title: Phylogenetic analysis of two Plectus mitochondrial genomes (Nematoda: Plectida) supports a sister group relationship between Plectida and Rhabditida within Chromadorea.
abstract: Plectida is an important nematode order with species that occupy many different biological niches. The order includes free-living aquatic and soil-dwelling species, but its phylogenetic position has remained uncertain. We sequenced the complete mitochondrial genomes of two members of this order, Plectus acuminatus and Plectus aquatilis and compared them with those of other major nematode clades. The genome size and base composition of these species are similar to other nematodes; 14,831 and 14,372bp, respectively, with AT contents of 71.0% and 70.1%. Gene content was also similar to other nematodes, but gene order and coding direction of Plectus mtDNAs were dissimilar from other chromadorean species. P. acuminatus and P. aquatilis are the first chromadorean species found to contain a gene inversion. We reconstructed mitochondrial genome phylogenetic trees using nucleotide and amino acid datasets from 87 nematodes that represent major nematode clades, including the Plectus sequences. Trees from phylogenetic analyses using maximum likelihood and Bayesian methods depicted Plectida as the sister group to other sequenced chromadorean nematodes. This finding is consistent with several phylogenetic results based on SSU rDNA, but disagrees with a classification based on morphology. Mitogenomes representing other basal chromadorean groups (Araeolaimida, Monhysterida, Desmodorida, Chromadorida) are needed to confirm their phylogenetic relationships.
authors.affiliation: Freshwater Biodiversity Research Division, Nakdonggang National Institute of Biological Resources, Sangju, Gyeongsangbuk-do 37242, Republic of Korea; Division of EcoScience, Ewha Womans University, 52 Ewhayeodae-gil, Seodaemungu, Seoul 03760, Republic of Korea.
authors.forename: Jiyeon
authors.initials: J
authors.lastname: Kim
authors.affiliation: Division of EcoScience, Ewha Womans University, 52 Ewhayeodae-gil, Seodaemungu, Seoul 03760, Republic of Korea.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Kern
authors.affiliation: Division of Environmental Science and Ecological Engineering, College of Life Sciences and Biotechnology, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, Republic of Korea.
authors.forename: Taeho
authors.initials: T
authors.lastname: Kim
authors.affiliation: Department of Stem Cell and Regenerative Biology, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 05029, Republic of Korea.
authors.forename: Mikang
authors.initials: M
authors.lastname: Sim
authors.affiliation: Department of Stem Cell and Regenerative Biology, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 05029, Republic of Korea.
authors.forename: Jaebum
authors.initials: J
authors.lastname: Kim
authors.affiliation: Division of EcoScience, Ewha Womans University, 52 Ewhayeodae-gil, Seodaemungu, Seoul 03760, Republic of Korea.
authors.forename: Yuseob
authors.initials: Y
authors.lastname: Kim
authors.affiliation: School of Biological Sciences and Technology, Chonnam National University, Gwangju 500-757, Republic of Korea.
authors.forename: Chungoo
authors.initials: C
authors.lastname: Park
authors.affiliation: Department of Entomology and Nematology, University of California, Davis, CA 95616, USA.
authors.forename: Steven A
authors.initials: SA
authors.lastname: Nadler
authors.affiliation: Division of EcoScience, Ewha Womans University, 52 Ewhayeodae-gil, Seodaemungu, Seoul 03760, Republic of Korea. Electronic address: jkpark@ewha.ac.kr.
authors.forename: Joong-Ki
authors.initials: JK
authors.lastname: Park
mesh_terms: D000818:Animals; D001499:Bayes Theorem; D005075:Biological Evolution; D004247:DNA / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D004272:DNA, Mitochondrial / Q000737:chemistry / Q000145:classification / Q000235:genetics; D054629:Genome, Mitochondrial; D009348:Nematoda / Q000145:classification* / Q000235:genetics; D010802:Phylogeny; D017168:Rhabditida / Q000145:classification* / Q000235:genetics
chemical_list: D004272:DNA, Mitochondrial; D004247:DNA
keywords: Mitogenome; Molecular phylogeny; Nematoda; Plectida; Plectus acuminatus; Plectus aquatilis