High-efficiency 18S microalgae barcoding by coalescent, distance and character-based approaches: a test in Chlorella and Scenedesmus

Abstract

The relatively conserved 18S is often used in the phylogenetic analysis of microalgae. However, whether it can really help in barcoding microalgae needs to be evaluated. In this study the multiple approaches of coalescent, distance and character-based barcoding are first employed in Chlorella and Scenedesmus to test the efficiency of 18S sequences for barcoding green microalgae. We show that most Chlorella and Scenedesmus species, including the cryptic species, can be distinguished by 18S sequences with all coalescent General Mixed Yule-coalescent (GMYC), poisson tree process (PTP), and P ID, distance (ABGD) and character-based approaches. Both GMYC and PTP analyses produce more genetic groups. The P ID and ABGD analyses only cluster some species. All species (apart from a few of lineages) can be separated in character-based barcoding analysis with more than three character attributes. In comparison with previous barcoding results with rbcL, tufA, ITS and 16S, 18S produces good resolution in identifying Chlorella and Scenedesmus. Our results reveal that 18S is highly efficient in identifying taxa of green microalgae at species level, based on a combination of multiple barcoding approaches. Combining 18S with other gene markers may be useful in barcoding microalgae.