Abstract
Complete mitochondrial genomes (mitogenomes) can provide useful information for phylogenetic relationships, gene rearrangement, and molecular evolution. In this study, the complete mitogenomes of two hermit crabs, Dardanus arrosor and Dardanus aspersus, were sequenced for the first time and compared with other published mitogenomes of Paguroidea. Each of the two mitogenomes contains an entire set of 37 genes and a putative control region, but they display different gene arrangements. The different arrangements of the two mitogenomes might be the result of transposition, reversal, and tandem duplication/random loss events from the ancestral pancrustacean pattern. Genome sequence similarity analysis reveals the gene rearrangement in 15 Paguroidea mitogenomes. After synteny analysis between the 15 Paguroidea mitogenomes, an obvious rearranged region is found in D. aspersus mitogenome. Across the 13 protein-coding genes (PCGs) tested, COI has the least and ND6 has the largest genetic distances among the 15 hermit crabs, indicating varied evolution rates of PCGs. In addition, the dN/dS ratio analysis shows that all PCGs are evolving under purifying selection. The phylogenetic analyses based on both gene order and sequence data present the monophyly of three families (Paguridae, Coenobitidae, and Pylochelidae) and the paraphyly of the family Diogenidae. Meanwhile, the phylogenetic tree based on the nucleotide sequences of 13 PCGs shows that two Dardanus species formed a sister group with five Coenobitidae species. These findings help to better understand the gene rearrangement and phylogeny of Paguroidea, as well as provide new insights into the usefulness of mitochondrial gene order as a phylogenetic marker.
Highlights
Complete mitochondrial genomes can provide useful information for phylogenetic relationships, gene rearrangement, and molecular evolution
Four mechanisms have been proposed to account for mitogenomic rearrangements, including tandem duplication/random loss (TDRL) model[21], transfer RNA genes (tRNAs) mis-priming model[22], intramitochondrial recombination model[23], and tandem duplication/non-random loss m odel[24]
Each mitogenome contains a typical set of 37 genes (13 protein-coding genes (PCGs), 22 tRNAs, and two rRNAs) and a putative CR
Summary
Complete mitochondrial genomes (mitogenomes) can provide useful information for phylogenetic relationships, gene rearrangement, and molecular evolution. The phylogenetic tree based on the nucleotide sequences of 13 PCGs shows that two Dardanus species formed a sister group with five Coenobitidae species These findings help to better understand the gene rearrangement and phylogeny of Paguroidea, as well as provide new insights into the usefulness of mitochondrial gene order as a phylogenetic marker. Hermit crabs (the superfamily Paguroidea Latreille, 1802) consist of Coenobitidae, Diogenidae, Paguridae, Parapaguridae, Pylochelidae and Pylojacquesidae, with more than 1100 species inhabiting diverse biotopes from intertidal to deep s eas[26]. They represent an intermediate group of crustaceans from Macrura to Brachyura, which occupy an important position in crustacean e volution[27]. The phylogenetic location of the genus Dardanus has not been well resolved
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