The ongoing biodiversity crisis calls for a complete biodiversity inventory of marine and terrestrial ecosystems. The task is particularly challenging for fragmented island territories, where baseline biodiversity information is often difficult to procure. By centralising information from different sources (museums, research institutions, citizen scientists), ‘big-data’ platforms provide an opportunity to evaluate species biodiversity information of understudied regions. Using data from the Global Biodiversity Information Facility (GBIF), we curated the first biogeographic dataset for both marine and terrestrial animal species in French Polynesia, a large territory composed of 124 islands and atolls that belongs to the Central Pacific region, a marine biodiversity hotspot facing conservation challenges. The dataset revealed heterogeneous species richness across archipelagos and islands, prompting an investigation into potential sampling biases (institutional, taxonomic, spatial) as well as an assessment of island-specific accessibility biases. We estimated that the archipelagos and islands had an inventory completeness rate that ranges from 12 to 85%, suggesting that a large proportion of the studied area remains poorly documented. Spatial and temporal sampling biases were partly explained by accessibility constraints (proximity to airports, roads or ports), and inventory completeness was higher for marine than terrestrial species. The biases quantified here challenge our ability to conduct biogeographic analyses that integrate the land-sea meta-ecosystem. Our database allows identifying taxa and sampling locations that require urgent attention, as well as comprehensively recorded species that can serve as indicators for environmental degradation. Explicitly acknowledging the inherent biases of biodiversity datasets is the first step towards a more comprehensive characterization of species diversity across fragmented territories. This information is crucial for guiding sound adaptive-management and conservation planning strategies.

Identifying the molecular mechanisms involved in rapid adaptation to novel environments and determining their predictability, are central questions in evolutionary biology and pressing issues due to rapid global changes. Complementary to genetic responses to selection, faster epigenetic variations such as modifications of DNA methylation may play a substantial role in rapid adaptation. In the context of rampant urbanization, joint examinations of genomic and epigenomic mechanisms are still lacking. Here, we investigated genomic (SNP) and epigenomic (CpG methylation) responses to urban life in a passerine bird, the Great tit (Parus major). To test whether urban evolution is predictable (i.e parallel) or involves mostly non-parallel molecular processes among cities, we analysed both SNP and CpG methylation variations across three distinct pairs of city and forest Great tit populations in Europe. Our analyses reveal a polygenic response to urban life, with both many genes putatively under weak divergent selection and multiple differentially methylated regions (DMRs) between forest and city great tits. DMRs mainly overlapped transcription start sites and promotor regions, suggesting their importance in modulating gene expression. Both genomic and epigenomic outliers were found in genomic regions enriched for genes with biological functions related to the nervous system, immunity, or behavioural, hormonal and stress responses. Interestingly, comparisons across the three pairs of city-forest populations suggested little parallelism in both genetic and epigenetic responses. Our results confirm, at both the genetic and epigenetic levels, hypotheses of polygenic and largely non-parallel mechanisms of rapid adaptation in novel environments such as urbanized areas.

The intensification of warming-induced mass-mortalities in invertebrate populations is a critical phenomenon that affects many regions worldwide, including temperate ones. Mesophotic zones (from 30 to 150 meters depth) have been hypothesized to provide refuge from climate change to gorgonian populations, a promise for re-seeding damaged or destroyed shallow populations. Using a proteomic approach, we investigated the responses and acclimatization ability of the yellow gorgonian Eunicella cavolini along an environmental gradient following reciprocal transplantations between shallow (20m) and mesophotic (70m) zones. Our results suggested that yellow gorgonians from mesophotic waters exhibit a more plastic response when transplanted into shallow waters, compared to shallow gorgonians when placed at 70m. Colonies transplanted from mesophotic to shallow waters presented a down-regulation of immune response compared to colonies that stayed at 70m. Despite immunodepression, transplanted colonies displayed no signs of necrosis or apoptosis, underscoring the potential acclimation capacity of mesophotic populations. Under future climate change scenarios, Eunicella cavolini populations could thus exhibit physiological plasticity in the face of environmental stress, suggesting that no physiological barrier may limit natural colonization from mesophotic populations. This analysis provides new insights into the cellular and molecular responses of gorgonians to environmental changes.