Abstract
Dispersal ability and environmental adaptability are profoundly associated with colonization and habitat segregation of deep-sea animals in chemosynthesis-based communities, because deep-sea seeps and vents are patchily distributed and ephemeral. Since these environments are seemingly highly different, it is likely that vent and seep populations must be genetically differentiated by adapting to their respective environments. In order to elucidate dispersal ability and environmental adaptability of deep-sea mussels, we determined mitochondrial ND4 sequences of Bathymodiolus platifrons and B. japonicus obtained from seeps in the SagamiBayand vents in the Okinawa Trough. Among more than 20 species of deep-sea mussels, only three species in the Japanese waters including the above species can inhabit both vents and seeps. We examined phylogenetic relationships, genetic divergences (Fst), gene flow (Nm), and genetic population structures to compare the seep and vent populations. Our results showed no genetic differentiation and extensive gene flow between the seep and vent populations, indicating high dispersal ability of the two species, which favors colonization in patchy and ephemeral habitats. Our results also indicate that the environmental type (vent or seep) is not the primary factor responsible for habitat segregation in the two species.
Highlights
Deep-sea vents and seeps flourish dense biological assemblages, i.e., chemosynthesis-based communities, which contain endemic animals such as vesicomyid clams, Provaniid gastropods, and vestimentiferan tubeworms whose primary production is based on bacterial chemosynthesis [1]
In the phylogeny of bathymodioline and related mussels constructed based on the concatenated sequences of mitochondrial ND4 and COI [23], the four species, B. childressi, B. platifrons, B. japonicus, and B. mauritanicus, formed a marginally supported cluster in Group 1
The phylogenetic relationships of the four species with an outgroup species B. securiformis was depicted (Figure 2) based on the ND4 sequences including all the specimens of B. platifrons and B. japonicus used in this study
Summary
Deep-sea vents and seeps flourish dense biological assemblages, i.e., chemosynthesis-based communities, which contain endemic animals such as vesicomyid clams, Provaniid gastropods, and vestimentiferan tubeworms whose primary production is based on bacterial chemosynthesis [1]. Deep-sea vents and seeps are patchily distributed and separated from each other by a few hundred kilometers in vent sectors and by hundreds of meters to a few kilometers in vent fields within the vent sector [2]. One of the topics in deep-sea biology is how those animals can disperse to maintain the communities and avoid extinction and how they can be isolated to accumulate genetic differentiations leading to consequent speciation. The dispersal ability of deep-sea animals is profoundly associated with the evolutionary process of deep-sea animals
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