DNA barcoding cannot discriminate between Sardinella tawilis and S. hualiensis (Clupeiformes: Clupeidae)

摘要

Sardinella tawilis , the only known freshwater sardinella in the world, is endemic to Taal Lake, Philippines. Previous studies found the Taiwan sardinella, S. hualiensis , to be morphologically very similar to S. tawilis and identified it as the marine sister species of S. tawilis . In this study, DNA barcoding using the mitochondrial cytochrome c oxidase I (COI) gene was carried out to analyze species demarcation in the Sardinella genus, focusing primarily on the relationship between S. tawilis and S. hualiensis . The neighbour-joining (NJ) tree that was constructed using Kimura 2-parameter (K2P) model showed a single clade for the two species with 100% bootstrap support. K2P interspecific genetic divergence ranged from 0% to 0.522%, which is clearly below the suggested 3–3.5% cutoff for species discrimination. Recombination activating gene 1 (RAG1), mitochondrial control region (CR), cytochrome b, 16S rRNA, and S7 markers were used to further validate the results. Sardinella tawilis and S. hualiensis clustered together with a bootstrap support of 99–100% in each of the NJ trees. Low interspecific genetic distances between S. tawilis and S. hualiensis for all the markers except CR could be attributed to incipient allopatric speciation.