Phylogeographic and morphological analysis ofBotrylloides nigerHerdman, 1886 from the northeastern Mediterranean Sea

Abstract

AbstractBotrylloides nigeris an invasive marine filter-feeding invertebrate that is believed to originate from the West Atlantic region. This species of colonial tunicate has been observed on several locations along the coasts of Israel and around the Suez Canal but it has not yet been reported on the coasts of the northeastern Mediterranean Sea (NEMS), suggesting an ongoing Lessepsian migration. However, the extent of this invasion might be concealed by reports of other potentially misidentified species ofBotrylloides, given that the strong morphological similarities within this genus renders taxonomical identification particularly challenging. In this study, we performed a phylogeographic and morphological analysis ofB. nigerin the NEMS. We collected 241 samples from 8 sampling stations covering 824 km of coastlines of NEMS. We reported 14 different morphotypes, of which the orange-brown, orange and brown-striped morphs were the most abundant. Using the mitochondrial cytochrome C oxidase I (COI), one of the four most commonly used DNA barcoding marker, we identified 4 haplotypes with the Konacık (H4) and the Mezitli (H3) ones being the most diverged. The COI haplotypes clustered with the referenceB. nigersequences from GenBank and separated from sisterBotrylloidesspecies with high confidence. We confirmed our identification using the three additional barcoding markers (Histone 3, 18S rRNA and 28S rRNA), which all matched with over 99% similarity to the reference sequences. In addition, we monitored the Kızkalesi station for a year and applied temporal analysis to the colonies collected. The colonies regressed during winter while resettled and expanded during summer. We performed gene flow analysis on our spatial data that identified a possible population subdivision at the sampling site of Side, which might be caused by a local freshwater input. Overall, we here present the first report on the presence ofBotrylloides nigerin the NEMS, we show that this species is commonly present throughout this region and with a particularly high morphological as well as genomic diversity.