Wolbachia modification of sperm does not always require residence within developing sperm.

Wolbachia are maternally inherited intracellular bacteria known to manipulate the reproduction of their arthropod hosts. Wolbachia commonly affect the sperm of infected arthropods. Wolbachia-modified sperm cannot successfully fertilize unless the female is infected with the same Wolbachia type. A study of spermatogenesis in the parasitic wasp Nasonia vitripennis reveals that Wolbachia are not required in individual spermatocytes or spermatids to modify sperm. In N. vitripennis, Wolbachia modify nearly all sperm, but are found only in approximately 28% of developing sperm, and are also found in surrounding cyst and sheath cells. In the beetle Chelymorpha alternans, Wolbachia can modify up to 90% of sperm, but were never observed within the developing sperm or within the surrounding cyst cells; they were abundant within the outer testis sheath. We conclude that the residence within a developing sperm is not a prerequisite for Wolbachia-induced sperm modification, suggesting that Wolbachia modification of sperm may occur across multiple tissue membranes or act upstream of spermiogenesis.

Phylogenetic relationships of egg parasitoids (Hymenoptera: Eulophidae) and correlated life history characteristics of their Neotropical Cassidinae hosts (Coleoptera, Chrysomelidae).

Egg parasitoids in the family Eulophidae (Hymenoptera) are an important part of the community of insects attacking neotropical leaf beetles in the subfamily Cassidinae. We present a phylogeny of 24 species of oophagous Eulophidae, using the 28S rDNA, the ITS2 rDNA and the cytochrome b genes, applying the NJ, MP, ML and Bayesian tree reconstruction methods on each data set. We ask whether the phylogenetic relationships of the parasitoids are linked with the life history characteristics of their beetle hosts. We show that cladogenesis in the oophagous Eulophidae does correlate with ovipositional behaviour and, to a lesser extent, diet and tribal affinities of their hosts. Additionally using two methods of simultaneous analysis of several gene sets: the Total Evidence method, and the construction of a "supertree" by Matrix Representation Parsimony (MRP), we substantiate the same major phylogenetic relationships within the Eulophidae.

Reproductive effects and geographical distributions of two Wolbachia strains infecting the Neotropical beetle, Chelymorpha alternans Boh. (Chrysomelidae, Cassidinae).

Wolbachia are maternally inherited endocellular bacteria known to alter insect host reproduction to facilitate their own transmission. Multiple Wolbachia infections are more common in tropical than temperate insects but few studies have investigated their dynamics in field populations. The beetle, Chelymorpha alternans, found throughout the Isthmus of Panama, is infected with two strains of Wolbachia, wCalt1 (99.2% of beetles) and wCalt2 (53%). Populations infected solely by the wCalt1 strain were limited to western Pacific Panama, whereas populations outside this region were either polymorphic for single (wCalt1) and double infections (wCalt1 + wCalt2) or consisted entirely of double infections. The wCalt2 strain was not found as a single infection in the wild. Both strains caused cytoplasmic incompatibility (CI). The wCalt1 strain caused weak CI (approximately 20%) and the double infection induced moderate CI (approximately 70-90%) in crosses with uninfected beetles. The wCalt1 strain rescued about 75% of eggs fertilized by sperm from wCalt2 males. Based on the relationships of beetle mtDNA and infection status, maternal transmission, and repeated population sampling we determined that the double infection invaded C. alternans populations about 100,000 years ago and that the wCalt2 strain appears to be declining in some populations, possibly due to environmental factors. This may be the first study to demonstrate an association between widespread strain loss and environmental factors in the field.

Wolbachia infection frequencies in insects: evidence of a global equilibrium?

Wolbachia are a group of cytoplasmically inherited bacteria that cause reproduction alterations in arthropods, including parthenogenesis, reproductive incompatibility, feminization of genetic males and male killing. Previous general surveys of insects in Panama and Britain found Wolbachia to be common, occurring in 16-22% of species. Here, using similar polymerase chain reaction methods, we report that 19.3% of a sample of temperate North American insects are infected with Wolbachia, a frequency strikingly similar to frequencies found in two other studies in widely separated locales. The results may indicate a widespread equilibrium of Wolbachia infection frequencies in insects whose maintenance remains to be explained. Alternatively, Wolbachia may be increasing in global insect communities. Within each of the three geographic regions surveyed, Hymenoptera are more frequently infected with A group Wolbachia and Lepidoptera more frequently infected with B group Wolbachia.

Timing the radiations of leaf beetles: hispines on gingers from latest cretaceous to recent.

Stereotyped feeding damage attributable solely to rolled-leaf hispine beetles is documented on latest Cretaceous and early Eocene ginger leaves from North Dakota and Wyoming. Hispine beetles (6000 extant species) therefore evolved at least 20 million years earlier than suggested by insect body fossils, and their specialized associations with gingers and ginger relatives are ancient and phylogenetically conservative. The latest Cretaceous presence of these relatively derived members of the hyperdiverse leaf-beetle clade (Chrysomelidae, more than 38,000 species) implies that many of the adaptive radiations that account for the present diversity of leaf beetles occurred during the Late Cretaceous, contemporaneously with the ongoing rapid evolution of their angiosperm hosts.

Disruptive Coloration in Butterflies: Lack of Support in Anartia fatima.

Experimental obliteration of high-contrast wing stripes of the neotropical butterfly Anartia fatima affected neither survival nor wing damage in a natural population over a 5-month period. There is no direct evidence supporting the hypothesis that so-called disruptive wing patterns function as protective coloration in butterflies.