Functional Morphology of the Antennae and Sensilla of Coeloides qinlingensis Dang et Yang (Hymenoptera: Braconidae).

Coeloides qinlingensis Dang et Yang, 1989 (Hymenoptera: Braconidae) is a biocontrol agent of several scolytid pine pests in Southwest China. We examined the fine morphology of the antennae of adult C. qinlingensis, as well as the type, shape, and distribution of antennal sensilla, via scanning electron microscopy. The antennae of female and male C. qinlingensis are filiform and comprise a scape, pedicel, and 31-36 flagellomeres. We detected sexual dimorphism in antennal flagellar length but not in the length of other subsegments. A total of nine morphological types of antennal sensilla varying in cuticular pore structure are present in both sexes, including nonporous types (sensilla trichodea, sensilla chaetica (2 subtypes), and sensilla coeloconica); apical pore types (sensilla basiconica and sensilla auricillica); and multiporous types (dome-shaped sensilla and sensilla placodea (2 subtypes)). Dome-shaped sensilla and sensilla auricillica are reported for the first time for C. qinlingensis, and their shape differs from that of sensilla in other parasitic wasps. The functional morphology of the sensilla of C. qinlingensis was compared with that of the sensilla of other parasitic wasps, including those that parasitize concealed insects. This information provides a foundation for further research on the chemical communication and behavior of C. qinlingensis.

Maintenance of specificity in sympatric host-specific fig/wasp pollination mutualisms.

Background: Fig/wasp pollination mutualisms are extreme examples of species-specific plant-insect symbioses, but incomplete specificity occurs, with potentially important evolutionary consequences. Why pollinators enter alternative hosts, and the fates of pollinators and the figs they enter, are unknown. Methods: We studied the pollinating fig wasp, Ceratosolen emarginatus, which concurrently interacts with its typical host Ficus auriculata and the locally sympatric alternative host F. hainanensis, recording frequencies of the wasp in figs of the alternative hosts. We measured ovipositor lengths of pollinators and style lengths in female and male figs in the two host species. Volatile organic compounds (VOCs) emitted by receptive figs of each species were identified using GC-MS. We tested the attraction of wasps to floral scents in choice experiments, and detected electrophysiologically active compounds by GC-EAD. We introduced C. emarginatus foundresses into figs of both species to reveal the consequences of entry into the alternative host. Results: C. emarginatus entered a low proportion of figs of the alternative host, and produced offspring in a small proportion of them. Despite differences in the VOC profiles of the two fig species, they included shared semiochemicals. Although C. emarginatus females prefer receptive figs of F. auriculata, they are also attracted to those of F. hainanensis. C. emarginatus that entered male figs of F. hainanensis produced offspring, as their ovipositors were long enough to reach the bottom of the style; however, broods were larger and offspring smaller than in the typical host. Female figs of F. hainanensis failed to produce seeds when visited by C. emarginatus. These findings advance our current understanding of how these species-specific mutualisms usually remain stable and the conditions that allow their diversification.

Identification and characterization of chemosensory gene families in the bark beetle, Tomicus yunnanensis.

The bark beetle, Tomicus yunnanensis (Coleoptera: Scolytinae), is a seriously destructive pest of Yunnan pine (Pinus yunnanensis) and is distributed solely in Southwestern China. It has been a challenge to control this pest owing to its resistance to chemical pesticides, which have been used as the main control strategy of this species in recent years. Since this approach will continue until an alternative mitigation strategy is implemented, it is essential to develop novel or improved biocontrol approaches. In the current study, we aimed to identify most, if not all, of the bark beetle's chemosensory genes, and to address their respective phylogenetic relationships and expression characteristics. Digital gene expression (DGE) profiling and a comparison of the profiles at three developmental stages yielded 40,287,265 clean reads and a large number of differentially expressed genes (DEGs), with 21 up- and 20 down-regulated DEGs involved in chemoreception. Transcriptome of the three mixed stages revealed a total of 80 transcripts encoding chemosensory-related proteins comprising 45 odorant-binding proteins (OBPs), 12 chemosensory proteins (CSPs), 20 receptor proteins [9 odorant receptors (ORs), 8 gustatory receptors (GRs) and 3 ionotropic receptors (IRs)] and 3 sensory neuron membrane proteins (SNMPs). As many as 38 full-length sequences were acquired with a combination of transcriptomic analysis and rapid amplification of cDNA ends (RACE) strategy. Phylogenetic analysis showed that T. yunnanensis OBPs were clustered into four sub-groups: 27 Minus-C OBPs, 5 antennal binding proteins (ABPIIs), 10 Classic OBPs and one Plus-C OBP; meanwhile, the ORs were grouped into four clades (1, 2, 7b and Orco). Expression profiles revealed that 66 of 80 genes were detected in the three DGE libraries, and 15 soluble olfactory proteins were antennae-predominant, possibly guiding olfactory-associated behaviors of this beetle. Taken together, our study has provided valuable data for further functional studies of this beetle and will facilitate the identification of potential molecular targets associated with chemosensory reception for use in biocontrol strategies.

Has pollination mode shaped the evolution of ficus pollen?

BACKGROUND: The extent to which co-evolutionary processes shape morphological traits is one of the most fascinating topics in evolutionary biology. Both passive and active pollination modes coexist in the fig tree (Ficus, Moraceae) and fig wasp (Agaonidae, Hymenoptera) mutualism. This classic obligate relationship that is about 75 million years old provides an ideal system to consider the role of pollination mode shifts on pollen evolution. METHODS AND MAIN FINDINGS: Twenty-five fig species, which cover all six Ficus subgenera, and are native to the Xishuangbanna region of southwest China, were used to investigate pollen morphology with scanning electron microscope (SEM). Pollination mode was identified by the Anther/Ovule ratio in each species. Phylogenetic free regression and a correlated evolution test between binary traits were conducted based on a strong phylogenetic tree. Seventeen of the 25 fig species were actively pollinated and eight species were passively pollinated. Three pollen shape types and three kinds of exine ornamentation were recognized among these species. Pollen grains with ellipsoid shape and rugulate ornamentation were dominant. Ellipsoid pollen occurred in all 17 species of actively pollinated figs, while for the passively pollinated species, two obtuse end shapes were identified: cylinder and sphere shapes were identified in six of the eight species. All passively pollinated figs presented rugulate ornamentation, while for actively pollinated species, the smoother types - psilate and granulate-rugulate ornamentations - accounted for just five and two among the 17 species, respectively. The relationship between pollen shape and pollination mode was shown by both the phylogenetic free regression and the correlated evolution tests. CONCLUSIONS: Three pollen shape and ornamentation types were found in Ficus, which show characteristics related to passive or active pollination mode. Thus, the pollen shape is very likely shaped by pollination mode in this unique obligate mutualism.