Does a sap feeding marsupial choose trees with specific chemical characteristics?

Only about 20 vertebrate species are known to feed regularly on tree sap. One of these is the yellow‐bellied glider (Petaurus australis), a marsupial that obtains between 16% and 80% of its diet from eucalypt sap. We reviewed the literature on sap feeding by the yellow‐bellied glider and identified 10 species from which it most frequently obtains sap. These species come mainly from a few sections of the subgenus Symphyomyrtus, which accounts for two‐thirds of over 2000 sap trees reported, but more specifically sections Latoangulatae and Maidenii within this subgenus. Some of these key species contain relatively high concentrations of foliar nutrients and each is an important food tree for at least one of the arboreal folivores – koala (Phascolarctos cinereus), greater glider (Petauroides volans), and common ringtail (Pseudocheirus peregrinus) and brushtail possums (Trichosurus vulpecula). Because yellow‐bellied gliders, like the arboreal folivores, prefer to feed from certain individuals within a species, we hypothesized that these trees possess a unique chemical signature that links sap‐feeding with the concentrations of available nitrogen and formylated phloroglucinol compounds in leaves – the nutritive and defensive chemicals that influence feeding on these species by marsupial folivores. We tested this hypothesis in samples of leaves and bark collected from E. punctata and E. viminalis but found no link between chemistry and sap feeding and conclude that other aspects of an individual tree, such as sap flow or sap chemistry, determine whether gliders will target it for sap.     

Biology and monitoring of Dryocosmus kuriphilus on Castanea sativa in Southern Italy

• 1 The cynipid gall wasp Dryocosmus kuriphilus Yasumatsu (Hymenoptera: Cynipidae) is an invasive wasp in Europe and is one of the major pests of chestnuts worldwide. An investigation of this cynipid was started in Campania, Southern Italy, in 2008, with the aim of providing guidelines for its sustainable control.
• 2 The number of larvae/gall increased in the second year of colonization relative to the first one but thereafter decreased in the third year of colonization, whereas the volume of the galls after the initial increase in the second year of colonization became stable. Adult emergence generally peaked between the middle of June and July.
• 3 The only reliable method for assessing the presence of the pest at its earliest stage was through dissecting the buds because oviposition scars on the buds tended to disappear during the winter.
• 4 Yellow traps were shown to be an effective method for assessing the emergence of cynipid adults and could potentially be used to time chemical applications in those cases in which this control method is feasible.
• 5 No correlation was recorded between the relative durations of the final stages (pupae, pharate adults and emergence).
• 6 Possible control strategies for this invasive pest are discussed.

     

Rapid and specific identification of four Agrobacterium species and biovars using multiplex PCR

On the basis of 23S rRNA gene sequences, 1 universal forward and 4 taxon (species/biovar)-specific reverse primers were designed for multiplex PCR to aid in identification and differentiation of Agrobacterium rubi, Agrobacterium vitis and Agrobacterium biovars 1 and 2. In reactions with DNA of 119 bacterial strains belonging to: Agrobacterium, Allorhizobium, Mesorhizobium, Rhizobium, Sinorhizobium and Phyllobacterium, as well as phytopathogenic bacteria representing various genera, the primers developed for identification of A. vitis, A. rubi or Agrobacterium biovar 1 amplified only DNA of strains belonging to these taxa, producing fragments of the expected sizes: 478, 1006 and 184bp, respectively. However, in the case of the primer developed for identification of Agrobacterium biovar 2, the characteristic 1066bp PCR product was obtained not only with DNA of this biovar, but also with DNA of 3 atypical biovar 1 strains and some rhizobial strains. Differentiation between Agrobacterium biovar 2 and the other strains was possible using the restriction analysis of this product with endonuclease Alw26I. The method developed is an excellent tool for rapid classification of these 4 taxa of Agrobacterium.     

枸杞木虱成虫携带瘿螨越冬

多年来一直认为枸杞瘿螨Aceria pallida Kefer以成螨在树皮缝和芽缝内越冬,我们在宁夏中宁最新调查发现,大量瘿螨若螨潜伏于枸杞木虱越冬成虫体壁缝隙,尤其以后足基节与腹部缝隙最多。初步调查结果显示,越冬枸杞木虱Poratrioza sinica Yang et Li成虫雌性和雄性成虫均携带瘿螨成螨和若螨,平均2~3头,最多的可达30头。如果枸杞瘿螨随枸杞木虱越冬成虫越冬成为主要途径,那么对枸杞木虱越冬成虫的防治将成为控制枸杞瘿螨危害的重要防治策略和技术手段。     

High species richness and genetic diversity of the genus Caloglossa (Delesseriaceae,Rhodophyta) in New Ireland,Papua New Guinea

Distribution patterns and genetic diversity of Caloglossa species have been studied in various regions but are still poorly understood around the tropical western Pacific where many marine organisms show high species richness. We explored the diversity of Caloglossa species in New Ireland, Papua New Guinea using morphological and genetic analyses. Seven species of Caloglossa (C. adhaerens, C. leprieurii, C. ogasawaraensis, C. bengalensis, C. postiae, C. saigonensis and C. vieillardii) were collected from eight sites; the latter four species are new records in Papua New Guinea. All specimens collected were cultured to compare their morphology under the same culture condition. Reproductive structures of gametophytes and/or sporophytes were described for the first time in some species from these collections. In C. leprieurii, gall‐like structure appeared in most gametophyte strains but not in tetrasporophytes. Such galls were produced from wing cells, and spermatangia and/or procarps were formed on many galls. The LSU rDNA and rbcL analyses revealed high intraspecific diversity in many species although the number of samples was limited and the sampling sites were within 200 km. We revealed high species richness and intraspecific genetic variation in Papua New Guinea, suggesting a hot spot for the diversity of Caloglossa.     

Gall wasps and their parasitoids in cork oak fragmented forests

Abstract.  1. This paper explores the potential effects of host-plant fragmentation on cork oak gall wasp populations (Cynipidae, Hymenoptera) and on their predators, lethal inquilines, and parasitoids. To address this objective, galls were collected across a gradient of cork oak ( Quercus suber ) forest fragmentation in the East Pyrenees (Albera, Spain), and they were incubated to obtain the parasitism rates.
2. Two hypotheses were tested: (1) Host-plant fragmentation may induce a decline in gall wasp populations because of area and isolation effects on local extinction and dispersal; as a consequence of that, parasitoids may decline even more strongly in fragmented habitats than their prey. (2) Host-plant fragmentation may cause a decline in gall wasp parasitoid populations that, in turn, can lead to an ecological release in their prey populations.
3. Among the eight cork oak gall wasps sampled in the study area of Albera, the gall abundances of three species ( Callirhytis glandium , Callirhytis rufescens , and Andricus hispanicus ) were significantly related to forest fragmentation. The overall abundance of gall wasps was affected by a radius of ≈ 890 m surrounding landscape, presenting constant abundances with forest loss until forest cover is reduced at ≈ 40%; below that value the abundance increased rapidly. Three inquilines and 23 parasitoids species were recorded after gall incubation. In 25 cases, species of inquilines and parasitoids were newly recorded for the corresponding host in the Iberian peninsula.
4. Although the overall parasitism rate was high (1.1), it was uncorrelated with fragmentation and with overall cynipid abundance. These results indicate that host-plant fragmentation was correlated with higher abundance of gall wasps, whereas the parasitism rate could not explain this hyper-abundance in small forest fragments.     

Description,phenology and biology of Zelostemma chionochloae Buhl sp. nov., a platygastrid parasitoid of Eucalyptodiplosis chionochloae (Diptera: Cecidomyiidae) in New Zealand

Abstract

A platygastrid wasp that feeds on the snow tussock flower midge in the inflorescences of New Zealand snow tussock grasses (Chionochloa spp.) is formally described. Zelostemma chionochloae is a specialist natural enemy of Eucalyptodiplosis chionochloae Kolesik which is the most ubiquitous and sophisticated seed predator of Chionochloa. Z. chionochloae is a koinobiont parasitoid and some larvae enter prolonged diapause inside their host for at least 2 years. Methods for adult rearing are described. The phenology of Z. chionochloae is highly synchronised with its host even after 2 years in diapause. Parasitism levels were found to differ between years and elevations, while sex ratios differed among years. Z chionochloae probably suffers inter‐specific competition with another host‐specific hymenopteran parasitoid (Gastrancistrus sp.) which also parasitises E. chionochloae.     

Natural selection on gall size: variable contributions of individual host plants to population-wide patterns

Studies that provide estimates of the form and magnitude of selection on herbivore traits at the level of individual plants in natural populations represent a vital step in understanding the interaction of selection and gene flow among host-affiliated insect populations when individual plants equate to differing selective regimes. We analyzed phenotypic selection on the trait gall size for a host-specific gall former at both the individual host plant and population level (across host plants) in each of two years. Linear and nonlinear selection and the fitness function relating gall size to the probability of survivorship in the absence of natural enemies were estimated for each level and year. Selection imposed by the host plant was observed in 19 of the 22 subpopulations monitored. At the population level, linear and nonlinear selection were evident each year. However, population-level estimates masked the significant heterogeneity in the form and direction of selection evident among plants each year. Heterogeneity among gall-former subpopulations is emphasized by our findings that selection varied from directional to stabilizing among plants and the majority of selection gradients estimated for individual plants did not fall within the 95% CIs of the population-level estimates.     

EVOLUTION OF PARASITISM AMONG CLOSELY RELATED SPECIES: PHYLOGENETIC RELATIONSHIPS AND THE ORIGIN OF INQUILINISM IN GALL WASPS (HYMENOPTERA,CYNIPIDAE)

A new term, agastoparasitism, is proposed for parasitism among closely related species. Cynipid inquilines are typical agastoparasites. They cannot induce galls; instead their larvae live inside the galls formed by other cynipids. As in many other groups of agastoparasites, there are two competing hypotheses for the evolutionary origin of cynipid inquilines: either they arose from one of their cynipid hosts, and later radiated to exploit other gall-inducing cynipids (monophyletic origin), or they arose repeatedly, each inquiline from its host (polyphyletic origin). These hypotheses for the origin of cynipid inquilines were tested by a phylogenetic analysis of representative species of cynipid gall inducers and inquilines based on adult morphological characters. The analysis supported the monophyly of the inquilines and indicated an origin from gall inducers related to the genus Diastrophus, one of the current host groups. To examine whether the result of the analysis was influenced by convergent similarities among inquilines because of their similar mode of life, all putative apomorphies shared by some or all of the inquilines but not occurring in any of the gall inducers were removed. Despite this, the phylogenetic conclusions essentially remained the same, that is, the support for inquiline monophyly was not caused by convergent evolution. Based on these results, adaptive aspects of the evolutionary origin and maintenance of cynipid inquilinism are discussed, as well as general patterns in the evolution of agastoparasitism.     

Intra‐plant heterogeneity influences the preference and performance of juveniles and adults of a gall midge

Abstract 1. Field studies were conducted to evaluate the preference and performance of a gall‐inducing midge (Harmandia tremulae) within the crown of trembling aspen (Populus tremuloides). Females did not select oviposition sites preferentially within leaves, but did lay preferentially on young leaves. 2. Larvae were the only life stage involved in gall site selection within leaves and in gall initiation and development. Gall size, which was positively related to survival, was highest for galls on mid veins that were located close to the petiole. However, one‐third of galls were located on lateral veins and most galls were not adjacent to the petiole, indicating that many larvae choose sub‐optimal gall initiation sites. 3. Gall density was positively associated with leaf length, and leaf length, was positively associated with gall size. However, gall density per leaf was not related to larval survival in galls. This latter result may be a result of an observed inverse relationship between gall size and gall density for similar‐sized leaves. 4. The results partially support the plant vigour and optimal plant module size hypotheses, which predict that galler fitness in successfully induced galls should be highest on large, fast‐growing plant modules. The lack of a strong preference‐performance link supports the confusion hypothesis, which predicts that oviposition and gall site selection may often be suboptimal in systems where galler lifespan is short. This study suggests that small‐scale variations in plant quality within leaves, can render gall site selection by juveniles as important as that previously reported for adult females.