Molecular systematics and biogeography of Nicrophorus in part--the investigator species group (Coleoptera: Silphidae) using mixture model MCMC

Identification of Forensically Important Carrion Beetles (Coleoptera: Staphilinidae) in China Based on COI and COII

Unambiguous and speedy necrophagous insect species identification is common task in forensic entomological study. Carrion beetles (Staphilinidae: Silphinae) belong to a small group of Coleoptera with less than 200 species worldwide. Some species are commonly found on dead body during forensic entomological investigation. Despite some species are hard to be categorized morphologically, present DNA-based technologies offer a potential identification strategy. Here, 37 carrion beetle specimens were collected from 15 locations throughout Chinese mainland. The cytochrome oxidase subunit I (COI) and II (COII) genes among all specimens were successfully sequenced, which provided reliable markers for precise identification. Mostly, the interspecific distance could clarify the capability of these genes for identifying included carrion beetle species. Exceptions existed between close species in Nicrophorus genus (Fabricius 1775). The sequenced gene's phylogenetic analysis revealed that all carrion beetle specimens were correctly classified into eight genera, and most have relatively high supporting values (>90%). Our data gives genetic diversity and a reference for global forensically important carrion beetle species identification, as well as a conductive significance for future application of Chinese carrion beetles in forensic entomology.

Cryptic diversity within the Poecilochirus carabi mite species complex phoretic on Nicrophorus burying beetles: Phylogeny, biogeography, and host specificity

Coevolution is often considered a major driver of speciation, but evidence for this claim is not always found because diversity might be cryptic. When morphological divergence is low, molecular data are needed to uncover diversity. This is often the case in mites, which are known for their extensive and often cryptic diversity. We studied mites of the genus Poecilochirus that are phoretic on burying beetles (Silphidae: Nicrophorus). Poecilochirus taxonomy is poorly understood. Most studies on this genus focus on the evolutionary ecology of Poecilochirus carabi sensu lato, a complex of at least two biological species. Based on molecular data of 230 specimens from 43 locations worldwide, we identified 24 genetic clusters that may represent species. We estimate that these mites began to diversify during the Paleogene, when the clade containing P. subterraneus branched off and the remaining mites diverged into two further clades. One clade resembles P. monospinosus. The other clade contains 17 genetic clusters resembling P. carabi s.l.. Among these are P. carabi sensu stricto, P. necrophori, and potentially many additional cryptic species. Our analyses suggest that these clades were formed in the Miocene by large-scale geographic separation; co-speciation of mites with the host beetles can be largely ruled out. Diversification also seems to have happened on a smaller scale, potentially due to adaptation to specific hosts or local abiotic conditions, causing some clusters to specialize on certain beetle species. Our results suggest that biodiversity in this genus was generated by multiple interacting forces shaping the tangled webs of life.

Genomic analysis of novel Yarrowia-like yeast symbionts associated with the carrion-feeding burying beetle Nicrophorus vespilloides

Background

Mutualistic interactions with microbes can help insects adapt to extreme environments and unusual diets. An intriguing example is the burying beetle Nicrophorus vespilloides, which feeds and reproduces on small vertebrate carcasses. Its fungal microbiome is dominated by yeasts that potentially facilitate carcass utilization by producing digestive enzymes, eliminating cadaver-associated toxic volatiles (that would otherwise attract competitors), and releasing antimicrobials to sanitize the microenvironment. Some of these yeasts are closely related to the biotechnologically important species Yarrowia lipolytica.

Results

To investigate the roles of these Yarrowia-like yeast (YLY) strains in more detail, we selected five strains from two different phylogenetic clades for third-generation sequencing and genome analysis. The first clade, represented by strain B02, has a 20-Mb genome containing ~ 6400 predicted protein-coding genes. The second clade, represented by strain C11, has a 25-Mb genome containing ~ 6300 predicted protein-coding genes, and extensive intraspecific variability within the ITS–D1/D2 rDNA region commonly used for species assignments. Phenotypic microarray analysis revealed that both YLY strains were able to utilize a diverse range of carbon and nitrogen sources (including microbial metabolites associated with putrefaction), and can grow in environments with extreme pH and salt concentrations.

Conclusions

The genomic characterization of five yeast strains isolated from N. vespilloides resulted in the identification of strains potentially representing new YLY species. Given their abundance in the beetle hindgut, and dominant growth on beetle-prepared carcasses, the analysis of these strains has revealed the genetic basis of a potential symbiotic relationship between yeasts and burying beetles that facilitates carcass digestion and preservation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-07597-z.

New MacrochelePratums species (Acari, Mesostigmata, Macrochelidae) associated with burying beetles (Silphidae, Nicrophorus) in North America

Burying beetles (Silphidae, Nicrophorus) are hosts to a broad diversity of mites (Acari), including several species of Macrocheles Latreille, 1829 (Mesostigmata, Macrochelidae). The macrochelid fauna associated with silphids primarily in North America was surveyed; in total, 1659 macrochelids representing seven species were collected from 112 Nicrophorus beetles representing nine host species. Three new species of Macrocheles were discovered during the survey and described as Macrocheles willowaesp. n., M. pratumsp. n., and M. kaijusp. n. The barcode region of cytochrome oxidase subunit I (COI) was amplified from the three new described species, as well as M. nataliae and M. praedafimetorum, and analysed in a small phylogeny.

Molecular phylogeny of the burying beetles (Coleoptera: Silphidae: Nicrophorinae)

Burying beetles (Silphidae: Nicrophorus) are well-known for their monopolization of small vertebrate carcasses in subterranean crypts and complex biparental care behaviors. They have been the focus of intense behavioral, ecological, and conservation research since the 1980s yet no thorough phylogenetic estimate for the group exists. Herein, we infer relationships, test past hypotheses of relationships, and test biogeographic scenarios among 55 of the subfamily Nicrophorinae's currently valid and extant 72 species. Two mitochondrial genes, COI and COII, and two nuclear genes, the D2 region of 28S, and the protein coding gene CAD, provided 3,971 nucleotides for 58 nicrophorine and 5 outgroup specimens. Ten partitions, with each modeled by GTR+I+G, were used for a 100 M generation MrBayes analysis and maximum likelihood bootstrapping with Garli. The inferred Bayesian phylogeny was mostly well-resolved with only three weak branches of biogeographic relevance. The common ancestor of the subfamily and of the genus Nicrophorus was reconstructed as Old World with four separate transitions to the New World and four reverse colonizations of the Old World from the New. Divergence dating from analysis with BEAST indicate the genus Nicrophorus originated in the Cretaceous, 127-99 Ma. Most prior, pre-cladistic hypotheses of relationships were strongly rejected while most modern hypotheses were largely congruent with monophyletic groups in our estimated phylogeny. Our results reject a recent hypothesis that Nicrophorus morio Gebler, 1817 (NEW STATUS as valid species) is a subspecies of N. germanicus (L., 1758). Two subgenera of Nicrophorus are recognized: NecroxenusSemenov-Tian-Shanskij, 1933, and NicrophorusFabricius, 1775.

Description of Nicrophorus efferens, new species, from Bougainville Island (Coleoptera, Silphidae, Nicrophorinae)

A new species of Nicrophorus in the nepalensis species-group, Nicrophorus efferens Sikes and Mousseau, is described from Bougainville Island in the Solomon Islands archipelago. It is distinguished from the known species of the genus Nicrophorus and its likely closest relative, Nicrophorus reticulatus Sikes and Madge, based on external morphology. A comparison among the four Nicrophorus species known from the Solomon Island archipelago and Papua New Guinea is presented.