The accurate taxonomic identity for the worldwide-distributed invasive ascidian Botryllus schlosseri has not been resolved. Employing molecular tools, primarily mtDNA, previous studies unveiled five divergent clades (A-E), suggesting a complex of five cryptic species. A recent study allocated clades A and E to different species. Here, worldwide B. schlosseri's COI distribution map has been drawn, based on 2927 specimens, elucidating 160 haplotypes (100 singletons). Clade A emerged as the most abundant and globally widespread, while other clades had more limited distributions (primarily B, C). Inter-clade and intra-clade divergences were similar, with no clear barcoding gaps between the clades, illuminating no more than two putative OTUs. Network analyses for the genetic similarities among the clades' haplotypes identified different groups, depending on threshold values and away from the suggested clades' boundaries. Three additional genetic markers (H3, 18S, 28S) disclosed clade A, segregating from other clades and clades D and E strongly integrating. Allorecognition assays between clades resulted in indifference and rejection outcomes, characteristics of the within-species allorecognition repertoire. The question as to whether Botryllus schlosseri is a single species or a species complex is further discussed, leading to the assertion that while it is a widely variable species, there is not enough evidence for its designation as a species complex.
|Number of pages||14|
|Journal||Journal of the Marine Biological Association of the United Kingdom|
|State||Published - 2022|
Bibliographical noteFunding Information:
We thank G. Paz for technical support and graphic design, to G. Greenbaum for assisting in the implementation of the NetStruct software, to G. Achaz and S. Brouillet from the MNHN for helping with the ABGD results, to D. Reem for assisting with computational issues and to G. Schires and S. Henry from the Roscoff Biological station for friendly support in sampling and rearing the B. shlosseri colonies and finally to X. Turon and two other anonymous reviewers for their most helpful comments. This study was supported by the Israel Science Foundation (to BR no. 172/17), by the United States–Israel Binational Science Foundation (to BR no. 2015012), by the Mediterranean Sea Research Center of Israel (to ER), by the Tauber Bioinformatics Research Center at Haifa University (to ER) and by the ASSEMBLE PLUS project (to ER; European Union's Horizon 2020 research and innovation program, no. 730984).
This study was supported by the Israel Science Foundation (to BR no. 172/17), by the United States Israel Binational Science Foundation (to BR no. 2015012), by the Mediterranean Sea Research Center of Israel (to ER), by the Tauber Bioinformatics Research Center at Haifa University (to ER) and by the ASSEMBLE PLUS project (to ER; European Union's Horizon 2020 research and innovation program, no. 730984).
© The Author(s), 2022. Published by Cambridge University Press on behalf of Marine Biological Association of the United Kingdom.
- Allorecognition assays
- barcoding gap
- genetic markers
- network theory
- phylogenetic analysis
- species delineation
ASJC Scopus subject areas
- Aquatic Science