After the last glacial retreat in Europe, multiple recolonizations led to intraspecific differentiation in many of the recolonizing taxa. Here we investigate the genetic diversification across central Europe in two recolonizing taxa, the tephritid fruit flies Rhagoletis alternata (Fallén, 1814) and Carpomya schineri (Loew, 1856), which attack rose hips. Analysis of amplified and sequenced fragments of the mitochondrial genes encoding cytochrome oxidase I (800 bp), cytochrome oxidase II (470 bp) and cytochrome b (450 bp), indicate that all the individuals of R. alternata (n = 21) collected from across Europe share the same haplotype. Two individuals of C. schineri form Berlin, which is further north of the range than previously reported in the literature, differ from the other individuals (n = 13) in one nucleotide position on the cytochrome oxidase II gene fragment. This level of genetic variation in sequences with a summed length of 1720 bp is unexpectedly lower than in other insect taxa (n = 63). This might have been caused by a selective sweep by a cytoplasmic symbiont such as Wolbachia, or a recent range expansion associated with a host shift or a single recolonization event.
The effectiveness of natural enemies in controlling pests may be determined by many traits linked to their ability to regulate the density of their prey. In this respect, the phenomenon of pseudoparasitism, in which female parasitoids reject a host after inserting their ovipositor into it, is fairly common among hymenopteran parasitoids. However, in spite of this its effect on hosts is rarely reported in entomological and biological control literature. For this reason, in the present study, the pseudoparasitism by the parasitoid Spalangia cameroni Perkins of the Mediterranean pest Ceratitis capitata (Wiedemann) and its effect on several biological parameters of the host were studied under laboratory conditions. The results indicate that the percentage pseudoparasitism by S. cameroni of medfly in the laboratory is high, even slightly higher than host-feeding, which is commonly used to evaluate the potential of parasitoids as biological control agents. In addition, the adults that emerge from pseudoparasitized medfly pupae have a male-biased sex ratio, low levels of survival and are frequently damaged, which results in small adults and an inability to mate successfully. In conclusion, our results indicate that pseudoparasitism is common and enhances the effectiveness of S. cameroni attacking medfly, which highlights the importance of this phenomenon when selecting parasitoids to be included in a biological control programme., Luis De Pedro, Francisco Beitia, Josep D. Asís, José Tormos., and Obsahuje bibliografii
A nonpigmenting strain of Serratia marcescens Bizio isolated from dead and apparently diseased wild apple maggot flies, Rhagoletis pomonella (Walsh), was shown to be pathogenic to healthy apple maggot flies upon ingestion. The microorganism was detected in live adult alimentary canal organs four days post ingestion but produced death in some flies within 24 h when flies fed on a cell concentration of 4.7 × 104 cfu/ml and within 8 h when flies fed on filter-sterilized culture medium that previously contained a 21 h culture of S. marcescens. Increasing the cell concentration 10,000 fold did not lead to an increased rate of kill. Young flies (7-10 days old) were more susceptible to infection leading to death than were older flies (21-28 days old). The potential use of S. marcescens cells as control agents against apple maggot flies is negated by their pathogenicity to vertebrates; however, the potential use of toxic compounds produced by this strain of S. marcescens is discussed.