Data from: High connectivity across the fragmented chemosynthetic ecosystems of the deep Atlantic Equatorial Belt: efficient dispersal mechanisms or questionable endemism?

Chemosynthetic ecosystems are distributed worldwide in fragmented habitats
harbouring seemingly highly specialized communities. Yet, shared taxa have
been reported from highly distant chemosynthetic communities. These
habitats are distributed in distinct biogeographical regions, one of these
being the so-called Atlantic Equatorial Belt (AEB). Here, we combined
genetic data (COI) from several taxa to assess the possible existence of
cryptic or synonymous species and to detect the possible occurrence of
contemporary gene flow among populations of chemosynthetic species located
on both sides of the Atlantic. Several Evolutionary Significant Units
(ESUs) of Alvinocarididae shrimp and Vesicomyidae bivalves were found to
be shared across seeps of the AEB. Some were also common to hydrothermal
vent communities of the Mid-Atlantic Ridge (MAR), encompassing taxa
morphologically described as distinct species or even genera. The
hypothesis of current or very recent large-scale gene flow among seeps and
vents was supported by microsatellite analysis of the shrimp species
Alvinocaris muricola/Alvinocaris markensis across the AEB and MAR. Two
nonmutually exclusive hypotheses may explain these findings. The
dispersion of larvae or adults following strong deep-sea currents,
possibly combined with biochemical cues influencing the duration of larval
development and timing of metamorphosis, may result in large-scale
effective migration among distant spots scattered on the oceanic seafloor.
Alternatively, these results may arise from the prevailing lack of
knowledge on the ocean seabed, apart from emblematic ecosystems
(chemosynthetic ecosystems, coral reefs or seamounts), where the
widespread classification of endemism associated with many chemosynthetic
taxa might hide wider distributions in overlooked parts of the deep sea.