Phylogenetics, biogeography and population genetics of the ascidian Botryllus schlosseri in the Mediterranean Sea and beyond

Eitan Reem, Jacob Douek, Guy Paz, Gadi Katzir, Baruch Rinkevich

Research output: Contribution to journalArticlepeer-review


The wide distribution of the ascidian Botryllus schlosseri along the Mediterranean coasts has been documented since the eighteenth century. However, despite copious documentation, analyses of dispersal modes and genetic profiles were limited to local populations or restricted regions. In order to get a pan-Mediterranean overview, 288 specimens from 11 populations of B. schlosseri from the western and eastern Mediterranean basins were sampled and analyzed using five microsatellite loci and COI sequences. Both molecular markers revealed high polymorphisms, with 182 microsatellites alleles and 54 COI haplotypes. Overall, Fst, Dest, and COI Фpt values were 0.146, 0.635 and 0.322, respectively, reflecting a high genetic diversity and a significant genetic structure as compared to other B. schlosseri populations worldwide, reflected by substantially higher values for effective number of alleles (Ne) in the Mediterranean. A phylogenetic analysis of the COI sequences resulted in four distinct clades and two molecular operational taxonomic units (OTUs). We recorded a stronger genetic structure among the populations of the eastern basin compared to the western basin (microsatellites Fst = 0.217 versus 0.082; COI Фpt = 0.416 versus 0.171), suggesting either a restricted connectivity between the basins or a stronger genetic drift in each basin. The occurrence of two OTUs and different ecological conditions may also contribute to this finding. Mean Nei's genetic distance in the eastern Mediterranean populations was more than three times higher compared to the western basin. No correlation was observed between geographic and genetic distances (Mantel test), suggesting that maritime transport is the main dispersal vector of B. schlosseri colonies. The possibility that the Mediterranean is a center of diversity for B. schlosseri, and probably its site of origin, is further discussed.

Original languageEnglish
Pages (from-to)221-231
Number of pages11
JournalMolecular Phylogenetics and Evolution
StatePublished - 1 Feb 2017
Externally publishedYes

Bibliographical note

Funding Information:
We thank Y. Yudkovski for the 3D figure preparation, to Mari-Carmen Pineda and Daniel Reem for their support with the implementation of R and Adgenet packages. This study is part of E. Reem’s PhD dissertation and was supported by a grant from the Israel Science Foundation (no. 68/10 ).

Publisher Copyright:
© 2016 Elsevier Inc.


  • COI
  • Dispersal
  • Genetic diversity
  • Microsatellites
  • Phylogenetic analysis
  • Species divergence

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Molecular Biology
  • Genetics


Dive into the research topics of 'Phylogenetics, biogeography and population genetics of the ascidian Botryllus schlosseri in the Mediterranean Sea and beyond'. Together they form a unique fingerprint.

Cite this