Biology subjects

Baur, H.

Publications and source records attributed to Baur, H..

3 recordsLinked to original sources

bioRxiv2022

The Chalcidoidea bush of life - a massive radiation blurred by mutational saturation

Capturing phylogenetic signal from a massive radiation can be daunting. The superfamily Chalcidoidea is an excellent example of a hyperdiverse group that has remained recalcitrant to phylogenetic resolution. Chalcidoidea are mostly parasitoid wasps that until now included 27 families, 87 subfamilies and as many as 500,000 estimated species. We combined 1007 exons obtained with Anchored Hybrid Enrichment with 1048 Ultra-Conserved Elements (UCEs) for 433 taxa including all extant families, over 95% of all subfamilies and 356 genera chosen to represent the vast diversity of the superfamily. Going back and forth between molecular results and our collective morphological and biological knowledge, we detected insidious bias driven by the saturation of nucleotide data and highlighted morphological convergences. Our final results are based on a concatenated analysis of the least saturated exons and UCE data sets (2054 loci, 284,106 sites). Our analyses support a sister relationship with Mymarommatoidea. Seven of the previously recognized families were not monophyletic, so foundations for a new classification are discussed. Biology appears potentially more informative than morphology, as illustrated by the elucidation of a clade of plant gall associates and a clade of taxa with planidial first-instar larvae. The phylogeny suggests a shift from smaller soft-bodied wasps to larger and more heavily sclerotized wasps. Deep divergences in Chalcidoidea coincide with an increase in insect families in the fossil record, and an early shift to phytophagy corresponds with the beginning of the "Angiosperm Terrestrial Revolution". Our dating analyses suggest a Middle Jurassic origin of 174 Ma (167.3-180.5 Ma) and a crown age of 162.2 Ma (153.9-169.8 Ma) for Chalcidoidea. During the Cretaceous, Chalcidoidea underwent a rapid radiation in southern Gondwana with subsequent dispersals to the Northern Hemisphere. This scenario is discussed with regard to knowledge about host taxa of chalcid wasps, their fossil record, and Earths paleogeographic history.

evolutionary biology↗

bioRxiv2021

Standardized nuclear markers advance metazoan taxonomy

Species are the fundamental units of life and their recognition is essential for science and society. DNA barcoding, the use of a single and often mitochondrial gene, has been increasingly employed as a universal approach for the identification of animal species. However, this approach faces several challenges. Here, we demonstrate with empirical data from a number of metazoan animal lineages that multiple nuclear-encoded markers, so called universal single-copy orthologs (USCOs) performs much better than the single barcode gene to discriminate closely related species. Overcoming the general shortcomings of mitochondrial DNA barcodes, USCOs also accurately assign samples to higher taxonomic levels. These loci thus provide a powerful and unifying framework for species delimitation which considerably improves the DNA-based inference of animal species.

molecular biology↗

bioRxiv2020

Cuticular Hydrocarbons on Old Museum Specimens of the Spiny Mason Wasp, Odynerus spinipes, (Hymenoptera: Vespidae: Eumeninae) Shed Light on the Distribution and on Regional Frequencies of Distinct Chemotypes

The mason wasp Odynerus spinipes shows an exceptional case of intrasexual CHC dimorphism. Females of this species express one of two cuticular hydrocarbon (CHC) profiles (chemotypes) that differ qualitatively and quantitatively from each other. The ratio of the two chemotypes was previously shown to be close to 1:1 at three sites in Southern Germany, which might not be representative given the Palearctic distribution of the species. To infer the frequency of the two chemotypes across the entire distributional range of the species, we analyzed with GC-MS the CHC profiles of 1,042 dry-mounted specimens stored in private and museum collections. We complemented our sampling by including 324 samples collected and preserved specifically for studying their CHCs. We were capable of reliably identifying the chemotypes in 91% of dry-mounted samples, some of which collected almost 200 years ago. We found both chemotypes to occur in the Far East, the presumed glacial refuge of the species, and their frequency to differ considerably between sites and geographic regions. The geographic structure in the chemotype frequencies could be the result of differential selection regimes and/or different dispersal routes during the colonization of the Western Palearctic. The presented data pave the route for disentangling these factors by providing information where to geographically sample O. spinipes for population genetic analyses. They also form the much-needed basis for future studies aiming to understand the evolutionary and geographic origin as well as the genetics of the astounding CHC dimorphism that O. spinipes females exhibit.

ecology↗