Abstract
Characterizing the mitochondrial genomes of reef-building corals, which are crucial for marine ecosystems, offers profound insights into their phylogenetic relationships and evolutionary history. The genus Porites is extensively distributed across the Indo-Pacific region. Nevertheless, few analyses of the mitochondrial genome characteristics of Porites have been performed. Here, we report the sequencing and de novo assembly of the complete mitochondrial genome of Porites cylindrica, a dominant Indo-Pacific reef-building coral. Subsequently, a comparative phylogenetic analysis was performed using this new assembly and 12 publicly available mitogenomes derived from 10 Porites species. Mitochondrial genome size was highly conserved, ranging from 18,628 to 18,658 bp across the dataset, and contained 13 protein-coding genes, two rRNA genes, and 1-12 different numbers of tRNAs. Sixteen mutation hotspot regions were identified (ND5-exon1, trnE-ND1, ND1, ND1-CYTB, CYTB, CYTB-trnM, trnM, ATP6, ATP6-ND4, ND4, ND4-rrnS, rrnS, rrnS-COX3, COX3, COX2 and ND5-exon2), and they can serve as effective molecular markers for further phylogenetic analysis and species identification. In addition, microsatellite loci in mitochondrial genomes were highly conserved among various species. Strong purifying selection was observed in the 13 protein-coding genes of Porites. The phylogenetic results support the monophyly of Porites among scleractinian corals, and this genus has diverged into two clades. This study reports the initial assembly and annotation of P. cylindrica, thus providing valuable data for future research on the mitochondrial genomes of Porites.