DNA barcoding and phylogenetics of marine molluscs in Maltese waters

Abstract

The Phylum Mollusca is the second largest phylum with regards to extant species in the kingdom Animalia. Molluscs boast a very high species diversity, being divided into several major taxonomic groups, the most important of which for this study being the classes Gastropoda, Bivalvia, Polyplacophora and Cephalopoda. Marine molluscs are known to have a high level of importance due to their applications in ecosystems, commercial products, ecological/eco-toxicological research, and biomedical research, despite this they are still faced with threats, including habitat loss and degradation, over-exploitation, pollution, climate change and disease.

To formulate effective conservation strategies to counteract these threats, species must first be properly identified to be monitored within specific localities. Although morphological identification is an important tool for this, phenotypic plasticity and subjectivity tend to lead to misidentifications, hence the need for a complementary approach, DNA barcoding. DNA barcoding using the cytochrome c oxidase subunit one gene was used to identify marine mollusc species in Maltese waters, successfully identifying 76 out of 119 specimens. In addition to this, phylogenetic analysis was used to check the evolutionary relationships between analysed specimens.

This study shows that DNA barcoding is an effective method of identifying Maltese marine molluscs of the relevant four classes when paired with morphological identification, as it bypasses issues such as phenotypic plasticity, damaged specimens, cryptic species complexes and different life stages and could identify species relevant to conservation including invasive and vulnerable species.

Future studies should utilise other primers and DNA markers and to test their effectiveness on marine molluscs. Sampling should also be done in more localities to assess Maltese marine mollusc biodiversity more effectively.