Département Ecologie aquatique

DNA methylation (DNAm) is a mechanism for rapid acclimation to environmental conditions. In natural systems, small effect sizes relative to noise necessitates large sampling efforts to detect differences. Large numbers of individually sequenced libraries are costly. Pooling DNA prior to library preparation may be an efficient way to reduce costs and increase sample size, yet there are to date no recommendations in ecological epigenetics research. We test whether pooled and individual libraries yield comparable DNAm signals in a natural system exposed to different pollution levels by generating whole-epigenome data from two invasive molluscs (Corbicula fluminea, Dreissena polymorpha) collected from polluted and unpolluted localities (Italy). DNA of the same individuals were used for pooled and individual epigenomic libraries and sequenced with equivalent resources per individual. We found that pooling effectively captures similar genome-wide and global methylation signals as individual libraries, highlighting that pooled libraries are representative of the global population signal. However, pooled libraries yielded orders of magnitude more data than individual libraries, which was a consequence of higher coverage. We would therefore recommend aiming for a high initial coverage of individual libraries (15×) in future studies. Consequently, we detected many more differentially methylated regions (DMRs) with the pooled libraries and a significantly lower statistical power for regions from individual libraries. Computationally pooled data from the individual libraries produced fewer DMRs and the overlap with wet-lab pooled DMRs was relatively low. We discuss possible causes for discrepancies, list benefits and drawbacks of pooling, and provide recommendations for future epigenomic studies.

How barriers to gene flow arise and are maintained are key questions in evolutionary biology. Speciation research has mainly focused on barriers that occur either before mating or after zygote formation. In comparison, postmating prezygotic (PMPZ) isolation—a barrier that acts after gamete release but before zygote formation—is less frequently investigated but may hold a unique role in generating biodiversity. Here we discuss the distinctive features of PMPZ isolation, including the primary drivers and molecular mechanisms underpinning PMPZ isolation. We then present the first comprehensive survey of PMPZ isolation research, revealing that it is a widespread form of prezygotic isolation across eukaryotes. The survey also exposes obstacles in studying PMPZ isolation, in part attributable to the challenges involved in directly measuring PMPZ isolation and uncovering its causal mechanisms. Finally, we identify outstanding knowledge gaps and provide recommendations for improving future research on PMPZ isolation. This will allow us to better understand the nature of this often-neglected reproductive barrier and its contribution to speciation.

Patella caerulea (Linnaeus, 1758) is a mollusc limpet species of the class Gastropoda. Endemic to the Mediterranean Sea, it is considered a keystone species due to its primary role in structuring and regulating the ecological balance of tidal and subtidal habitats. It is currently being used as a bioindicator to assess the environmental quality of coastal marine waters and as a model species to understand adaptation to ocean acidification. Here, we provide a high-quality reference genome assembly and annotation for P. caerulea. We generated ∼30 Gb of Pacific Biosciences high-fidelity data from a single individual and provide a final 749.8 Mb assembly containing 62 contigs, including the mitochondrial genome (14,938 bp). With an N50 of 48.8 Mb and 98% of the assembly contained in the 18 largest contigs, this assembly is near chromosome-scale. Benchmarking Universal Single-Copy Orthologs scores were high (Mollusca, 87.8% complete; Metazoa, 97.2% complete) and similar to metrics observed for other chromosome-level Patella genomes, highlighting a possible bias in the Mollusca database for Patellids. We generated transcriptomic Illumina data from a second individual collected at the same locality and used it together with protein evidence to annotate the genome. A total of 23,938 protein-coding gene models were found. By comparing this annotation with other published Patella annotations, we found that the distribution and median values of exon and gene lengths was comparable with other Patella species despite different annotation approaches. The present high-quality P. caerulea reference genome, available on GenBank (BioProject: PRJNA1045377; assembly: GCA_036850965.1), is an important resource for future ecological and evolutionary studies.

he Research Topic on the 16^th Deep Sea Biology Symposium compiles a range of articles presented during the conference that was held in Brest (France) in September 2021 and hosted by the Institut Français de Recherche pour l’Exploitation de la Mer (Ifremer). This triannual event is the central meeting for deep-sea research, where scientists from all over the world gather together to showcase and discuss the latest advances in their field. For the first time in 2021, this event was held in a hybrid mode with participants attending on site and online. Puccinelli et al. showed that, while meetings organized by the Deep-Sea Biology Society had typically less than 400 participants, the use of a hybrid format increased participation by 33% (581 attendees), 73% of whom joined online.
The 26 articles of this Research Topic span research conducted by 138 authors across all ocean basins, encompassing a range of topics that we classified in four sections: 1) zoology and systematics, 2) biodiversity, 3) ecology and 4) conservation and policy. These works investigated most trophic levels from phytoplankton to benthos, fish and whales, across diverse deep-sea environments such as mesopelagic to abyssal environments, vents, seeps and seamounts. This Research Topic provides novel insights on the largest biome of the planet, while advancing our understanding of the complex interactions between organisms and their physical environment, and how such equilibrium is affected by human-induced activities and climate change.

Hybrid conferences are in-person events that have an online component. This type of meeting format was rare before the COVID-19 pandemic, but started to become more common recently given the asynchronous global progression of the pandemic, the uneven access to vaccines and different travel regulations among countries that led to a large proportion of participants being unable to attend conferences in person. Here we report the organization of a middle-sized (581 participants: 159 onsite, 422 online) international hybrid conference that took place in France in September 2021. We highlight particular organizational challenges inherent to this relatively new type of meeting format. Furthermore, we surveyed both in-person and online participants to better understand their conference experience and to propose improvements based on the feedback received. Finally, we compare the advantages and disadvantages of three types of conferences (onsite-only, online-only and hybrid) and suggest that hybrid events should be favored in the future because they offer the most flexibility to participants. We conclude by proposing suggestions and ways forward to maximize accessibility and inclusivity of hybrid conferences. Our study brings novel insights on the challenges and opportunities created by hybrid conferences, by reporting not only the organizing committee experience but also by considering the participants’ perspective.