Evolution and diversity of cuticular hydrocarbon profiles in cleptoparasitic and parasitoid cuckoo wasps and their significance for chemical mimicry
Final Report Abstract
The cuticle of insects is coated with a layer of waxes that serves as protection against desiccation. The non-polar fraction of these waxes are cuticular hydrocarbons (CHCs). Their composition differs between most species and often between sexes, and insects use them as cues and signals. Our research project aimed to elucidate whether or not positive Darwinian selection on females to mimic the CHC profile of their host is a major force that drives the evolution of CHC profiles in a group of cleptoparasitic and parasitoid insects: cuckoo wasps (Hymenoptera: Chrysididae). We collected CHC extracts of ~ 4,600 cuckoo wasps, their hosts, and of selected outgroups. Characterization of a major fraction of these profiles revealed that almost all cuckoo wasps (and each sex of them) exhibit a unique CHC profile. The distinct CHC profiles of most species let to the discovery of a likely undescribed cryptic species as well as to clarification of another, previously already discussed cryptic species (both occurring in Germany). To provide a basis of comparative analysis of cuckoo wasp CHC profiles, we inferred the phylogeny of the family using three data ascertainment methods: (1) PCR amplification and sequencing of ten nuclear genes and one mitochondrial gene in > 180 cuckoo wasp species; (2) analysis of 3,258 protein-coding genes in 57 cuckoo wasp species whose transcriptome we sequenced; (3) additional analysis of 502 protein-coding genes accessed via target DNA enrichment in 32 phylogenetically important species whose transcriptome we could not sequence. Analysis of the above nucleotide sequence data have proceeded far (but are not final yet) and revealed that the generic classification of cuckoo wasps is in major parts artificial, with many currently accepted genera being polyphyletic (e.g., Cephaloparnops, Chrysis, Chrysura, Euchroeus, Hedychridium, Omalus, Pseudospinolia, Spinolia). Given this knowledge, our preliminary analysis of the CHC profiles suggest that the CHC profiles of cuckoo wasp males are phylogenetically informative while those of females are not (of at least significantly less so on the investigated divergence scale). We furthermore found that many (but not all) female cuckoo wasps apply a chemical mimicry strategy, possibly explaining partially the sex specific CHC differences. However, due to the comprehensive size of our chemical and molecular datasets, final statistical analyses have yet to be conducted. Yet, we already conducted (and in parts published) in-depth case studies (e.g., on the mason wasp Odynerus spinipes and their cuckoo wasps and on digger wasps of the genera Cerceris and Philanthus and their cuckoo wasps). These case studies revealed that cuckoo wasps whose hosts are not able to alter their CHC profiles due to ecological constraints are better mimicked by cuckoo wasps than those that are able to alter their CHC profile. One extreme outcome of such an arms race we found in the mason wasp, Odynerus spinipes, which is capable of expressing two qualitatively very different CHC profiles (differing in 70 components). The results from these studies have given rise to follow up studies that are meant to shed light on the biosynthesis CHCs and the perception of CHC in Hymenoptera and in preparation of which we sequenced the genomes of various cuckoo wasp species as well as of their respective hosts. Samples from the present study made these sequencing efforts possible.
Publications
- (2012): Oligonucleotide primers for targeted amplification of single-copy nuclear genes in apocritan Hymenoptera. – PLoS ONE 7: e39826
Hartig G, Peters RS, Borner J, Etzbauer C, Misof B, Niehuis O
(See online at https://doi.org/10.1371/journal.pone.0039826) - (2014): Nachweise von Chrysura rufiventris (Dahlbom, 1854) in Deutschland und weitere bemerkenswerte Wespenfunde in Baden-Württemberg, Hessen und Rheinland-Pfalz (Hymenoptera: Aculeata). – Ampulex 6: 5–12
Reder G, Niehuis O
- (2014): Phylogenomics resolves the timing and pattern of insect evolution. – Science 346: 763–767
Misof B, Liu S, Meusemann K, Peters RS, ..., Niehuis O, et al.
(See online at https://doi.org/10.1126/science.1257570) - (2014): Zur Kenntnis der Stechimmenfauna des Roßsteins bei Dörscheid und der Goldwespenfauna im Oberen Mittelrheintal (Hymenoptera: Aculeata et Chrysididae). – Fauna und Flora in Rheinland-Pfalz 12: 1315–1334
Frommer U, Niehuis M, Niehuis O
- (2015): Erste Nachweise von Chrysis marginata aliunda Linsenmaier, 1959, in Deutschland und der Schweiz und Hinweise zum Wirt dieser sich ausbreitenden Goldwespe (Hymenoptera, Chrysididae). – Ampulex 7: 6–11
Herrmann M, Niehuis O
- (2015): Striking cuticular hydrocarbon dimorphism in the mason wasp Odynerus spinipes and its possible evolutionary cause (Hymenoptera: Chrysididae, Vespidae). – Proceedings of the Royal Society B 282: 20151777
Wurdack M, Herbertz S, Dowling D, Kroiss J, Strohm E, Baur H, Niehuis O, Schmitt T
(See online at https://doi.org/10.1098/rspb.2015.1777) - (2016): BaitFisher: a software package for multispecies target DNA enrichment probe design. – Molecular Biology and Evolution 33: 1875–1886
Mayer C, Sann M, Donath A, Meixner M, Podsiadlowski L, Peters RS, Petersen M, Meusemann K, Liere K, Wägele JW, Misof B, Bleidorn C, Ohl M, Niehuis O
(See online at https://doi.org/10.1093/molbev/msw056)
