Bisexual Generation Research Articles

Andricus cydoniae Giraud, 1859 Junior Synonym of Cynips conifica Hartig, 1843, as Experimentally Demonstrated (Hymenoptera: Cynipidae: Cynipini).

Simple SummaryPhytophagous members of the family Cynipidae induce a spectacular diversity of plant galls that are often complex in structure. Knowledge of the biology, life cycle, and life history of known cynipid species is largely fragmentary; gall wasps can exhibit an alternation of generations known as heterogony in which an all-female alternates with a bisexual generation. The unisexual generation produces eggs parthenogenetically, and these are usually inserted into a specific plant part. At the site of oviposition, galls are induced, within which a bisexual generation develops and later emerges. Emergent males and females mate, and females in turn induce galls from which the unisexual generation emerges. Females of the two generations may be morphologically dissimilar and may induce galls that differ greatly morphologically. Differences in the morphology of both wasps and galls between generations of the same species, coupled with incomplete knowledge of life cycles, have led to considerable taxonomic confusion. Alternating generations of numerous species have been described as separate species or even genera. Here, we demonstrate experimentally that two cynipid species, Cynips conifica (presently Andricus conificus) and Andricus cydoniae, which are morphologically different and produce very different galls on different host oaks, represent alternate generations of a single species.We demonstrated the life cycle closure of Cynips conifica Hartig, 1843 (presently Andricus conificus), previously supposed on the basis of molecular data, and the identity of the sexual generation, through laboratory experiments. As a consequence, Andricus cydoniae Giraud, 1859 became a junior synonym of A. conificus (Hartig, 1843). We provide illustrations and a diagnosis for adults and galls, observations on biology, and information on distribution. Moreover, as sexual galls of A. conificus cannot be distinguished from those of Andricus multiplicatus, a detailed comparison between sexual galls and adults of these two species is reported.

Contribution to the Knowledge of Incidence, Development and Galls of the Bisexual Generation of Biorhiza pallida (Hymenoptera: Cynipidae)

The research study deals with the occurrence, cecidogenesis and development of the bisexual generation of Biorhiza pallida in the Brno region. Galls were found most frequently on Quercus petraea and on Q. robur. At the end of the winter season, females deposited 2–290 (on average 83.6) eggs, mainly into the above average sized buds on last‑year’s shoots. Larvae came to age in May in the 3rd instar, in the extremely warm and dry growing period of 2015 already in the 2nd instar. Adult individuals were leaving galls from the end of May to the end of July. Females were 3–4.5 – times superior to males in numbers. Females, males and individuals of both sexes emerged from 64.3%, 21.4% and 14.3% of galls, respectively. Galls were created from the beginning of April. In the second half of April (or at the beginning of May) they were 3–35 (on average 15.2) mm high and 3–45 (on average 20.2) mm wide. The percentage of buds infestation, average number of deposited eggs and average size of galls were increasing with the increasing mean diameter of shoots. Parasitoids (incl. parasitoid inquilines) killed 30–100 (on average 65) percent of gall wasp population. We found as many as 40% and 10% of galls with the developing Curculio villosus (Curculionidae) and Synergus spp. (Cynipidae), respectively. In the spring of 2016, nearly the whole gall wasp population in Brno‑Komín was killed by late frosts. The pest infests mid‑aged woody plants, sporadically also young growths and epicormic shoots of old oak trees.

Багаторічна динаміка щільності стану розвитку міжвидових популяцій злакових попелиць (Homoptera, Aphididae) упродовж вегетації пшениці озимої в умовах Лісостепу України

Багаторічна динаміка щільності стану розвитку міжвидових популяцій злакових попелиць (Homoptera, Aphididae) упродовж вегетації пшениці озимої в умовах Лісостепу України

Microsatellite DNA and behavioural studies provide evidence of host-mediated speciation in Myzus persicae (Hemiptera: Aphididae)

In many parts of the world, the tobacco specialist Myzus persicae nicotianae is isolated from the generalist Myzus persicae s.s. because either or both taxa reproduce parthenogenetically. Here we investigated how the genomic integrity of the tobacco specialist is maintained in Greece, where both taxa have a bisexual generation on peach. Microsatellite DNA analysis revealed greatest genetic divergence between populations in tobacco-growing regions and those in a region where tobacco is not cultivated. This was irrespective of reproductive mode, which has an important effect on population structure. Bayesian clustering and admixture analyses split the aphid genotypes into three groups, corresponding with persicae, bisexual nicotianae and unisexual nicotianae, respectively. Genetic distance parameters showed strong regional differentiation but marked year-on-year stability, indicating low interpopulation migration. Assortative mating between taxa is promoted by differences in the daily rhythm of female signalling behaviour, with peak activity coinciding with periods of consubspecific male searching activity. Males showed greater attraction to the sex pheromone of their own subspecies. Thus, despite relatively low overall genetic differentiation, processes are in place facilitating further genomic divergence and eventual speciation. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 91, 687–702.

Parallelism in secondary loss of sex from a heterogonic life cycle on different host plants in the Andricus mukaigawae complex (Hymenoptera: Cynipidae), with taxonomic notes

The Andricus mukaigawae complex consists of bivoltine heterogonic ( = cyclically parthenogenetic) and univoltine thelytokous (parthenogenetic) populations. The bivoltine heterogonic populations are divided into A. mukaigawae (2n = 12), which produces bur‐shaped unisexual galls (producing only asexual females) on Quercus aliena, Q. mongolica, and Q. serrata; and A. kashiwaphilus (2n = 10), which produces flower‐shaped unisexual galls on Q. dentata. The univoltine thelytokous populations have to date been treated as one species, A. targionii (s. lat.), but the population on Q. aliena produces bur‐shaped galls and that on Q. dentata produces flower‐shaped galls. I investigated the karyotype of the population of A. targionii (s. lat.) on Q. dentata. This population had the same karyotype as that of A. kashiwaphilus. The karyotype and shape of galls indicate that A. targionii (s. lat.) on Q. dentata is derived from A. kashiwaphilus, and that on Q. aliena is derived from A. mukaigawae through the parallel deletion of the bisexual (sexually reproducing) generation on different host plants. Since A. targionii (s. lat.) is thus shown to be polyphyletic, the name A. targionii (s. str.) should be applied to the univoltine thelytokous population on Q. aliena, and the univoltine thelytokous population on Q. dentata should be identified as A. pseudoflos comb. n., judging from the original descriptions.

Doses <I>Wolbachia</I> Induce Unisexuality in Oak Gall Wasps? (Hymenoptera: Cynipidae)

Heterogony (cyclical parthenogenesis) is a remarkable characteristic of oak gall wasps, Cynipini, which is the largest tribe in Cynipidae. A few species of Cynipini are exceptionally univoltine and thelytokous, probably due to deletion of the bisexual generation from their heterogonic ancestor-species. Since the close association between Wolbachia presence and unisexuality has been known in two other tribes of Cynipidae, we searched for Wolbachia using polymerase chain reaction (PCR) primers for the ftsZ and wsp genes in a taxon of the Cynipini, the Andricus mukaigawae complex. This taxon consists of closely related bivoltine heterogonic and univoltine thelytokous species, so that it is a most suitable taxon to clarify a possible role of Wolbachia in unisexuality of heterogonic and thelytokous species of Cynipini. Our PCR assay on the unisexual adults showed that only two of the six populations of the bivoltine heterogonic species tested were highly infected with Wolbachia. The nucleotide sequence of bacterial wsp fragment indicates that these endosymbiotic bacteria are a member of supergroup A. Conversely, Wolbachia were not detected from any populations of the univoltine thelytokous species examined. In conclusion, Wolbachia is not responsible for unisexuality in heterogonic or thelytokous species of Cynipini.

Occurrence of sexual morphs in Trama troglodytes von Heyden, 1837 (Hemiptera, Aphididae)

The root-feeding aphids of the tribe Tramini have been cited as a possible case of ancient apomixis, as there are no substantiated records in the literature of a functional bisexual generation, even in common and well-known European species. The karyotypic variation found in this group, involving considerable structural heterozygosity within species, also pointed to the decay of diploidy that would be an expected consequence of loss of sexuality and absence of meiosis. However, we have now found a small number of oviparae (mating females) and males in populations of the common species Trama troglodytes. Fertilized eggs were not obtained, but adult oviparae contained large, yolky eggs. The single adult male was apterous, small and blind, but had fully developed mouthparts and genitalia, and contained mature sperm. Both sexual morphs are described, and the karyotrypic variation is reassessed in the light of these findings. Occasional sexual reproduction is in concordance with recent molecular evidence that some recombination occurs in T. troglodytes and related species.

Host-correlated morphological variation of Myzus persicae (Hemiptera: Aphididae) populations in Greece.

Morphological variation in nine characters of 157 clones of Myzus persicae (Sulzer) was examined by multivariate analysis. The clones were collected from peach, Prunus persica, the primary host and the secondary hosts tobacco, Nicotiana tabacum, cabbage, Brassica oleracea, sugarbeet, Beta vulgaris and pepper Capsicum annuum. The 156 clones originated from various regions of Greece, both in the north, where a large part of the population has an annual bisexual generation on peach, and in more southerly regions, where populations are predominantly unisexual. One clone was collected from tobacco in Caserta, Italy. All clones were laboratory-reared on potato. Canonical variate analysis, hierarchical cluster analysis and a non-parametric classification tree method both revealed morphological differences associated with the host-plant on which they were collected. The scores of the first two canonical variates separated the tobacco-feeding clones from those originating from other secondary host-plants. However, in tobacco-growing areas the tobacco-feeding form predominated in spring populations on peach, and was sometimes found on other secondary hosts. In addition, using cluster analysis, the clones from tobacco which were sampled in the most southeasterly region showed a relatively large phenotypic distance from those collected further north and west. Moreover, clonal phenotypes were affected both by host plant and by long-term parthenogenetic rearing. However, in spite of these effects, the tobacco form was generally distinguishable from aphids originating from other hosts, indicating that the difference must have a genetic basis. In separate analyses of the clones originating from secondary hosts no association was found between morphology and either life cycle category or colour. Discriminant analysis showed that 89% of 1723 specimens could be correctly classified into the two groups.

Hybridisation Study of Closely Related Aphid Species Aphis Grossulriae and A. Triglochinis (Hemiptera: Aphididae)

Aphis grossulariae Kaltenbach, 1843 and A. triglochinis Theobald, 1926 produced fertile hybrid eggs after they had been hybridised under experimental conditions. Most hybrid clones (10) reproduced normally on the primary host, Ribes nigrum. However, only eight of them were able to establish themselves on the secondary host. Three hybrid clones succeeded in producing a bisexual generation. During these experiments we tried to investigate the inheritance of morphological characters and host preferences of the hybrid clones. The morphology and host plant acceptance showed the dominance of features characteristic of maternal species. We also conducted backcross experiments with paternal species and examined morphology and host plant acceptance of the backcross hybrids. Our results were compared with the previous results obtained during crossing experiments on the same species (Rakauskas, 1999).

Möglichkeiten genetischer Bekämpfung von Blattläusen (Homoptera: Aphidina)1, 2

AbstractPossibilities of genetical control in aphids (Homoptera: Aphidina). In principle, genetical control methods (sterile male technique, incompatibility technique) can be used in all holocyclic‐heterogenetic aphid species, provided that the following basic requirements are met: 1. Hibernation has solely to be performed on the primary host, by the diapause egg produced by the bisexual generation, or by the first larval stage of the fundatrix developing from the gamogenetic egg. 2. The to be sterilized male of the bisexual generation must be winged, and thus have a wider range of action than the possibly unwinged female to be mated by it. On the contrary, all heterogenetic‐holocyclic species in which, a parthenogenetic generation hibernates at the secondary or also at the primary host, have to be omitted from genetical control. Equal obstructions are effective for anholocyclic‐parthenogenetic species which solely hibernate by non‐gamogenetic generations. On the strength of these biological facts the following conclusions have to be noted: As far as aphids are concerned, a general refusal of chemical insecticides and their substitution by biological or genetical control methods, is not possible. On the other side, there are many aphid species which meet all preconditions for the application of genetical and thereby environment preserving control methods. To use these possibilities should be the task of further research.ZusammenfassungEine Prüfung der eidonomischen und ökologischen Eigenheiten der Blattläuse ergibt, daß viele Biospecies dieser Schädlingsgruppe alle Voraussetzungen zur Anwendung neuzuerarbeitender genetischer Bekämpfungsverfahren (Sterilmännchen‐Methode, Inkompatibilitätsmethode) bieten: Ausschließlicher Vollzug der Überwinterung durch eine gamogenetische Generation und Vorhandensein geflügelter Sexualis‐♂♂. Alle anderen Aphidina‐Biospecies und sämtliche Agamospecies dagegen sind diesen umweltschonenden Methoden nicht zugänglich.

Intertree Distributions of Some Cynipid (Hymenoptera) Galls on Quercus lobata

More galls of the bisexual generation of Neuroterus saltatorius (H. Edwards) were found on Quercus lobata trees whose buds opened earlier than those on surrounding trees. An unidentified leaf vein gall was also more numerous on trees with earlier dates of 1st bud opening as well as on trees that developed more rapidly during early spring. Trees that grew little from May to September supported more galls of the agamic generation of N. saltatorius . More Andricus californicus Bassett galls were found on trees that developed rapidly during April, but fewer galls were found on trees that grew substantially from May to September. The distributions of A. fimbrialis Weld, A. fullawayi Beutenmuller, and Disholcaspis eldoradensis (Beutenmuller) were independent of time of bud opening, tree size, and tree growth rate.

THE BISEXUAL AND AGAMIC GENERATIONS OF BESBICUS MIRABILIS (HYMENOPTERA: CYNIPIDAE), AND THEIR ASSOCIATE INSECTS

AbstractAlternation of generations, or heterogony, wherein progeny resemble their grandparents but not their parents, is a little-known aspect of some cynipid life histories. This study represents the first record of its occurrence within the genus Besbicus, until now recognized solely from agamic females. The bisexual generation described herein has not been described previously. The literature on B. mirabilis (Kinsey) is reviewed briefly and some of the difficulties of cynipid study are assessed. The life history and ecology of both generations is presented and the immediate insect associates are discussed.

Studies on Strongyloides. VI. Comparison of Two Homogonic Lines of Singly Established S. ratti

In Strongyloides ratti, a free-living bisexual generation may alternate with a parasitic generation composed only of females. Such a process has come to be called the heterogonic, or indirect, life cycle. On the other hand, a homogonic, or direct, life cycle may occur in which the progeny of the parasitic generation metamorphose directly into infective filariform larvae. The latter are then ready to infect a new rat host. These direct development larvae are morphologically indistinguishable from those produced by the free-living, bisexual generation. There is a fundamental question involved in the life cycle of this parasite-and it applies to other species in the genus as well: Is the direction of development in the progeny of the parasite determined at the time the egg is formed or is it determined at a later time, i.e., is the destiny of the young larvae determined by the environment in which it develops? Beach (1936) contended that the mode of development of S. simiae larvae was not predetermined in the egg, but was governed by influences in their developmental environment. Faust (1936) considered it significant that this reported behavior the part of S. simliae was apparently not based genetic factors, being contingent instead solely on environmental factors.