A new method for population studies of Halichondria panicea : comparing suitability of mtDNA and rRNA as genetic markers

Abstract

Mitochondrial DNA (mtDNA) gene cytochrome oxidase subunit (CO1) is a barcode frequently used across the metazoan tree for species and population level analyses due to its mutation rate and resolution. However, in many anthozoan species, the unsuitability of mtDNA for population studies has been explored in the literature, due to its low evolution rates and high conservancy between conspecifics. The rRNA 28S region has been suggested to provide higher resolution, but not fully investigated. In this study, partial sequences of mtDNA CO1 (N=43) and rRNA 28S-region (N=30) of individuals of Halichondria panicea were taken from four populations around the North Sea. These were analysed to determine whether rRNA can provide more information at a population level, than the mtDNA counterpart. Very low variability was observed in the mtDNA data, identifying only 8 haplotypes, with a low nucleotide diversity of 0.00190, whereas rRNA identified 20 haplotypes and had a nucleotide diversity of 0.079424. Overall, mtDNA has the capacity to strongly identify species, but provides no useful information at a population level due to the very high conservancy between populations, even those separated by >2000km. rRNA, on the other hand, was able to reveal significant population structure and provide more detailed insight into their genetic diversity. We suggest this rRNA 28S region barcode to be more suitable for population studies than the mtDNA CO1 region for Halichondria panicea.