Abstract
BackgroundDeep-sea hydrothermal vent animals occupy patchy and ephemeral habitats supported by chemosynthetic primary production. Volcanic and tectonic activities controlling the turnover of these habitats contribute to demographic instability that erodes genetic variation within and among colonies of these animals. We examined DNA sequences from one mitochondrial and three nuclear gene loci to assess genetic diversity in the siboglinid tubeworm, Riftia pachyptila, a widely distributed constituent of vents along the East Pacific Rise and Galápagos Rift.ResultsGenetic differentiation (FST) among populations increased with geographical distances, as expected under a linear stepping-stone model of dispersal. Low levels of DNA sequence diversity occurred at all four loci, allowing us to exclude the hypothesis that an idiosyncratic selective sweep eliminated mitochondrial diversity alone. Total gene diversity declined with tectonic spreading rates. The southernmost populations, which are subjected to superfast spreading rates and high probabilities of extinction, are relatively homogenous genetically.ConclusionsCompared to other vent species, DNA sequence diversity is extremely low in R. pachyptila. Though its dispersal abilities appear to be effective, the low diversity, particularly in southern hemisphere populations, is consistent with frequent local extinction and (re)colonization events.
Highlights
Deep-sea hydrothermal vent animals occupy patchy and ephemeral habitats supported by chemosynthetic primary production
Tectonic spreading at Eastern Pacific vents (Figure 1C) varies from moderate rates (65 mm/yr) along the Galápagos Rift (GAR) to fast rates (85-116 mm/yr) along the northern East Pacific Rise (NEPR) and superfast rates (142-158 mm/yr) along the southern EPR (SEPR)
We examined DNA sequences from three independent nuclear loci and another mitochondrial locus, Cytochrome b (Cytb), from R. pachyptila
Summary
Deep-sea hydrothermal vent animals occupy patchy and ephemeral habitats supported by chemosynthetic primary production. Volcanic and tectonic activities controlling the turnover of these habitats contribute to demographic instability that erodes genetic variation within and among colonies of these animals. The number of colonists, their sources (i.e. migrant vs propagule pools), and ongoing rates of gene flow all affect the degree to which demographic instability affects geographical differentiation [5,6,7]. These parameters are rarely known; instead they are commonly. Eastern Pacific vents (Figure 1C) that host R. pachyptila are ephemeral, persisting for a few years to several decades before fluid conduits are blocked, magma supplies shift, or lava flows extirpate local communities [17]. Cycles of habitat disturbance associated with these events are expected to favor organisms with rapid individual growth rates, early reproduction, and effective dispersal capabilities [20]
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