Global genetic homogeneity in the deep-sea foraminiferan Epistominella exigua (Rotaliida: Pseudoparrellidae)

Epistominella exigua is one of the most common deep-sea foraminiferal morphospecies and has a world-wide
distribution. A recent molecular study revealed high genetic similarity between Arctic, Atlantic and Antarctic
populations of this species. Here, we show that the small-subunit (SSU) and internal transcribed spacer (ITS) rDNA
sequences of an E. exigua population from Pacific are almost identical to those reported previously from the other three
oceans. This result confirms the genetic homogeneity of E. exigua, which contrasts with the prevalence of highly
differentiated populations in planktonic and shallow-water benthic foraminiferans. We discuss special features of
diversifications mechanisms in the deep sea that may be responsible for the lack of genetic differentiation and global
distribution of some meiofauna species.