title: Contrasting global genetic patterns in two biologically similar, widespread and invasive Ciona species (Tunicata, Ascidiacea).
abstract: Human-mediated dispersal interplays with natural processes and complicates understanding of the biogeographical history of species. This is exemplified by two invasive tunicates, Ciona robusta (formerly Ciona intestinalis type A) and C. intestinalis (formerly Ciona intestinalis type B), globally distributed and sympatric in Europe. By gathering new mitochondrial sequences that were merged with published datasets, we analysed genetic patterns in different regions, with a focus on 1) their sympatric range and 2) allopatric populations in N and S America and southern Europe. In the sympatric range, the two species display contrasting genetic diversity patterns, with low polymorphism in C. robusta supporting the prevalent view of its recent introduction. In the E Pacific, several genetic traits support the non-native status of C. robusta. However, in the NE Pacific, this appraisal requires a complex scenario of introduction and should be further examined supported by extensive sampling efforts in the NW Pacific (putative native range). For C. intestinalis, Bayesian analysis suggested a natural amphi-North Atlantic distribution, casting doubt on its non-native status in the NW Atlantic. This study shows that both natural and human-mediated dispersal have influenced genetic patterns at broad scales; this interaction lessens our ability to confidently ascertain native vs. non-native status of populations, particularly of those species that are globally distributed.
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 6, CNRS, UMR 7144, Equipe Div&Co, Station Biologique de Roscoff, Place Georges Teissier, 29680 Roscoff, France.
authors.forename: Sarah
authors.initials: S
authors.lastname: Bouchemousse
authors.affiliation: Marine Biological Association, Citadel Hill, Plymouth PL1 2PB, UK.
authors.forename: John D D
authors.initials: JD
authors.lastname: Bishop
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 6, CNRS, UMR 7144, Equipe Div&Co, Station Biologique de Roscoff, Place Georges Teissier, 29680 Roscoff, France.
authors.forename: Frédérique
authors.initials: F
authors.lastname: Viard
mesh_terms: D000818:Animals; D002938:Ciona intestinalis / Q000145:classification* / Q000235:genetics*; D004272:DNA, Mitochondrial / Q000235:genetics; D005060:Europe; D014644:Genetic Variation; D009656:North America; D058974:Phylogeography; D017422:Sequence Analysis, DNA; D013020:South America
chemical_list: D004272:DNA, Mitochondrial