Infectious agents such as the bacteria Vibrio aestuarianus or Ostreid herpesvirus 1 (OsHV-1) have been repeatedly associated with dramatic disease outbreaks of Crassostrea gigas beds in Europe. Beside roles played by these pathogens microbial infections in C. gigas may derive from the contribution of a larger number of microorganisms than previously thought, according to an emerging view supporting the polymicrobial nature of bivalve disease. In this study, the microbial communities associated with a large number of C. gigas samples collected during recurrent mortality episodes at different European sites were investigated by real-time PCR and 16SrRNA gene-based microbial profiling. A new target enrichment next-generation sequencing protocol for selective capturing of 884 phylogenetic and virulence markers of the potential microbial pathogenic community in oyster tissue was developed allowing high taxonomic resolution analysis of the bivalve pathobiota. Comparative analysis of contrasting C. gigas samples conducted using these methods revealed that oyster experiencing mortality outbreaks displayed signs of microbiota disruption associated with the presence of previously undetected potential pathogenic microbial species mostly belonging to genus Vibrio and Arcobacter. The role of these species and their consortia should be targeted by future studies aiming to shed light on mechanisms underlying polymicrobial infections in C.gigas. This article is protected by copyright. All rights reserved.

Objectives In the 14th century AD, medieval Europe was severely affected by the Great European Famine as well as repeated bouts of disease, including the Black Death, causing major demographic shifts. This high volatility led to increased mobility and migration due to new labor and economic opportunities, as evidenced by documentary and stable isotope data. This study uses ancient DNA (aDNA) isolated from skeletal remains to examine whether evidence for large-scale population movement can be gleaned from the complete mitochondrial genomes of 264 medieval individuals from England (London) and Denmark. Materials and Methods Using a novel library-conserving approach to targeted capture, we recovered 264 full mitochondrial genomes from the petrous portion of the temporal bones and teeth and compared genetic diversity across the medieval period within and between English (London) and Danish populations and with contemporary populations through population pairwise ΦST analysis. Results We find no evidence of significant differences in genetic diversity spatially or temporally in our dataset, yet there is a high degree of haplotype diversity in our medieval samples with little exact sequence sharing. Discussion The mitochondrial genomes of both medieval Londoners and medieval Danes suggest high mitochondrial diversity before, during and after the Black Death. While our mitochondrial genomic data lack geographically correlated signals, these data could be the result of high, continual female migration before and after the Black Death or may simply indicate a large female effective population size unaffected by the upheaval of the medieval period. Either scenario suggests a genetic resiliency in areas of northwestern medieval Europe.

Abstract. Understanding why some groups of organisms are more diverse than others is a central goal in macroevolution. Evolvability, or the intrinsic capacity

Aim The Lesser Sunda Islands are situated between the Sunda and Sahul Shelves, with a linear arrangement that has functioned as a two-way filter for taxa dispersing between the Asian and Australo-Papuan biogeographical realms. Distributional patterns of many terrestrial vertebrates suggest a stepping-stone model of island colonization. Here we investigate the timing and sequence of island colonization in Asian-origin fanged frogs from the volcanic Sunda Arc islands with the goal of testing the stepping-stone model of island colonization. Location The Indonesian islands of Java, Lombok, Sumbawa, Flores and Lembata. Taxon Limnonectes dammermani and L. kadarsani (Family: Dicroglossidae) Methods Mitochondrial DNA was sequenced from 153 frogs to identify major lineages and to select samples for an exon-capture experiment. We designed probes to capture sequence data from 974 exonic loci (1,235,981 bp) from 48 frogs including the outgroup species, L. microdiscus. The resulting data were analysed using phylogenetic, population genetic and biogeographical model testing methods. Results The mtDNA phylogeny finds L. kadarsani paraphyletic with respect to L. dammermani, with a pectinate topology consistent with the stepping-stone model. Phylogenomic analyses of 974 exons recovered the two species as monophyletic sister taxa that diverged 7.6 Ma with no detectable contemporary gene flow, suggesting introgression of the L. dammermani mitochondrion into L. kadarsani on Lombok resulting from an isolated ancient hybridization event 4 Ma. Within L. kadarsani, the Lombok lineage diverged first while the Sumbawa and Lembata lineages are nested within a Flores assemblage composed of two parapatrically distributed lineages meeting in central Flores. Biogeographical model comparison found strict stepping-stone dispersal to be less likely than models involving leap-frog dispersal events. Main conclusions These results suggest that the currently accepted stepping-stone model of island colonization might not best explain the current patterns of diversity in the archipelago. The high degree of genetic structure, large divergence times, and absent or low levels of migration between lineages suggests that L. kadarsani represents five distinct species.