Species Distribution and Population Connectivity of Deep-Sea Mussels at Hydrocarbon Seeps in the Gulf of Mexico

PLoS One. 2015 Apr 10;10(4):e0118460. doi: 10.1371/journal.pone.0118460. eCollection 2015.

Abstract

Hydrocarbon seepage is widespread and patchy in the Gulf of Mexico, and six species of symbiont containing bathymodiolin mussels are found on active seeps over wide and overlapping depth and geographic ranges. We use mitochondrial genes to discriminate among the previously known and a newly discovered species and to assess the connectivity among populations of the same species in the northern Gulf of Mexico (GoM). Our results generally validate the morphologically based distribution of the three previously known GoM species of Bathymodiolus, although we found that approximately 10% of the morphologically based identifications were incorrect and this resulted in some inaccuracies with respect to their previously assigned depth and geographical distribution patterns. These data allowed us to confirm that sympatry of two species of Bathymodiolus within a single patch of mussels is common. A new species of bathymodiolin, Bathymodiolus sp. nov., closely related to B. heckerae was also discovered. The two species live at the same depths but have not been found in sympatry and both have small effective population sizes. We found evidence for genetic structure within populations of the three species of Bathymodiolinae for which we had samples from multiple sites and suggest limited connectivity for populations at some sites. Despite relatively small sample sizes, genetic diversity indices suggest the largest population sizes for B. childressi and Tamu fisheri and the smallest for B. heckerae and B. sp. nov. among the GoM bathymodiolins. Moreover, we detected an excess of rare variants indicating recent demographic changes and population expansions for the four species of bathymodiolins from the Gulf of Mexico.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • DNA, Mitochondrial / genetics
  • Ecosystem
  • Evolution, Molecular
  • Genes, Mitochondrial
  • Genetic Variation
  • Gulf of Mexico
  • Hydrocarbons
  • Mytilidae / classification*
  • Mytilidae / genetics*
  • Phylogeny
  • Population Dynamics
  • Species Specificity

Substances

  • DNA, Mitochondrial
  • Hydrocarbons

Grant support

This work was supported by a Lavoisier grant from the French Ministry of Foreign Affairs and by subcontracts to CRF from BOEM contracts 1435-01-05-39187 and M08PC20038 to TDI Brooks, with vessel and submergence facilities support provided by National Oceanic and Atmospheric Administration’s Office of Ocean Exploration and Research. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.