Multiple Mitochondrial Sequence Data Reveals The Phylogeny Of Decapoda And The Asian Helice Group

Recently, the broad pattern of decapod evolution appears to be emerging. Current studies find agreement at the 'base' and 'top' of the tree, but differ in the broader 'middle ground'. All cladistic analyses of freshwater crab relationships were all based on morphology, molecular analysis will help revealing the phylogeny. We use cox1～3, atp6 and atp8 complete sequences of 13 decapoda taxoa Phytogenies are reconstructed using the equally weighted maximum parsimony, maximum likelihood and Bayesian methods. The phylogenies reveal that Achelata is sister to Meiura. Astacidea is at the basal position of Eureptantia, and Meiura is at the top of the tree. The result give molecular evidence for the sister relationship of Acheleta and Meiura. Potamoidea is sister to Xanthoidea, Grapsoidea (Thoracotremata) is sister to this clade. Combined with fossil records and divergence times, phylogenies study indicates that Potamoidea may derive from some underived Xanthoidea-like clade.The taxonomic systematics of the Helice s. l. is currently revised. Thereafter, the Asian Helice s. l crabs are reclassified as three genera, Helice, Helicana and Pseudohelice. The last one is widespread around the Indo-West Pacific Ocean and with only a single species P. subquadrata (=H. leachii) found in Asia. The other two appear to be endemic to Asia. However, Phylogenetic affinities among the Asian components of the Helice s. l. are poorly understood, and different hypotheses of relationships within the Helice s. l. group from morphology-based taxonomic analyses remain untested. In the present study, we used sequence data from a mitochondrial gene-block spanning three different genes [16S rDNA - trnL₁ - IGS- nad1] to perform phylogenetic analyses by MP, ML and Bayesian inference. The results provide independent molecular evidence supporting the taxonomic splitting of the Asian species into two genera, Helice and Helicana. And suggested that the current genus Helice is paraphyletic with respect to the Asian P. subquadrata (= Helice leachii) from southern China. In addition, combined with the reference 16S sequences, the heterogeneity of the species P. subquadrata is detected from the Asian and East African lineages. It proposed that the morphospecies P. subquadrata is most likely a complex. And the two genera, Helice and Pseudohelice, are not monophyletic in their current composition. A putative variant of wuana locate in jiangsu and H. t. wuana show significant differece at both morphlogical and molucuar aspect. They primarily recognise as Helice (iridens) sheni, which is suggested to raise to species level by our study, and should renamed as Helice (Helicana) sheni. The genera Helice , and Chasmagnathus were separated on the basis of the character, anterolateral carapace border. This concept is very unsatisfactory because the distinction is not always clear. Sakai et al.(2006) grouped both genera as having several characters, and named them Helice/Chasmagnathus-complex. 16S rDNA - trnL1 sequeces of one Chasmagnathus and 8 helice species are used to test the hypothese. Both of them get the same trnL1 sequeces. The cladistic analyses based on 16S sequences give strong support for monophyly of Chasmagnathus + Helice clade. Chasmagnathus is clustered together with helicana group, which indicate that Chasmagnathus may have a close relationship with helicana speecies. The result gives molecular evidence for hypothese Helice/Chasmagnathus-complex...