Abstract
Phyllodiaptomus tunguidus (Copepoda: Calanoida) is largely endemic to and widespread in freshwater in southern China, where it inhabits a complex landscape from lowland to highland across an elevation gradient of 2000m. A deep genetic differentiation can be expected between its most distant geographic populations. Here, we sequenced nine mitogenomes from diverse populations. All mitogenomes contained 37 genes, including 13 protein-coding genes (PCG), two rRNA genes, 22 tRNA genes and one control region. Their base composition, genetic distance and tRNA structure indeed revealed a wide differentiation between mitogenomes. Two P. tunguidus from Guangxi near Vietnam differed from the other seven by up to 10.1%. Their tRNA-Arg had a complete clover-leaf structure, whereas that of the others did not contain an entire dihydrouridine arm. The nine mitogenomes also differed in the length of rRNA. NJ, ML, and Bayesian analyses all split them into two clades, viz. the two P. tunguidus from Guangxi (Clade 1), and the other seven (Clade 2). Both the structure and phylogeny of the mitogenomes suggest that P. tunguidus has complex geographic origin, and its populations in Clade 1 have long lived in isolation from those in Clade 2. They currently reach the level of subspecies or cryptic species. An extensive phylogenetic analysis of Copepoda further verified that Diaptomidae is the most recently diverging family in Calanoida and that P. tunguidus is at the evolutionary apex of the family.
Highlights
IntroductionThey are extremely abundant in freshwater and constitute a major component of most planktonic, benthic and groundwater communities, including semi-terrestrial situations such as damp mosses and leaf litter on forest floors (Boxshall and Jaume, 2000; Boxshall and Defaye, 2008)
Twenty-one genes are on the H-strand (13 Transfer RNA (tRNA), seven protein-coding genes (PCG), and two Ribosomal RNA (rRNA)), while 16 genes are on the L-strand
Combining the ratio of Ka/Ks and the genetic distance, we considered the P. tunguidus from NB and TB a unique lineage compared to the seven from the other sites, and the PCGs gene plays a crucial role in the evolutionary adaption under selection
Summary
They are extremely abundant in freshwater and constitute a major component of most planktonic, benthic and groundwater communities, including semi-terrestrial situations such as damp mosses and leaf litter on forest floors (Boxshall and Jaume, 2000; Boxshall and Defaye, 2008). Of an estimated 13,000 morphospecies known, about 2,800 species inhabit freshwater. Freshwater copepods are comprised of five orders (Calanoida, Harpacticoida, Cyclopoida, Gelyelloida, and Siphonostomatoida; Boxshall and Halsey, 2004). 1986; Blanco-Bercial et al, 2011). Diaptomidae (Sars, 1903) is the dominant family in inland waters of Europe, Asia, North America, Africa, and northern low-altitude South America
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