| Gecarcinucid freshwater crabs(Decapoda,Brachyura,Gecarcinucoidea)is the important component of freshwater crabs in China.The distribution range of the Gecarcinucidae Rathbun,1904 covers both the Oriental and Australasian zoogeographic regions,and it is the only freshwater crab family that crosses Wallace's Line,indicating that this family has strong dispersal abilities.It is an ideal material for studying species diversification and dispersal.Currently,only one genus 28 gecarcinucids(not including one invasive alien species)are reported from the mountainous regions of Southwest China and most of South China.Few molecular studies on the phylogeny of Gecarcinucidae previously,especially the gecarcinucids in China.There are not still have convincing analysis of the origin of gecarcinucids from China by relationship analysis and divergence time estimation to verify the hypothesis of Somanniathelphusa Bott,1968 originated in the South China Sea.In this study,we sequenced the mitogenomes of four genera eleven species from China and adjacent Southeast Asia countries(Myanmar and Laos)using highthroughput sequencing method.Combined with the nuclear histone 3 gene(H3),we inverstigated the relationship,origin and dispersal of gecarcinucids in China.Meanwhile,we explored the comparative mitophylogenomics of Gecarcinucidae.The main results and conclusions were as follows:1.A brachyuran ground-pattern mitochondrial gene order and a novel gecarcinucid mitochondrial gene order with 42 genes were discovered in Gecarcinucidae firstly(1)In this study,we obtained eleven mitogenomes of gecarcinucids.Ten species contain the entire set of 37 genes with the length of 15,692 bp to 17,740 bp,except for Esanthelphusa dugasti(Rathbun,1902)that contains a total of 42 genes(including two duplicated tRNAs:trnS1-2 and trnH2,two remolded tRNAs:trnS1-3 and trnV2,as well as one pseudogene:p-nad3)with the length of 19,437 bp,which was the largest mitogenome in the freshwater crabs.(2)Three different mitochondrial gene orders were discovered in eleven gecarcinucids:a brachyuran ground-pattern mitochondrial gene order was discovered in genus Abortelphusa(Abortelphusa sp.)firstly;a previously reported gecarcinucid mitochondrial gene order pattern in three genera nine gecarcinucids,with the positions of six tRNAs(trnR,trnN,trnF,trnP,trnQ and trnC),one PCGs(nad5),and one mNCR have been rearranged;a novel gecarcinucid mitochondrial gene order pattern in E.dugasti,with the positions of ten tRNAs(trnR,trnN,trnF,trnP,trnQ,trnH2,trnV2,trnS1-2,trnS1-3 and trnC)and two PCGs(nad5 and p-nad3)have been rearranged.(3)We extended the mitogenomic dataset of Gecarcinucidae to 13 species from four genera,increasing by four and seven times the specificity and generic level,respectively.2.High frequency of gene rearrangements in gecarcinucids from AsiaThe phylogenetic trees were reconstructed using ML and BI analyses based on 13 PCGs from 136 available brachyurans,and we labeled the mitogenomic gene order patterns on each species.Among the 13 known mitochondrial genomes of gecarcinucids,the rate of gene rearrangements(94.1)is second only to that of Potamidae Ortmann,1896(100).However,comparing the ratio of rearranged genes,it can be found that the measured ratio of rearranged genes in Asian gecarcinucids ranged from 16.2 to 35.1(20.9 on average).The ratio of rearranged genes in potamids ranged from 2.7 to 24.3(10.4 on average).We hypothesis that high frequency of rearrangements presumably accompanied adaptive diversification in freshwater environment in freshwater crabs such as gecarcinucids.3.Non-monophyletic relationship of genus Somanniathelphusa Bott,1968 speciesWe inferred the phylogenetic trees using cox1,rrnL and H3 from 176 available gecarcinucids.Our dataset covers 42.4%of known species of genus Somanniathelphusa.The Somanniathelphusa s.lato.can be separated into two lineages:clade ? was constituted by Somanniathelphusa zhapoensis Naiyanetr&Dai,1997,S.tongzhaensis Dai&Xing,1994,S.qiongshanensis and S.grayi(Alcock,1909),and genetically close to genus Esanthelphusa Naiyanetr,1994 from Myanmar and Laos;clade ?(Somanniathelphusa s.str.)was constituted by S.hainanensis Dai&Xing,1994,S.bawangensis Dai&Xing,1994,S.yangshanensis Naiyanetr&Dai,1997,S.sinensis(H.Milne-Edwards,1853),S.taiwanensis Bott,1968,S.zhangpuenss Naiyanetr&Dai,1997,S.zanklon Ng&Dudgeon,1992,S.boyangensis Dai,Peng&Zhou,1994 and S.ruijinensis Dai,Peng&Zhou,1994.The result of this phylogenetic relationship shown the genus Somanniathelphusa Bott,1968 is non-monophyly.We suggested to establish a new genus including the species of clade ?.4.The gecarcinucids of China was dispersal from Southeast Asia,including three dispersal routes,and diversification occurs in the mountainous regions of Southwest China and South ChinaBased on divergence time estimation and ancestral area reconstruction.The gecarcinucids in China origined from Southeast Asia.A.sp.firstly differented at Early Eocene and dispersed to Yunnan Province,China at Middle Eocene.In the Middle Miocene,the species of genus Somanniathelphusa then dispersed to China from Indochina Peninsula twice:one migrated to the South Yunnan,Southwest Guangxi and Southwest Hainan;the other migrated to the South China,such as Hong Kong,Central South Guangdong,Southwest Hainan,Southeast coast of Fujian,northernmost to Central North Jiangxi,and far east of Southwest Taiwan.The time not different between the two spreads,about in the Middle Miocene.This study is helpful to understand the composition and structural characteristics of the mitogenomes of gecarcinucids.It reveals the high frequency of gene rearrangements in gecarcinucids from Asia,and enriches the mitogenome data of gecarcinucids.It provides the basic data for studying the molecular evolution of mitogenomes in this group.As the same time,it provides the molecular basis for the phylogeny and spread of Somanniathelphusa from China,which is of great significance for the further study of the evolution of mitogenomes and phylogenetic relationships from gecarcinucids. |
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