Search

We provide the first description and analysis of species-rich communities of Fagaceae host plants, cynipid gall inducers and Hymenopteran parasitoids from two sites in western Sichuan, China. We use quantified interaction data to test the hypothesis that metabolically intimate cynipid-Fagaceae interactions are more specialised, resulting in more modular networks and stronger signatures of turnover than nestedness for beta diversity, than associations between parasitoids and Fagaceae. Rearing of nearly 27,000 cynipid gall specimens from 22 host plant species in Castanea, Castanopsis, Lithocarpus and Quercus (sections Cerris, Cyclobalanopsis, Ilex and Quercus) yielded 168 morphologically distinct cynipid gall morphotypes, and 3800 parasitoids in 67 morphospecies. The Sichuan parasitoid assemblage is similar in composition to cynipid-centred communities in the Western Palearctic and Nearctic. All of our predictions were confirmed. We discuss our findings in light of the processes thought to structure tritrophic interactions centred on gall inducing insect herbivores.

Co-evolutionary interactions between insect herbivores and their host plants underlie much contemporary biodiversity and are vital to assembly of natural ecosystems. Assemblages of galls on oaks induced by Cynipini wasps (Hymenoptera: Cynipidae) occur across much of the Northern Hemisphere, their diversity peaking in the Nearctic and on white oaks (Quercus section Quercus). However, the evolutionary history of the clade has been debated with respect to geographic origins, direction and timings of dispersal events, and shifts in host plant associations. We examined these questions using a global-scale, 6-gene phylogeny of 430 Cynipini species and a dataset of their associated host plants encompassing all eight sections within Quercus plus five Fagaceae genera. Likelihood-based ancestral state reconstructions demonstrate a Nearctic origin of the Cynipini followed by repeated colonisations of the Palearctic via both westwards and eastwards dispersal. These inferences are robust to bias in taxon sampling across continents and the inclusion of Protobalandricus as the sister lineage to Cynipini sensu stricto. Likewise, the association with white oaks is probably ancestral and has been retained by many Cynipini lineages. However, host shifts to other sections within Quercus and related Fagaceae genera are widely distributed across the cynipid phylogeny. They are associated with both global-scale range shifts and within-bioregion exploitation of alternative hosts, and their frequency typically correlates with host-plant relatedness. These findings highlight the evolutionary success of cynipids on white oak hosts and the connectedness of continental assemblages of gall wasps over evolutionary time.

Revealing processes that structure species interactions is central to understanding community assembly and dynamics. Species interact via their phenotypes, but identifying and quantifying the traits that structure species-specific interactions (links) can be challenging. Where these traits show phylogenetic signal, however, link properties are predictable using models that incorporate phylogenies in place of trait data. We analysed variation in link richness, frequency, and identity in a multi-site dataset of interactions between host oak cynipid galls and parasitoid natural enemies, using a Bayesian mixed modelling framework allowing concurrent fitting of terms for phylogenies of both trophic levels. In both link incidence (presence/absence) and link frequency datasets, we identified strong signatures of cophylogeny (related parasitoids attack related host galls) and patterns independent of either phylogeny. Our results are robust to simulations of substantially reduced sample completeness, and are consistent with the structuring of trophic interactions by a combination of phylogenetically conserved and convergently evolving traits at both trophic levels. We discuss our results in light of phenotypic traits thought to structure gall-parasitoid interactions and wider applications of this approach, including inference of underlying community assembly processes and prediction of economically important trophic interactions.

The taxonomy of oak gallwasps (Hymenoptera: Cynipidae: Cynipini) has a long and sometimes confusing history. Many large genera have become hold-alls for a diversity of lineages, and are often delimited by combinations of pleisiomorphic character states. At species level, the presence of alternating generations further complicates Cynipini taxonomy. With the increased use of molecular systematics, it is clear that current Cynipini taxonomy is inadequate and requires major revisions. Here we provide an overview of recent work helping to resolve the chaotic mess of Cynipini taxonomy. Some of this work has involved purely morphological re-assessment of particularly distinctive lineages, while much is based upon ongoing systematic work using a 6-gene molecular phylogeny containing 430 species representing all the known major lineages/genera within the Cynipini. Incorporation of phylogenetic information has revealed that all of the large, Holarctic-distributed genera are polyphyletic. In addition, the limits of many smaller genera require redefining, and widespread sampling indicates that many of these genera may be represented by a larger complement of species across a broader geographic area. Molecular data also provide a quick and simple method for matching alternate generations of Cynipini species. Development of collection genomics workflows has opened up biological collections to molecular analysis, potentially providing DNA sequence data for matching generations. Within Cynipini, this could allow for the sizeable series of specimens collected by early researchers such as Kinsey and Weld to be used for clarifying the species-level taxonomy of large numbers of Cynipini taxa.

Pollinators experience large spatiotemporal fluctuations in resource availability when mass-flowering crops are rotated with resource-poor cereal crops. Yet, few studies have considered the effect this has on pollinator population stability, nor how this might be mitigated to maintain consistent crop pollination services. We assess the potential of boundary features (standard narrow 1 m grassy margins, hedgerows and wide 4 m agri-environment margins) to support and stabilise pollinator populations and pollination service in agricultural landscapes under crop rotation. Assuming a 6-year rotation, we use a process-based pollinator model to predict yearly pollinator population size and in-crop visitation rates to oilseed rape and field bean across 117 study landscapes in England with varying amounts of boundary features. We model both ground-nesting bumblebees and solitary bees and compare the predictions including and excluding boundary features from the landscapes. Ground-nesting bumblebee populations, whose longer-lifetime colonies benefit from continuity of resources, were larger and more stable (relative to the no-features scenario) in landscapes with more boundary features. Ground-nesting solitary bee populations were also larger but not significantly more stable, except with the introduction of wide permanent agri-environment margins, due to their shorter lifetimes and shorter foraging/dispersal ranges. Crop visitation by ground-nesting bumblebees was greater and more stable in landscapes with more boundary features, partly due to increased colony growth prior to crop flowering. Time averaged crop visitation by ground-nesting solitary bees was slightly lower, due to females dividing their foraging time between boundary features and the crop. However, despite this, the minimum pollination service delivered was higher, due to the more stable delivery. Synthesis and applications. Field boundary features have an important role in stabilising pollinator populations a

A new species of inquiline, Lithosaphonecrus edurus Fang, Melika, and Tang, new species (Hymenoptera: Cynipidae: Synergini) is described from Emeishan, Sichuan Province, China. Lithosaphonecrus edurus is associated with an as yet undetermined cynipid gall on Lithocarpus cleistocarpus var. cleistocarpus and var. omeiensis, L. hancei and L. megalophyllus (Fagaceae). Description, diagnosis, phenology, and host association for the new species are given. The new species is supported by morphological and molecular data.