence. Sequence comparisons with satellite DNA from D. pulchellus and E. vuilleti provide plausible scenarios for the evolution of the satellite DNA in each genus. Palindromes and A-rich tracts in each consensus sequence suggest the formation, in vivo, of hairpin structures and bend centers that may play a role in heterochromatin condensation in insects. The insertions in the repeat units of each species also contain these structural features, suggesting that maintenance of these insertions requires constraints similar to those pertaining to the rest of the satellite-DNA unit.

Phylogeny of the Nasonia species complex (Hymenoptera: Pteromalidae) inferred from an internal transcribed spacer (ITS2) and 28S rDNA sequences

The phylogeny of the cryptic species complex of wasps in the genus Nasonia was inferred by analysis of nucleotide sequences of an rDNA internal transcribed spacer (ITS2) and the D2 region of 28S rDNA. Phylogenetic analysis showed that N. vitripennis descended from a theoretical common ancestor with that of a lineage that diverged into N. longicornis and N. giraulti. Differences in the ITS2 regions clearly distinguished two strains of N. giraulti. Another member of the Dibrachys Group, Trichomalopsis dubius, was placed outside of the Nasonia complex. The D2 region had a base substitution rate approximately 2 times slower than the ITS2 region and was used to resolve the phylogenetic affiliation of an eulophid, Melittobia digitata, to the pteromalids. Tree topology of the Nasonia complex was congruent with the phylogeny of a cluster of Wolbachia bacteria which infect these insects. The possible role of these bacteria in driving speciation is discussed.

Polydisperse viral DNA's in ichneumonid ovaries: a survey

Viruses are described from several genera of ichneumonid parasitoids. New morphologic categories have been observed, one of which is similar to typical baculoviruses. Calyx particles from several species were found to contain polydisperse DNA's. An electrophoretic method for screening individual field-collected wasps for the presence of such DNA's is reported. DNA profiles obtained by this procedure were sufficiently consistent, within any particular affected species, to suggest that they could provide useful taxonomic information.