Although substantial epidemiologic evidence links Streptococcus mutans to caries, the pathobiology of caries may involve more complex communities of bacterial species. Molecular methods for bacterial identification and enumeration now make it possible to more precisely study the microbiota associated with dental caries. The purpose of this study was to compare the bacteria found in early childhood caries (ECC) to those found in caries-free children by using molecular identification methods. Cloning and sequencing of bacterial 16S ribosomal DNAs from a healthy subject and a subject with ECC were used for identification of novel species or uncultivated phylotypes and species not previously associated with dental caries. Ten novel phylotypes were identified. A number of species or phylotypes that may play a role in health or disease were identified and warrant further investigation. In addition, quantitative measurements for 23 previously known bacterial species or species groups were obtained by a reverse capture checkerboard assay for 30 subjects with caries and 30 healthy controls. Significant differences were observed for nine species: S. sanguinis was associated with health and, in order of decreasing cell numbers, Actinomyces gerencseriae, Bifidobacterium, S. mutans, Veillonella, S. salivarius, S. constellatus, S. parasanguinis, and Lactobacillus fermentum were associated with caries. These data suggest that A. gerencseriae and other Actinomyces species may play an important role in caries initiation and that a novel Bifidobacterium may be a major pathogen in deep caries. Further investigation could lead to the identification of targets for biological interventions in the caries process and thereby contribute to improved prevention of and treatment for this significant public health problem.

Reproductive manipulations of hosts by maternally inherited bacterial endosymbionts often result in an increase in the proportion of infected female hosts in the population. When this involves the conversion of incipient males to genetic or functional females, it presents unique difficulties for symbionts invading hosts with sex‐specific reproductive behaviours, such as the autoparasitic Encarsia pergandiella. In sexual forms of this species, female eggs are laid in whitefly nymphs and male eggs are laid in conspecific or heterospecific parasitoids developing within the whitefly cuticle. Further, eggs laid in the ‘wrong’ host do not ordinarily complete development. This study explored the role of a bacterial symbiont, Cardinium, in manipulating oviposition behaviour in a thelytokous population of E. pergandiella. Oviposition choice was measured by the number and location of eggs deposited by both infected and uninfected adult waSPS in arenas containing equal numbers of hosts suitable for the development of male and female waSPS. Uninfected waSPS included antibiotic‐treated female waSPS and (untreated) daughters of antibiotic‐treated female waSPS. The choices of waSPS in the thelytokous population treatments were compared with those of a conspecific sexual population. We found that offspring of antibiotic‐cured thelytokous waSPS reverted to the behaviour of unmated sexual waSPS, laying their few eggs almost exclusively in hosts appropriate for male eggs. Infected thelytokous waSPS distributed their eggs approximately evenly between host types, much like mated sexual female waSPS. The antibiotic‐treated female waSPS exhibited choices intermediate to waSPS in the other two treatments. The change in the observed behaviour appears sufficient to allow invasion and persistence of Cardinium in sexual populations. Lastly, our results suggest a reduction in host discrimination as a possible mechanism by which Cardinium influences this change.

1. An increasing number of studies have addressed the mechanisms by which plant inter-specific variation influence interactions at higher trophic levels, but little is known about the underlying plant traits driving these dynamics.2. Here we investigated the effects of host plant species on herbivore-parasitoid interactions and the underlying traits driving such effects. For this, we measured the abundance of seed-eating bruchids and their parasitoids across seven sympatric populations of the bean species Phaseolus coccineus and Phaseolus vulgaris in Central Mexico. To investigate the mechanisms underlying differences between bean species in bruchid-parasitoid interactions, we carried out two laboratory experiments to test whether bruchid and parasitoid performance differed between plant species. We also measured seed size and phenolic compounds to investigate if seed traits mediate bruchid-parasitoid interactions by influencing herbivore susceptibility or resistance to parasitoids.3. Field surveys revealed that the rate of parasitoid recruitment to bruchids was significantly higher on P. vulgaris than on P. coccineus. Subsequent laboratory bioassays indicated that bruchids developed more slowly and exhibited lower fitness on P. vulgaris seeds than on P. coccineus seeds. Accordingly, we found that bean species differed in seed size, with P. vulgaris having smaller (less nutritious) seeds, which explains why bruchid development was slower on this plant species. 4. These results provide a mechanism for why bruchids exhibited higher parasitism rates on seeds of P. vulgaris in the field which could be due to Slow-Growth/ High-Mortality effects, a smaller physical refuge provided by the seed, or both factors. The roles of these mechanisms remain inconclusive without further study.

Horismenus parasitoids are an abundant and understudied group of eulophid wasps found mainly in the New World. Recent surveys based on morphological analyses in Costa Rica have quadrupled the number of named taxa, with more than 400 species described so far. This recent revision suggests that there is still a vast number of unknown species to be identified. As Horismenus wasps have been widely described as parasitoids of insect pests associated with crop plants, it is of high importance to properly establish the extant diversity of the genus, in order to provide biological control practitioners with an exhaustive catalog of putative control agents. In this study, we first collected Horismenus wasps from wild Phaseolus bean seeds in Central Mexico and Arizona to assess the genetic relatedness of three morphologically distinct species with overlapping host and geographical ranges. Sequence data from two nuclear and two mitochondrial gene regions uncovered three cryptic species within each of the three focal species (i.e., H. missouriensis, H. depressus and H. butcheri). The monophyly of each cryptic group is statistically supported (except in two of them represented by one single tip in which monophyly cannot be tested). The phylogenetic reconstruction is discussed with respect to differences between gene regions as well as likely reasons for the differences in variability between species.

Species of Horismenus Walker associated with bruchid beetles are investigated and five new species are described. Some of the new species are very similar to already described species and have previously been misidentified. The new species include H. depressoides sp. nov. similar to H. depressus Gahan , H. stator sp. nov. similar to H. missouriensis (Ashmead), and H. dennoi & H. multistriatus spp. nov., both similar to H. butcheri Hansson & Aebi and one species, H. gabrielae sp. nov., that is morphologically distinct from the other species but also associated with this host group. All 14 Horismenus species associated with bruchid beetles are included in a key. New host and distributional records are included for H. depressus.