ITS2 in calanoid copepods: reconstructing phylogenetic relationships and identifying a newly introduced species in the Mediterranean

Abstract

Phylogenetic inference and molecular taxonomy are becoming increasingly important approaches to classical morphological systematics and marine ecology. The number of molecular markers suitable for such goals is quite high, but general use restricts the list to a few of them, mainly mitochondrial (namely cytochrome c oxidase subunit I, COI and Cytochrome b), especially in copepods. The ribosomal cistronic regions have been widely used for broad phylogenetic analyses in different taxa. Among them, the internal transcribed spacers (ITS rDNA) are powerful tools for phylogenetic reconstructions at the different taxonomic levels, although not yet extensively used for copepods. In the present work, we tested the suitability of ITS2 rDNA marker to reconstruct the phylogenetic relationships of calanoid copepods using sequences retrieved from GenBank, complementing the phylogenetic positions of the species studied with their morphological and ecological traits. Through ITS2 rDNA we provided the first molecular evidence for the invasive calanoid Pseudodiaptomus marinus from the Mediterranean Sea (Lake Faro, Sicily, Italy), and compared it with the GenBank ITS2 sequences for P. marinus from Korea and other calanoid species. The divergence of the sequences of our P. marinus from those of Korean specimens was quite prominent (4.4%) and allowed us to hypothesise either a new forma living in the Mediterranean or a cryptic species. This study highlights the appropriateness of ITS2 for phylogenetic reconstructions and species identification, as well as for barcoding, meta-barcoding and phylogeographic approaches, and evidences the need for a more thorough knowledge of ribosomal regions in copepods from different sites.

Response to salinity and temperature changes in the alien Asian copepod Pseudodiaptomus marinus introduced in the Black Sea

“…The salinity and temperature tolerance of P. marinus reported here confirms the spreading potential of this species, together with behavioral plasticity (Sabia et al, ; Sabia et al, ), possible presence of different morphs (Sabia, Di Capua, Percopo, Uttieri, & Amato, ), and resistance to metallic stress (Tlili, Ovaert, Souissi, Ouddane, & Souissi, ). P. marinus was first recorded in Sevastopol Bay at the end of September 2016 in just a few number of individuals, but by November 2016 a numerous population was already established (Garbazey et al, ).…”

Pseudodiaptomus marinus Sato, 1913 in the Black Sea: morphology, genetic analysis, and variability in seasonal and interannual abundance

“…P. marinus was recorded in new areas of the Pacific Ocean since the 1940s ( Brodskii, 1948 ; Razouls et al, 2005–2020 ;–ref in Brylinski et al 2012) . Since 2007, the species has rapidly expanded into European waters ( De Olazabal & Tirelli, 2011 ; Sabia et al, 2017 ; Uttieri et al, 2020 ). The first appearance of P. marinus was reported to be in the Gulf of Izmir, Aegean Sea, Turkey (S Besiktepe, pers.…”

“…Currently, P. marinus is one of the most widespread copepods in the World Ocean. A number of studies have revealed P. marinus ’s invasion history and specific biological and behavioural traits that demonstrate its ability to successfully adapt to new environments ( Brylinski et al, 2012 ; Sabia et al, 2017 ; Uttieri et al, 2020 ).…”

“…The integration of classical morphology and molecular approaches has provided new prospects for solving taxonomic challenges and other complicated aspects of NIS biology and ecology ( Sabia et al, 2017 ; Uttieri et al, 2020 ). Nevertheless, molecular analysis has been carried out on only a small number of P. marinus specimens from only a few points in the World Ocean, which has limited the discussion of its dispersal pathways and possible origins ( Albaina et al, 2016 ; Uttieri et al, 2020 ).…”

Genetic analysis on <i>Pseudodiaptomus inopinus</i> (Copepoda, Calanoida) species complex in Japan: revival of the species name of <i>P. japonicus</i> Kikuchi, 1928

“…Based on these morphological and geographical facts, we considered that these forms are different species, but that a genetic comparison between the two forms would be necessary for the final conclusion as to their phylogenetic relationships. Hence, we analyzed their genetic differences, using the mitochondrial cytochrome c oxidase subunit I (COI) and the nuclear ribosomal internal transcribed spacer 1 (ITS1) regions, the latter of which is more variable than the ITS2 region and was recommended for inter-population surveys of Pseudodiaptomus by Sabia et al (2017). Soh et al (2012) analyzed the same regions of P. koreanus, the species to be compared with the present specimens.…”