ИСТИНА

The siboglinid tubeworm Sclerolinum contortum is renowned for its ability to colonise a variety of deep-sea habitats where reduced chemicals dominate, such as hydrothermal vents and cold seeps, as well as for its remarkable range, which spans the Arctic to the Antarctic. It apparently achieves this through characteristics typical of weeds, such as broad habitat preferences, tolerances, and wide dispersal capability. However, the ability to colonise such a vast range is highly unusual, even in an environment as seemingly continuous as the deep ocean. Here, we apply population genomic, transcriptomic, and microbiome analyses in S. contortum and the closely-related species S. brattstromi, to explore in greater resolution the connectivity of S. contortum populations, and how individuals from various reduced environments have adapted to diverse settings. Our findings indicate a lack of gene flow between the two polar oceans, with Southern Ocean S. contortum individuals being distinct to others, but found greater support for connectivity between the Gulf of Mexico and the Arctic. Our results also suggest a retention of similar adaptive traits despite separation by distance, and irrespective of habitat type, further supported by selection of the same endosymbiont despite geographic location or chemosynthetic habitat type in S. contortum. Transcriptomic data indicate that adaptation to local habitat conditions likely occurs through the activation of key genes involved in responding to environmental characteristics at the different sites, such as the heat response, nitrate assimilation, and denitrification processes. Our findings represent one of the most comprehensive investigations into a widespread deep-sea taxon, and suggest that pre-adaptation as well as adaptive plasticity are key weedy/invasive characteristics that favour the successful colonisation of new habitats for S. contortum.