Novel mitochondrial gene rearrangements pattern in the millipede
Polydesmus sp. GZCS-2019 and phylogenetic analysis of the Myriapoda
Abstract
The subphylum Myriapoda included four extant classes (Chilopoda,
Symphyla, Diplopoda and Pauropoda), but very little work has been done
to explore their phylogenetic relationships. Herein, we determined the
complete mitochondrial genome of Polydesmus sp. GZCS-2019 (Myriapoda:
Polydesmida) and the mitochondrial genomes are circular molecules of
15,036 bp, with all genes encoded on + strand. The A+T content is
66.1%, making the chain asymmetric, and exhibits negative AT-skew
(-0.236). Several genes rearrangements were detected and we propose a
new rearrangement model: “TD (N\R) L + C” based on the
genome-scale duplication + (non-random/random) loss + recombination.
Phylogenetic analyses demonstrated that Chilopoda and Symphyla both were
monophyletic group, whereas Pauropoda was embedded in Diplopoda to form
the Dignatha. Divergence time showed the first split of Myriapoda
occurred between the Chilopoda and other classes (Wenlock period of
Silurian). We combine phylogenetic analysis, divergence time, and gene
arrangement to yield valuable insights into the evolutionary history and
classification relationship of Myriapoda and these results support a
monophyletic Progoneata and the relationship (Chilopoda + (Symphyla +
(Diplopoda + Pauropoda))) within Myriapod. Our results help to better
explain the gene rearrangement events of the invertebrate mitogenome and
lay the foundation for further phylogenetic study of Myriapoda.