The Morphology And Molecular Phylogeny Of Diaphanosoma In China

The morphologic characteristics of 46 populations of Diaphanosoma,which were collected from twenty-one provinces in China, were measured and analyzed by principal component analysis (PCA) and cluster analysis in this study. Meanwhile, the mitochondrial (cytochrome c oxidase subunit I,COI) gene and nuclear gene (ribosomal internal transcribed spacer 2, ITS2) were measured. By using morphological and genetic information, we explored the genetic phylogeny and taxonomy of five species of Diaphanosoma.According to morphological information,46 populations of Diaphanosoma were identified to D. dubium,D. orghidani, D. excisum, D. brachyurum and D. mongolianum. Seven mophological variables:body length, head length, head height, eye diameter, length of swimming antennule (length of basipodite, length of exopodite and endopodite) were measured. Principle component analsysis (PCA) extracted three principal components, i.e., the swimming antennal comprehensive impact factors, the size of head factor and the comprehensive factors of eye-diameter and exopodite. Cluster analysis of the morphological characteristics showed that the present seven morphological variables were not able to support enough messages for Diaphanosoma identification in species-level.By using NJ, MP and Bayes methods, the COI gene-based phylogenetic tree grouped the 44 populations into six clades:A (D. excisum), B (D. orghidani), C (D. brachyurum), D (D. mongolianum), E (Diaphanosoma sp) and F (D. dubium). The morphological species of D. orghidani, which collected from TA (Lake Taihu), fully comprised clade E, their genetic diversity is beyond 17.16% from the other clades. we consider the TA species into a new species (Diaphanosoma sp) which needs a further identification.By using the NJ,MP and Bayes methods,. The ITS2 gene-based phylogenetic tree organized the 48 populations into 5 clades:A (D. excisum), B (D. orghidani), C (D. brachyurum), E (Diaphanosoma sp) and F (D. dubium). The morphological species D. excisum collected from four islands (HN,WS,WD,NZ) in the South China Sea and the specimens of the same species from Australian was diverged. The island individuals HNEX1-3,WD2-3,WS1-2 and the type species (D1-2) were grouped into Clade A, but the individuals of NZ1-3,WS3 and WD1 were grouped into Clade F. The morphological species D. mongolianum (HL population) was grouped into Clade F. We suggested that there are hybrid individuals in the four islands and HL, can not be distinguished from maternal parent in morphology.