Coastal environments are increasingly recognised as reservoirs of known antibiotic resistance genes (ARGs), but are less frequently identified as sources of novel ARGs. Here, we investigated class A β‐lactamases circulating in European coastal environments used for oyster farming. We examined their diversity, function, and the ecological factors associated with their geographic distribution and environmental dynamics. A high d...

It is in the very nature of coastal ecosystems to respond rapidly to external driving factors from land, sea, and man. Human-induced environmental change from local to global scale, and introduced species in particular, has accelerated ecological transformation at many coasts worldwide. A series of major events has fundamentally changed the macrobenthos in a tidal bay of the Wadden Sea (Königshafen, south-eastern North Sea, At...

An increase in temperature due to climate change may affect the geographic ranges of invasive parasites and alter their impact on native hosts. Our goal was to determine if the effects of infection by two species of invasive endoparasitic copepods on native blue mussel hosts ( Mytilus edulis ) change with increasing temperatures. We investigated this with a laboratory experiment using temperatures that represent annual mean an...

Phages depend on their bacterial hosts to replicate. The habitat, density and genetic diversity of host populations are therefore key factors in phage ecology, but our ability to explore their biology depends on the isolation of a diverse and representative collection of phages from different sources. Here, we compared two populations of marine bacterial hosts and their phages collected during a time series sampling program in...

For about a century, biodiversity in the tidal Wadden Sea (North Sea, European Atlantic) has increased by more than one hundred introduced species from overseas. Most originate from warmer waters and could facilitate the transformation of this coastal ecosystem to comply with climate warming. Some introduced species promote sediment stabilization and mud accretion. This could help tidal flats to keep up with sea level rise. Al...

In species introductions, non-native species are often confronted with new niches occupied by more specialized natives, and for introduced parasites this conflict can be amplified because they also face novel hosts. Despite these obstacles, invasions of introduced parasites occur frequently, but the mechanisms that facilitate parasite invasion success are only rarely explored. Here, we investigated how the parasitic copepod My...

Bare sandy flats at and below low tide level of the Wadden Sea (eastern North Sea, European Atlantic) were observed in 2020 to have been invaded by an introduced grass-like alga, Vaucheria cf. velutina (Xanthophyceae). A dense algal turf accumulated and stabilized mud, where resident seniors of the lugworm Arenicola marina had reworked rippled sand . Algae and worms were incompatible. Initially, rising patches with algal turf...

Rapid climate change is placing many marine species at risk of local extinction. Recent studies show that epigenetic mechanisms (e.g. DNA methylation, histone modifications) can facilitate both within and transgenerational plasticity to cope with changing environments. However, epigenetic reprogramming (erasure and re‐establishment of epigenetic marks) during gamete and early embryo development may hinder transgenerational epi...

The conservation and active restoration of European flat oyster ( Ostrea edulis ) populations are a major focus of ecological restoration efforts to take advantage of the wide‐ranging ecosystem functions and services this species provides. Accordingly, additional and new demands for seed oysters have arisen. In commercial aquaculture (mariculture), the production of O. edulis is still largely based on natural seed collection....

With globally growing aquaculture activities, the co-introduction of parasites alongside large-scale movements of commercial species poses an increasing risk for marine ecosystems. Here, we present the first record of the shell-boring polychaete Polydora websteri Hartman in Loosanoff and Engle, 1943 in invasive Pacific oysters Crassostrea ( Magallana ) gigas (Thunberg, 1793) in the European Atlantic Ocean. In October 2014, mud...

Summary Pacific oyster mortality syndrome affects juveniles of Crassostrea gigas oysters and threatens the sustainability of commercial and natural stocks of this species. Vibrio crassostreae ( V . crassostreae ) has been repeatedly isolated from diseased animals, and the majority of the strains have been demonstrated to be virulent for oysters. In this study, we showed that oyster farms exhibited a high prevalence of a virule...

On theoretical grounds, antagonistic co‐evolution between hosts and their parasites should be a widespread phenomenon but only received little empirical support so far. Consequently, the underlying molecular mechanisms and evolutionary steps remain elusive, especially in nonmodel systems. Here, we utilized the natural history of invasive parasites to document the molecular underpinnings of co‐evolutionary trajectories. We appl...

Summary Microbiota can have positive and negative effects on hosts depending on the environmental conditions. Therefore, it is important to decipher host–microbiota–environment interactions, especially under natural conditions exerting (a)biotic stress. Here, we assess the relative importance of microbiota in different tissues of Pacific oyster for its successful establishment in a new environment. We transplanted oysters from...

One of the key features of major histocompatibility complex (MHC) genes is the frequent occurrence of trans‐species polymorphism, that is ‘the passage of allelic lineages from ancestral to descendant species’ ( Klein et al. 2007 ). Selectively maintained ancestral polymorphism may, however, be hard to distinguish from introgression of MHC alleles between hybridizing species ( Fig. 1 ). In this issue of Molecular Ecology, Nadac...

Latitudinal variation in thermal reaction norms of key fitness traits may inform about the response of populations to climate warming, yet their adaptive nature and evolutionary potential are poorly known. We assessed the contribution of quantitative genetic, neutral genetic and environmental effects to thermal reaction norms of growth rate for populations of the damselfly Ischnura elegans . Among populations, reaction norms d...

The power of population genetic analyses is often limited by sample size resulting from constraints in financial resources and time to genotype large numbers of individuals. This particularly applies to nonmodel species where detailed genomic knowledge is lacking. Next‐generation sequencing technology using primers ‘tagged’ with an individual barcode of a few nucleotides offers the opportunity to genotype hundreds of individua...