A genetic dimension to deep-sea biodiversity

Our knowledge of deep-sea biodiversity is based almost entirely on morpholo gical distinctions at the species level. Here, we use haplotype variations in the mitochondrial 16S ribosomal gene to assess biodiversity at the genom e level in four deep-sea molluscan morphospecies. Genetic divergence levels among populations of the morphospecies fall within the range of interspeci fic divergence found in coastal marine and aquatic molluscan genera. Result s indicate a rich population structure at the genetic level in deep-sea mol lusks, and suggest the possibility that some seemingly coherent morphospeci es are composed of cryptic species. (C) 1999 Elsevier Science Ltd. All righ ts reserved.