Long-term population genetic structure of an invasive urochordate: The ascidian Botryllus schlosseri

Eitan Reem, Jacob Douek, Gadi Katzir, Baruch Rinkevich

Research output: Contribution to journalArticlepeer-review


The accelerated pace of marine biological invasions raises questions pertaining to genetic traits and dynamics underlying the successful establishment of invasive species. Current research stresses the importance of multiple introductions and prolonged gene flow as the main sources for genetic diversity, which, along with genetic drift, affect invasive species success. We here attempt to determine the relative contribution of gene flow and mutation rates as sources of genetic variability using the invasive tunicate Botryllus schlosseri as a model. The study was performed over a 13-year period in the Santa Cruz Harbor, California. With a characteristic life history of five generations/year, the Santa Cruz Botryllus population has already experienced approximately 155 generations since the onset of its invasion. The results (278 specimens, 127 scored alleles, five microsatellite loci) support limited gene flow rate (2. 89 × 10-3) and relative genetic isolation. Furthermore, the study population was found to be influenced by both, genetic drift and a high mutation rate (2. 47 × 10-2). These findings were supported by high fluctuations in the frequencies of microsatellite alleles, the appearance of new alleles and the loss of others. The balance between genetic drift and a high mutation rate is further elucidated by the high, stable level of genetic variation. We suggest that rapid mutation rates at the microsatellite loci reflect genome-wide phenomena, helping to maintain high genetic variability in relatively isolated populations. The potential adaptability to new environments is discussed.

Original languageEnglish
Pages (from-to)225-241
Number of pages17
JournalBiological Invasions
Issue number1
StatePublished - Jan 2013
Externally publishedYes

Bibliographical note

Funding Information:
Acknowledgments We thank Alan Templeton and Per Erik Jorde for their constructive remarks and suggestions on earlier drafts. Daniel Reem for help with data analysis, Tim Morley from Santa Cruz Harbor for helpful information and Guy Paz for technical help and figure preparation. This study is part of the PhD dissertation of E. Reem and was supported by grants from the Israel Science Foundation (1342/08 and 68/10).


  • Genetic diversity
  • Genetic drift
  • Invasions
  • Microsatellites
  • Mutations

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Ecology


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