Effects of diet and activity on lipid levels of adult Mediterranean fruit flies

Abstract. The objectives of this study were to determine whether adult Mediterranean fruit flies, Ceratitis capitata Wiedeman (Diptera: Tephritidae), are capable of synthesizing lipids, and whether adult diet affects this ability.Lipid levels in females fed protein and carbohydrate or carbohydrate alone declined significantly from emergence to the fourth day of life and then rose back to teneral levels on the fifth day, before oviposition took place on the sixth day.In males fed protein and carbohydrate, lipid levels initially declined as males aged and then stabilized.In carbohydrate-fed males lipid levels declined following emergence and recovered somewhat by the sixth day.Lipid levels declined significantly when flies underwent post-emergence starvation, but after substantial feeding on the above-mentioned diets they eventually (within 6–7 days) reached teneral levels in all experimental groups.Multivariate analysis of variance revealed that differences in lipid contents are primarily related to the flies' age, which corresponds to the various sex-specific activities these flies exhibit.Average lipid investment in eggs was found to equal teneral lipid levels in females.Without lipogenic abilities, oviposition would completely deplete female lipid reserves.We conclude that adult medflies are capaple of lipid synthesis, and that this capability is modulated by individual and sex-specific activity patterns.     

Endosymbiont metacommunities,mtDNA diversity and the evolution of the Bemisia tabaci (Hemiptera: Aleyrodidae) species complex

Bemisia tabaci, an invasive pest that causes crop damage worldwide, is a highly differentiated species complex, divided into biotypes that have mainly been defined based on mitochondrial DNA sequences. Although endosymbionts can potentially induce population differentiation, specialization and indirect selection on mtDNA, studies have largely ignored these influential passengers in B. tabaci, despite as many as seven bacterial endosymbionts have been identified. Here, we investigate the composition of the whole bacterial community in worldwide populations of B. tabaci, together with host genetic differentiation, focusing on the invasive B and Q biotypes. Among 653 individuals studied, more than 95% of them harbour at least one secondary endosymbiont, and multiple infections are very common. In addition, sequence analyses reveal a very high diversity of facultative endosymbionts in B. tabaci, with some bacterial genus being represented by more than one strain. In the B and Q biotypes, nine different strains of bacteria have been identified. The mtDNA‐based phylogeny of B. tabaci also reveals a very high nucleotide diversity that partitions the two ITS clades (B and Q) into six CO1 genetic groups. Each genetic group is in linkage disequilibrium with a specific combination of endosymbionts. All together, our results demonstrate the rapid dynamics of the bacterial endosymbiont–host associations at a small evolutionary scale, questioning the role of endosymbiotic communities in the evolution of the Bemisia tabaci species complex and strengthening the need to develop a metacommunity theory of inherited endosymbionts.     

Mate availability contributes to maintain the mixed‐mating system in a scolytid beetle

We investigated the mating system and population genetic structure of the beetle, Coccotrypes dactyliperda, with life history characteristics that suggest the presence of a stable mixed‐mating system. We examined the genetic structure of seven populations in Israel and found significant departures from the Hardy–Weinberg equilibrium and an excess of homozygosity. Inbreeding coefficients were highly variable across populations, suggesting that low levels of outbreeding occur in nature. Experiments were conducted to determine whether the observed high inbreeding in these populations is the result of a reproductive assurance strategy. Females reared in the laboratory took longer to mate with males from the same population (inbreeding) than with males from a different population (outbreeding). These results suggest that females delayed inbreeding, and were more inclined to outbreed when possible. Thus inbreeding, which predominates in most populations, may be due to a shortage of mates for outbreeding rather than a preference for inbreeding. We conclude that C. dactyliperda has a mixed‐mating system that may be maintained by a reproductive assurance strategy.     

Nutritional reserves regulate male participation in Mediterranean fruit fly leks

1. The mating system of Mediterranean fruit flies ( Ceratitis capitata , Diptera: Tephritidae), is based on male leks that form on the foliage of trees. Following observations that not all males participate in leks, the hypotheses that (a) small males are absent from leks and (b) males with inadequate nutrient reserves are unable to participate in leks were examined.
2. The size and weight of lekking males ( n = 183) and resting males captured at the same time in the vicinity of leks ( n = 148) were established. In addition, using biochemical techniques, the amounts of sugar, glycogen, lipid and protein in each individual were established quantitatively.
3. There was no significant size difference between lekking and resting males. However, lekking males were significantly heavier and contained significantly more sugars and protein than resting males.
4. In conclusion, leks are exclusive, and only males with adequate nutritional reserves may join. Thus, in this species, reproductive success is closely linked to foraging success.     

Leishmaniasis in the Jordan Valley. V. Dispersal characteristics of the sandfly Phlebotomus papatasi

Several characteristics of dispersing and non-dispersing Phlebotomus papatasi (Scopoli) were quantified and compared. The majority of dispersing sandflies, trapped crossing fallow fields, were females (68.5% v. 51.1%); of the dispersing females, 55.4% were parous, 48.1% were inseminated and 11.6% were gravid. In the population of sandflies sampled exiting from burrows of the sand rat Psammomys obesus Cretschmar, these categories, respectively, represented 39%, 90% and 26% of the females examined. Leishmania promastigotes were found in 9% of females exiting from P. obesus burrows, and in 2.7% of the dispersing females. The anthrone test established that the reason for activity of gravid females is sugar feeding. These females do not disperse and are suitable targets for future control measures.     

Time limitation affects offspring traits and female's fitness through maternal oviposition behaviour

Plasticity of various life‐history traits has evoked continuing interest among biologists. For example, the plasticity of offspring characteristics as well as maternal effects may be affected by time limitation and by limitation caused by changing environmental conditions. However, it is difficult to tell apart the effect of a time constraint, experienced by the mother, from food limitation, which is experienced by the offspring at the end of the season. In this study, we controlled for food limitation and simulated a time constraint for the mother. We tested how the seed beetle, Coccotrypes dactyliperda, adapts its reproductive investment after encountering a period of low availability of seeds as oviposition sites, as compared with females that encountered a seed at an early adult stage, while maintaining a similar food supply for offspring of both groups. We show that time limitation has a significant effect on the reproductive investment patterns of females. Females that were prevented from ovipositing, but provided with abundant food and later given oviposition sites, produced more, but smaller offspring than control females. Although the number of offspring increased, there was no indication of competition for food between offspring. We propose that, in order to compensate for the loss of time, mothers that experienced a shortage of oviposition sites influence their offspring to mature faster at the cost of a smaller than average body size. This study emphasizes the importance of considering more than one offspring generation in order to correctly estimate female fitness. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102 , 728–736.     

High relative abundance of the stable fly Stomoxys calcitrans is associated with lumpy skin disease outbreaks in Israeli dairy farms

The vector of lumpy skin disease (LSD), a viral disease affecting Bovidae, is currently unknown. To evaluate the possible vector of LSD virus (LSDV) under field conditions, a yearlong trapping of dipterans was conducted in dairy farms that had been affected by LSD, 1‐2 years previously. This was done in order to calculate monthly relative abundances of each dipteran in each farm throughout the year. The relative abundances of Stomoxys calcitrans (Diptera: Muscidae) in the months parallel to the outbreaks (December and April) were significantly higher than those of other dipterans. A stable fly population model based on weather parameters for the affected area was used to validate these findings. Its results were significantly correlated with S. calcitrans abundance. This model, based on weather parameters during the epidemic years showed that S. calcitrans populations peaked in the months of LSD onset in the studied farms. These observations and model predictions revealed a lower abundance of stable flies during October and November, when LSD affected adjacent grazing beef herds. These findings therefore suggest that S. calcitrans is a potential vector of LSD in dairy farms and that another vector is probably involved in LSDV transmission in grazing herds. These findings should be followed up with vector competence studies.     

Morphological variation of the Oncocyclus irises (Iris: Iridaceae) in the southern Levant

Morphological traits of Iris section Oncocyclus (Siems.) Baker in the southern Levant (Israel, Jordan, The Palestinian Authority and Sinai/Egypt) were analysed in order to clarify taxonomic relationships among taxa and the validity of diagnostic characters. Floral and vegetative characters were measured in 42 populations belonging to nine species during the peak of the flowering season in 1998–2000. Pearson's Coefficient of Racial Likelihood (CRL) was used to calculate morphological distances between populations. Twelve of the measured populations, distributed along the north-south aridity gradient in Israel, were further explored for morphological changes along the gradient. Cluster analysis revealed two major clusters: the first includes most of the dark-coloured Iris populations, with populations of I. petrana Dinsmore and I. mariae W. Barbey forming a subcluster; the second consists of all the light-coloured populations but also some dark-coloured populations. Pearson's CRL and geographical distance were significantly correlated among the dark-coloured populations. Along the geographical gradient, flower, stem and leaf size traits decrease towards the south, probably as an adaptation to aridity. This suggests that natural selection promoted the differences between populations. Almost no discrete phenotypic groups exist within the Oncocyclus species of the southern Levant except for variation in the floral colours. Most of the suggested diagnostic characters proved unreliable in that they varied continuously across populations. The taxonomical difficulties encountered in this study reflect the special evolutionary state of the Oncocyclus irises as a group in the course of speciation.  © 2002 The Linnean Society of London. Botanical Journal of the Linnean Society , 2002, 139 , 369–382.