Reference DNA barcodes and other mitochondrial markers for identifying Caribbean Octocorals

Area of Science:

• Marine Biology
• Molecular Ecology
• Genomics

Background:

• DNA barcoding is crucial for metazoan diversity assessment.
• Standard markers like cytochrome oxidase c subunit I (COI) and 16S ribosomal RNA (16S) have limitations for "basal" metazoan phyla.
• Metabarcoding studies often utilize these markers despite potential limitations.

Purpose of the Study:

• To create a reference barcode dataset for 27 Caribbean octocoral species.
• To compare the utility of COI and 16S markers against other commonly used octocoral markers.
• To assess the effectiveness of DNA barcoding for octocoral species identification.

Main Methods:

• Sequencing of mitochondrial DNA fragments: cytochrome oxidase c subunit I (COI), 16S ribosomal RNA (16S), and NADH dehydrogenase subunits (ND2, ND6, ND4L).
• Analysis of genetic variation and sequence differences among 27 Caribbean octocoral species.
• Comparison of marker performance for distinguishing genera and species.

Main Results:

• COI and 16S markers effectively distinguished most common Caribbean octocoral genera based on sequence differences.
• Genera like Gorgonia and Antillogorgia were distinguishable by unique haplotypes, but genetic differences were too small for distance-based methods.
• Genera Plexaura, Pseudoplexaura, and Eunicea were indistinguishable from each other, suggesting rapid radiation.

Conclusions:

• Cytochrome oxidase c subunit I (COI) and 16S ribosomal RNA (16S) are useful for distinguishing many Caribbean octocoral genera.
• Limited genetic divergence in certain genera necessitates careful marker selection and analytical approaches for species identification.
• The findings support the hypothesis of a rapid endemic radiation event within the Caribbean for genera like Plexaura, Pseudoplexaura, and Eunicea.