ALBERT

Description: The largest and commercially appealing mineral deposits can be found in the abyssal sea floor of the Clarion-Clipperton Zone (CCZ), a polymetallic nodule province, in the NE Pacific Ocean, where experimental mining is due to take place. In anticipation of deep-sea mining impacts, it has become essential to rapidly and accurately assess biodiversity. For this reason, ophiuroid material collected during eight scientific cruises from five exploration licence areas within CCZ, one area being protected from mining (APEI3, Area of Particular Environmental Interest) in the periphery of CCZ and the DISturbance and re-COLonisation (DISCOL) Experimental Area (DEA), in the SE Pacific Ocean, was examined. Specimens were genetically analysed using a fragment of the mitochondrial cytochrome c oxidase subunit I (COI). Maximum-likelihood and neighbour-joining trees were constructed, while four tree-based and distance-based methods of species delineation (automatic barcode gap discovery, ABGD; barcode index numbers, BINs; general mixed Yule–coalescent, GMYC; multi-rate Poisson tree process, mPTP) were employed to propose secondary species hypotheses (SSHs) within the ophiuroids collected. The species delimitation analyses' concordant results revealed the presence of 43 deep-sea brittle star SSHs, revealing an unexpectedly high diversity and showing that the most conspicuous invertebrates in abyssal plains have been so far considerably underestimated. The number of SSHs found in each area varied from five (IFREMER area) to 24 (BGR (Federal Institute for Geosciences and Natural Resources, Germany) area) while 13 SSHs were represented by singletons. None of the SSHs were found to be present in all seven areas while the majority of species (44.2 %) had a single-area presence (19 SSHs). The most common species were Ophioleucidae sp. (Species 29), Amphioplus daleus (Species 2) and Ophiosphalma glabrum (Species 3), present in all areas except APEI3. The biodiversity patterns could be mainly attributed to particulate organic carbon (POC) fluxes that could explain the highest species numbers found in BGR (German contractor area) and UKSRL (UK Seabed Resources Ltd, UK contractor area) areas. The five exploration contract areas belong to a mesotrophic province, while conversely the APEI3 is located in an oligotrophic province, which could explain the lowest diversity as well as very low similarity with the other six study areas. Based on these results the representativeness and the appropriateness of APEI3 to meet its purpose of preserving the biodiversity of the CCZ fauna are questioned. Finally, this study provides the foundation for biogeographic and functional analyses that will provide insight into the drivers of species diversity and its role in ecosystem function.

Description: The deep ocean is the largest biome on Earth and yet it is among the least studied environments of our planet. Life at great depths requires several specific adaptations, however their molecular mechanisms remain understudied. We examined patterns of positive selection in 416 genes from four brittle star (Ophiuroidea) families displaying replicated events of deep-sea colonization (288 individuals from 216 species). We found consistent signatures of molecular convergence in functions related to protein biogenesis, including protein folding and translation. Five genes were recurrently positively selected, including CCTα (Chaperonin Containing TCP-1 subunit α), which is essential for protein folding. Molecular convergence was detected at the functional and gene levels but not at the amino-acid level. Pressure-adapted proteins are expected to display higher stability to counteract the effects of denaturation. We thus examined in silico local protein stability of CCTα across the ophiuroid tree of life (967 individuals from 725 species) in a phylogenetically-corrected context and found that deep sea-adapted proteins display higher stability within and next to the substrate-binding region, which was confirmed by in silico global protein stability analyses. This suggests that CCTα not only displays structural but also functional adaptations to deep water conditions. The CCT complex is involved in the folding of ∼10% of newly synthesized proteins and has previously been categorized as ‘cold-shock’ protein in numerous eukaryotes. We thus propose that adaptation mechanisms to cold and deep-sea environments may be linked and highlight that efficient protein biogenesis, including protein folding and translation, are key metabolic deep-sea adaptations.

Description: Wallace's Line demarcates the transition between the differentiated regional faunas of Asia and Australia. However, while patterns of biotic differentiation across these two continental landmasses and the intervening island groups (Wallacea) have been extensively studied, patterns of long-term dispersal and diversification across this region are less well understood. Frogmouths (Aves: Podargidae) are a relictual family of large nocturnal birds represented by three extant genera occurring, respectively, in Asia, ‘Sahul’ (Australia and New Guinea) and the Solomon Islands, thus spanning Wallace's Line. We used new mitochondrial genomes from each of the extant frogmouth genera to estimate the timeline of frogmouth evolution and dispersal across Wallace's Line. Our results suggest that the three genera diverged and dispersed during the mid-Cenozoic between approximately 30 and 40 Mya. These divergences are among the oldest inferred for any trans-Wallacean vertebrate lineage. In addition, our results reveal that the monotypic Solomons frogmouth ( Rigidipenna inexpectata ) is one of the most phylogenetically divergent endemic bird lineages in the southwest Pacific. We suggest that the contemporary distribution of exceptionally deep divergences among extant frogmouth lineages may be explained by colonization of, and subsequent long-term persistence on, island arcs in the southwest Pacific during the Oligocene. These island arcs may have provided a pathway for biotic dispersal out of both Asia and Australia that preceded the formation of extensive emergent landmasses in Wallacea by at least 10 million years.