Marine Biology

, Volume 148, Issue 6, pp 1249–1262 | Cite as

Ecological gradients and relative abundance of native (Mytilus trossulus) and invasive (Mytilus galloprovincialis) blue mussels in the California hybrid zone

  • Caren E. BrabyEmail author
  • George N. Somero
Research Article


Marine communities are experiencing unprecedented rates of species homogenization due to the increasing success of invasive species, but little is known about the mechanisms that allow a species to invade and persist in a new habitat. In central California, native (Mytilus trossulus Gould 1850) and invasive (Mytilus galloprovincialis Lamarck 1819) blue mussels and their hybrids co-exist, providing an opportunity to analyze the mechanisms that determine the distributions of these taxa. Spatial and temporal variation in temperature and salinity and the relative frequencies of these mussel taxa were examined between 2000 and 2004 at four sites in San Francisco Bay and four in Monterey Bay, which were chosen for their different positions along inferred estuarine/oceanic gradients in the hybrid zone. Mussels were genetically identified as the parent species or hybrids by amplifying regions of two species-specific loci: the adhesive byssal thread protein (Glu-5′) and the internal transcribed spacer region of ribosomal DNA (ITS 1). The proportion of M. trossulus at the eight hybrid zone sites correlated negatively with average salinity (R 2=0.60) and positively with maximal temperature (R 2≥0.72), a somewhat unexpected result given what is known about the phylogeography of this species. The proportion of M. galloprovincialis showed the opposite pattern. The proportion of hybrids was correlated neither with habitat temperature nor salinity. Genotypes of mussel populations at an additional 13 sites from Coos Bay, Oregon (latitude 43.35°N) to Long Beach, California (latitude 33.72°N), sampled at various intervals between 2000 and 2004, were also determined. This survey confirmed previous reports that the hybrid zone lies between Monterey and the Cape Mendocino region (latitudes 36.63°N–40.5°N). Within Monterey and San Francisco Bays, however, the temporal comparisons (1990s vs. 2000s) revealed abrupt changes in the proportions of the two parent species and their hybrids on annual and decadal time scales. These changes indicate that the blue mussel populations are in a highly dynamic state. The survey also showed that, regardless of habitat, M. trossulus is consistently of smaller average size than either M. galloprovincialis or hybrids.


Internal Transcribe Space Hybrid Zone Blue Mussel Estuarine Site Modify Cycling Condition 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



This research was supported by (1) the National Sea Grant College Program of the U.S. Department of Commerce’s National Oceanic and Atmospheric Administration under NOAA Grant no. NA06RG0142, project no. RC/Z-179, through the California Sea Grant College Program, and in part by the California State Resources Agency; (2) the Partnership for Interdisciplinary Study of Coastal Oceans (PISCO)(this is PISCO publication #196), (3) National Science Foundation grant IBN-0133184, and (4) the Earl and Ethel Myers Marine Biological and Oceanographic Trust. This work benefited from the aid of many especially including J.P. Lopez, M. Chaney, M. Phillips, Dr. G. Hofmann, Dr. A. Whitmer, and C. Rerig. The experiments contained herein comply with the current laws of the United States, in which they were performed.


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Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  1. 1.Monterey Bay Aquarium Research InstituteMoss LandingUSA
  2. 2.Hopkins Marine Station, Department of Biological SciencesStanford UniversityPacific GroveUSA

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