It has become increasingly evident that many organisms rely on microbial symbionts for defense against natural enemies, but the ecological importance of defensive symbionts for natural communities still needs to be investigated. A well-known example is Hamiltonella defensa, a heritable endosymbiotic bacterium commonly found in aphids. Laboratory experiments have shown that H. defensa strongly protects aphids against parasitic wasps (parasitoids), although this protection is not equally effective against different species of parasitoids, or even different genotypes of the same species. These results suggest that H. defensa plays an important role in reducing aphid mortality by parasitoids and presumably affects the community composition of parasitoids relying on aphids as a resource. However, there is little evidence that this is indeed the case under natural conditions. We tested this in a field experiment with black bean aphids (Aphis fabae) by setting up replicated field plots with genetically identical aphids that did or did not harbor H. defensa and following their colonization by natural enemies over a growing season. We observed a clear reduction in parasitism of symbiont-protected aphids, particularly by the parasitoids posing the highest risk. However, protected aphids did not develop larger populations than unprotected ones, possibly reflecting the balancing effect of costs associated with harboring H. defensa. We also observed shifts in the parasitoid species composition on aphids protected by H. defensa, showing that defensive symbionts have the potential to alter the diversity and structure of food webs, with likely consequences for their function and stability.

The Charipinae (Cynipoidea: Figitidae) are a small group of Hymenoptera biologically characterized as being secondary parasitoids of aphids and psyllids (Hemiptera) (Menke & Evenhuis, 1991).  A total of 281 species of Charipinae have been described since the first species was described by Westwood (1833) (including two fossils, one of them recently transferred in a new family, Protimaspidae). An updated world catalogue of the Charipinae is presented here, with 168 valid species: 111 included in Alloxysta Förster, 31 in Phaenoglyphis Förster, 13 in Dilyta Förster, 5 in Apocharips Fergusson, 4 in Thoreauana Girault, and 1 in Dilapothor Paretas-Martínez & Pujade-Villar, Lobopterocharips Paretas-Martínez & Pujade-Villar, Lytoxysta Kieffer and †Protocharips Kovalev. Eight species are considered as nomen nudum: Allotria fusca Dahlbom, 1842; Allotria thoreyi Dahlbom, 1842; Xystus xanthocephala Dahlbom, 1842; Allotria pusillina Giraud, 1877; Charips aphidiinaecida de Santis, 1937; Alloxysta keudelli Hedicke, 1927; Allotria amygdali Buckton, 1879 and  Allotria polita Provancher, 1881. Six as nomen dubium: Allotria (Allotria) recticornis atra Kieffer, 1902; Allotria (Allotria) brevicornis Kieffer, 1902;  Allotria (Allotria) orthocera Kieffer, 1902; Xystus femoralis Hartig, 1841; Charipsella laevigata Brèthes, 1913; Dilyta (Alloxysta) ignorata Kieffer, 1900. Three species are incertae sedis: Charips silvicola Belizin, 1928, Cynips atriceps Buckton, 1879 and Allotria (Allotria) testaceipes Kieffer, 1902. Two species are here synonymized: Alloxysta discreta (Förster, 1869) with A. ramulifera (Thomson, 1862) and A. megaptera (Cameron, 1889) with A. ruficollis (Cameron, 1883). Two species are raised from synonymy and considered here as valid species: Alloxysta cameroni (Cameron, 1883) and A. marshalliana (Kieffer, 1900). New names for species of Alloxysta are presented for homonimies with other Alloxysta species derived from the new combinations: Alloxysta ionescui Pujade-Villar & Ferrer-Suay new name for Alloxysta luteipes (Ionescu, 1969) n. comb., Alloxysta forshagei Pujade-Villar & Ferrer-Suay new name for Alloxysta bicolor (Ionescu, 1959) n. comb., and Alloxysta mattiasi Pujade-Villar & Ferrer-Suay new name for Alloxysta luteipes (Ionescu, 1959) n. comb. Also a new name to Phaenoglyphis is presented for the same reason before mentioned but without new combination: Phaenoglyphis hedickei Pujade-Villar & Ferrer-Suay new name for Phaenoglyphis longicornis Hedicke, 1928 and two new combinations are presented: Alloxysta rufa (Ionescu, 1959) n. comb and Alloxysta consobrina (Zetterstedt, 1838) Forshage n. comb. This catalogue includes: (i) a diagnosis of the subfamily with the most important taxonomic characters for species recognition, and illustrations of these characters; (ii) a key to genera; (iii) a list of all authors describing species of Charipinae; and (iv) a host table. The distribution of the Charipinae includes 106 Palaearctic species, 37 Nearctic, 11 Neotropical, 10 Afrotropical, 7 Oriental and 11 Australian. The species Alloxysta victrix (Westwood, 1833), A. fuscicornis (Hartig, 1841) and Phaenoglyphis villosa (Hartig, 1841) are cosmopolitan.

The cotton aphid, Aphis gossypii (Hemiptera: Aphididae), is a serious pest of cotton across the globe, particularly in the cotton agroecosystems of northern China. Parasitic wasps are deemed to be important natural enemies of A. gossypii, but limited information exists about their species composition, richness and seasonal dynamics in northern China. In this study, we combine sampling over a broad geographical area with intensive field trials over the course of three cropping seasons to describe parasitoid-hyperparasitoid communities in cotton crops. We delineate a speciose complex of primary parasitoids and hyperparasitoids associated with A. gossypii. Over 90% of the primary parasitoids were Binodoxys communis. Syrphophagus sp. and Pachyneuron aphidis made up most of the hyperparasitoids. Parasitism rates changed in a similar way following the fluctuation of the aphid population. Early in the growing period, there were more hyperparasitoids, while later, the primary parasitoids provided control of A. gossypii. The first systematic report of this cotton aphid parasitoid complex and their population dynamics in association with their hosts presented a comprehensive assessment of cotton parasitoid species and provided important information for the establishment and promotion of their biological control of cotton aphids.

Parasitoids are important natural enemies of aphids in wheat fields of northern China, and interest in them has increased in recent years. However, little is known regarding parasitoids of wheat aphids, which has hindered the study and understanding of aphid-parasitoid interactions. In the present study, three primary parasitoids and 15 hyperparasitoids were collected in wheat fields during a 2-year survey in northern China (2014, 2015) and a 2-year investigation at Langfang, Hebei Province (2015, 2016). Among them, Aphidius uzbekistanicus Luzhetski was found most frequently among the primary parasitoids, while Pachyneuron aphidis (Bouché) dominated the hyperparasitoid community. Investigation of the dynamics of wheat aphids and parasitoids revealed that the primary parasitoids appeared early in the growing period and that the hyperparasitoids appeared later. Analysis of the seasonal dynamics revealed that growth of the parasitoid population followed that of the aphid population and that the parasitism rates were highest in the late growing period.

This tutorial demostrates the use of ordination methods in R package vegan. The tutorial assumes familiarity both with R and with community ordination. Package vegan supports all basic ordination methods, including non-metric multidimensional scaling. The constrained ordination methods include constrained analysis of proximities, redundancy analysis and constrained correspondence analysis. Package vegan also has support functions for fitting environmental variables and for ordination graphics.