Sci Rep. 2018 Jan 24;8(1):1480. doi:10.1038/s41598-018-19811-2

Malfant M, Darras S and Viard F.

Coupling molecular data and experimental crosses sheds light about species delineation: a case study with the genus Ciona.

C. robusta sperm can fertilise C. intestinalis eggs, but fertilisation rates in the converse crosses are much lower. Phylogenetic analysis of mitochondrial CO1 sequences suggests that there are no hybrids in wild populations.